Multisensory interactions comprise a class of processes through which our senses communicate to facilitate perception and behavior. Although much research has focused on the dominance of vision over audition, under some conditions, sounds have been demonstrated to alter visual perception as well. For example, during the double flash illusion, the auditory system's high temporal resolution can override visual cues, such as when a single visual flash paired with two auditory beeps results in the illusory experience of two distinct visual flashes. Additionally, the auditory system's high sensitivity to events occurring outside the central vision field allows fast and accurate localization of auditory-visual targets, which in turn enhances subsequent visual discrimination of targets. Here we examined the cortical networks underlying auditory influences on visual perception using subdural electrocorticographic (ECoG) measures of local field potentials in patients with epilepsy as they performed a double flash illusion task and an auditory detection task. When participants experienced auditory-induced double flashes, we observed rapid communication between primary auditory areas, extrastriate visual regions, and the angular gyrus, suggesting that each of these areas is involved in the generation of the illusory second flash. As these data suggest that activity in visual areas is evoked by simple sounds, we tested this hypothesis in the same participants using an auditory detection paradigm. Participants detected centrally presented 1 kHz tones and ignored laterally presented noise bursts. Consistent with results from the double-flash paradigm, visual activity was evoked by sounds between 80 and 250 ms post stimulus onset, following primary auditory cortex activity by 20 ms, and this auditory-evoked visual activity was greater in the contralateral hemisphere. These results suggest the existence of a fast and dynamic pathway between auditory and visual cortices, allowing auditory signals to activate visual cortex in order to facilitate the detection of non-foveal visual stimuli.
Meeting abstract presented at VSS 2014