RESUMO
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. Hypotheses were that nicotine improves auditory performance and that the degree of improvement is inversely proportional to baseline performance. Young (19-23 years old) normal-hearing nonsmokers and elderly (61-80) nonsmokers with normal hearing between 500 and 2000 Hz 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 pre- and post-treatment, as well as between post-treatment nicotine and placebo conditions as a function of pre-treatment baseline performance. Compared to pre-treatment performance, nicotine significantly improved frequency discrimination. Compared to placebo, nicotine significantly improved performance for intensity discrimination, and the improvement was more pronounced in the elderly with lower baseline performance. Nicotine had no effect on frequency modulation identification. Nicotine effects are task-dependent, reflecting possible interplays of subjects, tasks and neural mechanisms.
Assuntos
Envelhecimento/fisiologia , Percepção Auditiva/efeitos dos fármacos , Nicotina/farmacologia , não Fumantes , Afeto/efeitos dos fármacos , Idoso , Idoso de 80 Anos ou mais , Estudos Cross-Over , Discriminação Psicológica/efeitos dos fármacos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Nicotina/administração & dosagem , Goma de Mascar de Nicotina , não Fumantes/psicologia , Oxigênio/sangue , Percepção da Altura Sonora/efeitos dos fármacos , Desempenho Psicomotor , Receptores Nicotínicos/efeitos dos fármacos , Receptores Nicotínicos/fisiologia , Projetos de Pesquisa , Razão Sinal-Ruído , Método Simples-Cego , Adulto JovemRESUMO
RATIONALE: Electrophysiological studies show that systemic nicotine narrows frequency receptive fields and increases gain in neural responses to characteristic frequency stimuli. We postulated that nicotine enhances related auditory processing in humans. OBJECTIVES: The main hypothesis was that nicotine improves auditory performance. A secondary hypothesis was that the degree of nicotine-induced improvement depends on the individual's baseline performance. METHODS: Young (18-27 years old), normal-hearing nonsmokers received nicotine (Nicorette gum, 6mg) or placebo gum in a single-blind, randomized, crossover design. Subjects performed four experiments involving tone-in-noise detection, temporal gap detection, spectral ripple discrimination, and selective auditory attention before and after treatment. The perceptual differences between posttreatment nicotine and placebo conditions were measured and analyzed as a function of the pre-treatment baseline performance. RESULTS: Nicotine significantly improved performance in the more difficult tasks of tone-in-noise detection and selective attention (effect size = - 0.3) but had no effect on relatively easier tasks of temporal gap detection and spectral ripple discrimination. The two tasks showing significant nicotine effects further showed no baseline-dependent improvement. CONCLUSIONS: Nicotine improves auditory performance in difficult listening situations. The present results support future investigation of nicotine effects in clinical populations with auditory processing deficits or reduced cholinergic activation.