P 65. The effect of controlled behavior during 10 Hz rTMS administration on subsequent offline performance in a visual attention task

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Repetitive transcranial magnetic stimulation (rTMS) in ‘offline’ experiments is commonly administered to participants that are in a relaxed ’resting state’. Clearly, this approach leads to an ill controlled baseline state of the participants’ brain, in face of evidence that the mental baseline influences how the brain is affected by TMS (e.g., Silvanto and Pascual-Leone (2008) Brain Topography 21). The aim of the present study was to assess the effect of uncontrolled vs. controlled behavior during rTMS administration on participants’ performance in a subsequent visual localization task. We compared the offline effects of 10 Hz rTMS for standard TMS administration (uncontrolled ‘resting’ behavior without task) to 10 Hz rTMS administered while the participants were performing a visual localization task (controlled behavior with task). Tasks during the online and offline period were identical, testing the participants’ ability to allocate attention to the detection of peripheral unilateral (left or right) or bilateral (left and right) peri-threshold visual stimuli. rTMS or sham stimulation (by vertically tilted coil) were applied to the 10–20 coordinate P4, located in the right posterior parietal cortex. Performance after rTMS in the ‘resting’ condition appeared similar to the performance in the ‘with task’ condition. Importantly, however, when compared to sham stimulation conditions, rTMS induced a deterioration of offline performance relative to sham stimulation in the ‘resting’ condition, whereas it led to better performance relative to sham in the ‘with task’ condition ( Fig. 1 ). We conclude that in the present paradigm, the manipulation ‘with task’ versus ‘resting’ during the administration of rTMS might be too weak to induce brain states that are distinct enough to induce different levels of performance in the subsequent task. From this perspective, controlling the participants’ behavior during rTMS administration does not appear to matter for their offline behavior after rTMS. However, the results of the study also demonstrate that whether rTMS leads to a deterioration or improvement of performance critically depends on the baseline to which the offline performance is compared. Offline performance after rTMS or sham stimulation applied to participants during a behavioral task or at rest. Performance was evaluated as inverse efficiency, computed as reaction time/ proportion of correct trials. Shown are the results for bilateral visual stimuli. Within-subject error bars were created using the method of Cousineau (2005).