Plasticity of auditory selective attention in adults: A behavioral and physiological analysis

In the last decade, neurophysiological investigations have revealed that adult neural systems are mutable. This phenomenon is referred to as plasticity . The present study was aimed at understanding plastic mechanisms of auditory selective attention in adults. Behavioral and electrophysiological data were collected simultaneously as subjects performed an auditory selective attention task which used low frequency tones. Failure of auditory selective attention was associated with reduced sensitivity (d$\sp\prime$ values) and higher criterion scores (c), reflecting conservative judgements. Electrophysiologically, failure was associated with a smaller Mismatch Negativity (MMN) response reflecting reduced discriminability. Channel separation as measured by Processing Negativity (PN) was found to be smaller in magnitude. Results revealed that training in an auditory selective attention task improved sensitivity and caused judgements to become less conservative. MMN increased in the experimental group. PN enhanced, especially in the trained ear. Enhancements of PN in the 200-300 msec latency range were associated with improved selective attention. A measure of the ability to tune out a salient stimulus was obtained in PN-II. This response showed the largest gains in the post-test. Transfer of auditory selective attention skills was investigated by using high frequency pure tones and synthesized speech stimuli. Behaviorally, an improvement in sensitivity to high frequency pure tones was noted, with no significant changes in criterion. The behavioral results with speech stimuli did not show any changes after training. For both sets of stimuli, MMN increased for the experimental group. PN was enhanced once again, with greater increases noted in the 200-300 msecs latency range in the trained ear for the experimental subjects. PN-II increased as well. This mirrored the pattern seen for the trained stimuli. Subjects in the control group did not show any transfer to high frequency tones and limited transfer in the form of enhanced channel separation to speech stimuli. This study demonstrates that auditory selective attention is a plastic ability in adults. Auditory attention can be systematically improved through training