The video below demonstrates the use of blue light to stimulate channelrhodopsin-2 (ChR-2) proteins that have been artificially expressed in the membranes of neurons in the motor cortex of a live mouse. The experimenter is able to control the mouse's movement optically by using ChR-2 as a light-gated ion channel. Since motor control is lateralized and only one side of the motor cortex has been transfected with ChR-2, the mouse involuntarily walks in a circle when the light is on, and can walk normally when the light is off.

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Demonstration of using ChR-2 to optically control neuronal activity in a mouse.