Nov. 17, 2010 New research shows that the perceived location of a noise depends in part on the sights noticed before the sound. The results have implications for the development of hearing aids and rehabilitation from brain injury.
The findings were presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience, held in San Diego.
"The auditory map of space is not static like the world atlas," said lead author Ladan Shams, PhD, of the University of California, Los Angeles. "Instead, it can change from one moment to the next."
People navigate their surroundings based on maps built by sensory perceptions from their eyes, ears, and other senses. The brain combines these maps into a single experience. What happens, however, when one perception is flawed and becomes out of sync with the others? Studies show that when one of the sensory maps is wrong, the others will recalibrate to make it consistent and more accurate. But while previous studies held that this correction only occurs after hundreds or thousands of errors, new research shows that recalibration happens only a fraction of a second after an incident.
In this study, the researchers exposed 146 participants to 35-millisecond bursts of radio static-like noise, as well as flashes of light. In some trials, the lights and sounds were simultaneous; in others, there was static only. The researchers found that the perceived location of a sound was influenced by the direction of the flash in the previous trial. For example, if in the previous test the flash was to the left of the sound, the volunteer's perception of the sound alone in the next test was shifted to the left.
"This is the first evidence that sensory recalibration can occur rapidly, not after days or even seconds, but after milliseconds of exposure to discrepancy," Shams said. "This indicates that the recalibration of auditory space does not require a large amount of evidence to become triggered, and instead operates at all times."
Research was supported by the University of California, Los Angeles, and the National Institute of Biomedical Imaging and Bioengineering.
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