Abstract
The delayed discrimination task has been extensively used in the studies of perceptual learning. Plastic changes at sensory cortex or decision-related brain areas are suggested to contribute to the observed training effect, whereas an important cognitive process involved in this task, working memory (WM), is mostly ignored. The underestimate of the WM process may stem from studies showing that the discrimination threshold was barely affected by the inter-stimulus interval (ISI), indicating that WM is perfect (Magnussen et al., 1990). However, recent studies measured the fidelity of WM directly and found that the precision of WM is lower than that of perception (Brady et al., 2013). This result raised the question of whether the delayed discrimination training enhances the fidelity of WM, perception, or both of them. To address this issue, we trained participants with an orientation discrimination task (peripheral, 6.5°, at the top left corner; ISI, 0.6 s; orientation, 45°). Before and after the training, we measured the fidelities of WM and perception. The fidelity was defined as the reciprocal of the standard deviation of the error distribution in a recall task. In this task, a Gabor patch and a red line, both in random orientations (drawn from uniform distribution over [40°-50°] independently), were presented either successively (for measuring WM precision, ISI = 0.6 s, 4 s or 8 s) or simultaneously (for measuring perceptual precision). Participants were instructed to adjust the orientation of the line until it matched the orientation of the Gabor patch. Our results showed significant training effect on WM precision, but not on perceptual precision. The changed fidelity of WM was highly correlated with the learning effect across participants and was specific to the trained location and ISI. These results suggest that the enhanced precision of WM may play an important role in perceptual learning.
Meeting abstract presented at VSS 2016