Abstract
It has been reported that visual perceptual learning (VPL) is facilitated by external reward as well as feedback as to the accuracy of subjects' response. Since both reward and feedback inform of response accuracy, it has been generally assumed that the underlying mechanism for the facilitation of VPL by these two factors was the same (e.g., reinforcement processing). However, this assumption has never been examined by a neuroscientific method. Here, we tested this assumption by comparing fMRI signals when feedback contained a high reward value with those with little or no reward value. Methods: In the high value condition, subjects (n=9) were asked not to eat or drink for five hours before a daily training session. In the low value condition, subjects (n=6) were allowed to eat or drink. FMRI measurements were conducted before, in the middle of and after training. In each trial of both the training and fMRI sessions, subjects were asked to perform a texture discrimination task. For a correct response to the target orientation, water was provided with subjects in both conditions through a tube from a water feeder. Results: First, although improvements in the task performance were observed in both conditions, the degree of improvement in the high value condition was significantly higher than in the low value condition. Second, the degree of fMRI signals in the trained region of V1 in both conditions was highly correlated with performance improvements. Third, as learning proceeded, fMRI signals in the hippocampus became increasingly higher in the high value condition, whereas those in the low value condition showed no change. Conclusions: The hippocampus is particularly involved in VPL by reward and not by feedback alone. Thus, the neural mechanism of facilitation of VPL by reward is not the same as that by feedback alone.
Meeting abstract presented at VSS 2016