Decoding reveals plasticity in V3A as a result of motion perceptual learning

Abstract

Visual perceptual learning (VPL) is defined as visual performance improvement after visual experiences. VPL is often highly specific for a visual feature presented during training. Such specificity is observed in behavioral tuning function changes with the highest improvement centered on the trained feature and was originally thought to be evidence for changes in the early visual system associated with VPL. However, results of neurophysiological studies have been highly controversial concerning whether the plasticity underlying VPL occurs within the visual cortex. The controversy may be partially due to the lack of observation of neural tuning function changes in multiple visual areas in association with VPL. Here using human subjects we systematically compared behavioral tuning function changes after global motion detection training with decoded tuning function changes for 8 visual areas using pattern classification analysis on functional magnetic resonance imaging (fMRI) signals. We found that the behavioral tuning function changes were extremely highly correlated to decoded tuning function changes only in V3A, which is known to be highly responsive to global motion with human subjects. We conclude that VPL of a global motion detection task involves plasticity in a specific visual cortical area.

Figure 1. Task procedure and results of the behavioral session.

(A) The 2IFC global motion detection task in the behavioral session. One stimulus interval contains 15% coherent motion while the other interval contains random motion (0% coherence). After two motion presentations, the subjects were asked to report the interval (first or second) which contained 15% coherent motion. (B) Mean performance across the subjects during the training stage. A motion direction used in this stage was defined as a trained direction for each subject. After 10-day training, a significant training effect was obtained (day 1 vs day 10, paired t-test, P<10⁻⁴). Error bars represent SEM. (C) Mean behavioral performance across the subjects for the trained direction in the pre-test (blue) and post-test (red) stages. Significant performance improvement was found after the training stage (paired t-test, P = 0.01). Error bars represent SEM.

Figure 2. Comparing the two tuning improvement functions.

(A) A behavioral tuning improvement function. The behavioral tuning improvement function was defined by mean performance change across the subjects between the pre- and post-test stages for each of 9 motion directions. Error bars represent SEM. (B) Comparison between the behavioral tuning improvement function (blue) and decoded tuning improvement function for V3A (red). Each improvement function was scaled from 0 to 1 for visualization purpose. Between the two improvement functions, a significant correlation was found (r = 0.86, P<0.05, multiple correction by the number of ROIs with false discovery rate).

Figure 3. A decoded tuning improvement function for each ROI.

Mean decoding performance improvement across the subjects was calculated by subtracting decoding accuracy in the pre-fMRI stage from that in the post-fMRI stage for each of 9 motion directions. Significant improvement for the trained direction was obtained only in V3A (paired t-test, P<0.05, false discovery rate, corrected by the number of the ROIs). Error bars represent SEM.