Task-dependent effects of nicotine treatment on auditory performance in young-adult and elderly human nonsmokers
Abstract Rationale Electrophysiological studies show that nicotine enhances neural responses to characteristic frequency stimuli. Previous behavioral studies partially corroborate these findings in young adults, showing that nicotine selectively enhances auditory processing in difficult listening conditions. The present work extended previous work to include both young and older adults and assessed the nicotine effect on sound frequency and intensity discrimination. Objectives Hypotheses were that nicotine improves auditory performance and that the degree of improvement is inversely proportional to baseline performance. Methods Young (19–23 years old) normal-hearing nonsmokers and elderly (61–80) nonsmokers with normal hearing up to at least 2 kHz received nicotine gum (6 mg) or placebo gum in a single-blind, randomized crossover design. Participants performed three experiments (frequency discrimination, frequency modulation identification, and intensity discrimination) before and after treatment. The perceptual differences were analyzed between post-treatment nicotine and placebo conditions as a function of pre-treatment baseline performance. Results Nicotine significantly improved performance for intensity discrimination, and improvement was more pronounced in the elderly with lower baseline performance. Nicotine had no overall effect on the two frequency related tasks. Conclusions Nicotine effects are task-dependent, enhancing intensity discrimination but not frequency performance.