Early differentiation of memory retrieval processes for newly learned voices and phonemes as indexed by the MMN

Linguistic and vocal information are thought to be differentially processed since the early stages of speech perception, but it remains unclear if this differentiation also concerns automatic processes of memory retrieval. The aim of this ERP study was to compare the automatic retrieval processes for newly learned voices vs phonemes. In a longitudinal experiment, two groups of participants were trained in learning either a new phoneme or a new voice. The MMN elicited by the presentation of the two was measured before and after the training. An enhanced MMN was elicited by the presentation of the learned phoneme, reflecting the activation of an automatic memory retrieval process. Instead, a reduced MMN was elicited by the learned voice, indicating that the voice was perceived as a typical member of the learned voice identity. This suggests that the automatic processes that retrieve linguistic and vocal information are differently affected by experience.