Fig. 1: Study and experimental design.

a The study included one day of pre-screening, 4 days of psychophysics testing, 4 days of fMRI and 4 days of EEG. b Each day included (i) auditory pre-adaptation, (ii) left (i.e. VA) or right (AV) audiovisual adaptation and (iii) auditory post-adaptation phases. In the pre-adaptation and post-adaptation phases, observers were presented with unisensory auditory stimuli sampled from seven (±12°, ±5°, ±2° and 0° visual angle) locations along the azimuth. They performed a spatial (left vs. right) classification task on 22% of the trials (‘response trial’) that were indicated by a brief dimming of the fixation cross 500 ms after sound onset. In the audiovisual adaptation phases, observers were presented with audiovisual stimuli with a spatial disparity of ±15°: the visual signal was sampled from three locations along the horizontal plane (i.e. −5°, 0° and 5°) and the visual signal was spatially shifted by 15° either to the left (i.e. VA-adaptation) or to the right (i.e. AV-adaptation) with respect to the auditory stimulus. Observers were engaged in a non-spatial visual detection task on 10% of the trials (‘response-trial’) indicated by the lower contrast of the visual signals. Each day started with the pre-adaptation phase. Next, VA (or AV) adaptation phases alternated with postVA (or postAV) adaptation phases. This figure shows the experimental details for the fMRI experiments, which were slightly modified for EEG and psychophysics experiments (for details see Experimental design and procedure section).