Time course of visual multi-neuronal discharges evoked by eye movements in light

Abstract

Transient responses in the multineuronal activity along the visual pathways of ‘encéphale isolé’ cats were studied during movements of the eyes across a source of light. The time courses of this activity depended upon selective charcteristics of the ocular movements. When the movements were active and with a fast rising phase of the electro-oculogram, the transient increase in firing rate of the geniculo-cortical tract preceded the burst of activity evoked in the optic chiasm by retinal image shift produced by the eye movement. When the the movements were passive, or if active, had a slow rising phase, the phase response in the optic chiasm appeared before the transient increase in the geniculo-cortical tract. In both rapid and slow movements teh oculomotor activation preceded chiasmatic and lateral geniculate firing. These results are discussed in relation to previous observations in dark-adapted cats of transient increases in geniculo-cortical, cortico-fugal multineuronal activity and in lateral geniculate single units, without changes in the optic chiasm activity, coincident with active and fast eye movements but not with slow or passive ocular movements. The signifance of these observations in relation to the ‘coronally discharge’ hypothesis is also discussed.