As NMJ electrophysiology is performed in third instar larvae, the method is not easily applied to longitudinal studies. The giant fiber system (GFS) in adult flies, however, is amenable to in vivo electrophysiology. Electrodes are applied to the eye, stimulating the giant fiber neurons in the brain. The GFS then activates the fly’s “flight” muscles in response to change in light exposure. GFS recordings have been used to study epilepsy and seizures.