Abstract
In perceptual learning (PL), behavioral improvement is specific to trained stimuli and trained orientation. Some studies suggest that PL recruits V1 (Schiltz et al., 1999; Yotsumoto et al., 2008) and leads to a large-scale decrease in the recruitment of higher visual areas and of the dorsal attentional network (Mukai et al., 2007; Sigman et al., 2005). However, the designs do not address whether these effects are task-dependent, may result from mere exposure, and could generalize to training stimuli with variability in shape. Twelve participants were trained for 8 hours to search for objects in a target orientation among an array of 8 distracter objects. Within each display, all objects were identical in shape and varied only in orientation, but across displays, a number of similar objects were used. With fMRI, we compared neural activity in response to these objects before and after training. As in prior work (Sigman et al., 2005), behavioral improvement was specific to trained orientation but it generalized to similar objects, and neural activity in early visual areas was higher for objects at the trained orientation after training. Importantly, the neural inversion effect was observed in visual areas well beyond retinotopic cortex, including extrastriate face and object selective areas. These inversion effects were not obtained during shape discrimination with the same objects, or in a separate group of participants undergoing eight hours of naming training with the same object set in the same peripheral visual positions, suggesting that the inversion effects were task-dependent, and were not a result of mere exposure with the objects. Our results extend prior work to suggest that PL can sometimes recruit higher visual areas, possibly depending on the training objects and the variability within the object set.
This research was supported by grants to the Temporal Dynamics of Learning Center (NSF Science of Learning Center SBE.