Eye field in the cerebellar flocculus of pigmented rabbits determined with local electrical stimulation.

The cerebellar flocculus was mapped with local stimulation techniques in alert pigmented rabbits. Triple-barrelled microelectrodes filled with solutions each containing one of three different dyes (Fast Green FCF, Pontamine Sky Blue and Nigrosine) were used for recording and stimulation. The H-zone from which local stimulation through the microelectrode induced abduction in the ipsilateral eye was visualized on the reconstructed model of the flocculus to span across major folia of the flocculus, forming a narrow strip 0.5-1.0 mm wide. The H-zone was flanked with two V-zones, rostral and caudal, from which downward eye movements were induced in the ipsilateral eye. The R-zone, from which clockwise rotation was induced in the contralateral eye, was extended rostrocaudally across the H- and V-zones. In addition to these eye movement-related zones, a restricted area specifically related to eye blinking was found in the rostroventral area of the flocculus.