A dual Purkinje cell rate and synchrony code sculpts reach kinematics

Abstract

Cerebellar Purkinje cells (PCs) encode movement kinematics in their population firing rates. Firing rate suppression is hypothesized to disinhibit neurons in the cerebellar nuclei, promoting adaptive movement adjustments. Debates persist, however, about whether a second disinhibitory mechanism, PC simple spike synchrony, is a relevant population code. We addressed this question by relating PC rate and synchrony patterns recorded with high density probes, to mouse reach kinematics. We discovered behavioral correlates of PC synchrony that align with a known causal relationship between activity in cerebellar output. Reach deceleration was positively correlated with both Purkinje firing rate decreases and synchrony, consistent with both mechanisms disinhibiting target neurons, which are known to adjust reach velocity. Direct tests of the contribution of each coding scheme to nuclear firing using dynamic clamp, combining physiological rate and synchrony patterns ex vivo, confirmed that physiological levels of PC simple spike synchrony are highly facilitatory for nuclear firing. These findings suggest that PC firing rate and synchrony collaborate to exert fine control of movement.

Cerebellar Purkinje Cells Control Posture in Larval Zebrafish (Danio rerio)

“…This stochasticity could reflect normal fluctuations in basal levels of activity, or it could arise from cells going in and out of depolarization block 66 . Synchronized/precisely-timed Purkinje cell output is thought to shape movements [67][68][69][70][71][72] , though perhaps not for all behaviors 73 . Our imaging suggests that the set of Purkinje cells activated at any one moment in time is limited and random.…”