Figure 1.

Schematic of the brainstem–cerebellar saccade circuitry underlying an amplitude decrease of leftward saccades. A saccade command from the right SC reaches EBNs, which in turn drive left abducens MNs to generate a saccade. At the same time, a saccade signal from the SC also reaches both the left and right cerebellar vermis via the NRTP. P-cells in the OMV use this incoming signal to create a saccade-related change in SS activity, which inhibits neurons in the ipsilateral cFN. P-cells also receive a signal from the inferior olive (IO) that creates CSs. Left cFN neurons drive contralateral IBNs, which inhibit left abducens motoneurons. Right cFN neurons project to contralateral EBNs, which excite left abducens motoneurons. The solid vertical arrows indicate the changes in activity that should occur in this saccade circuit to produce smaller leftward saccades during adaptation (left solid arrow). The filled neurons are inhibitory, and the open neurons are excitatory.