UBC Theses and Dissertations

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UBC Theses and Dissertations

Novel methodology to map the motor cortex Ayling, Oliver G. S.


It is very well established that the motor cortex has a distinct cortical location that can be mapped in a variety of species from mice to humans. Traditionally, mapping the motor cortex requires electrodes to stimulate the brain and define motor output pathways. Although effective, electrode-based methods are labor-intensive, potentially damaging to the cortex, can have off-target effects, and are not well suited to long-term application in the same brain due to its invasive nature. As an alternative method to traditional motor mapping, transgenic mice expressing the light-sensitive ion channel channelrhodopsin-2 in predominantly layer-5 output cortical neurons were photostimulated. Implanted electromyogram electrodes or a noninvasive motion sensor were used as a readout of motor cortex output. In addition, electroencephalogram electrodes were used to directly monitor the activity of the motor cortex during periods of optical stimulation. Optical stimulation with a 473 nm laser was delivered to hundreds of cortical locations, in vivo, using a stage scanning laser system. Electrophysiological signals from the muscles and the cortex were used to create highly reproducible automated maps of the mouse forelimb and hindlimb motor cortex much faster than with previous methods. This method was well suited to mapping the same brain over a period of weeks using an implanted cranial window. It is anticipated that this novel methods will facilitate the study of changes in the location and properties of motor maps after skilled training or damage to the nervous system.

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