UB Study Maps How Brain Monitors Multiple Conversations

November 10, 1997

BUFFALO, N.Y. -- Typical scenario: You're at a party, listening to your friend's vacation plans, while straining to overhear the gossipy conversation nearby.

Your brain, meanwhile, is mustering its neuronal resources to allow you to concentrate on both conversations at once.

Neuroscientists at the University at Buffalo have been able to produce an image, or map, of this neural activity in one of the few studies using positron emission tomography (PET) and electrophysiology simultaneously to study brain function. Their findings may provide new insight into the basis of many attention disorders.

"We're learning how the brain attends to important information and screens out what is not important," said Janet Shucard, Ph.D., UB assistant professor of neurology and a leading researcher on the study. "Using electrophysiology and PET, we can identify how resources are allocated. What we end up with is an objective measure of attention."

Their findings showed that the brain can successfully complete a task requiring focused attention even in the presence of distractions, but it takes longer than without the distractions. When the brain is forced to divide its attention, however, such as processing two cocktail-party conversations at once, it founders.

"The brain can only divide up its resources so much," said David Shucard, Ph.D., a co-investigator on the research. Ralph Benedict, Ph.D., assistant professor of neurology; Alan Lockwood, M.D., professor of neurology, and Danielle McCabe, psychology graduate student, complete the research team.

Results of their work were presented at the Society for Neuroscience meeting in New Orleans in October.

Knowledge about the neurophysiology of attention will increase understanding and improve treatment of attention disorders such as attention deficits and hypervigilance, a symptom of post-traumatic stress disorder in which persons are unable to screen out irrelevant stimuli, Janet Shucard said. It also provides information about the neural demands of any job that commands intense concentration.

The team collected its electrophysiology data via electrodes attached to the scalp while study subjects wearing earphones identified a specific syllable -- in this case, the syllable "ba" -- from a sequence of syllables. Neural actions generated in response to this task are called "event-related potentials," and appear on a computer-generated map that reflects the pattern of electrical responses from the brain. The height, or amplitude, of a specific point on this wave, called the P300, indicates the acuteness of the brain's response to the relevant stimuli.

The P300 was recorded under three conditions:

"We found a huge reduction in the P300 in response to the divided-attention task," said David Shucard. "These findings are relevant to any activity that demands constant attention, such as piloting an aircraft or monitoring sensitive instruments. This is one of the major causes of 'human error' -- people get off target."

Simultaneous PET scanning pinpointed areas in the brain responsible for auditory attention tasks by recording the areas of increased cerebral blood flow during the tests.

"By combining PET and electrophysiology, we are able to determine the location of major brain areas that are responsible for these different types of attention processes, as well as the time it takes the brain to process information when there are different demands on attention," Janet Shucard said.

The researchers are applying their findings to persons with attention deficit disorder and post traumatic stress disorder, as well as persons with sleep disorders, some of whom have trouble concentrating on tasks.

University at Buffalo

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