Coherence analysis of scalp responses to amplitude-modulated tones

Abstract

Magnitude squared coherence is a method of auditory evoked potential (AEP) frequency-domain analysis, measuring the degree to which the AEP is determined by the stimulus as a function of frequency. In 10 normal-hearing human subjects, scalp responses to an amplitude-modulated (AM) tone (500 Hz carrier modulated with a 40 Hz envelope) were recorded. Critical value criteria were utilized in the statistical analysis of coherence-intensity functions for determination of threshold responses. When compared with subjective determination of AEP threshold from time-domain waveforms, coherence analysis provided a significantly (p < 0.001) more sensitive threshold measure. Coherence analysis provides information on the spectral content of the response, and allows for the objective determination of threshold which may potentially be utilized in a more expeditious threshold measurement scheme.

Key Words:

• auditory evoked potential
• auditory threshold
• frequency following response
• coherence
• amplitude modulation