Suppression of Spontaneous Activity before Visual Response in the Primate V1 Neurons during a Visually Guided Saccade Task
Visually guided saccadic eye movements 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. The response time of saccadic eye movements made toward a visual target is correlated with the time of the first spikes in V1 that are evoked by the target (Lee et al., 2010). This suggests that downstream neurons receiving the output of V1 are faced with a challenging task of discriminating first spikes of visual response against spontaneous discharge. Here we report a novel response property of the macaque V1 neurons. Immediately before neurons discharge a burst of activity to a visual saccade target, spontaneous discharges were transiently suppressed. This suppression was maximal ∼18 ms after target onset. Based on simulations of artificial spike trains, we propose that the transient suppression enhances temporal contrast for identifying the onset of visual response by increasing the reliability of detection of response onset by downstream neurons, thereby facilitating visually guided behavioral responses.