Human short-latency auditory responses obtained by cross-correlation

Short-latency auditory responses were obtained by cross-correlation of continuous, pseudorandom noise stimuli with averaged scalp potentials from adults with normal hearing. Responses were recorded for spectrum levels of 14-74 dB for noise bandwidths from 800 to 6000 Hz. At the lowest intensity level of broadband noise, all 10 subjects showed replicable cross-correlation functions (CCFs), which were characterized by prominent positive peaks at delays (latencies) of 5-7 msec. Male subjects exhibited longer delays than females. Delay (latency) increased with decreasing stimulus intensity. Very early responses (< 2 msec) attributable to cochlear microphonic, which were prominent in earlier work on guinea pigs, were not well seen in these human data. CCFs for responses to band-limited stimuli and off-line derivation of band-limited CCFs for responses evoked by broadband stimuli both showed that this technique is most sensitive to frequency-following behavior at low frequencies (< 800 Hz). However, definite phase-locked responses to even the highest passband (3100-6200 Hz) were seen. These results support the use of the CCF technique as an efficient method of frequency-specific assessment of the auditory system.