Neural substrates of visual perceptual learning of simple and complex stimuli

Objective The two experiments described here used event-related potentials (ERPs) to investigate whether perceptual learning of different complexities of stimuli involves different levels of visual cortical processing in human adults. Methods Reaction times and ERPs were recorded during 3 consecutive training sessions in which subjects discriminated between simple stimuli made of line segments or complex stimuli made of compound shapes. Results Reaction times in both experiments were shortened across training sessions. For simple stimuli, training resulted in a decreased N1 (125–155 ms) and an increased P2 (180–240 ms) over the occipital area. For complex stimuli, however, training resulted in a decreased N1 (125–155 ms) and N2 (290–340 ms) and an increased P3 (350–550 ms) over the central/parietal areas. Conclusions These findings suggest that perceptual learning modifies the response at different levels of visual cortical processing related to the complexity of the stimulus. Significance The neuronal mechanisms involved in perceptual learning may depend on the nature (e.g. the complexity) of the stimuli used in the discrimination task.