Human Auditory Attention: The Olivocochlear Bundle May Function as a Peripheral Filter

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Abstract
Two experiments examined whether focused attention toward a visual display would alter the sensory transmission properties of the human auditory nerve and brainstem centers to irrelevant auditory tone pips. In the first experiment, 16 subjects either listened to 1000 Hz, 50dB SL tone pips presented binaurally at 10/sec (“Listen”), or mentally counted letters flashed rapidly on a screen (“Look”). The auditory brainstem potentials recorded from the vertex were averaged on‐line in groups of 500 with a 10‐msec sweep and a bandpass of 150–1500 Hz. Results indicated that during the “Look” trials, Wave 5 generated from the inferior colliculus (7.322 msec latency) was significantly reduced in amplitude by 16.4% and increased in latency by 27 μsec. A second experiment with 8 subjects demonstrated that the effects of attention are limited to the auditory nerve component when using 8000 Hz stimuli but are significant for both the auditory nerve and collicular components when a mid‐frequency (2000 Hz) tone pip is used. These results suggest that during concentrated attention toward visual stimuli, irrelevant auditory stimuli may be attenuated at a peripheral level possibly through the action of the efferent olivocochlear bundle.