Dr. Ning Qian (Department of Neuroscience, Columbia University)
时间： 2016-09-26 14:30 - 16:30
地点： #1113, Wangkezhen Building, Peking University
When a stimulus is presented, its neural encoding progresses from simple, low-level features to complex, high-level features. How these features are decoded to produce perception is less clear and proposed decoding hierarchies are not quantitatively compared with perception. Moreover, observers often inspect different parts of a scene sequentially yet no decoding model considers working memory. We probed decoding hierarchy by comparing absolute judgments of single orientations and relative/ordinal judgments between two sequentially presented orientations. We found that lower-level, absolute judgments failed to account for higher-level, relative/ordinal judgments. However, when ordinal judgment was used as a Bayesian prior to retrospectively decode memory representations of absolute orientations, striking aspects of absolute judgments, including correlation and forward/backward aftereffects between two orientations in a trial, were explained. We suggest that the brain prioritizes decoding of more useful, higher-level features, which are also more invariant and categorical and thus easier to specify and maintain in noisy working memory, and that more-reliable higher-level decoding constrains less-reliable lower-level decoding.2016-09-26
2016-09-26