Long-Lasting Perceptual Learning Occurs Not during but after Active Training

Previous behavioral studies have shown that human perceptual learning (PL) occurs not only within active training sessions but also between sessions when no actual training is conducted. Once acquired, the learning effect can last for a long term, from months to even years, without further training (Karni et al, Nature, 1993). It's not clear, however, whether fast (within-session) and slow (between-session) visual PL involves different neural mechanisms, and whether both contribute to the long-term preservation. Recently, by observing the time course of learning-associated ERP changes over a period of six months, we found that fast and slow learning involved distinct ERP changes, which played different role on the preservation of PL: while the ERP changes associated with fast learning can only last for a short term (several days), those associated with slow learning can be retained for a long-term (several months) after training has been stopped. We have observed these findings in two distinct visual tasks: line orientation detection (Qu et al., Neuropsychologia, 2010) and vernier tasks (Ding et al., in preparation) so far. A general model of PL was proposed based on our findings and literatures.