The proposed experiments test the feasibility of using a particular class of electrical responses extracted from the brainwaves as a non-behavioral method for measuring hearing at the audiometric frequencies. The High Rates Response (HRR) with which the research is concerned is recorded through scalp electrodes when brief tonebursts are presented at high rates (15-60 per sec.) through an earphone; it is closely related to the so-called middle latency (8 to 80 msec.) auditory evoked potentials and has other names (e.g., 40 Hz ERP, MLR40, SMLR, etc.). Previous research has shown that the HRR predicts hearing thresholds less accurately in uncooperative or sleeping children than in quiet, wide-awake adults. We believe this lack of accuracy is due in part at least to current use of a single measure only--HRR amplitude at one stimulus rate--in the data analysis. Our research proposes to replace this with a single response statistic developed out of the multiple measures available after the Fourier transformation of the HRR, an approach that should theoretically improve both the accuracy of HRR measurements and the detectability of threshold responses. If successful, the research will first of all describe the design requirements for a practical electric response audiometer that will use the HRR to make threshold estimates quickly, accurately and automatically. Second, it will provide a new, efficient measure of brain responses to above-threshold stimuli that may find useful neurological applications in sleep studies and the diagnosis of abnormal brain states.
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