Capture of auditory motion by vision is represented by an activation shift from auditory to visual motion cortex

The brain is capable of integrating motion information arising from visual and auditory input. Such integration between sensory modalities can aid one another and helps to stabilize the motion percept. However, if motion information differs between sensory modalities, it can also result in an illusory auditory motion percept. This phenomenon is referred to as the cross-modal dynamic capture (CDC) illusion. We used functional magnetic resonance imaging to investigate whether early visual and auditory motion areas are involved in the generation of this illusion. Among the trials containing conflicting audiovisual motion, we compared the trials in which CDC occurred to those in which it did not and used a region of interest approach to see whether the auditory motion complex (AMC) and the visual motion area hMT/V5+ were affected by this illusion. Our results show that CDC reduces activation in bilateral auditory motion areas while increasing activity in the bilateral hMT/V5+. Interestingly, our data show that the CDC illusion is preceded by an enhanced activation that is most dominantly present in the ventral intraparietal sulcus. Moreover, we assessed the effect of motion coherency, which was found to enhance activation in bilateral hMT/V5+ as well as in an area adjacent to the right AMC. Together, our results show that audiovisual integration occurs in early motion areas. Furthermore, it seems that the cognitive state of subjects before stimulus onset plays an important role in the generation of multisensory illusions.