Hearing colors, seeing sounds: New research explores sensory overlap in the brain

New research indicates that the integration of senses and functions in the brain is common. About two percent of the population has a condition called synesthesia, in which two different sensations, like color and sound, are experienced at once. Although this condition is rare, the new findings suggest the brain is wired in complex and sometimes overlapping ways to help people interpret and understand their environments. The research was presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news on brain science and health. Today's new findings show that:

• Researchers have pinpointed the brain region responsible for the McGurk Effect, an auditory phenomenon in which viewing lips moving out of sync with words creates the perception of other words. A brain area known to play a role in language and eye gaze processing is the hub of the sensory overlap (Michael Beauchamp, PhD, abstract 400.2, see attached summary).
• People adjust the perceived location of sensory stimuli faster than previously thought. Results show that exposure to light for only a fraction of a second alters the perceived source of a subsequent sound. The findings have implications for the development of hearing aids and rehabilitation from brain injury (Ladan Shams, PhD, abstract 125.1, see attached summary).

Other recent findings discussed show that:

• Synesthetes who describe colors as either inside their minds or outside in the world have distinct brain structures and processes (Romke Rouw, PhD, see attached speaker's summary).
• People who share one type of synesthesia, in which letters and numbers create the experience of color, describe drastically different sensations from one another. This indicates that synesthetic experiences are more idiosyncratic than is commonly realized (Avinash Vaidya, see attached speaker's summary).
• In people with synesthesia, scientists found the brain's color-processing area was active five to 10 milliseconds after the visual processing areas, suggesting synesthesia occurs through direct communication between the senses (David Brang, see attached speaker's summary).

"While synesthesia reflects an extreme manner in which the senses communicate, there's evidence that synesthesia operates through mechanisms present in all individuals," said press conference moderator Vilayanur Ramachandran, MD, PhD, of the University of California, San Diego, an expert on visual perception and behavioral neurology. "Understanding these mechanisms can help us answer fundamental questions about how the brain works."

Source: Society for Neuroscience