The effects of nembutal anesthesia on the auditory steady-state response (ASSR) from the inferior colliculus and auditory cortex of the chinchilla

In the IC, the administration of nembutal resulted in either no change in ASSR amplitude or an amplitude increase for difference tone (DT) frequencies below 90 Hz, while an amplitude decrease was typically seen for DT frequencies at or above 90 Hz. In the AC, a decrease in amplitude was seen across DT frequencies and stimulus levels after the administration of nembutal anesthesia. Our results suggest that both the AC and IC may contribute to the scalp-recorded ASSR in the awake state. However, in the nembutal-anesthetized state, it seems unlikely that the AC contributes substantially to the surface-recorded ASSR, as the AC response was greatly attenuated under nembutal anesthesia. In contrast, the IC ASSR responses remained robust, which makes it a likely contributor to the surface-recorded responses under nembutal anesthesia.