Changes in early acoustic-evoked potentials by mildly arousing priming stimuli in carp (Cyprinus carpio).

1. Averaged acoustic-evoked potential (AEPs) in the medulla and midbrain were recorded, as were changes in heart rate, indicating arousal, to a previous non-acoustic priming stimulus. 2. Useful AEP measures were amplitude of the early biphasic wave (less than 10 msec) in medulla and amplitude and duration of this wave in midbrain. 3. There was a negative regression of heart rate and medullary AEP amplitude especially evident for a 2 sec light stimulus. Decreased AEP amplitude in both regions was induced by water movement and an increase in midbrain AEP duration by the tactile stimulus. 4. Arousal effects even on these early AEP measures are specific to the form of arousing stimulus.