Brain region responsible for speech illusion identified; Study explains how visual cues disrupt speech perception

The findings were presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience, held in San Diego.

Scientists at the University of Texas Medical School found that the superior temporal sulcus, known to play a role in language and eye gaze processing, is the hub of the sensory overlap. In the study, researchers first had volunteers experience the McGurk Effect while undergoing functional magnetic resonance imaging (fMRI). The fMRI showed the authors which part of the brain was active during the effect.

The activity in that region was then disrupted using transcranial magnetic stimulation, while participants remarked on what they heard during the speech and vision tests. The researchers discovered that the McGurk Effect disappeared when they targeted the superior temporal sulcus. As importantly, the participants perceived other sounds and sights normally.

"These results demonstrate that the superior temporal sulcus plays a critical role in the McGurk Effect and auditory- visual integration of speech," said Michael Beauchamp, PhD, who led the study.

Research was supported by the National Science Foundation and the National Institute of Neurological Disorders and Stroke.