Abstract
Reward plays an important role in visual perceptual learning (VPL, Seitz, Kim, & Watanabe, 2009). Does this mean that the neural changes particularly associated with VPL trained with reward is essential to VPL in general (Law & Gold, 2009)? To address this question, 8 subjects were trained on the texture discrimination task (TDT, Karni & sagi, 1991) for 14 daily training sessions. Subjects were asked to perform the TDT during BOLD measurements at 3 different stages: pre-training, and after the 1st and 14th training sessions. All subjects were asked to refrain from eating or drinking for 5 hours before each training and measurement sessions. Trial-based water reward was given to subjects for a correct response. Diffusion tensor imaging (DTI) was also performed immediately after each scan of the BOLD measurement. In addition, a different group of 11 subjects participated in a control experiment whose procedure was identical to that of the main experiment except that no reward was given to the subjects. Results showed that the caudate, thalamus, amygdala, and hippocampus from the trained hemisphere showed significant BOLD activation increases at the second BOLD measurement stage. However, BOLD activations in the caudate and thalamus significantly dropped at the 3rd stage, whereas the hippocampus and amygdala showed the sustained BOLD activations at the 3rd stage. DTI results showed that fractional anisotropy of the cingulum-cingulate gyrus bundle, which connects the basal ganglia and limbic system through the thalamus significantly decreased at the 2nd DTI stage but increased again in the 3rd DTI, whereas the mean length of the bundle decreased over the stages, suggesting the axonal rewiring in these regions. In the control experiment, no such change in any of the above-mentioned areas was observed. These results indicate that neural changes in reward processing are not essential to perceptual learning in general.
Meeting abstract presented at VSS 2014