Internal Connectivity of the GlobusPallidus and the Arbitration System
2013 (English)Manuscript (preprint) (Other academic)
The rodent globus pallidus (homologue of primate external globus pallidus) has been shown to be composed of two types neuronal groups based on their location and local axon collaterals. The rostral outer layer near the striatopallidal border (GPr) has shorter but more dense local axon collaterals while the caudal inner layer (GPc) has wider and less dense axon collaterals. Moreover, the connection between the two segments is unidirectional with outer layer neurons sending inhibitory projections to the inner layer. Both segments inhibit the substantia nigra and the entopeduncular nucleus (homologue of primate internal globus pallidus). We have created a model of the basal ganglia arbitration subsystem composed of the subthalamic nucleus, the two segments of the pallidus as well as the entopeduncular nucleus and the substantia nigra in order to assess functional roles of the two pallidal segments. The simulations reveal that both segments of the pallidum are involved in winner-take-all structure of the arbitration system but the type of information competing is different in the two subsystems. In the STN-GPr network, strong lateral inhibition between pallidal neurons representing muscles leads to selection of a muscle which has been (due to noise or other reasons) randomly overactivated. In contrast, in STN-GPc network actions (each utilizing many muscles) compete. Our simulations suggest that both networks are active during selection and execution of movements. If overactivation of a muscle is accompanied with dopamine flow, the GPr-GPc connection together with local axonal network of GPc suppress other muscles and reinforce the muscle whose overactivity has caused the dopaminergic flow. Simulated lesions of these neuronal groups also show different results. Lesioning GPr results in synchronous activity in GPc and SNr but the mean firing rate of these nuclei remains untouched. Lesioning GPc on the other hand lifts the activity in the SNr drastically but does not create synchrony in any of the nuclei. The results suggest that STN-GPc and STN-GPr can be considered as two different subsystems working both in synergy and in competition.
Place, publisher, year, edition, pages
Research subject The KTH Railway Group - Tribology
IdentifiersURN: urn:nbn:se:kth:diva-136743OAI: oai:DiVA.org:kth-136743DiVA: diva2:677015
QS 20132013-12-092013-12-092016-02-02Bibliographically approved