The cortical endogenous late potential in response to ultrasonic signals in the estrous rat.

The evoked responses to 100-ms tone signals of 8, 22, 50 or 70 kHz were recorded from the frontal cortex in the conscious female rat throughout the estrous cycle. The stimulus-bound evoked potentials did not vary with the estrous cycle. At estrus, 50 kHz sounds produced a negative potential peaking at 200 ms in the cortex. In other combinations of sound frequency and estrous stage no late potentials were detected. This finding demonstrates the presence of human 'Event-related potential'-like endogenous potentials in the rat that responds to ultrasonic signals which mimic those used in intraspecific communication.