Learning and plasticity in the human brain

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The primary goals of this research are i) to establish differences in brain processing in the context of nervous system damage or dysfunction, and ii) to determine the potential for learning-induced plasticity to ameliorate the negative consequences of such changes. Over the past year we have primarily focused on Autism Spectrum Disorders (ASD) and the impact of amputation, and on establishing the structural brain changes that accompany learning/training. 1) Loss of somatosensory input (NCT00623818) Following limb amputation, over 90% of people report phantom sensations in their missing limb, often painful sensations (Phantom Limb Pain, or PLP). One current theory suggests that PLP is a direct result of cortical reorganization, an example of maladaptive plasticity. Mirror therapy has been used as a treatment for PLP. During this therapy, patients move their intact limb while looking in a mirror, making it seem as if their missing limb is moving. We are currently investigating the neural consequences of amputation and the impact of mirror therapy on brain activity over time. We are continuing to recruit unilateral limb amputees and monitoring brain activity with fMRI over a period of four weeks while the amputees undergo mirror therapy. We are trying to establish whether the presence of PLP correlates with cortical reorganization in the somatosensory and motor cortex (similar to that observed in our participants with macular degeneration) and whether the mirror therapy works by reducing the extent of cortical reorganization. 2) Autism Spectrum Disorders (NCT01031407) We have been investigating motion processing, decision-making and attention in Autism Spectrum Disorders (ASD), processes that are supported by well-characteristic brain networks. In the context of motion processing, previous studies had reported conflicting results with some studies finding impaired motion processing in ASD and other finding no impairment. By varying the time allowed to make judgments, we found that motion processing in ASD is impaired, but only at short durations. Further, this deficit in performance is reflected in the activity of brain regions involved in visual motion processing, with reduced responses in autistic compared with control participants. In the context of attention, we asked participants to perform a simple visual discrimination and measured the spatial gradient of attentional enhancement. We found that this gradient was sharper in autism than in matched control participants (Robertson et al, 2013, Journal of Neuroscience). 3) Learning/training (NCT00001360) We are conducting a long-term longitudinal study of participants learning different tasks (e.g. motor sequences) to determine how structural properties of the brain change over time. Establishing the nature, degree and consequences of plasticity in the adult cortex provides important insights into the potential for rehabilitative brain therapies following injury or dysfunction in the nervous system.