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

Area of Science:

• Neuroscience
• Cognitive Neuroscience

Background:

• Sharp-wave ripples (SWRs) are synchronous neuronal events primarily studied in the hippocampus during rest and sleep.
• SWRs are traditionally associated with memory consolidation, spatial navigation, and decision-making.
• Recent studies suggest SWRs may also occur during active behaviors like visual search.

Purpose of the Study:

• To investigate the presence and role of ripple activity in the macaque neocortex during active, goal-directed behaviors, specifically focused spatial attention.
• To determine if ripple occurrence is modulated by attentional focus and stimulus characteristics.
• To explore the functional impact of ripples on behavioral performance during attentive states.

Main Methods:

• Electrophysiological recordings were performed in visual areas V1 and V4 of macaques.
• Neural activity was analyzed for ripple events during tasks involving focused spatial attention.
• Behavioral data, including reaction times, were correlated with ripple occurrence and characteristics.

Main Results:

• Ripple activity was detected in macaque visual areas V1 and V4 during focused spatial attention.
• The occurrence of ripples was significantly modulated by stimulus properties and the size of the attentional focus.
• The presence of ripples during attention was associated with reduced reaction times for detecting relevant events.

Conclusions:

• Ripple activity is not confined to the hippocampus or offline states; it also occurs in the neocortex during active attentive states.
• Neocortical ripples play a role in supporting ongoing goal-directed behaviors, such as focused attention and vigilance.
• These findings broaden the understanding of SWRs' functional significance in cognitive processes during wakefulness.