Mapping of the motor cortex using transcranial magnetic stimulation

Investigators: Dr Bev Phillips, Ms Ro Packer, Prof Mary Galea

Chronic stroke patients currently involved in a trial of task-related training are also invited to participate in this study which involves using transcranial magnetic stimulation (TMS) to map the representation of the hand in the motor cortex of the brain. Recent research into the potential for motor recovery suggests that the brain has dynamic and plastic properties and that a higher level of recovery should be possible given the appropriate intervention. The aim is to compare the degree of brain reorganisation pre- and post-intervention. This may provide some insight into the mechanisms underlying any change in upper limb function that is recorded as a result of the intervention.

TMS is a non-invasive process that involves placing a plastic cap with markings at 1cm intervals on the head of the subject. Magnetic stimulation is applied systematically over the skull and scalp positions where an EMG response is recorded in the first dorsal interrosseus or deltoid muscles are recorded. The stimulus is not painful and each one lasts for less than a second. EMG response is recorded using surface skin electrodes. The process will be repeated on the non-affected side of the brain for comparison. Adequate rests will be given during testing to reduce fatigue in weakened muscles. Variables to be evaluated include motor conduction time, duration of the silent period, threshold of stimulus intensity, MEP amplitude and location of map centre.

A project will also be undertaken to collect mapping data in healthy individuals and to examine the reproducibility of the techniques within our laboratory.

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