Modeling of primate optokinetic and vestibulo-ocular systems based on single unit recording of cerebellar flocculus Purkinje cell activity

A model of the vertical optokinetic reflex (VOKR) and the vestibulo-ocular reflex (VVOR) systems was constructed based on the known synaptic linkage to identify the site or sites responsible for VVOR motor learning. The model consists of floccular (FL) and non-FL systems, the former divided into pre-FL and post-FL subsystems. Characteristics of each subsystem were identified at different VOR gains by reconstructing single unit recordings of cerebellar FL Purkinje cells (P-cell) in squirrel monkeys during VOKR and VVOR by means of the multiple linear regression technique. Model adequacy was checked by evaluating the residuals following the regression and by predicting P-cell firing during visuo-vestibular mismatch paradigms. The pre-FL system including flocculus itself and the non-FL system changed their gain characteristics in parallel with VOR gain while the post-FL system did not. A new role for the floccurus in VVOR motor learning is suggested