Abstract
Whether adult early visual cortex has sufficient plasticity to allow for behavioral and/or sensitivity changes remains a point of great controversy. Many studies have examined how activity changes in the brain are correlated with visual performance improvements resulting from repetitive training, known as visual perceptual learning (VPL). However, such a correlational approach has not conclusively settled the adult plasticity debate, partially because most VPL studies have examined correlations between behavioral and neural activity changes rather than cause-and-effect relationships. To address the question of whether early visual areas are that plastic, we developed a new functional magnetic resonance imaging (fMRI) online-feedback method (Shibata, Watanabe, Sasaki & Kawato, 2011, Science), by which activation patterns only in early visual areas corresponding to the pattern evoked by the presentation of a real and specific target orientation stimulus were repeatedly induced without subjects’ knowledge of what is being learned and without external stimulus presentation. Before and after fMRI online-feedback training for several days, subjects’ performance on an orientation discrimination task was measured. We found that the mere induction of the activation patterns in early visual areas resulted in significant sensitivity improvement on the target orientation, but not on other orientations. Moreover, the induced activation patterns in early visual areas significantly correlated with sensitivity improvement on the target orientation. Activity patterns in other areas did not change in concert with the induced pattern in early visual areas, indicating no spillover of the patterns from the early areas. Our results indicate that the adult early visual cortex is so plastic that mere repetition of the activity pattern corresponding to a specific feature in the cortex is sufficient to cause VPL of the feature, even without stimulus presentation, conscious awareness of the meaning of the neural patterns that subjects induced, or knowledge of the intention of the experiment.
Meeting abstract presented at VSS 2012