Open Access

Ricardo Kienitz, Joscha Tapani Schmiedt, Katharine A. Shapcott, Kleopatra Kouroupaki, Richard C. Saunders, Michael Christoph Schmid

• Summary: Growing evidence suggests that distributed spatial attention may invoke theta (3-9 Hz) rhythmic sampling processes. The neuronal basis of such attentional sampling is however not fully understood. Here we show using array recordings in visual cortical area V4 of two awake macaques that presenting separate visual stimuli to the excitatory center and suppressive surround of neuronal receptive fields elicits rhythmic multi-unit activity (MUA) at 3-6 Hz. This neuronal rhythm did not depend on small fixational eye movements. In the context of a distributed spatial attention task, during which the monkeys detected a spatially and temporally uncertain target, reaction times (RT) exhibited similar rhythmic fluctuations. RTs were fast or slow depending on the target occurrence during high or low MUA, resulting in rhythmic MUA-RT cross-correlations at at theta frequencies. These findings suggest that theta-rhythmic neuronal activity arises from competitive receptive field interactions and that this rhythm may subserve attentional sampling. Highlights: * Center-surround interactions induce theta-rhythmic MUA of visual cortex neurons * The MUA rhythm does not depend on small fixational eye movements * Reaction time fluctuations lock to the neuronal rhythm under distributed attention