Spontaneous electrical activity of a trigeminal mesencephalic neuron responsive to spontaneous macrovibrissae movement and masseter stretching. (A) Spontaneous electrical activity of a trigeminal mesencephalic neuron under basal conditions (i.e., with vibrissae in resting position). (B) The same activity during the masseter stretch. Arrows indicate the beginning ("on") and the end ("off") of muscle stretching. (C) The same activity during fan-like movement of the macrovibrissae bundle and (D, E) during rhythmic whisking movements at different frequencies. Calibrations: horizontal, indicated in picture; vertical 250 μV for all recordings.