Abstract
An important question in perceptual learning is elucidation of the neural loci of learning-induced plasticity. Here, we aimed to psychophysically disentangle contributions of V1, MT and higher decision areas to learning-included plasticity for motion. To this end, we took advantage of the well-known difference between V1 and MT responses to drifting grating (component motion) and plaid (pattern motion) stimuli. METHODS: Participants (N = 14) were split into two groups. Each group trained on a left-right motion discrimination task, but with a different stimulus. Group A stimulus was a vertical grating with 4 °/s horizontal motion, while Group B stimulus was a plaid composed of two obliquely moving gratings, which resulted in 4 °/s horizontal plaid motion. A battery of pre- and post-tests was used to assess the nature of learning transfer. The battery included horizontally moving gratings and plaids as well as obliquely moving gratings and plaids. We also manipulated other low-level visual features (e.g., motion direction, speed, size and contrast) as a way to test for plasticity in decision areas beyond MT. RESULTS and CONCLUSIONS: We found a bi-directional transfer of learning between component gratings and plaid stimuli as long as they moved in the same apparent directions (e.g., both moving horizontally). However, we found no transfer between stimuli with different apparent directions even if they shared some of the same components (e.g., no transfer between a horizontally moving grating and a plaid stimulus that includes a horizontally moving grating). These results are inconsistent with the plasticity in V1. We also noted a strong learning specificity to other low-level visual features (e.g., size and contrast), suggesting against plasticity in higher-level decision making areas. In sum, our results strongly support that perceptual learning of motion mainly alters neuronal functions in the sensory areas, most likely in cortical area MT.
Meeting abstract presented at VSS 2016