There are three general classes of behavioral responses to a novel stimulus: startle, arousal and orientation. The startle response is a short latency set of muscular contractions induced by a brief stimulus, typically visual or acoustic. It is characteristic for the startle threshold to be much greater than the animal's detection threshold. Arousal behavior is characterized by a suite of physical responses. Although more subtle than startle behavior, both the effective stimuli and the responses are quite general with arousal, making investigation of the individual neural elements involved in novelty detection problematic. Although orienting responses have not been well defined in fish, the novelty response of pulse-type weakly electric fish fits best into this category as defined for mammals. The novelty response is a transient acceleration of the pacemaker which drives the fish's electric organ. Elicited by small stimulus changes near detection threshold, it is a subtle but reliable behavior which is not explosive, has a short refractory period, and involves a single effector pathway. The novelty response of pulse-type weakly electric fish is well suited to neurophysiological analysis and permits simultaneous measurement of behavioral and neural responses. Dr. Randy Zelick will continue his work on novelty detection in electric fish. This work is significant since it will give us a better understanding of the means by which the nervous system distinguishes novel from background sensory input. //
