Rj. Krauzlis et Sg. Lisberger, SIMPLE SPIKE RESPONSES OF GAZE VELOCITY PURKINJE-CELLS IN THE FLOCCULAR LOBE OF THE MONKEY DURING THE ONSET AND OFFSET OF PURSUIT EYE-MOVEMENTS, Journal of neurophysiology, 72(4), 1994, pp. 2045-2050
1. We recorded the simple spike firing rate of gaze velocity Purkinje
cells (GVP-cells) in the flocculus/ventral paraflocculus of two monkey
s during the smooth pursuit eye movements evoked by a target that was
initially at rest, started suddenly, moved at a constant velocity, and
then stopped. 2. For target motion in the preferred direction, GVP-ce
lls showed a large transient increase in firing rate at the onset of p
ursuit, a smaller but sustained increase during the maintenance of pur
suit, and a smooth return to baseline firing with little undershoot at
the offset of pursuit. For target motion in the nonpreferred directio
n, GVP-cells showed a small decrease in firing rate at the onset of pu
rsuit, a similar sustained decrease during the maintenance of pursuit,
but a large transient increase in firing rate at the offset of pursui
t before returning to baseline firing. 3. We pooled the data in our sa
mple of horizontal GVP-cells by subtracting the population average of
firing rate recorded during pursuit in the nonpreferred direction from
the population average recorded during pursuit in the preferred direc
tion. We transformed this net population average by passing it through
a model of the brain stem final common pathway and the oculomotor pla
nt. This yielded a signal that closely matched the observed trajectory
of eye velocity during pursuit. We conclude that the transient oversh
oots exhibited in the firing rate of GVP-cells can provide appropriate
compensation for the lagging dynamics of the oculomotor plant.