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KNOXVILLE — Nicotine, the substance that makes tobacco products addictive, also may help the human nervous system ignore distractions and concentrate on specific sounds, a University of Tennessee audiologist has found.

Dr. Ashley Harkrider, an assistant professor in audiology and speech pathology, made the finding while studying the effect of nicotine on the nerve pathways that sound impulses follow from the ear to the brain.

“Nicotine appears to improve the travel of sound from the ear to the brain,” Harkrider said. “At the same time, it seems to reduce the auditory system’s response to repetitive, distracting sound.

“Nicotine seems to increase auditory awareness and improve the efficiency of auditory processing.”

Harkrider studied 10 male and 10 female nonsmokers with normal hearing. She applied an across-the-counter, low-dose nicotine skin patch to their arms and applied electrodes on their scalps to measure brain activity when they heard sounds. To gauge the amount of nicotine in their bodies, she tested subjects’ plasma.

As a control, she performed the same tests on the same subjects using a placebo patch that contained no nicotine.

Harkrider said that chemical receptors in the brain and nervous system bind with the nicotine, which excites some neurons and suppresses others.

Nicotine excites the cortex of the brain, which releases a chemical that moderates further incoming stimulation.

“The brain is more alert on an organic level,” she said, but she cautioned that her research is not a recommendation to smoke or use nicotine to increase alertness.

Harkrider studied nonsmokers because they do not experience the effects of other products of smoking, including carbon monoxide. She said that she could not generalize the results to smokers and that the long-term effects of smoking on hearing are not known.

“There are a lot of risks to having nicotine in your system,” she said. “This is not a recommendation to use patches or smoke. Although there may be beneficial effects, there are tons and tons of harmful effects.”

Harkrider and Dr. Craig Champlin, an associate professor in communication sciences and disorders at the University of Texas, conducted the research, which will be presented at a meeting of the Acoustical Society of America in Atlanta this month.