Low-Frequency activity shapes fine-scale information routing in the early visual cortex

Abstract

Visual processing requires flexible routing of task-relevant information across cortical hierarchies. One proposed mechanism is nested oscillatory activity, in which low-frequency rhythms dynamically modulate local excitability and inter-areal communication. However, the specific predictions of this framework have not been tested during active stimulus processing at fine spatial and temporal scales. Here, we reanalyzed local field potentials (LFPs) and multi-unit activity (MUA) recorded from V1 and V4 in macaque monkeys performing a figure-ground segregation task. We show that alpha-band activity in V1 carries information about the position of the figure and the orientation of the stimulus with fine spatial specificity within a transient post-stimulus window, a period that coincides with the emergence of figure-ground modulation and the dominant V4[->]V1 feedback. During this window, both local spiking activity and inter-areal coupling between V1 and V4 depended on alpha amplitude and on the instantaneous V1-V4 phase difference, indicating that low-frequency synchronization shapes effective communication between cortical populations. Together, these findings support the view that alpha-band activity reflect fine-scale information routing during visual processing through coordinated modulation of local excitability and hierarchical feedback interactions.