Visually guided saccadic responses are thought to involve multiple stages of processing in diverse brain structures including the primary visual cortex (V1). The variability of neural activity in each of these structures may present ambiguities for downstream stages in identifying sensory and motor signals among spontaneous discharges. Response time of saccadic eye movements made toward a visual target is correlated with the time of first spike of V1 evoked by the target (Lee et al., 2010 Journal of Neurophysiology 104 2556–2572). This suggests that downstream neurons receiving the output of V1 are faced with a challenging task of discriminating spikes of visual response against spontaneous discharge. Here we report a novel response property of the output activity of the V1 so that, immediately before neurons discharge a burst of activity to a visual target, spontaneous discharges were transiently suppressed. This suppression was ultra-fast and peaked around 20 ms after target onset. The results of a simulation indicated that the suppression enhanced reliability of detecting activity onset. Thus, the initial transient suppression is hypothesized to enhance temporal contrast for identifying the onset of visual response by downstream neurons.
