Scientists Use MRI to Prove How Brain Re-maps Motor and Sensory Pathways after TMSR

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Targeted muscle and sensory reinnervation (TMSR) alters the style the brain processes somatosensory input and motor output. To show how the TMSR affects the upper limb representations in the brains of patients and with amputations, EPFL has been using the ultra high end field 7 Tesla fMRI. The findings are published in the Brain. However, the investigation of the detailed brain mechanisms has never been done in the past.

To improve the control of upper limb prosthesis, targeted muscle and sensory reinnervation (TMSR) is used. In order to reinnervate and activate new muscle targets, residual nerves from the amputated limb are transferred. This is the process how a patient with TMSR prosthetic sends motor commands to the re innervated muscles, where the patient’s movement intentions are decoded and forwarded to the prosthetic limb.

In order to measure the activities of the brain by detecting changes in the blood flow, ultra high field 7T functional magnetic resonance imaging (FMRI) were used by the scientists. The patients who were using standard prosthesis showed that the motor cortex maps of the amputated limb differed in terms of extent, strength and topography and were similar to individuals without limb amputation. This technique could even figure out maps of missing (phantom) fingers in the somatosensory cortex of the TMSR patients that got activated from the chest or residual limb through the reinnervated skin regions.

The study has also showed that TMSR requires more improvement and that the connections between the motor cortex and primary sensor with high level embodiment regions were weak in the TMSR patients and differed from healthy subjects.

 

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