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  • 1. Bergenius, J.
    et al.
    Tribukait, Arne
    Karolinska Hospital.
    Brantberg, K.
    The subjective horizontal at different angles of roll-tilt in patients with unilateral vestibular impairment1996In: Brain Research Bulletin, ISSN 0361-9230, E-ISSN 1873-2747, Vol. 40, no 5-6, p. 385-390Article in journal (Refereed)
    Abstract [en]

    The subjective visual horizontal is mainly dependent on the otolithic system. A group of 11 patients with sudden unilateral vestibular impairment were asked to set a dimly illuminated bar according to their subjective horizontal when they were seated upright and tilted 10, 20, and 30 degrees to the right and left in a completely darkened room (Bias test). The patients were examined within 1 week, after 3 and 6 weeks, and 9 patients consented to the 11-week follow-up. The results were compared with ENG examinations. In the acute stage of the disease all patients, when they were in upright position, set the light bar tilted towards the affected side. At roll tilt to the affected side, 9 of the 11 patients set the light bar in the same direction as their body tilt (undercorrection). At a tilt to the unaffected side 6 of the 11 patients made an undercorrection. For the group of patients the magnitude of undercorrection was larger at tilt to the affected side than to the unaffected side. The patients' ability to correctly align the light bar with the true horizontal gradually improved but was found normal in both upright and tilted positions in only three of the nine patients at the last follow-up. In four of the six patients who still demonstrated pathologic results, these were met only in tilted positions. No significant correlation was found between the intensity of spontaneous nystagmus or the degree of caloric side difference and the deviation in setting of the light bar in upright or tilted positions. The large asymmetric perceptual responses at tilt found at onset might be explained by the two-directional organisation of the utricle.

  • 2. Brantberg, K.
    et al.
    Bergenius, J.
    Mendel, L.
    Witt, H.
    Tribukait, Arne
    Karolinska Hospital.
    Ygge, J.
    Symptoms, findings and treatment in patients with dehiscence of the superior semicircular canal2001In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 121, no 1, p. 68-75Article in journal (Refereed)
    Abstract [en]

    Recently Minor and co-workers described patients with sound- and pressure-induced vertigo due to dehiscence of the superior semicircular canal. Identifying patients with this 'new' vestibular entity is important, not only because the symptoms are sometimes very incapacitating, but also because they can be treated. We present symptoms and findings in eight such patients, all of whom reported pressure-induced vertigo that increased during periods of upper respiratory infections. Pulse-synchronous tinnitus and gaze instability during head movements were also common complaints. All patients lateralized Weber's test to the symptomatic ear. In some of the patients the audiogram also revealed a small conductive hearing loss. However, the stapedius reflexes were always normal. A vertical/torsional eye movement related to the superior semicircular canal was seen in most of the patients in response to pressure changes and/or sound stimulation. One patient also had superior canal-related positioning nystagmus. Testing vestibular evoked myogenic potentials revealed in all patients a vestibular hypersensitivity to sounds. In the coronal high-resolution 1-mm section CT scans the dehiscence was visible on 1 to 4 sections. Moreover, the skull base was rather thin in this area and cortical bone separating the middle ear and the antrum from the middle cranial fossa was absent in many of the patients. Two of the patients have undergone plugging of the superior semicircular canal using a transmastoid approach and both patients were relieved of the pressure-induced symptoms.

  • 3. Brantberg, K.
    et al.
    Bergenius, J.
    Tribukait, Arne
    Karolinska Hospital .
    Gentamicin treatment in peripheral vestibular disorders other than Ménière's disease1996In: Journal for Oto-Rhino-Laryngology, ISSN 0301-1569, E-ISSN 1423-0275, Vol. 58, no 5, p. 277-279Article in journal (Refereed)
    Abstract [en]

    Intratympanic instillation of gentamicin may not exclusively be a treatment for Ménière's disease. We present case reports of successful vertigo control in peripheral vestibular disorders other than Ménère's disease. Cases 1 and 2 illustrate treatment of vertigo attacks caused by vestibular dysfunction in deaf ears. Case 3 illustrates treatment of brief sensations of linear acceleration in a patient who had suffered idiopathic sudden hearing loss a few years earlier. Case 4 illustrates treatment of disabling benign paroxysmal positioning vertigo. Case 5 illustrates treatment of severe and frequent attacks of vertigo in an elderly patient with a medium-sized acoustic neuroma who did not want surgical extirpation of the tumor.

  • 4. Brantberg, K.
    et al.
    Bergenius, J.
    Tribukait, Arne
    Karolinska Hospital.
    Vestibular-evoked myogenic potentials in patients with dehiscence of the superior semicircular canal1999In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 119, no 6, p. 633-640Article in journal (Refereed)
    Abstract [en]

    Recently Minor and co-workers described patients with sound- and pressure-induced vertigo due to dehiscence of bone overlying the superior semicircular canal. Identifying patients with this "new" vestibular entity is important, not only because the symptoms can be very incapacitating, but also because they are surgically treatable. We present symptoms and findings for three such patients. On exposure to sounds, especially in the frequency range 0.5-1 kHz, they showed vertical/torsional eye movements analogous to a stimulation of the superior semicircular canal. They also showed abnormally large sound-induced vestibular-evoked myogenic potentials (VEMP), i.e. the short latency sternomastoid muscle response considered to be of saccular origin. The VEMP also had a low threshold, especially in the frequency range 0.5-1 kHz. However, in response to saccular stimulation by skull taps, i.e. when the middle ear route was bypassed, the VEMP were not enlarged. This suggests that the relation between the sound-induced and the skull tap-induced responses can differentiate a large but normal VEMP from an abnormally large response due to dehiscence of bone overlying the labyrinth, because only the latter would produce large sound-induced VEMP compared to those induced by skull taps.

  • 5. Brantberg, K.
    et al.
    Fransson, P A
    Bergenius, J.
    Tribukait, Arne
    Karolinska Hospital.
    Tilt suppression, OKAN, and head-shaking nystagmus at long-term follow-up after unilateral vestibular neurectomy1996In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 6, no 4, p. 235-241Article in journal (Refereed)
    Abstract [en]

    The functional status of the velocity storage mechanism was studied in patients at long-term follow-up (2 to 4 years) after unilateral vestibular neurectomy. The time constant of the vestibulo-ocular reflex (VORtc), the effect of head tilt on postrotatory nystagmus, optokinetic after-nystagmus (OKAN), and nystagmus after rapid head shaking were studied in 10 patients. In agreement with previous findings, VORtc was found to be short and most patients manifested OKAN, suggesting that unilateral peripheral vestibular loss is associated with a complete loss of storage within the the VOR but only a partial loss of velocity storage for visual input. However, at postrotatory head tilt the VOR time constant was further shortened, supposedly due to discharge of functioning velocity storage. Moreover, most patients manifested nystagmus after head shaking. These findings on tilt suppression and head-shaking nystagmus suggest that velocity storage within the VOR may function even in patients with complete unilateral vestibular lesions.

  • 6. Brantberg, Krister
    et al.
    Löfqvist, Lennart
    Westin, Magnus
    Tribukait, Arne
    Swedish Defence Research Agency.
    Skull tap induced vestibular evoked myogenic potentials: an ipsilateral vibration response and a bilateral head acceleration response?2008In: Clinical Neurophysiology, ISSN 1388-2457, E-ISSN 1872-8952, Vol. 119, no 10, p. 2363-2369Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To explore the mechanisms for skull tap induced vestibular evoked myogenic potentials (VEMP).

    METHODS: An electro-mechanical "skull tapper" (that provided a constant stimulus intensity) was used to test the effects of different midline stimulus sites/directions in healthy subjects (n=10) and in patients with severe unilateral loss of vestibular function (n=8).

    RESULTS: The standardized midline skull taps caused highly reproducible VEMP. There were highly significant differences in amplitude and latency in both normals and patients depending on site/direction of tapping (suggesting a stimulus direction dependency). Occiput skull taps caused, in comparisons to forehead and vertex taps, larger amplitude VEMP with more pronounced differences between the lesioned and the healthy side in the patients.

    CONCLUSIONS: The present data, in conjunction with earlier findings, support a theory that skull tap VEMP are mediated by two different mechanisms. It is suggested that skull tapping causes both skull vibration and head acceleration. Further, the VEMP would be the sum of the direction-independent vibration-induced response (from the sound-sensitive part of the saccule) and the direction-dependent head acceleration response (from other parts of the labyrinth).

    SIGNIFICANCE: Skull tap VEMP, as a diagnostic test, is not equivalent to sound-induced VEMP.

  • 7. Brantberg, Krister
    et al.
    Tribukait, Arne
    Karolinska Hospital.
    Vestibular evoked myogenic potentials in response to laterally directed skull taps2002In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 12, no 1, p. 35-45Article in journal (Refereed)
    Abstract [en]

    In recent years it has been demonstrated that loud clicks generate short latency vestibular evoked myogenic potentials (VEMP). It has also been demonstrated that midline forehead skull tap stimulation evokes similar VEMP. In the present study, the influence of skull tap direction on VEMP was studied in 13 normal subjects and in five patients with unilateral vestibular loss. Gentle skull taps were delivered manually above each ear on the side of the skull. The muscular responses were recorded over both sternocleidomastoid muscles using skin electrodes. Among the normals, laterally directed skull taps evoked "coordinated contraction-relaxation responses", i.e. skull taps on one side evoked a negative-positive "inverted" VEMP on that side and a positive-negative "normal" VEMP on the other side. Among patients with unilateral vestibular function loss, skull taps above the lesioned ear evoked similar coordinated contraction-relaxation responses. However, skull taps above the healthy ear did not evoke that type of response. These findings suggest that laterally directed skull taps activate mainly the contralateral labyrinth.

  • 8. Brantberg, Krister
    et al.
    Tribukait, Arne
    Karolinska Hospital.
    Fransson, Per-Anders
    Vestibular evoked myogenic potentials in response to skull taps for patients with vestibular neuritis2003In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 13, no 2-3, p. 121-130Article in journal (Refereed)
    Abstract [en]

    In recent years it has been demonstrated that loud clicks generate short latency vestibular evoked myogenic potentials (VEMP). It has also been demonstrated that skull tap stimulation evokes similar VEMP. In the present study, the differences between the click-induced and the skull-tap induced VEMP were studied in 18 patients at onset of vestibular neuritis. Gentle skull taps were delivered manually above each ear on the side of the skull and on the forehead midline. The muscular responses were recorded over both sternocleidomastoid muscles using skin electrodes. Abnormal skull tap VEMP were found in the majority of the patients (10/18, 56%). However, only 4/18 (22%) showed asymmetry in the click-induced VEMP. The high percentage of abnormal skull tap VEMP might suggest that this response is not only dependent on the inferior division of the vestibular nerve, because the inferior division of this nerve is usually spared in vestibular neuritis. Moreover, the patients with abnormal skull tap VEMP differed from those with normal VEMP in their settings of the subjective visual horizontal with static head tilt in the roll plane. This might suggest that skull tap VEMP are (also) related to utricular function.

  • 9. Brantberg, Krister
    et al.
    Westin, Magnus
    Löfqvist, Lennart
    Verrecchia, Luca
    Tribukait, Arne
    Swedish Defence Research Agency.
    Vestibular evoked myogenic potentials in response to lateral skull taps are dependent on two different mechanisms2009In: Clinical Neurophysiology, ISSN 1388-2457, E-ISSN 1872-8952, Vol. 120, no 5, p. 974-979Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To explore the mechanisms for skull tap induced vestibular evoked myogenic potentials (VEMP).

    METHODS: The muscular responses were recorded over both sternocleidomastoid (SCM) muscles using skin electrodes. A skull tapper which provided a constant stimulus intensity was used to test cervical vestibular evoked myogenic potentials (VEMP) in response to lateral skull taps in healthy subjects (n=10) and in patients with severe unilateral loss of vestibular function (n=10).

    RESULTS: Skull taps applied approximately 2 cm above the outer ear canal caused highly reproducible VEMP. There were differences in VEMP in both normals and patients depending on side of tapping. In normals, there was a positive-negative ("normal") VEMP on the side contra-lateral to the skull tapping, but no significant VEMP ipsi-laterally. In patients, skull taps above the lesioned ear caused a contra-lateral positive-negative VEMP (as it did in the normals), in addition there was an ipsi-lateral negative-positive ("inverted") VEMP. When skull taps were presented above the healthy ear there was only a small contra-lateral positive-negative VEMP but, similar to the normals, no VEMP ipsi-laterally.

    CONCLUSIONS: The present data, in conjunction with earlier findings, support a theory that skull-tap VEMP responses are mediated by two different mechanisms. It is suggested that skull tapping causes both a purely ipsi-lateral stimulus side independent SCM response and a bilateral and of opposite polarity SCM response that is stimulus side dependent. Possibly, the skull tap induced VEMP responses are the sum of a stimulation of two species of vestibular receptors, one excited by vibration (which is rather stimulus site independent) and one excited by translation (which is more stimulus site dependent).

    SIGNIFICANCE: Skull-tap VEMP probably have two different mechanisms. Separation of the two components might reveal the status of different labyrinthine functions.

  • 10.
    Eiken, Ola
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    Tribukait, Arne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Environmental Physiology.
    High G centrifuge training; Vestibular mechanisms for motion sickness during high-G training. CBH Report 2015-0197.2018Report (Other academic)
  • 11.
    Eriksson, Lars
    et al.
    Swedish Defence Research Agency.
    von Hofsten, Claes
    Swedish Defence Research Agency.
    Tribukait, Arne
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Andersson, Peter
    Swedish Defence Research Agency.
    Hedström, Johan
    Swedish Defence Research Agency.
    Visual flow scene effects on the somatogravic illusion in non-pilots2008In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 79, no 9, p. 860-866Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: The somatogravic illusion (SGI) is easily broken when the pilot looks out the aircraft window during daylight flight, but it has proven difficult to break or even reduce the SGI in non-pilots in simulators using synthetic visual scenes. Could visual-flow scenes that accommodate compensatory head movement reduce the SGI in naive subjects?

    METHODS: We investigated the effects of visual cues on the SGI induced by a human centrifuge. The subject was equipped with a head-tracked, head-mounted display (HMD) and was seated in a fixed gondola facing the center of rotation. The angular velocity of the centrifuge increased from near zero until a 0.57-G centripetal acceleration was attained, resulting in a tilt of the gravitoinertial force vector, corresponding to a pitch-up of 30 degrees. The subject indicated perceived horizontal continuously by means of a manual adjustable-plate system. We performed two experiments with within-subjects designs. In Experiment 1, the subjects (N = 13) viewed a darkened HMD and a presentation of simple visual flow beneath a horizon. In Experiment 2, the subjects (N = 12) viewed a darkened HMD, a scene including symbology superimposed on simple visual flow and horizon, and this scene without visual flow (static).

    RESULTS: In Experiment 1, visual flow reduced the SGI from 12.4 +/- 1.4 degrees (mean +/- SE) to 8.7 +/- 1.5 degrees. In Experiment 2, the SGI was smaller in the visual flow condition (9.3 +/- 1.8 degrees) than with the static scene (13.3 +/- 1.7 degrees) and without HMD presentation (14.5 +/- 2.3 degrees), respectively.

    CONCLUSION: It is possible to reduce the SGI in non-pilots by means of a synthetic horizon and simple visual flow conveyed by a head-tracked HMD. This may reflect the power of a more intuitive display for reducing the SGI.

  • 12. Levin, Britta
    et al.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Lemming, Dag
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Utvärdering av utbildning i spatial desorientering; redovisning av frågeformulär2011Report (Other academic)
    Abstract [sv]

    En kombinerad grundutbildning i spatial desorientering (SD) och flygning med night vision goggles (NVG) ges av företaget AMST Systemtechnik GmbH i dess lokaler i Ranshofen i Österrike.Denna utbildning blev föremål för en ingående utvärdering i samband med att två grupper av svenska flygförare deltog under hösten 2010.Den del av utvärderingen som redovisas i denna rapport är baserad på deltagarnas egna åsikter och bygger på en metod som omfattar såväl öppna frågor som skattningsfrågor och även möjlighet att ange fria kommentarer.Eleverna uppgav att det är viktigt att genomföra både grundläggande och repeterande SD-utbildning.De värdesatte SD-teori generellt sett och efterfrågade ett mer omfattande och djupare teoretiskt paket än vad de hittills har erhållit.Eleverna ansåg också att utbildningen på AMST på ett effektivt sätt ger en ökad förståelse för illusioner, en ökad förmåga att känna igen en illusion och även att komma över en villa om den skulle inträffa.När det gäller night vision (NV) delen uppgav eleverna att utbildningen på ett effektivt sätt ger en ökad förståelse för problematiken runt flygning med night vision goggles (NVG), en ökad förmåga att känna igen NV-relaterade fenomen och en förberedelse för att kunna hantera flygning med NVG.Eleverna framhöll att kursen i större utsträckning borde ha koordinerats med avseende på tid och innehåll med annan redan genomgången utbildning eller sådan som är inplanerad längre fram.I de fall eleverna redan upplevt en del illusioner eller erfarit NV-fenomen etc. uppfattades utbildningen som ett bra komplement och en repetition.Eleverna ansåg att utbildningen på AMST delvis var ineffektiv och man hade förväntat sig både mer teori och tid i simulatorn.Ett stort antal elever i kombination med begränsad tillgång till simulatorutrustning ledde till en ansenlig väntetid mellan passen.Eleverna ansåg också att det finns möjlighet till förbättringar av den SD-utbildning som ges i stort och avgav ett antal olika förslag.

  • 13.
    Nobel, Gerard
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Motion sickness increases the risk of accidental hypothermia2006In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 98, no 1, p. 48-55Article in journal (Refereed)
    Abstract [en]

    Motion sickness (MS) has been found to increase body-core cooling during immersion in 28 degrees C degrees C water, an effect ascribed to attenuation of the cold- induced peripheral vasoconstriction (Mekjavic et al. in J Physiol 535(2):619-623, 2001). The present study tested the hypothesis that a more profound cold stimulus would override the MS effect on peripheral vasoconstriction and hence on the core cooling rate. Eleven healthy subjects underwent two separate head-out immersions in 15 degrees C water. In the control trial (CN), subjects were immersed after baseline measurements. In the MS-trial, subjects were rendered motion sick prior to immersion, by using a rotating chair in combination with a regimen of standardized head movements. During immersion in the MS-trial, subjects were exposed to an optokinetic stimulus (rotating drum). At 5-min intervals subjects rated their temperature perception, thermal comfort and MS discomfort. During immersion mean skin temperature, rectal temperature, the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (Delta T (ff)), oxygen uptake and heart rate were recorded. In the MS-trial, rectal temperature decreased substantially faster (33%, P < 0.01). Also, the Delta T (ff) response, an index of peripheral vasomotor tone, as well as the oxygen uptake, indicative of the shivering response, were significantly attenuated (P < 0.01 and P < 0.001, respectively) by MS. Thus, MS may predispose individuals to hypothermia by enhancing heat loss and attenuating heat production. This might have significant implications for survival in maritime accidents.

  • 14.
    Nobel, Gerard
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I.B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Effects of motion sickness on thermoregulatory responses in a thermoneutral air environment2011Conference paper (Refereed)
  • 15.
    Nobel, Gerard
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Effects of motion sickness on thermoregulatory responses in a thermoneutral air environment2012In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 112, no 5, p. 1717-1723Article in journal (Refereed)
    Abstract [en]

    Motion sickness (MS) has been identified as a non-thermal factor that can moderate autonomic thermoregulatory responses. It has been shown that MS exaggerates core cooling during immersion in cold (15A degrees C) and luke-warm (28A degrees C) water by attenuating cold-induced vasoconstriction. The aim of the present study was to investigate whether MS affects thermal balance in a thermoneutral air environment. Eleven subjects were exposed to rotation in two conditions, control (CN) and MS. In the CN condition subjects refrained from head movements, whereas in the MS condition they performed a sequence of maximal head movements (left, right, up, down) at 15-s intervals until they were very nauseous. Sweating rate, rectal temperature (T (re)), the difference in temperature between the right forearm and tip of the second finger (T (ff)) as an index of cutaneous vasomotor tone, perceived MS, thermal comfort and temperature perception were recorded before and during rotation, and during 90-min post-rotation. During the post-rotation period, T (re) dropped and sweating rate increased in the MS but not in the CN condition. The T (ff) response suggests that MS-induced peripheral vasodilatation which, together with the sweating resulted in increased heat loss. During rotation, subjects perceived temperature to be uncomfortably high, suggesting that MS may also affect thermoregulatory behaviour. It thus appears that also in a thermoneutral air environment MS may substantially affect thermal balance.

  • 16.
    Nobel, Gerard
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, Igor B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Histaminergic and cholinergic neuron systems in the impairment of human thermoregulation during motion sickness2010In: Brain Research Bulletin, ISSN 0361-9230, E-ISSN 1873-2747, Vol. 82, no 3-4, p. 193-200Article in journal (Refereed)
    Abstract [en]

    Motion sickness (MS) exaggerates body cooling during cold-water immersion. The aim of the present study was to investigate whether such MS-induced predisposition to hypothermia is influenced by two anti-MS drugs: the histamine-receptor blocker dimenhydrinate (DMH) and the muscarine-receptor blocker scopolamine (Scop). Nine healthy male subjects were immersed in 15 degrees C water for a maximum of 90 min in five conditions: (1) control (CN): no medication, no MS provocation; (2) MS-control (MS-CN): no medication, MS provocation; (3) MS-placebo (MS-P): placebo DMH and placebo Scop, MS provocation; (4) MS-DMH: DMH and placebo Scop, MS provocation; (5) MS-Scop: Scop and placebo DMH, MS provocation. MS was induced by use of a rotating chair. Throughout the experiments rectal temperature (T-re), the difference in temperature between the non-immersed right forearm and third finger (T-ff) as an index of peripheral vasoconstriction, and oxygen uptake (VO2) as a measure of shivering thermogenesis, were recorded. DMH and Scop were similarly efficacious in ameliorating nausea. The fall in T-re was greater in the MS-CN and MS-P conditions than in the CN condition. DMH, but not Scop, prevented the MS-induced increase in body-core cooling. MS attenuated the cold-induced vasoconstriction, an effect which was fully prevented by DMH but only partially by Scop. MS provocation did not affect VO2 in any condition. The results suggest that the MS-induced predisposition to hypothermia is predominantly mediated by histaminergic mechanisms and that DMH might be useful in conjunction with maritime accidents or other scenarios where exposure to cold and MS are imminent features.

  • 17. Pansell, Tony
    et al.
    Tribukait, Arne
    Karolinska Institutet.
    Bolzani, Roberto
    Schworm, Hermann D
    Ygge, Jan
    Drift in ocular counterrolling during static head tilt2005In: Annals of the New York Academy of Sciences, ISSN 0077-8923, E-ISSN 1749-6632, Vol. 1039, p. 554-557Article in journal (Refereed)
    Abstract [en]

    A decreasing drift of the counter-rolled eye position (OCR) during head tilt was recently described. The underlying mechanism is not known. OCR in eleven healthy subjects was recorded (Search coil, Skalar) during a head tilt paradigm in two test conditions. The head was tilted with a velocity below (test 1) and above (test 2) detection threshold for the semicircular canals (SC) and held static for eight minutes. A significant drift of OCR was revealed in test 2 (P = .0006, ANOVA) and close to significant in test 1 (P = .07). No statistical difference was found between the two test conditions. The results suggest that the OCR drift was not caused by the SC complex merely.

  • 18. Pansell, Tony
    et al.
    Tribukait, Arne
    Karolinska Institutet.
    Bolzani, Roberto
    Schworm, Hermann D
    Ygge, Jan
    Drift in ocular torsion during sustained head tilt2005In: Strabismus, ISSN 0927-3972, E-ISSN 1744-5132, Vol. 13, no 3, p. 115-121Article in journal (Refereed)
    Abstract [en]

    PURPOSE: A head tilt towards the shoulder (roll) induces an ocular counter-roll (OCR), i.e. torsion in the opposite direction to the head. How this counter-rolled position is maintained during a static head tilt is in debate. In a previous study, we reported an OCR-increasing drift subsequent to the head tilt. This finding is in contrast to other reports where no such response was found. The primary aim of this study was to repeat the experiment during a prolonged head-tilt test and to describe the OCR characteristics. A secondary aim was to investigate the influence of spatial visual cues on OCR.

    METHODS: Five male subjects performed a head tilt (30 degrees ) towards the right shoulder while the eye position was recorded during a 10-minute interval. In test 1, the subjects viewed a target with no cues for spatial orientation. The same head-tilt paradigm was repeated in test 2 with a visual target with spatial cues. Two samples of data were extracted from the start and the end of the recordings for statistical analysis.

    RESULTS: Subsequent to the head tilt, a slow OCR-increasing drift in the opposite direction to the head roll was found in all subjects. On average, this drift lasted for 30 sec (+/- 5) in test 1 and for 55 sec (+/- 18) in test 2. The drift was then found to change its direction, i.e. the eyes were rotated in the same direction as the head roll. When measured after 10 minutes, the OCR was significantly decreased.

    CONCLUSIONS: The OCR during static head tilt is not constant. During the first minute there is a gradually increasing OCR. Thereafter, the amplitude of the OCR decreases gradually. These changes are influenced to some extent by spatial visual cues. Possible mechanisms are adaptive responses in otolithic afferents as well as central nervous memory functions related to the semicircular canal system.

  • 19.
    Tribukait, Arne
    Karolinska Hospital.
    Human vestibular memory studied via measurement of the subjective horizontal during gondola centrifugation2003In: Neurobiology of Learning and Memory, ISSN 1074-7427, E-ISSN 1095-9564, Vol. 80, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Measurements of the subjective visual horizontal (SVH) were made in a large swing-out gondola centrifuge. Rotation of the centrifuge was anti-clockwise, as seen from above. Test subjects were seated upright in the gondola, facing forwards. In front of the subject, at a straight-ahead eye-level position, there was a narrow luminous line, which could be rotated, by remote control, about the visual axis. At gravitoinertial force levels of 1.1-1.3G the subjects were asked to indicate, by repeatedly setting the line in darkness, what they perceived as horizontal (the SVH). During gondola centrifugation, the head and body length axis is always parallel with the resultant gravitoinertial force vector (vectorial sum of earth gravity force and the centrifugal force) i.e., the horizontal plane of the head or body does not change with respect to the gravitoinertial horizontal. Hence, the otolith organs, as well as the somatosensory system, continually signal upright position. However, the swing-out of the gondola during acceleration of the centrifuge (25 degrees at 1.1G) is a roll (frontal plane) change-in-position stimulus to the vertical semicircular canals, thus creating an otolith-semicircular canal conflict. After acceleration of the centrifuge, the SVH was initially tilted up to 20 degrees to the right relative to the gravitoinertial horizontal. Since there was no roll-tilt stimulus to gravity receptors, this SVH tilt must be related to stimulation of the semicircular canals. However, it decayed much more slowly than any known effects of angular-velocity stimulation of the semicircular canals. The decay was bi-phasic with two time constants, the smaller in the region of 1-2 min, the other being too large to be reliably estimated on the basis of data collected during only 10 min. This persistence of the SVH tilt suggests a memory for angular changes in roll head position detected by the semicircular canals-a position-storage mechanism. Further, the SVH seems to be dependent on two different mechanisms related to semicircular canal stimulation.

  • 20.
    Tribukait, Arne
    Karolinska Hospital.
    Semicircular canal and saccular influence on the subjective visual horizontal during gondola centrifugation1999In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 9, no 5, p. 347-357Article in journal (Refereed)
    Abstract [en]

    Measurements of the subjective visual horizontal (SVH) were performed in 11 healthy test persons during an increase of the resultant gravitoinertial force vector in a large swing-out gondola centrifuge. Three levels of hypergravity (1.5 g, 2.0 g, 2.5 g) were used, each with a duration of 4 minutes and with 1-2 minute pauses at 1.0 g in between. The direction of the resultant gravitoinertial force vector was always parallel with the head and body length axis. Hence, there was no roll stimulus to the otolith organs. The swing-out of the gondola during acceleration, however, is sensed by the vertical semicircular canals as a change in roll head position, thus creating an otolith-semicircular canal conflict. After acceleration of the centrifuge there was a tilt of the SVH relative to the resultant gravitoinertial horizontal. This tilt gradually decayed during the 4-minute period of recordings. For a subgroup of seven test subjects who had completely normal ENG-recordings in 1 g environment, the initial offset of SVH and the time constants for exponential decay were determined for each g level; initial offsets: 9.9 degrees (1.5 g), 7.7 degrees (2.0 g), 6.1 degrees (2.5 g); time constants: 89s (1.5 g), 74s (2.0 g), 37s (2.5 g). The offset of SVH is interpreted as being the result of mainly the stimulus to the vertical semicircular canals during acceleration of the centrifuge. The slow decay, however, does not correspond to the dynamics of the semicircular canal system, and is suggested to reflect some kind of central position storage mechanism. A smaller offset and more rapid decay for the higher g loads may be explained by an increasing dominance of graviceptive input, presumably from the saccules. In conclusion, these results might suggest the role of the vertical semicircular canals as well as the sacculus in the formation of SVH. They may also have relevance with regard to the spatial disorientation problem in aviators.

  • 21.
    Tribukait, Arne
    Karolinska Hospital.
    Subjective visual horizontal in the upright posture and asymmetry in roll-tilt perception: independent measures of vestibular function2006In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 16, no 1-2, p. 35-43Article in journal (Refereed)
    Abstract [en]

    The subjective visual horizontal (SVH) was measured in the upright position and at 10, 20, and 30 degrees of head and body tilt to the right and left. Normal subjects (n=25) were tested on two separate occasions with an interval of 1-14 days. Test variables considered were the SVH in the upright position, the perception of tilt to the right and left, calculated on the basis of the SVH in the upright and tilted positions, and the asymmetry in tilt perception. There was no correlation between the perception of tilt to the right and to the left r=0.10). Neither was there any correlation between the SVH in the upright position, representing a resting asymmetry, and the asymmetry in tilt perception, i.e. the response asymmetry (r=0.17). However, for each variable, there was a high correspondence between data obtained at test and retest (r ranged from 0.68 to 0.89, p<0.001), suggesting that the independence between variables is not due to noise. Findings are discussed taking into consideration the possible roles of otoliths and semicircular canals in the formation of the SVH. In an attempt to explain the independence between the two measures of asymmetry it is hypothesized that while the otoliths must be essential for the perception of static lateral tilt, the SVH in the upright position to a considerable degree reflects semicircular canal function.

  • 22.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The ability of pilots and non-pilots to perceive angular displacements in centrifuge and helicopter2013In: Proceedings from the Italian Association of Aviation and Space Medicine , XXVI National Meeting, Vatikanstaten 11-14 sep., 2013Conference paper (Refereed)
  • 23.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Visual indicators in the study of spatial orientation in a gondola centrifuge2013In: Italian Journal of Aerospace Medicine, ISSN 2279-8994, Vol. 9, p. 56-69Article in journal (Refereed)
  • 24.
    Tribukait, Arne
    et al.
    Karolinska Hospital.
    Bergenius, J.
    The subjective visual horizontal after stapedotomy: evidence for an increased resting activity in otolithic afferents1998In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 118, no 3, p. 299-306Article in journal (Refereed)
    Abstract [en]

    The subjective visual horizontal (SVH) was measured by means of a small rotatable luminous line in darkness in the upright body position and at 10, 20 and 30 degrees of body tilt to the right and left prior to, and during a follow-up period after, stapedotomy in 12 patients with otosclerosis. In the acute stage after surgery, SVH in the upright body position was significantly tilted away from the operated side. In addition, the perception of roll tilt towards the operated side (Kop) was significantly increased after stapedotomy, while the perception of roll tilt towards the healthy side (Khe) showed a slight but not significant reduction. After exclusion of two outliers, a statistically significant correlation was found between changes in Kop and in Khe. The slope of the regression line was 1.8:1, probably corresponding to a preference of the utricle for ipsilateral as opposed to contralateral head tilt. In four patients there was a weak ( < 1 degrees/s) spontaneous nystagmus, not systematically related to the side of surgery, while in most cases there were no nystagmus or subjective vertigo symptoms. These specific changes in the subjective horizontal show that the otolithic effects on perception can be dissociated from canal effects. Further, the results are opposite to those for patients with unilateral loss of vestibular function. The tilt of SVH after stapedotomy indicates an increase in resting activity of utricular afferents. In addition, based on recent theories on otolith function, we suggest that an increased activity in saccular afferents is of major importance for the changes in roll-tilt perception because of its interaction with the utricle on the central nervous level.

  • 25.
    Tribukait, Arne
    et al.
    Karolinska Hospital.
    Bergenius, J.
    Brantberg, K.
    Subjective visual horizontal during follow-up after unilateral vestibular deafferentation with gentamicin1998In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 118, no 4, p. 479-487Article in journal (Refereed)
    Abstract [en]

    The subjective visual horizontal (SVH) was measured by means of a small, rotatable, luminous line in darkness in the upright head and body position and at 10, 20 and 30 degrees of tilt to the right and left before, and repeatedly during a follow-up period of 1 year after intratympanic gentamicin instillations in 12 patients with recurrent vertigo attacks. This treatment caused a loss of the bithermal caloric responses on the diseased side. Shortly after treatment there was a significant tilt of SVH towards the treated side (group mean = 10.6 degrees). Repeated testing made it possible to characterize mathematically the changes with time for SVH. For the group of patients as a whole this otolithic component of vestibular compensation was best described by a power function, SVH = 8.65t(-0.16) degrees, where t is time in days after maximum tilt of SVH. After 1 year, SVH was still significantly tilted towards the treated side (group mean = 3.16 degrees). Gentamicin treatment also caused a significant reduction in the perception of head and body tilt towards the deafferented side, while the perception of tilt towards the healthy side did not show any significant changes. During follow-up there was a gradual improvement in the perception of tilt towards the treated side. However, a significant asymmetry in roll-tilt perception was still present 1 year after deafferentation. There was no correlation between SVH in the upright position and roll-tilt perception, suggesting that these parameters are to some extent dependent on different afferent input from the vestibular organ. They were also found to be complementary for the detection of vestibular disturbance.

  • 26.
    Tribukait, Arne
    et al.
    Karolinska Hospital.
    Bergenius, J.
    Brantberg, K.
    The subjective visual horizontal for different body tilts in the roll plane: characterization of normal subjects1996In: Brain Research Bulletin, ISSN 0361-9230, E-ISSN 1873-2747, Vol. 40, no 5-6, p. 375-383Article in journal (Refereed)
    Abstract [en]

    In order to establish a method for estimation of the perceptual horizontal as a test of otolith function in diagnosis of atypical vertigo, in a first study we have standardized a test procedure and characterized a body of normal material consisting of 72 healthy subjects, 24 of them examined with tests followed by retests. The perceptual visual horizontal in darkness was estimated in the upright body position and at body tilts of 10, 20, and 30 degrees to the right and to the left by means of a narrow luminous bar. The deviation of the perceptual horizontal relative to the gravitational horizontal is expressed as a function of body tilt. In the upright body position, 95% had a perceptual horizontal within the range of +/- 2.5 degrees. In the tilted positions, there was a tendency to set the light bar tilted oppositely with respect to the body tilt. The results suggest that roll tilt to the right and to the left is sensed by two independent functional units. Furthermore, the results imply that some other factor might be of importance and that the perceptual horizontal in the upright position and tilt perception are complementary in reflecting vestibular function. Differences between individuals were great in comparison with intraindividual variability and the test-retest variability. The results are discussed against the background of the extensive literature.

  • 27.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Individual characteristics in the perception of roll tilt during a simulated coordinated turn2013Conference paper (Refereed)
  • 28.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Individuella särdrag i spatial orienteringsförmåga vid en simulerad koordinerad sväng i gondolcentrifug/dfs2013In: Hygiea, 2013Conference paper (Refereed)
    Abstract [sv]

    Individuella särdrag i spatial orienteringsförmåga vid en simulerad koordinerad sväng i gondolcentrifug. Stora skillnader i skattningen av roll-position, dessa var ej slumpmässiga.

  • 29.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Möjligheterna att i dynamisk flygsimulator (DFS) återskapa rörelsemönster som vid flygning är grundläggande. 2. Positionsändring vid hovring2014Conference paper (Refereed)
  • 30.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Pitch-Plane Angular Displacement Perception During Helicopter Flight and Gondola Centrifugation2016In: Aerospace Medicine and Human Performance, ISSN 2375-6314, Vol. 87, no 10, p. 852-861Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: During hovering with a helicopter, an involuntary change in attitude (during brownout) results in reduced lifting force and a horizontal acceleration component. This movement pattern is difficult to perceive via the otolith organs. If the angular displacement occurs rapidly, it will, however, activate the semicircular canals. The major aim of this study was to establish to what extent pitch-plane angular displacements can be perceived based on canal information when there is no tilt stimulus to the otoliths. METHODS: In a helicopter, 9 nonpilots (N) and 8 helicopter pilots (P) underwent 5-6 pitch-forward displacements (magnitude 14-33 degrees, angular velocity 2-7 degrees. s(-1)). In a swing-out gondola centrifuge, 9 N and 3 P were exposed to a similar canal-otolith conflict (acceleration, seated centripetally) with four displacements of 25 degrees and two of 60 degrees. The visually perceived eye level (VPEL) was continuously recorded using an adjustable luminous dot in darkness. For each helicopter dive and centrifuge run the gain was calculated as the ratio (VPEL deflection)/(displacement of helicopter or gondola). RESULTS: In the helicopter there was no difference between N (0.28 +/- 0.13) and P (0.36 +/- 0.22). In the centrifuge the gains were 0.34 +/- 0.18 degrees (25 degrees displacements) and 0.30 +/- 0.16 degrees (60 degrees displacements). Values obtained in the helicopter did not differ significantly from those in the centrifuge. There was a correlation between data obtained during the 25 degrees and 60 degrees displacements in the centrifuge. CONCLUSION: There was a pronounced underestimation of pitch angular displacements in a helicopter. The interindividual variability was considerable. Gains for perceived displacement were similar in helicopter and centrifuge.

  • 31.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Variability in Perceived Tilt During a Roll Plane Canal-Otolith Conflict in a Gondola Centrifuge2013In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 84, no 11, p. 1131-1139Article in journal (Refereed)
    Abstract [en]

    Background: During a simulated coordinated turn in a gondola centrifuge, the perceived roll-tilt, quantified as the subjective visual horizontal (SVH), may differ tenfold between individuals. One aim of this study was to discern whether this variability reflects real individual characteristics or is due to noise or day-to-day variation. We also wanted to establish whether there are any habituation or learning effects of the centrifuge test. Methods: In nine nonpilots (NP) and nine student pilots (SP), with a flight experience of 150 h, the SVH was measured using an adjustable luminous line in darkness. At two test occasions (T1, T2) (interval 5-14 d) subjects underwent two runs (R1, R2; acceleration to 2 G in 10 s, gondola inclination 60 degrees, 5 min at 2 G, deceleration to 1 g in 10 s, interval between runs 5 min) in a centrifuge (r = 9.1 m). Initial and final SVH was determined for each individual run. Results: Acceleration of the centrifuge induced a tilt of the SVH. At T1R1, this SVH tilt was, in NP, initially 24 +/- 18 degrees and finally 8 +/- 10 degrees. The corresponding values for SP were 28 +/- 18 degrees and 31 +/- 33 degrees. The SVH tilt was slightly larger at R2 than at R1. There was no difference between T1 and T2. Reliability coefficients ranged between 0.86 and 0.98 for NP and between 0.78 and 0.99 for SR. Conclusion: The large interindividual variability combined with a very high reproducibility suggests the existence of persistent individual characteristics in the perception of complex vestibular stimuli. Habituation or learning effects of gondola centrifugation appears to be small.

  • 32.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Bergsten, Eddie
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Visual sensations of roll rotation during complex vestibular stimulation2008In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 79, no 5, p. 479-487Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: In aviation, vestibular-induced spatial disorientation is a significant cause of accidents. Recreating flight-like vestibular stimuli in simulators might be a means for training pilots to respond adequately in disorienting situations. Due to the physical constraints of land-based simulators, the question arises whether a given illusion may be created in different ways. For instance, is it possible to induce sensations of tilt by rotary stimuli? The present study concerns the relationship between sensations of rotation and tilt during complex vestibular stimulation.

    METHODS: The visual sensation of roll rotation was quantified by means of a velocity-matching procedure. In a large gondola centrifuge eight subjects underwent four runs (2 G, 2 min) with different heading positions (forward, backward, centripetally, and centrifugally). The inclination of the gondola persistently corresponded with the vector sum of the Earth gravity force and the centrifugal force (60 degrees at 2 G). Thus, the semicircular canal stimulus in roll was combined in different ways with stimuli in yaw and pitch, as well as with an increasing or decreasing G vector.

    RESULTS: The magnitude of the responses was only dependent on the roll component of the stimulus. The gain, defined as the ratio between the response and the roll stimulus, was 7-10%. The responses decayed with a time constant ranging from 4 to 5.5 s.

    CONCLUSION: The visual sensation of roll rotation reflects the roll plane canal velocity stimulus independently of other stimulus components. This is in contrast to earlier findings on the sensation of changes in position (roll tilt).

  • 33.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Brink, Andreas
    Möjligheterna att i dynamisk flygsimulator (DFS) återskapa rörelsemönster som vid flygning är grundläggande. 1. Koordinerad kurvtagning2014Conference paper (Refereed)
  • 34.
    Tribukait, Arne
    et al.
    Karolinska Hospital.
    Brantberg, Krister
    Bergenius, Johan
    Function of semicircular canals, utricles and saccules in deaf children2004In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 124, no 1, p. 41-48Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To study vestibular function in deaf children.

    MATERIAL AND METHODS: In 36 deaf children the function of the semicircular canals, saccules and utricles was measured by means of caloric testing, recordings of vestibular-evoked myogenic potentials (VEMPs) and measurements of the subjective visual horizontal (SVH) at different body tilts, respectively.

    RESULTS: In total, 30% of subjects had caloric hypo- or areflexia and 24% had a caloric asymmetry. VEMPs were weak or absent bilaterally in 22% of cases, and asymmetric in 19%. Regarding the utricle, 17% of subjects had a pathologically reduced perception of roll tilt to both sides and 25% had an asymmetry. In total, 30% of subjects were pathologic in all 3 tests and 30% were completely normal. Semicircular canal function correlated best with the function of the saccule. If hearing was better than 90 dB (pure-tone average of 0.5, 1.0 and 2.0 kHz) vestibular function was often normal. For hearing levels of 100-120 dB, otolith function declined significantly.

    CONCLUSIONS: Vestibular function tends to be preserved up to a point where hearing is nearly extinct. Hearing level correlates more closely with otolith function, especially that of the utricle, than with semicircular canal function.

  • 35.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Changes in the perceived head transversal plane and the subjective visual horizontal induced by Coriolis stimulation during gondola centrifugation2006In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 16, no 3, p. 105-116Article in journal (Refereed)
    Abstract [en]

    For studying the influence of the vertical semicircular canals on spatial orientation in roll, the subjective visual horizontal (SVH) and the subjective transversal plane of the head (STP) were measured in a situation where the vertical canals sense a roll-velocity stimulus while the otolith organs persistently signal that the head is upright in roll. During gondola centrifugation (resultant gravitoinertial force vector 2.5 G, gondola inclination 66 degrees) subjects were exposed to controlled rotational head movements (angular speed 27 degrees/s, magnitude 40 degrees) about the yaw (body z-) axis, produced by means of a motor-driven helmet. This causes a roll-plane Coriolis stimulus to the canals, while the otoliths persistently sense upright head position in roll. The subjects reported intense sensations of rotation and tilt in the roll plane. This was reflected in tilts of both the SVH and STP. The initial tilt of the SVH was 13.0 +/- 9.7 degrees (mean +/- S.D., n=10). The STP was changed in the opposite direction. The initial tilt was 23.8 +/- 12.2 degrees (mean +/- S.D., n=5). The changes in the SVH and STP were not of equal magnitude. A few subjects who had almost no deviations in the SVH showed pronounced tilts of the STP. The time constant for exponential decay of the tilts of the SVH and STP was on average approximately 1 minute. These findings indicate that a difference in activity of the vertical canals in the right versus left ear may cause substantial tilts of the SVH even if there is no asymmetry in the activity of the otolith system. Further, the canal stimulus may induce a tilt of the fundamental egocentric frame of reference.

  • 36.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Flight Experience and the Perception of Pitch Angular Displacements in a Gondola Centrifuge2012In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 83, no 5, p. 496-503Article in journal (Refereed)
    Abstract [en]

    Background: It has been shown that flight experience may induce an adaptation of the vestibular system. The aim of the present work was to elucidate whether pilots, in comparison with non-pilots, have an increased responsiveness to angular displacement canal stimuli in the pitch plane during a conflict between the otolith organs and the semicircular canals. Methods: In a large swing-out gondola centrifuge, eight non-pilots, eight fighter pilots, and eight helicopter pilots underwent three runs (2 G, 5 min) heading forward, centripetally, and centrifugally. The direction of the gravitoinertial force was constant with respect to the subject. The visually perceived eye level (VPEL.) was measured in darkness by means of an adjustable luminous dot. Results: In the forward position the three groups produced similar results. After acceleration there was a sensation of backward tilt and an increasing depression of VPEL. This effect was smaller in the centripetal position and larger in the centrifugal position. The difference in VPEL between the opposite positions constitutes a measure of the ability to sense the pitch angular displacement canal stimulus related to the swing out of the gondola (600). This difference was most pronounced initially at the 2-G plateau (mean +/- SD): 13.5 +/- 12.9 degrees (non-pilots), 41.6 +/- 21.10 degrees (fighter pilots), and 19.5 +/- 14.0 degrees (helicopter pilots). There was no significant difference between non-pilots and helicopter pilots. Fighter pilots differed significantly from both non-pilots and helicopter pilots. Conclusion: Vestibular learning effects of flying may be revealed in a centrifuge. Fighter pilots had an increased ability, as compared to non-pilots and helicopter pilots, to perceive pitch angular displacements.

  • 37.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Flygplanshaveriet vid Oajevagge 8/1 2016 (SRL 2016:01); händelseförloppet med fokus på spatial desorientering.2016Report (Other academic)
  • 38.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Instrument Failure, Stress, and Spatial Disorientation Leading to a Fatal Crash With a Large Aircraft2017In: Aerospace Medicine and Human Performance, ISSN 2375-6314, E-ISSN 2375-6322, Vol. 88, no 11, p. 1043-1048Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: An aircraft's orientation relative to the ground cannot be perceived via the sense of balance or the somatosensory system. When devoid of external visual references, the pilot must rely on instruments. A sudden unexpected instrument indication is a challenge to the pilot, who might have to question the instrument instead of responding with the controls. In this case report we analyze, from a human-factors perspective, how a limited instrument failure led to a fatal accident.

    CASE REPORT: During straight-ahead level flight in darkness, at 33,000 ft, the commander of a civil cargo airplane was suddenly confronted by an erroneous pitch-up indication on his primary flight display. He responded by pushing the control column forward, making a bunt maneuver with reduced/negative Gz during approximately 15 s. The pilots did not communicate rationally or cross-check instruments. Recordings of elevator and aileron positions suggest that the commander made intense efforts to correct for several extreme and erroneous roll and pitch indications. Gz displayed an increasing trend with rapid fluctuations and peaks of approximately 3 G. After 50 s the aircraft entered a turn with decreasing radius and finally hit the ground in an inverted attitude.

    DISCUSSION: A precipitate maneuvring response can, even if occurring in a large aircraft at high altitude, result in a seemingly inexorable course of events, ending with a crash. In the present case both pilots were probably incapacitated by acute psychological stress and spatial disorientation. Intense variations in Gz may have impaired the copilot's reading of the functioning primary flight display.Tribukait A, Eiken O. Instrument failure, stress, and spatial disorientation leading to a fatal crash with a large aircraft. Aerosp Med Hum Perform. 2017; 88(11):1043-1048.

  • 39.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    On the role of otoliths and semicircular canals in spatial orientation: Dynamics of the visually perceived eye level during gondola centrifugation.2005In: Perception & Psychophysics
    , ISSN 0031-5117, E-ISSN 1532-5962, Vol. 67, no 7, p. 1242-1251
    Article in journal (Refereed)
    Abstract [en]

    The visually perceived eye level (VPEL) was measured during gondola centrifugation. Subjects (N = 11) were seated upright, facing motion in a swing-out gondola The head was adjusted so that Reid's baseline was tilted 10 degrees anterior end up. The subjects were requested to adjust the position of a small luminous dot so that it was perceived as gravitationally at eye level. In the 1-g environment, the VPEL was a few degrees below the true gravitational eye level (M = -1.75 degrees, SD = 1.90 degrees). After rapid acceleration of the centrifuge to 2 G (vectorial sum of the earth gravity force and the centrifugal force), there was an exponentially increasing depression of the VPEL. The initial value was -6.4 degrees +/- 5.2 degrees. During 10 min at 2 G, the VPEL approached an asymptotic value of -24.8 degrees +/- 5.4 degrees. The time constant showed a large interindividual variability, ranging from 59 to 1,000 sec (M = 261 sec, median = 147 sec). The findings are discussed, taking into consideration otolith-semicircular-canal interaction, as well as memory functions of the vestibular system.

  • 40.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    On the time course of short-term forgetting: A human experimental model for the sense of balance2016In: Cognitive Neurodynamics, ISSN 1871-4080, E-ISSN 1871-4099, Vol. 10, no 1, p. 7-22Article in journal (Refereed)
    Abstract [en]

    The primary aim of this study was to establish whether the decline of the memory of an angular displacement, detected by the semicircular canals, is best characterized by an exponential function or by a power function. In 27 subjects a conflict was created between the semicircular canals and the graviceptive systems. Subjects were seated, facing forwards, in the gondola of a large centrifuge. The centrifuge was accelerated from stationary to 2.5Gz. While the swing out of the gondola (66°) during acceleration constitutes a frontal plane angular-displacement stimulus to the semicircular canals, the graviceptive systems persistently signal that the subject is upright. During 6 min at 2.5Gz the perceived head and body position was recorded; in darkness the subject repeatedly adjusted the orientation of a luminous line so that it appeared to be horizontal. Acceleration of the centrifuge induced a sensation of tilt which declined with time in a characteristic way. A three-parameter exponential function (Y = Ae−bt + C) and a power function (Y = At−b + C) were fitted to the data points. The inter-individual variability was considerable. In the vast majority of cases, however, the exponential function provided a better fit (in terms of RMS error) than the power function. The mean exponential function was: y = 27.8e−0.018t + 0.5°, where t is time in seconds. Findings are discussed with connection to possible underlying neural mechanisms; in particular, the head-direction system and short-term potentiation and persistent action potential firing in the hippocampus are considered.

  • 41.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Perception of the head transversal plane and the subjective horizontal during gondola centrifugation2005In: Perception & Psychophysics
    , ISSN 0031-5117, E-ISSN 1532-5962, Vol. 67, no 3, p. 369-382
    Article in journal (Refereed)
    Abstract [en]

    The subjective visual horizontal (SVH) and the subjective head transversal plane (STP) were measured by means of an adjustable luminous line in darkness during centrifuging. Subjects (N = 10) were seated upright, facing forward in a swing-out gondola. After acceleration of the centrifuge to 2G (vectorial sum of the earth's gravity and the centrifugal force; gondola inclination 60 degrees), subjects had to set the line either so that it was perceived as gravitoinertially horizontal (SVH) or so that it was perceived as parallel with the transversal ("horizontal") plane of the head (STP). Initially after acceleration, the SVH was tilted with respect to the gravitoinertial horizontal of the gondola (M = 16.6 degrees). This tilt was compensatory with respect to the gondola inclination. However, the STP was tilted in the opposite direction (M = 12.4 degrees), which might suggest a vestibular-induced distortion of the mental representation of one's own body. Similar results were obtained when measuring the subjective visual vertical (SVV) and the subjective midsagittal plane (SSP) in 5 subjects. The perceived roll angle (obtained as SVH-STP or SVV-SSP) was considerably larger than had previously been reported. Time constants for exponential decay of the tilt of the SVH or SVV were often 2-3 min, indicating a memory for semicircular canal information on changes in head orientation--a position-storage mechanism.

  • 42.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Roll-tilt perception during gondola centrifugation: influence of steady-state acceleration (G) level.2006In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 77, no 7, p. 695-703Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Spatial disorientation is an important problem in aviation. The significance of the C level for illusions elicited from the semicircular canals is not clear. The aim of the present investigation was to elucidate how a gravitoinertial force, acting in parallel with the subject's long (z) axis, may influence the magnitude and persistence of canal-induced tilts of the subjective visual horizontal (SVH) present after acceleration in a gondola centrifuge.

    METHODS: The SVH was measured by means of an adjustable luminous line in darkness. Two series of experiments were performed. In series 1, the SVH was measured in 13 subjects at 1.1 G, 1.7 G, and 2.5 G. In series 2, it was measured in 8 subjects at 2.5 G and 4.5 G.

    RESULTS: After acceleration of the centrifuge the SVH was tilted relative to the gravitoinertial horizontal. The direction of tilt was compensatory to the gondola inclination. In series 1 the initial SVH tilt was: 16.2 +/- 7.0 degrees (1.1 G), 24.2 +/- 10.2 degrees (1.7 G), and 27.1 +/- 13.9 degrees (2.5 G). In series 2 it was: 27.6 +/- 14.6 degrees (2.5 G), and 31.2 +/- 18.8 degrees (4.5 G). The gain for this response, defined as the ratio between the initial tilt and the inclination of the gondola, was: 0.65 +/- 0.28 (1.1 G), 0.45 +/- 0.19(1.7 G), 0.41 +/- 0.21 (2.5 G) (series 1); and 0.42 +/- 0.22 (2.5 G), and 0.40 +/- 0.24 (4.5 G) (series 2). Thus, an increase from 1.1 G to 1.7 G caused a reduction in the gain, but at G levels beyond 1.7 G there was no further decrease. The time constant for exponential decay tended to increase with the G level. It was: 61 +/- 31 s (1.1 G), 84 +/- 36 s (1.7 G), 89 +/- 42 s (2.5 G) (series 1); and 67 +/- 49 s (2.5 G), and 101 +/- 73 s (4.5 G) (series 2).

    CONCLUSION: It appears that otolithic stimulation via an increased gravitoinertial force vector, acting in parallel with the head and body long axis, does not substantially influence the magnitude of the canal-mediated sensation of roll-tilt after acceleration in a swing-out gondola centrifuge. Nor does it reduce the duration of this sensation.

  • 43.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Semicircular canal contribution to the perception of roll tilt during gondola centrifugation2005In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 76, no 10, p. 940-946Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Spatial disorientation is an important problem in aviation. The mechanisms behind the sensation of roll tilt during coordinated turns are not well known. The present study aimed at elucidating what kind of semicircular canal information might cause tilts of the subjective horizontal during gondola centrifugation.

    METHODS: The subjective visual horizontal (SVH) was measured by means of an adjustable visual line in darkness. Subjects (n = 8) underwent four centrifuge runs (2 G, 5 min), sitting in different positions, i.e., heading forwards, backwards, centripetally, and centrifugally. The roll position of the gondola (60 degrees at 2 G) was controlled so that the subject was always upright with respect to the resultant gravitoinertial force vector. Thus, the semicircular-canal stimulus components in yaw, pitch, and roll were varied to some extent independently of each other.

    RESULTS: For the forward position the SVH was substantially tilted in a direction compensatory with respect to the inclination of the gondola. For the backward position there was also a tendency to a compensatory SVH tilt. In all subjects the magnitude of tilt was larger for the forward position than for the backward. The group means were +20.9 +/- 8.4 degrees and -6.9 +/- 10.5 degrees (positive sign designates a clockwise deviation of the SVH), p < 0.001, n = 8. There were no significant SVH tilts for the centripetal (+6.4 +/- 10.7 degrees) and centrifugal (+2.1 +/- 4.8 degrees) positions. The effects of deceleration of the centrifuge were very small for all positions.

    CONCLUSION: These findings suggest that the substantial SVH tilt after acceleration heading forwards is not directly related to any single component of semicircular canal stimulation but depends on the ability of the brain to expediently process complex stimulus patterns.

  • 44.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    Semicircular canal influence on the visually perceived eye level during gondola centrifugation2006In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 77, no 5, p. 500-508Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: When exposed to an increased gravitoinertial force, a subject, sitting upright, experiences an illusion of being tilted backwards. This so-called "G-excess illusion" is generally ascribed to the otolith organs. The present study aimed at elucidating how stimulation of the semicircular canals may influence the development of the G-excess illusion.

    METHODS: The visually perceived eye level (VPEL) was measured by means of a visual indicator in a large swing-out gondola centrifuge. The roll position of the gondola was controlled so that the subject was always upright with respect to the resultant vector of the Earth gravity force and the centrifugal force. Subjects (n = 8) underwent four centrifuge runs (2 G, 5 min), sitting in different positions, i.e., heading forwards, backwards, centripetally, and centrifugally.

    RESULTS: At the 2-G plateau there was a depression of the VPEL which was initially small but increased with a time constant of 90 +/- 30 s toward an asymptote of -22.0 +/- 6.9 degrees (mean and 1 SD for all positions). The initial depression was significantly smaller for the centripetal (+2.0 +/- 14.6 degrees) than for the centrifugal position (-14.5 +/- 10.4 degrees). However, there was no difference between the forward (-5.6 +/- 4.8 degrees) and backward (-4.0 +/- 4.5 degrees) positions. Initially after deceleration of the centrifuge to 1 G there was still a significant depression of the VPEL (-13.5 +/- 7.9 degrees), decreasing with a time constant of 100 +/- 46 s.

    CONCLUSIONS: The considerable delay in the otolith-mediated changes in the VPEL is interpreted as due to the absence of adequate canal information for a change in head position. The difference in VPEL between the centripetal and centrifugal positions suggests an influence of canal change-in-position information. However, pitch-plane angular velocity, being of considerable magnitude but of opposite sign for the forward and backward positions, did not influence the VPEL.

  • 45.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Semicircular canal influence on the visually perceived eye level in pilots during centrifugation2011In: 82nd Annual Scientific Meeting of the Aerospace Medical Association, 2011Conference paper (Refereed)
  • 46.
    Tribukait, Arne
    et al.
    Swedish Defence Research Agency.
    Eiken, Ola
    Swedish Defence Research Agency.
    The human sense of the head's polarity is influenced by changes in the magnitude of gravity2007In: Brain and Cognition, ISSN 0278-2626, E-ISSN 1090-2147, Vol. 63, no 1, p. 24-30Article in journal (Refereed)
    Abstract [en]

    The present investigation concerns the integrity of a primary mental function, the egocentric frame of reference and the sense of polarity of one's own head. The visually perceived eye level (VPEL) and the subjective antero-posterior axis of the head were measured by means of a visual indicator in darkness during two stimulus conditions: static pitch (sagittal-plane) tilting in the 1-g environment and gondola centrifugation (2G). It is demonstrated that an increase in the magnitude of the gravitoinertial (G) force, acting in the direction of the head and body long (z) axis, causes a substantial change not only in the VPEL but also in the perceived direction of the antero-posterior axis of the head.

  • 47.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lemming, D.
    Levin, B.
    Use of an adjustable hand plate in studying the perceived horizontal plane during simulated flight2013In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 84, no 7, p. 739-745Article in journal (Refereed)
    Abstract [en]

    Background: Quantitative data on spatial orientation would be valuable not only in assessing the fidelity of flight simulators, but also in evaluation of spatial orientation training. In this study a manual indicator was used for recording the subjective horizontal plane during simulated flight. Methods: In a six-degrees-of-freedom hexapod hydraulic motion platform simulator, simulating an F-16 aircraft, seven fixed-wing student pilots were passively exposed to two flight sequences. The first consisted in a number of coordinated turns with visual contact with the landscape below. The visually presented roll tilt was up to a maximum 67. The second was a takeoff with a cabin pitch up of 10, whereupon external visual references were lost. The subjects continuously indicated, with the left hand on an adjustable plate, what they perceived as horizontal in roll and pitch. There were two test occasions separated by a 3-d course on spatial disorientation. Results: Responses to changes in simulated roll were, in general, instantaneous. The indicated roll tilt was approximately 30% of the visually presented roll. There was a considerable interindividual variability. However, for the roll response there was a correlation between the two occasions. The amplitude of the response to the pitch up of the cabin was approximately 75%; the response decayed much more slowly than the stimulus. Discussion: With a manual indicator for recording the subjective horizontal plane, individual characteristics in the response to visual tilt stimuli may be detected, suggesting a potential for evaluation of simulation algorithms or training programs.

  • 48.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Betydelsen av flygerfarenhet för förmågan att uppfatta förändringar i pitch–position i gondolcentrifug/DFS2011In: Svenska Läkaresällskapets handlingar. Hygiea, 2011Conference paper (Refereed)
  • 49.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    The perception of roll tilt in pilots during a simulated coordinated turn in a gondola centrifuge.2011In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 82, no 5, p. 523-30Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: It has previously been reported that nonpilots underestimate the roll tilt angle after acceleration in a gondola centrifuge. The aim of the present work was to elucidate the significance of flight experience for roll tilt perception based on vestibular information.

    METHODS: The subjective visual horizontal (SVH) was measured by means of an adjustable luminous line in darkness. Eight nonpilots (N), nine fighter pilots (F), and eight helicopter pilots (H) underwent two centrifuge runs (2 G, 5 min) heading forward and backward, respectively. The roll position of the gondola (60 degrees at 2 G) was controlled so that the subject was always upright with respect to the gravitoinertial force.

    RESULTS: Upon acceleration of the centrifuge there was a tilt of the SVH in a direction compensatory to the inclination of the gondola. This tilt was larger in the forward position [N: 17.2 +/- 6.4 degrees, F: 31.2 +/- 16.4 degrees, H: 33.6 +/- 18.2 degrees (means +/- SD)] than in the backward position (N: -5.0 +/- 6.8 degrees, F: -12.2 +/- 17.4 degrees, H: -10.4 +/- 15.4 degrees). In N the tilt declined with time, approaching zero by the end of the 2-G plateau. In the pilots it was significantly larger and did not decline.

    CONCLUSION: Flight experience results in an increased ability to perceive the roll tilt during movement along a curved path. That this can be revealed in a centrifuge might suggest that acceleration of the centrifuge constitutes a movement pattern which is similar, from a vestibular point of view, to that of an airplane entering a coordinated turn.

  • 50.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Nobel, Gerard
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Mekjavic, I. B.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Effects of anti-histaminic and anti-cholinergic substances on human thermoregulation during cold provocation2010In: Brain Research Bulletin, ISSN 0361-9230, E-ISSN 1873-2747, Vol. 81, no 1, p. 100-106Article in journal (Refereed)
    Abstract [en]

    The roles of histaminergic and cholinergic neuron systems in the regulation of body temperature have been studied almost exclusively in animals. Recently, we have found that motion sickness, i.e. a condition where hippocampal cholinergic mismatch signals induce a release of histamine in the vomiting centre, accelerates the decline in body temperature in men during exposure to cold. In the present study we measured the thermoregulatory effects of two substances commonly used against motion sickness, i.e. the histamine (H1) receptor blocker dimenhydrinate (DMH) and the muscarine receptor blocker scopolamine (SCOP). In three trials, control (CN), DMH and SCOP, 10 male subjects were immersed in 15 degrees C water for a maximum of 90 min. The trials were separated by a minimum of three days and their order was alternated between subjects. In all trials the subject received, in a double blind fashion, a transdermal patch (SCOP or placebo) 12-14 h before immersion and a tablet (DMH or placebo) 1 h before immersion. Mean skin temperature, rectal temperature (T-rec), the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (T-ff), and oxygen uptake (VO2) were recorded. The fall in T-rec was smaller in the DMH than in the CN and SCOP conditions. The recordings of T-ff and VO2 suggest that SCOP attenuates peripheral vasoconstriction while DMH increases shivering thermogenesis. Notably, thermal discomfort was reduced in the SCOP condition. Findings are thoroughly discussed in the context of animal studies on the neuropharmacology and neurophysiology of thermoregulation and motion sickness.

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