Abstract
We asked whether biased feedback during training could cause human subjects to lose perceptual acuity in a vibrotactile frequency discrimination task. Prior to training, we determined each subject's vibration frequency discrimination capacity on one fingertip, the Just Noticeable Difference (JND). Subjects then received 850 trials in which they performed a same/different judgment on two vibrations presented to that fingertip. They gained points whenever their judgment matched the computer-generated feedback on that trial. Feedback, however, was biased: the probability per trial of “same” feedback was drawn from a normal distribution with standard deviation twice as wide as the subject's JND. After training, the JND was significantly widened: stimulus pairs previously perceived as different were now perceived as the same. The widening of the JND extended to the untrained hand, indicating that the decrease in resolution originated in non-topographic brain regions. In sum, the acuity of subjects' sensory-perceptual systems shifted in order to match the feedback received during training.
Highlights
When two inputs evoke sufficiently different neuronal responses, our sensory-perceptual systems recognize two distinct events; in contrast when two inputs evoke similar neuronal responses, we perceive two instances of the same event
The findings suggest that both improving and lessening discriminative capacity might involve a single underlying mechanism, one that can achieve higher or lower perceptual acuity according to the feedback given to the sensory system
This study looked for changes in individual subjects’ acuity in relation to the form of feedback employed during training
Summary
When two inputs evoke sufficiently different neuronal responses, our sensory-perceptual systems recognize two distinct events; in contrast when two inputs evoke similar neuronal responses, we perceive two instances of the same event. How do our sensoryperceptual systems learn to parse our experience with the optimal degree of resolution? A sensory system can be “tuned” to recalibrate and to perform progressively finer discriminations of visual stimuli (Herzog and Fahle, 1997; Dill and Fahle, 1998), auditory stimuli (Kishon-Rabin et al, 2001; Bosnyak et al, 2004) or tactile stimuli (Recanzone et al, 1992a,b; Sathian and Zangaladze, 1997; Ostwald et al, 2012), temporal events or even multisensory stimuli (Fujisaki et al, 2004; Vroomen et al, 2004; Keetels and Vroomen, 2008; Yamamoto et al, 2012). In many of the cases cited above, recognition of small differences between stimuli was rewarded and, subjects showed improvements in sensory resolution
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