Functional Dissociation Between Regularity Encoding and Deviance Detection Along the Auditory Hierarchy Publisher Pubmed



Aghamolaei M^{1, 2, 3} ; Zarnowiec K^{1, 2} ; Grimm S^{1, 2, 4} ; Escera C^{1, 2} Show Affiliations
Source: European Journal of Neuroscience Published:2016

Abstract

Auditory deviance detection based on regularity encoding appears as one of the basic functional properties of the auditory system. It has traditionally been assessed with the mismatch negativity (MMN) long-latency component of the auditory evoked potential (AEP). Recent studies have found earlier correlates of deviance detection based on regularity encoding. They occur in humans in the first 50 ms after sound onset, at the level of the middle-latency response of the AEP, and parallel findings of stimulus-specific adaptation observed in animal studies. However, the functional relationship between these different levels of regularity encoding and deviance detection along the auditory hierarchy has not yet been clarified. Here we addressed this issue by examining deviant-related responses at different levels of the auditory hierarchy to stimulus changes varying in their degree of deviation regarding the spatial location of a repeated standard stimulus. Auditory stimuli were presented randomly from five loudspeakers at azimuthal angles of 0°, 12°, 24°, 36° and 48° during oddball and reversed-oddball conditions. Middle-latency responses and MMN were measured. Our results revealed that middle-latency responses were sensitive to deviance but not the degree of deviation, whereas the MMN amplitude increased as a function of deviance magnitude. These findings indicated that acoustic regularity can be encoded at the level of the middle-latency response but that it takes a higher step in the auditory hierarchy for deviance magnitude to be encoded, thus providing a functional dissociation between regularity encoding and deviance detection along the auditory hierarchy. Using a spatial oddball paradigm that manipulated the difference between the standard and deviant stimuli, this study provides evidence for a functional dissociation between two levels of the auditory hierarchy in deviance processing. While higher levels of the hierarchy, associated to MMN, are able to detect the deviants and track the degree of deviance, lower levels associated to middle-latency response (MLR) generation, can only encode for regularities and detect deviance, but are unable to encode for the magnitude of change. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.