We developed a neurofeedback paradigm based on the mirror neuron system in order to influence the function of neurons in the motor cortex with the goal of promoting therapeutic neuroplasticity. We used magnetoencephalography (MEG) to record sensorimotor rhythm activity from the motor cortex of people with chronic tetraplegia. Real-time video-based feedback was provided as they attempted to grasp or rest their hand. This essential connected intact cortical activity to a virtual limb. By directly targeting neuronal activity, we aim to facilitate neuroplasticity measured as increased sensorimotor rhythm modulation.
A system diagram is illustrated below (Reproduced from Foldes et al. Journal of NeuroEngineering and Rehabilitation (2015) 12:85). Beginning in the upper left, first, the power spectrum of data recorded from 36 sensorimotor MEG sensors (shown on a top-down view of the MEG helmet) are computed using 300 ms sliding windows. A mask is applied to these features to remove any components that did not exhibit desynchronization during calibration. Then a linear decoder applies weights (W) to the neural signal (N) to compute a hand velocity value (VH). The velocity output from the decoder is scaled (g) to ensure movement speeds are appropriate for the task. The previous hand position (an image from the video sequence) is then updated more closed or more opened within the ROM based on the scaled velocity command. The picture representing the desired aperture is chosen from 25 possible images. A progressive change in the images appeared to participants as a grasping movie with a 76 ms refresh rate
Initial results indicate that subjects are able to perform the neurofeedback task using modulation of sensorimotor rhythm activity after a short calibration period (<5 minutes). Some subjects have experienced significant changes in sensorimotor rhythm modulation after a single session. Long term neurofeedback training may be able to strengthen corticospinal pathways to the impaired upper limb and possibly with long term training improve function (increased strength) in muscles with partially intact corticospinal pathways, though this remains to be tested. This project was funded by the VA Rehabilitation Research and Development Service and the Craig H. Neilsen Foundation.