A rapid startle response in larval lampreys.

Electromyography (EMG) and cinematography revealed a rapid, vibration-evoked startle response in intact larval lampreys. Vibratory stimuli produce simultaneous contraction of both sides of the body, and the response is lost after labyrinthectomy. Midbody EMGs exhibit a stimulus-response latency of 26.5 +/- 4.2 ms. Direct stimulation of the otic capsules, using an electrically driven probe applied to a semi-intact preparation, first evokes a volley of giant axon spikes in the spinal cord followed by the bilateral trunk response.