Abstract
Visual perceptual learning (VPL) is traditionally attributed to early cortical neural plasticity or response reweighting. However, our double training studies demonstrate often complete learning transfer to untrained locations, orientations, and physical stimuli, suggesting that VPL involves learning at a conceptual level (e.g., learning an abstract orientation concept). It is unclear whether such a concept is abstracted after learning (e.g., abstracting the rules of reweighting that define a concept), or before learning (e.g., abstracting stimulus information before reweighting). Subjects practiced orientation discrimination with a Gabor that either rotated trial-by-trial in 12 locations (anti-clockwise) and 4 orientations (clockwise) at 5-deg eccentricity, or in a roving order (47 conditions excluding the pre/post one that was never practiced). Each condition received 2 trials per block, 12 trials per session, over 5 daily sessions. A staircase controlled the orientation difference from trial to trial. The multiple stimulus conditions and scarce number of trials per condition minimize the possibility of early cortical plasticity and response reweighting (and so abstraction of reweighting rules). Both rotating and roving training conditions produced significant orientation learning. Training also improved the untrained pre/post condition, as much as when training was performed at the pre/post condition with equal number of trials. Similar effects were seen with orientation training using symmetry dot-patterns whose global orientation rotated. However, training with an irrelevant contrast discrimination task with multiple conditions had no significant effect on orientation performance at the pre/post condition, indicating that orientation learning is genuine and not caused by improved attention to the periphery. These results suggest that early cortical plasticity and response reweighting, as well as abstraction of reweighting rules, are unnecessary for VPL. Instead the brain may abstract the stimulus information in advance before reweighting, which explains VPL and its transfer in various double training studies and in current multiple-condition training study.
Meeting abstract presented at VSS 2017