PURPOSE: Despite training makes perfect improvement in most perceptual tasks, the neural and functional mechanisms of perceptual learning are still under debate. Here we used a combination of psychophysics, event-related potentials (ERPs), and quantitative modeling to explicitly link learning-induced behavioral improvements with changes in neural activities.
METHODS: Twenty subjects underwent ten sessions of training to identify the orientation of a peripherally presented sinewave grating. A set of psychophysics and ERP measurements at different retinal locations, contrast levels, and eyes were conducted before and after training.
RESULTS: We found that training substantially improved visual acuity and contrast sensitivity functions, increased the amplitude, and decreased the latency of the ERP components at the trained location. The learning effect was particularly pronounced around the trained condition, consistent with previous findings. Modeling analysis revealed that training led to changes in both contrast, slope and response gains for different ERP component, and learning induced changes encompassed different sensory gain from the early to the late ERP components. Moreover, the learning effects and improvements in latency at the trained location were largely retained over a three-month period.
CONCLUSIONS: Our results support a model of PL in which neuronal plasticity occurs at both early and late ERP components, but with different mechanisms.
The results of the late ERP components may reflect top-down effects such as attention involved in the processing of the stimuli which amplify the increase of the amplitude or decrease the latency of the late ERP components.