The effects of saccadic eye movements on the activity of geniculate relay neurons in the monkey

Saccadic suppression is the reduced visibility that occurs during saccadic eye movements. recent psychophysical studies have suggested that this is du e to a reduction in responsiveness of magnocellular (M), but not parvocellu lar (P), cells of the later al geniculate nucleus. To address this and othe r phenomena of responsiveness during saccades, we recorded from geniculate neurons in the behaving monkey before, during, and after saccades. Specific ally, we measured neuronal responses to a flashing, whole-field illuminatio n. Contrary to the prediction, most M neurons showed pronounced c enhanceme nt of visual activity during saccades, whereas such responsiveness of parvo cellular (P) neurons was not significantly affected by saccades. We also an alyzed the extent to which saccades affected burst firing, which results fr om activation of a voltage-dependent Ca2+ conductance. We found that both h i and P cells displayed a significant suppression of burst firing during sa ccades. These results do not support the idea that saccadic suppression has an obvious substrate in reduced responsiveness of geniculate cells, but th is suppression may be related to an increased visual threshold fur detectio n associated with reduced burst firing.