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UCSD Neuroscientists Find That Attention to Sound Influences Ability to See 

Study Has Implications for the Role of Attention in Brain Disorders and the Work Environment

In studies of how people process sound and sight together to make sense of the complex world around them, neuroscientists at the UCSD School of Medicine have found that attention drawn to a sound also enhances an individual's ability to see.

Published in the Oct. 19, 2000 issue of Nature, the study provides important insights into normal brain activities, and may lead to better understanding of the role attention plays in dysfunctional neurological conditions such as attention deficit disorder and schizophrenia. Another potential application is in the workplace for design of warning systems and man-machine interfaces where attention is crucial.

The study's lead author is John J. McDonald, Ph.D., a post-doctoral fellow in the lab of Steven Hillyard, Ph.D., UCSD professor of neurosciences and study co-author along with UCSD assistant project scientist Wolfgang A. Teder-Sälejärvi, Ph.D.

"These studies show a stronger linkage between sight and hearing than previously demonstrated," Hillyard said. "Our results suggest that you will see an object or event more clearly if it makes a sound before you see it."

McDonald noted that the majority of past studies looked at only one sense, such as vision or sound or touch. In order to study the role of attention in more realistic situations and the specific connection between sound and sight, the UCSD researchers conducted two experiments with 33 volunteers. The subjects were told to indicate whether a dim, obscured light appeared soon after a sound was presented. The sound and light appeared either on the same side or on opposite sides of the subject's direction of gaze. Using a mathematical model called signal detection theory to weed out guesses by the volunteers, researchers found that the light was detected more accurately when it appeared on the same side as the sound.

"We found that what people hear significantly influences what they see," McDonald said. "Researchers have known for many years that the brain integrates information received from multiple stimuli in the environment, and ignores nonessential information. What we haven't understood are the processes that enable us to selectively pay attention to events occurring in different modalities. In this study, we found that paying attention to a sudden sound enhances our ability to see visual stimuli that appear at the same location."

"As we continue to learn how individuals perceive the multiple stimuli taking place around them, we'll have data from normal brain function to compare with and help us understand abnormal conditions, such as attention deficit disorder, " McDonald said.

Teder-Sälejärvi added that the findings also hold promise for the "ergonomic design of warning systems in assembly lines and for other high-risk work environments such as radar operation. Studies like ours also may help in the design of man-machine interfaces where focussing of attention on a primary task is mandatory."

While the results reported in Nature covered the behavioral performance of subjects, the researchers also recorded the brain's responses to sound and light stimuli to see whether paying attention to sound influences neural activity in visual areas of the brain.

"We're now compiling this data to give us a precise measurement of the moment to moment changes in the visual cortex that arise from paying attention to sound," McDonald said.

Next steps in the research include more studies of normal brain function involving different senses and comparisons to individuals with abnormal brain function.