Abstract
Perceptual skills can improve dramatically even with minimal practice. A major and practical benefit of learning, however, is in transferring the improvement on the trained task to untrained tasks or stimuli, yet the mechanisms underlying this process are still poorly understood. Reduction of internal noise has been proposed as a mechanism of perceptual learning, and while we have evidence that frequency discrimination (FD) learning is due to a reduction of internal noise, the source of that noise was not determined. In this study, we examined whether reducing the noise associated with neural phase locking to tones can explain the observed improvement in behavioral thresholds. We compared FD training between two tone durations (15 and 100 ms) that straddled the temporal integration window of auditory nerve fibers upon which computational modeling of phase locking noise was based. Training on short tones resulted in improved FD on probe tests of both the long and short tones. Training on long tones resulted in improvement only on the long tones. Simulations of FD learning, based on the computational model and on signal detection theory, were compared with the behavioral FD data. We found that improved fidelity of phase locking accurately predicted transfer of learning from short to long tones, but also predicted transfer from long to short tones. The observed lack of transfer from long to short tones suggests the involvement of a second mechanism. Training may have increased the temporal integration window which could not transfer because integration time for the short tone is limited by its duration. Current learning models assume complex relationships between neural populations that represent the trained stimuli. In contrast, we propose that training-induced enhancement of the signal-to-noise ratio offers a parsimonious explanation of learning and transfer that easily accounts for asymmetric transfer of learning.
Highlights
Perceptual learning is a long-lasting improvement in the perception of a stimulus due to experience or training
−0.1 Learning groups depending on tone duration (F 1,30 = 7.1, p = 0.012). This interaction resulted from an asymmetric transfer of learning; only in the group trained on short tones did the training transfer to the untrained tone duration (Figure 2C)
Learning and transfer of reduction in phase locking noise To test the hypothesis that frequency discrimination (FD) learning for short tones was consistent with improved phase locking, we first tested whether this mechanism could account for the transfer from 15- to 100-ms tones in the T15 group
Summary
Perceptual learning is a long-lasting improvement in the perception of a stimulus due to experience or training. We are still far from a consensus on exactly what is being learned and, by extension, the neural mechanisms of that learning. Understanding the rules and mechanisms of transfer and, specificity is important both for constraining hypotheses of what is being learned and for incorporating perceptual training into applications designed to improve sensory-perceptual and cognitive processing in aging or impaired populations. Research in visual perceptual learning has revealed an almost ubiquitous specificity of learning to the trained stimulus parameters such as retinal position or orientation (e.g., Karni and Sagi, 1991; Schoups et al, 1995). A major shortcoming of these models is that, in order to explain a growing number of observations of asymmetric transfer of learning, they have to resort to complex relationships between the neural populations involved in processing, such as unidirectional connections or nested populations (e.g., Matthews et al, 1999; Mossbridge et al, 2008)
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