Regularity of background auditory scene and selective attention: A brain oscillatory study.

There are scarce data related to the facilitative effects of regularity encoding on auditory selective attention during every day listening conditions. Therefore, present study aimed to investigate how temporal and spectral regularities of background auditory stream affect auditory selective attention at both levels of brain neural oscillatory activities and involved cortical locations. EEG was recorded in healthy young adults listening to two concurrent auditory streams including background and foreground ones in three conditions differing for background auditory stream which was characterized by having spectral or temporal sound regularities and random structure. The neural sources of EEG bands during recognizing target sounds in the foreground stream were determined via standardized Low-Resolution brain Electromagnetic Tomography (sLORETA). Sound regularities of the background auditory stream had no significant effect on the EEG relative power during the task of selective attention. In all conditions, there was a significant increase in the relative power of EEG alpha and beta frequency bands. sLORETA localized significant increase of mentioned bands in the precuneus of parietal lobe; medial frontal gyrus of frontal lobe and insula of sub-lobar in temporal regularity, spectral regularity and random conditions respectively. These results revealed that although temporal and spectral acoustic regularities of competitor auditory stream had no facilitative effect on alpha-related brain processing during selective attention, different brain cortical locations were activated with the introduction of these regularities. This result might provide preliminary evidence for some degree of brain neural specialization in the processing of temporal and spectral regularities during auditory selective attention tasks.