Learning and plasticity in the human brain

National Institute Of Mental Health

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Abstract

The primary goals of this research are to i) establish how learning and experience impact the structure and function of the brain, and ii) determine how learning and plasticity can be modulated. Work was conducted under clinical protocol NCT00001360. Our recent work has focused extensively on understanding how body maps in the brain change following amputation. Sensorimotor experiences throughout our lifespan are thought to shape the neural representation of the body. What happens to the adult brain when it loses a key source of input, for example, following the amputation of an arm? We longitudinally investigated the stability of the cortical hand representation, before and after elective hand amputation due to an underlying medical condition (e.g. bone cancer). Three patients underwent functional brain imaging twice pre-amputation and at two separate time-points following amputation: 3 months and 6 months as well as long term follow ups at 1.5 and 5 years post-amputation, respectively. Additionally, we scanned 15 age-matched able-bodied control participants across the same timescale (60 scans in total). Using mapping of digit topography, representational similarity analysis and decoding over time, we show a remarkably consistent inter-digit representational structure of the pre-amputation hand and the post-amputation phantom (missing) hand. Further we find no evidence that other parts (e.g. lips, feet) are now being represented in the deprived cortex in contrast to prior cross-sectional work. Overall, this work provides the first pre- and post-amputation longitudinal evidence for preserved representation of the phantom (missing) hand following amputation. Such evidence is critical for thinking about the development of brain computer interfaces (BCI) and prosthetic devices. 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.