Abstract 657, Date 1:00 pm, Tuesday, February 22, 2005 (24 hours)
Session O9: Otoacoustic Emissions: SFOAEs, Efferent Effects
     Effects of Selective Attention on DPOAE Amplitude and Rapid Adaptation in Humans
Rony Aouad, Tom Heil, David W. Smith
     It has been suggested that the medial efferent innervation of outer hair cells might play a role in mediating selective auditory attention at the auditory periphery. The present study investigated the effects of selective attention on the 2f1</sub>-f2</sub></I> DPOAE in humans. DPOAE (2f1</sub>/f2</sub></I> = 1.21, L1</sub></I>= 0 dB SPL, L2</sub></I>= 65 dB SPL) levels were measured simultaneously in both ears for a range of f2</sub></I> frequencies (1.2 to 10.0 kHz). The f2</sub></I> frequency producing the largest amplitude DPOAE was used for further testing. Two experiments are reported. In the first experiment, DPOAE recordings were compared under two conditions; while the subject was reading a book (ignoring the tones) and while counting the eliciting tones (attending). In the second experiment, DPAOEs recorded while the subject was watching a movie with subtitles (no sound; not attending) were compared with DPOAEs measured while counting tones (attending). Forty-eight human subjects participated in the first experiment and twenty-one in the second, with most being female (9% and 6% respectively). The magnitudes and time constants for the rapid DPOAE adaptation component was similar across all recording conditions. The DPOAE steady-state levels, however, were statistically different when compared while subjects read a book (non-attending; 1.8 dB) with levels measured while counting the tones (attending; 1.5 dB) (p</I><0.003). The steady-state levels of the slow adaptation components were also statistically different under the condition of reading DVD subtitles (non-attending; 1.8 dB) compared with the tone counting condition (attending; 16.8 dB) (p</I><0.001). Interestingly, attending to the movie (moving, dynamic visual objects) produced a much larger difference in DPOAE levels, compared with reading (static objects). These data provide evidence that selective auditory attention can modulate auditory activity, likely through the action of the medial olivocochlear efferent system, at the most peripheral aspects of the auditory system.