Training can significantly improve performance on even the most basic visual tasks, such as detecting a faint patch of light or determining the orientation of a bar (for reviews, see [1, 2]). The neural mechanisms of visual learning, however, remain controversial. One simple way to improve behavior is to increase the overall neural response to the trained stimulus by increasing the number or gain of responsive neurons. Learning of this type has been observed in other sensory modalities, where training increases the number of receptive fields that cover the trained stimulus [3, 4]. Here, we show that visual learning can selectively increase the overall response to trained stimuli in primary visual cortex (V1). We used functional magnetic resonance imaging (fMRI) to measure neural signals before and after one month of practice at detecting very low-contrast oriented patterns. Training increased V1 response for practiced orientations relative to control orientations by an average of 39%, and the magnitude of the change in V1 correlated moderately well with the magnitude of changes in detection performance. The elevation of V1 activity by training likely results from an increase in the number of neurons responding to the trained stimulus or an increase in response gain.
Bibliographical noteFunding Information:
We are grateful to Mark Cohen for assistance with fMRI and Dario Ringach and Laura Eldridge for comments on the manuscript. We also thank John Mazziotta, the University of California, Los Angeles Brain Mapping Medical Organization, the Ahmanson Foundation, the Pierson-Lovelace Foundation, the Tamkin Foundation, and the Jennifer Jones-Simon Foundation for their support. This work was supported by NIH-EY11862.
Copyright 2008 Elsevier B.V., All rights reserved.