Guided visual search is associated with target boosting and distractor suppression in early visual cortex

Visual attention paradigms have revealed that neural excitability in higher-order visual areas is modulated according to a priority map guiding attention towards task-relevant locations. Neural activity in early visual regions, however, has been argued to be modulated based on bottom-up salience. Here, we combined Magnetoencephalography (MEG) and Rapid Invisible Frequency Tagging (RIFT) in a classic visual search paradigm to study feature-guidance in early human visual cortex. Our results demonstrate evidence for both target boosting and distractor suppression when the participants were informed about the task-relevant and -irrelevant colour (guided search) compared to when they were not (unguided search). These results conceptually replicated using both a magnitude-squared coherence approach and a General Linear Model based on a single-trial measure of the RIFT response. The present findings reveal that feature-guidance in visual search affects neuronal excitability as early as primary visual cortex, possibly contributing to a priority-map-based mechanism.