Auditory perceptual learning and changes in the conceptualization of auditory cortex
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Date
2018-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier B.V.
Abstract
Perceptual learning, improvement in discriminative ability as a consequence of training, is one of the forms of sensory system plasticity that has driven profound changes in our conceptualization of sensory
cortical function. Psychophysical and neurophysiological studies of auditory perceptual learning have indicated that the characteristics of the learning, and by implication the nature of the underlying neural changes, are highly task specific. Some studies in animals have indicated that recruitment of neurons to
the population responding to the training stimuli, and hence an increase in the so-called cortical “area of representation” of those stimuli, is the substrate of improved performance, but such changes have not
been observed in other studies. A possible reconciliation of these conflicting results is provided by evidence that changes in area of representation constitute a transient stage in the processes underlying
perceptual learning. This expansion - renormalization hypothesis is supported by evidence from studies of the learning of motor skills, another form of procedural learning, but leaves open the nature of the
permanent neural substrate of improved performance. Other studies have suggested that the substrate might be reduced response variability - a decrease in internal noise. Neuroimaging studies in humans have also provided compelling evidence that training results in long-term changes in auditory cortical function and in the auditory brainstem frequency-following response. Musical training provides a valuable model, but the evidence it provides is qualified by the fact that most such training is multimodal and sensorimotor, and that few of the studies are experimental and allow control over confounding variables. More generally, the overwhelming majority of experimental studies of the various forms of
auditory perceptual learning have established the co-occurrence of neural and perceptual changes, but have not established that the former are causally related to the latter. Important forms of perceptual learning in humans are those involved in language acquisition and in the improvement in speech perception performance of post-lingually deaf cochlear implantees over the months following implantation.
The development of a range of auditory training programs has focused interest on the factors
determining the extent to which perceptual learning is specific or generalises to tasks other than those
used in training. The context specificity demonstrated in a number of studies of perceptual learning
suggests a multiplexing model, in which learning relating to a particular stimulus attribute depends on a
subset of the diverse inputs to a given cortical neuron being strengthened, and different subsets being
gated by top-down influences. This hypothesis avoids the difficulty of balancing system stability with
plasticity, which is a problem for recruitment hypotheses. The characteristics of auditory perceptual
learning reflect the fact that auditory cortex forms part of distributed networks that integrate the representation of auditory stimuli with attention, decision, and reward processes.
Description
Keywords
Frequency discrimination, Generalization, Musical training, Plasticity, Stability, Synaptic weights
Citation
Irvine, D. R. F. 2018. Auditory perceptual learning and changes in the conceptualization of auditory cortex. Hearing Research. 366: 3-16.