Adaptation and exogenous attention interact in the early visual cortex: A TMS study.

Our capacity to process information is constrained by the limited energy available to the brain and the high energy cost of cortical computation [1]. To help manage limited resources and optimize our sensitivity to visual information, adaptation diminishes sensitivity for repetitive stimuli, whereas attention enhances the representation of relevant information [2]. Transcranial magnetic stimulation (TMS) to early visual cortex (V1/V2) eliminates the response-gain effect of exogenous (involuntary) attention on contrast sensitivity: the benefit at the attended location and the cost at the unattended location [3]. Here we investigate whether adaptation modulates the exogenous attentional effect on perception under TMS to V1/V2. Observers performed an orientation discrimination task while attending to one of two stimuli, with or without adaptation. Following a valid, neutral or invalid attentional cue, two cortically-magnified Gabor patches were presented in the stimulated region (matching each observer's phosphene location) and its contralateral symmetric region. A response cue indicated the patch whose orientation observers had to discriminate. The response cue either matched-target stimulated-or did not match- distractor stimulated-the stimulated side. Without adaptation, the exogenous attention response-gain effect emerged in the distractor-stimulated condition-increased contrast sensitivity at the attended location and decreased at the unattended location-but these effects were eliminated in the target-stimulated condition, consistent with our previous findings. Critically, after adaptation, response gain of exogenous attention was observed in both distractor-stimulated and target-stimulated conditions. These results reveal that (1) adaptation and attention interact in the early visual cortex, (2) adaptation shields exogenous attention from TMS effects.