Specificity and generalization of visual perceptual learning in humans; an event-related potential study

To investigate the neural correlates of specificity and generalization of visual perceptual learning, we recorded event-related potentials from human adults when they were trained with a simple visual discrimination task. While reaction times decreased significantly across training sessions, event-related potentials showed larger P2 amplitudes (similar to210 ms) over the left occipital/parietal areas and smaller NI amplitudes (similar to140 ms) at the left parietal site with more practice. Similar to reaction times, the training effect on the P2 amplitudes was specific to stimulus orientation. However, the NI effect was generalized over differently oriented stimuli. These results indicated the complexity of the neural substance underlying perceptual learning, relative to behavioral level.