Early reduction of sensory processing within the visual cortex when switching from internal to external attention

The neurocognitive process underlying attention switches between external (perception-based) and internal (memory-based) attention is poorly characterized. Previous research has found that when participants switch attention either between two perception-based tasks (within-domain switches) or between a memory- and a perception-based task (between-domain switches), a substantial and similar processing cost was observed compared to the repetition of the same task (Verschooren, Schindler, De Raedt, & Pourtois, 2019). Here, we recorded 64-channel EEG while participants carried out within- versus between-domain switches of attention. ERP results showed that during early sensory processing, a marked P1 attenuation was associated with both switch types, suggesting that switching was associated with an early bottleneck during information processing. This early gating effect was stronger when switching from an internal to an external task, compared to switching between external tasks, suggesting different top-down requirements for them. These findings are in line with earlier proposals in the literature.