Abstract
Environmental sampling of spatial locations is a fundamentally rhythmic process. That is, both attention-related boosts in sensory processing and the likelihood of exploratory movements (e.g., saccades in primates and whisking in rodents) are linked to theta rhythms (3–8 Hz). I will present electrophysiological data, from humans and monkeys, demonstrating that intrinsic theta rhythms in the fronto-parietal network organize neural activity into two alternating attentional states. The first state is associated with both (i) the suppression of covert and overt attentional shifts and (ii) enhanced visual processing at a behaviorally relevant location. The second state is associated with attenuated visual processing at the same location (i.e., the location that received a boost in sensory processing during the first attentional state). In this way, theta-rhythmic sampling provides critical flexibility, preventing us from becoming overly focused on any single location. Every approximately 250 ms, there is a window of opportunity when it is easier to disengage from the presently attended location and shift to another location. Based on these recent findings, we propose a rhythmic theory of environmental sampling. The fronto-parietal network is positioned at the nexus of sensory and motor functions, directing both attentional and motor aspects of environmental sampling. Theta rhythms might help to resolve potential functional conflicts in this network, by temporally isolating sensory (i.e., sampling) and motor (i.e., shifting) functions. This proposed role for theta rhythms in the fronto-parietal network could be a more general mechanism for providing functional flexibility in large-scale networks.