Sneha Shrestha with Matthew I. Banks, Ph.D., Michael Rummel, Cullen Rotroff, and
Rita Burlingame

UW-Madison Medical School, Department of Anesthesiology

Human beings are capable of identifying a myriad of sounds of varying frequency and duration. How that sound is encoded and processed in the auditory cortex, however, remains unknown. In order to better understand these processes, we needed to correlate specific patterns of brain activity and behavior with specific auditory stimulus patterns. This study attempted to find a correlation between the limits of rats’ abilities to discriminate between frequency-modulated (FM) sweeps in a behavioral task and the auditory-evoked potentials in the auditory cortex during electrophysiological recordings. One set of female Sprague-Dawley rats (rattus norvegicus) were trained in a task that involved the discrimination of FM sweeps (upsweeps and downsweeps). Thirteen FM pairs, with stimulus parameter varying in duration and frequency range, were chosen as the total stimulus set. Chronic epidural electrodes, implanted above the left auditory cortex of a different set of rats, recorded the auditory-evoked potentials (AEP) using the same stimulus set as in the behavioral tasks. The behavioral rats showed a decrease in their ability to discriminate FM-sweeps as the stimulus parameter for duration and range decreased. In some animals, auditory-evoked responses to the two stimuli became more similar as stimulus parameters were systematically varied. A correlation could be made between these evoked responses and the behavioral task results—evoked responses show more similarity as the stimuli became harder to discriminate.