Frequency-following potentials in man by lock-in technique.
Frequency-following responses (FFR) from continuous tone stimulation were investigated by lock-in analysis. The technique is superior to conventional tone-burst stimulation, because it allows continuous registration of the response parameters with sweeping frequency. The scalp recorded FFR consists of at least two components separable from each other by their phase/frequency relationship. The microphonic component that dominates in ipsilateral records shows latencies of about 0.5 msec with negligible dispersion and must therefore originate in the basal cochlear turn. The neural component exhibits considerable dispersion, reflecting the travelling wave delay up to the region of best frequency. These long cochlear time delays are consistent with an apical FFR origin, and brain stem sources of the continuous tone response appear to be questionable. The present FFR analysis technique opens up a very direct and comprehensive way to assess the integrity of the entire inner ear for high frequency basal and low frequency apical cochlear regions as well.
D000161:Acoustic Stimulation; D000669:Amplifiers, Electronic; D001299:Audiometry / Q000379:methods*; D001300:Audiometry, Evoked Response / Q000379:methods*; D001921:Brain / Q000502:physiology; D003051:Cochlea / Q000502:physiology; D006801:Humans; D011930:Reaction Time; D013997:Time Factors