The influence of voice familiarity on the Mismatch Response in two- to four-month-old infants

Abstract

Our study investigated the influence of voice familiarity on the mismatch response (MMR) in infants between the age of two and four months (M: 98.53 days). The infant MMR is an event-related potential (ERP) component that reflects processes of preattentive deviance detection within a stream of frequent stimuli and is often described as a precursor of the adult mismatch negativity (MMN). In the past, the infant MMR and the adult MMN have been used to detect neural correlates for processes that lie beyond voice recognition. We targeted to elicited MMRs by an oddball paradigm that was presented to the infants. It consisted of the word ‘baby’ pronounced by three different female speakers (duration 10 min). The stimuli were presented as 1) a ‘standard stimulus’ (frequently presented stranger’s voice), 2) a ‘familiar deviant stimulus’ (in-frequently presented mother’s voice) and 3) an ‘unfamiliar deviant stimulus’ (infrequently presented stranger’s voice). For quantifying different subcomponents of the MMRs, the area amplitudes were determined for an early measurement window (100-300 ms post-stimulus) targeting an MMN-like early negativity (EN) and for a late measurement window (300-450 ms post-stimulus) capturing a positive component (PC). The MMRs to the mother’s and the stranger’s voice were compared. Between 100 and 300 ms, the area amplitude of the MMRs to the mother’s voice was significantly larger than the area amplitude of the MMRs to the stranger’s voice at a frontocentrally averaged scalp site. Our findings further suggest that an early MMN-like negative component (EN) was elicited in response to an infrequently presented unfamiliar voice. In the late measurement window, the area amplitude of the MMR to the mother’s voice tended to be more positive than to the stranger’s without reaching significance. From our results, it can be deduced that infants at the age of two-to-four months process a familiar voice differently than an unfamiliar one. A part of the processes behind voice recognition in early childhood presumably occurs preattentively and they seemed to be altered to some extend by long-term memory representations of the auditory recognition system.