Auditory Cortical N1 Response Evoked by Auditory Closure

This study aims to investigate auditory figure detection and related cortical N1 responses in auditory scenes in which some figure elements are not accessible to the listeners. For this aim, figure detection evoked cortical N1 response amplitude and latencies, behavioral detection hit rates, and reaction times are compared between two types of stimuli, where the auditory figure was either complete or some elements of the figure were replaced by random tones, both appearing after a chain of tones at randomly selected frequencies.

Behavioral auditory figure detection scores (hit rates and reaction times) and cortical N1 responses evoked by auditory figures were collected from 20 participants (10 females and 10 males) aged between 20 and 31 (mean = 23.95, SD = ±2.41) with self-reported normal hearing, without neurological or psychiatric problems or using related medication. The two types of auditory figures, both of which appeared after a chain of random tones, were as follows: an auditory figure made up of a repeating tone ("random-constant") and the same auditory figure with some of the figure elements replaced by random tones ("random-constant-interrupted"). As a control stimulus, a tonal chain made up of only randomly selected tones ("random") was also presented. Thirty "random," 35 "random-constant," and 35 "random-constant-interrupted" stimuli were generated. After a training session on detecting auditory figures, auditory evoked potentials were recorded with these three stimuli while participants engaged in an active detection task.

Figure detection N1 amplitudes were significantly larger, and latencies were shorter for "random-constant" compared with "random-constant-interrupted." In terms of behavioral results, reaction times were shorter, and hit rates were higher for the stimulus "random-constant" compared with "random-constant-interrupted."

Auditory figures can be detected even when some parts are replaced with random tones, rendering some tonal elements of the figures inaccessible. The figures appearing in isolation are more robustly represented in the auditory system compared with figures with missing parts. Utilization of more complex auditory figures with different levels of concealment may be suggested for future work.