In our everyday lives, we are frequently confronted with information from multiple sensory modalities. Recently, there has been increasing interest in the circumstances under which stimuli presented in one sensory modality influence sensations in a different modality. For instance, the sound of a mosquito buzzing seemingly enhances sensitivity to touch (tactile stimulation) on our skin; seeing an insect crawling on someone else's arm seems to affect our own tactile perception. Despite several recent studies examining the influence of audition and vision on touch, the brain mechanisms responsible for these interactions are poorly understood. An NSF-funded collaborative effort of Tony Ro (Rice University) and Michael Beauchamp (University of Texas Health Science Center, Houston) will use a combination of converging methods to examine tactile processing in isolation and the influence of vision and audition on touch in the human brain. Psychophysical studies will be conducted to determine the optimal stimulus parameters that demonstrate an influence of vision and audition on tactile perception. Functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and magnetoencephalography (MEG) will be used to localize the brain regions involved with integrating multisensory information. While most of these experiments will be conducted using normal controls, an additional series of experiments will be conducted in a unique patient who acquired auditory-tactile synesthesia following a stroke. Tactile sensitivity on the patient's left hand and arm was impaired, but he now feels tactile sensations in that area in response to sounds. Psychophysical and imaging experiment will be completed on this patient to determine the neural mechanisms responsible for the synesthesia, especially whether plastic neural changes have reconstituted the patient's somatosensory cortex so that it is now responds to sounds.
These studies will not only better our understanding of multisensory integration, but will provide a deeper appreciation of general information processing mechanisms of the human brain. Such knowledge will contribute towards the development of better rehabilitative tools for patients with congenital or acquired sensory deficits to one or more of the sensory systems. Additionally, this research will provide a better understanding of the mechanisms of natural and brain-damaged induced changes that take place in the adult human brain. The funding will be used to support research training opportunities for undergraduate, graduate, and post-doctoral trainees in cognitive neuroscience and brain imaging in the Houston area. In addition to training the next generation of brain scientists, the findings of this research will be disseminated through scientific and lay publications, as well as other media outlets, allowing for a deeper understanding and appreciation of the human brain in society.
