Effect of Cephalic Versus Noncephalic Electrode Montage on the Amplitude-Modulated Frequency-Following Response

The frequency-following response (FFR) is an auditory electrophysiological response that reflects the spectrotemporal characteristics of an acoustic stimulus with high fidelity. Electrode montage has a significant impact on the recorded response, likely because it influences the neural generator contributions. However, the relationship between montage configuration, especially the location of the inverting electrode, and FFR parameters remains unclear. This study aimed to investigate the effect of cephalic versus noncephalic inverting electrode placements on FFR characteristics in adults. Clarifying this relationship can help optimize montage selection for improving the clinical and research application of FFR recordings.

In this cross-sectional study, FFRs were recorded from 38 healthy adults (11 men, 27 women; mean age = 21.8 ± 2.3 years). Five amplitude-modulated tones with modulation frequencies of 85, 100, 115, 130, and 145 Hz were used. The responses were recorded simultaneously with 2 electrode montages of the vertex to ipsilateral mastoid (cephalic) and the vertex to the seventh cervical vertebra (noncephalic), and their amplitudes, phase values, and residual noises were measured and compared using independent sample t tests and repeated measures analysis of variance.

The results showed roughly similar amplitudes (85 Hz: P = 0.541, 100 Hz: P = 0.867, 115 Hz: P = 0.511, 130 Hz: P = 0.774, 145 Hz: P = 0.608), while significantly different noise (85 Hz: P = 0.526, 100 Hz: P = 0.244, 115 Hz: P = 0.022, 130 Hz: P = 0.003, 145 Hz: P = 0.071) and phase values (85 Hz: P = 0.720, 100 Hz: P = 0.002, 115 Hz: P = 0.001, 130 Hz: P = 0.001, 145 Hz: P = 0.704) were observed between the 2 electrode montages. Moreover, the noncephalic montage exhibited lower between-subject variability.

The results demonstrated that both electrode montages could be reliably used for recording FFR. However, noncephalic montage may offer practical advantages in clinical and research contexts due to reduced variability and improved response consistency, thus enhancing the diagnostic accuracy and efficiency of auditory assessments.