The effects of aging on early stages of the auditory deviance detection system

Abstract Objective The aging effects on auditory change detection have been studied using the Mismatch Negativity (MMN) potential. However, recent studies have found earlier correlates of deviance detection at the level of the middle-latency response (MLR) and the effects of aging on this deviant-related response have not yet been clarified. The purpose of this study was to examine the effects of aging on both levels of the auditory deviance detection system. Methods MMN and MLR responses were recorded in 33 young and 29 older adults from 32 scalp electrodes during frequency oddball and swapped-oddball conditions. Results In the young group, modulation of MLR and a clear MMN response were observed, whereas in the aged group, no evidence of deviance detection was found at the level of MLR and the MMN amplitude was significantly diminished. Conclusions Based on the obtained results, aging affects both levels of the auditory deviance detection system which seems to be a result of deficits in regularity encoding along the auditory hierarchy. Significance The current findings suggest that age-related physiological changes result in deficits in regularity encoding, starting from early stages of processing. This might eventually affect stream segregation and induce difficulties in understanding speech in complex environments.