Comparison of auditory cortical N1 responses evoked by regularity detection in different auditory contexts

Auditory scene analysis is the name of the process consisting of the integration and segregation of sound streams in highly complex environments. One of the processes in this analysis is the extraction of auditory regularities. Detecting auditory regularities is crucial for tracking important signals in a complex scene. Various electrophysiological studies exist in the literature on this issue using different stimulus sequences. To understand the organization of sound processing in the auditory system, using a variety of stimuli is noteworthy. In this sense, this study was conducted to compare the auditory cortical N1 responses evoked by regular sound patterns with a decreasing frequency which is embedded in random sounds (rand\_dec\_2) and regular sound with decreasing frequency in isolation (rand\_dec) both appearing after random frequency sounds. Moreover, behavioural responses were examined for these stimuli. 20 participants between the ages of 22-31 without hearing problems participated in the study. It was observed that the N1 amplitudes were smaller and latencies were longer for the N1 responses evoked by rand\_dec\_2 where auditory scene was more complicated (p<0.001). In addition, behavioural results showed that regularity detection for rand\_dec\_2 was more difficult compared to rand\_dec (p<0.001). The findings show that auditory regularities can also be noticed when they are embedded in different sounds and they have cortical representations. In addition, it is observed that these representations are less robust than the conditions in which regularities are isolated, and behavioral detection is more difficult than in the isolated condition. People with speech understanding in noise problems can be involved in future studies for investigating the relation between speech in noise scores and auditory cortical N1 responses.