Sensorimotor plasticity and brain stimulation
Research type
Research Study
Full title
Measuring and manipulating sensorimotor plasticity using brain stimulation
IRAS ID
121084
Contact name
Jacinta O'Shea
Contact email
Sponsor organisation
Oxford University
Research summary
Research Summary
Prism adaptation is a form of visuomotor learning that has been used to investigate motor control for over a hundred years. Recently, evidence has arisen that prism adaptation may be effective in treating a disorder of visual perception and cognitive processing that commonly occurs after stroke, called hemispatial ’neglect’. Although prism adaption is considered to hold great therapeutic potential for neglect patients, the mechanisms by which it alters brain function are poorly understood. Furthermore, the therapeutic effects of a single prism adaptation session typically last only up to one day, and repeated interventions are necessary for improvements to persist over a clinically meaningful timescale. The primary goal of the current protocol is to identify the neural circuits that mediate prism adaptation in healthy volunteers, and to investigate the potential utility of using Transcranial Direct Current Stimulation (TDCS) of the brain to boost learning and memory of prism adaptation. The secondary objective is to test whether individual differences in brain structure, function and neurochemistry predict variation in the magnitude of behavioural and physiological responses to prism adaptation and its combination with TDCS. Up to 420 participants will be recruited across five studies. Outcome measures will be learning and memory of prism adaptation as measured by pointing movements, and changes in brain activity as measured by Transcranial Magnetic Stimulation (TMS) and Magnetic Resonance Imaging (MRI). This research is funded by the Royal Society.
Summary of Results
This study aimed to understand and enhance a form of learning called “prism adaptation”. In this type of learning, people perform a pointing exercise while wearing glasses that bend light. This makes the pointing targets appear to be in a different position, more rightward shifted, which results in pointing errors. People learn quickly to correct their errors: they adapt to the prisms. After they take the glasses off, they then make pointing errors in the opposite direction. This is called the prism after-effect. That effect is interesting because it can be used for stroke rehabilitation to help people with symptoms called “spatial neglect”. In this study we recruited healthy adult volunteers to understand more about how this behaviour is controlled by the brain and to see if we could make the after-effect stronger by using non-invasive brain stimulation. Healthy adults volunteered to participate in several studies in which they did the prism adaptation learning task, while also experiencing brain stimulation. In some studies they also did brain scans. There were several findings. The experiments identified which region of the brain to stimulate to make the prism after-effect stronger, and in which regions stimulation had no effect or disruptive effects. Different individuals showed larger or smaller learning effects. Brain imaging revealed that these behavioural differences related to natural variation between people’s brains. Those who showed large, long-lasting prism after-effects had strong connections in the reaching circuits of their brain and high levels of excitation in the brain area that controls hand movement. Those who showed smaller, short-lasting prism after-effects showed the opposite. People also differed in their response to stimulation. This also related to neurochemical differences in the region controlling hand movement. We found that older people had naturally stronger after-effects, which was related to neurochemical changes in the brain that are known to occur with ageing. Overall, this study discovered new information about how the brain controls this form of learning and how it can be enhanced by stimulation, which is relevant for improving rehabilitation of “spatial neglect” symptoms after stroke.
REC name
South Central - Oxford A Research Ethics Committee
REC reference
13/SC/0163
Date of REC Opinion
22 May 2013
REC opinion
Further Information Favourable Opinion