Auditory click stimuli evoke event-related potentials in the visual cortex

The objective of this study was to determine whether unimodal auditory stimuli evoke event-related potentials (ERPs) in brain areas normally designated as the visual cortex (VC). The topographical distribution of ERPs evoked by auditory click stimuli was measured from (a) electroencephalographic electrodes on the scalp of six neurologically normal adult human participants and (b) intracranial electrodes implanted on the cortex of one epileptic adult human participant. In all participants, unimodal click stimuli evoked ERPs over both the auditory cortex (AC) and the VC. Relative amplitudes of ERPs at different scalp electrodes did not support the idea that the ERPs over VC were volume-conducted versions of those over AC, and intracranial records confirmed the origin of some click-evoked ERPs in both V1 and other regions of VC. We conclude that unimodal auditory stimuli can evoke ERPs in VC. This finding adds to the earlier evidence for the effect of visual stimuli on AC by providing new evidence for bidirectional functional connectivity in the audio-visual network of the human brain. The implication is that not only do visual stimuli affect hearing; auditory stimuli also affect visual perception.