Sound Enhances Sight, Study Shows

      SAN FRANCISCO, Oct. 18 (UPI) -- Brain researchers have found that sound enhances sight, an observation they say has implications for treating neurological disorders and attention deficits.

      In studying how humans process sound and sight simultaneously, scientists found that what we hear influences how well we see, the investigators said.

      "A sudden bang improves our perception of a flash in the same spot," lead author John McDonald and his colleagues at the University of California, San Diego, reported in the British journal Nature.

      "Sound can influence our ability to see," McDonald told United Press International. "Our study showed that paying attention to a sound enhances our ability to see a subsequent visual event. Basically, a sudden sound will capture our attention so that subsequent lights that appear nearby will be perceived better than subsequent lights appearing elsewhere. It is as if our visual system expects a light to occur at the location of the attended sound."

      While previous studies suggested that sound speeds up the brain''s reaction times to a subsequent nearby sight, they did not explain why -- something the new work tries to answer.

      "The study tells us that information in the two senses interacts somewhere in the brain to allow stimuli in one modality -- audition -- to alert us of possible events in other modalities -- vision," McDonald said. "This is important in the real world because objects that we might encounter are defined by features in many different modalities. Could you imagine if a sudden sound did not alert us of a corresponding visual object? We would certainly have less ability to avoid cars, predators and the like."

      The insights gained from the study into normal brain activities may lead to a better understanding of the role of attention in such neurological conditions as attention deficit disorder and schizophrenia, scientists said.

      "By furthering our understanding about how neurologically normal individuals selectively attend to environmental events, we can provide new methods for determining whether an individual has a specific attentional impairment," McDonald said.

      "New knowledge about cognitive function in ADD and schizophrenia will have important consequences for treatment. For example, early intervention is essential to improve the prognosis for individuals with schizophrenia. Because sensory and cognitive dysfunctions are early hallmarks of the disease, knowledge about the cognitive functions in neurologically normal individuals and in patients with schizophrenia will aid in the identification of the disease in its early stages. Medical treatment of ADD could also be tailored for specific impairments rather than for general problems in arousal."

      Beyond the realm of science and medicine, the research carries implications for everyday, work-place applications, such as for the design of systems that warn workers of impending danger or that help employees focus on jobs that demand absolute attention, said study co-author Wolfgang Teder-Slejrvi, UCSD assistant project scientist.

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

      "Our work has practical applications for the design of warning signals in a wide variety of industrial settings," McDonald said.

      "The basic problem is that we see only a portion of the environment at any given time, and our attention is usually focused on just the location at which we direct our gaze. Spatially coded warning sounds could be used to warn workers of the approach of a new and potentially dangerous object so that the worker has time to react."

      For example, he foresees an audio-visual radar screen in which a spatially coded auditory signal would precede the onset of a new visual marker so that an air-traffic controller would be less likely to miss new information entering the scenario. Or an audio-visual cockpit interface that would use a spatially coded sound to warn a pilot of the position of an oncoming aircraft.

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

      While previous research cast its eye on only one sense, such as vision or sound or touch, the new study with 33 volunteers had a twin focus -- sight and sound -- in studying the role of attention in a variety of situations.

      In the experiments, the subjects were to indicate whether a dim, obscured light appeared soon after a sound was presented. The sound and light came from either the same side or opposite sides of the direction of the subject''s gaze. Weeding out guesses, the researchers found the volunteers'' ability to correctly identify the presence of light improved when it shone on the same side as the sound was heard.

      "We found that what people hear significantly influences what they see," McDonald said.

      The investigators are compiling data to determine the precise measurement of the moment to moment changes in the visual cortex that arise from paying attention to sound. In the next phase, the scientists will analyze normal brain function involving different senses and compare it to abnormal brain function.

      Another question to consider is whether the special sight-sound relationship extends to other senses as well.

      "The types of cross-modal attention effects that we observed are probably not restricted to sights and sounds," McDonald said. "However, we will have to wait to see whether orienting attention to a touch on the hand affects perceptual processing of a subsequent light."

      The investigators are using measures of brain electricity to investigate whether paying attention to an irrelevant sound enhances brain cell activity in the visual cortex.

      "Our goal is to understand the neural processes that underlie our ability to pay attention to lights, sounds, and touches," McDonald said.

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