Category and perceptual learning in subjects with treated wilson's disease

Abstract

In category learning, observers improve their performance in classifying novel stimuli into discrete categories through trial-and-error with feedback. In perceptual learning, observers improve their discrimination or detection performance in perceptual tasks through repeated practice or training. Converging evidence from cognitive psychology, neuropsychology, and brain imaging has identified separate brain systems for rule-based explicit category learning and non-verbalizable implicit category learning. The neural circuitry for perceptual learning is however less clear. We investigated whether some brain structures important for category learning might also be important for perceptual learning. Specifically, we evaluated the speed and accuracy of explicit and implicit category learning, and the magnitudes of perceptual learning in low and high external noise environments for subjects with treated Wilson's disease and compared their performance with that of normal controls. Wilson's disease (WD), hepatolenticular degeneration, is an autosomal, recessively inherited disorder of copper metabolism with the greatest brain damage in the basal ganglia, a structure that is important in both explicit and implicit category learning. The WD subjects exhibited deficits in both forms of category learning as well as perceptual learning in high external noise. However, their perceptual learning in low external noise was relatively spared. Furthermore, there were significant correlations between the magnitude of perceptual learning in high external noise and both forms of category learning, but the magnitude of perceptual learning in low external noise was not significantly correlated with either form of category learning. The results imply that damage to brain structures in Wilson's disease, especially the basal ganglia, compromises both category learning and the development of templates in perceptual learning in high external noise, but may spare perceptual learning in low external noise, which may be served predominantly by other brain structures. Supported by NIMH, NEI, and the Chinese NSF.