2012年10月9日火曜日

Generalized Perceptual Learning in the Absence of Sensory Adaptation


Hila Harris, Michael Gliksberg, Dov Sagi
Current Biology, Volume 22, Issue 19, 1813-1817, 23 August 2012

Repeated performance of visual tasks leads to long-lasting increased sensitivity to the trained stimulus, a phenomenon termed perceptual learning. A ubiquitous property of visual learning is specificity: performance improvement obtained during training applies only for the trained stimulus features, which are thought to be encoded in sensory brain regions [1,2,3]. However, recent results show performance decrements with an increasing number of trials within a training session [4,5]. This selective sensitivity reduction is thought to arise due to sensory adaptation [5,6]. Here we show, using the standard texture discrimination task [7], that location specificity is a consequence of sensory adaptation; that is, it results from selective reduced sensitivity due to repeated stimulation. Observers practiced the texture task with the target presented at a fixed location within a background texture. To remove adaptation, we added task-irrelevant (“dummy”) trials with the texture oriented 45° relative to the target’s orientation, known to counteract adaptation [8]. The results indicate location specificity with the standard paradigm, but complete generalization to a new location when adaptation is removed. We suggest that adaptation interferes with invariant pattern-discrimination learning by inducing network-dependent changes in local visual representations.

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