Ripples in macaque V1 and V4 are modulated by top-down visual attention

Sharp-wave ripples (SWRs) are highly synchronous neuronal activity events. They have been predominantly observed in the hippocampus during offline states such as pause in exploration, slow-wave sleep, and quiescent wakefulness. SWRs have been linked to memory consolidation, spatial navigation, and spatial decision-making. Recently, SWRs have been reported during visual search, a form of remote spatial exploration, in macaque hippocampus. However, the association between SWRs and multiple forms of awake conscious and goal-directed behavior is unknown. We report that ripple activity occurs in macaque visual areas V1 and V4 during focused spatial attention. The occurrence of ripples is modulated by stimulus characteristics, increased by attention toward the receptive field, and by the size of the attentional focus. During attention cued to the receptive field, the monkey's reaction time in detecting behaviorally relevant events was reduced by ripples. These results show that ripple activity is not limited to hippocampal activity during offline states, rather they occur in the neocortex during active attentive states and vigilance behaviors.

Automated summary

Sharp-wave ripples (SWRs) are observed in the hippocampus during offline states, but their association with awake conscious and goal-directed behavior is unknown. This study found that ripple activity also occurs in macaque visual areas V1 and V4 during focused spatial attention. The occurrence of ripples is influenced by stimulus characteristics and attentional focus. During attention cued to the receptive field, ripples reduced the monkey's reaction time in detecting behaviorally relevant events. These findings suggest that ripple activity is not limited to offline states but occurs in neocortex during active attentive states.