"Seminar on the coupling and decoupling neural activity in speech perception" Faith Chiu

Faith Chiu, UCL

Speech perception relies on the accurate identification of phonemes within an auditory string. These phonemes have been argued to be the smallest of meaningfully contrastive units in speech ; a change in phoneme will concurrently induce a change in meaning. Previous modelling efforts implicate that a change in word meaning (caused by a change in phoneme) causes a change in coupling activity in the cortical hierarchy (Schofield et al., 2009). However, MMN has been shown to reflect language-specific phonemic representations regardless of word meaning, even in non-words (Näätänen et al., 1997). To disentangle this phoneme-meaning relationship, I present preliminary results from a current study which applies Dynamic Causal Modelling (Kiebel et al., 2006) on elicited Mismatch Negativity responses to categorical speech sound changes. We notice condition-specific significant changes in effective connectivity for connection strengths involving the superior temporal gyri (STG) which are located within higher levels of the auditory cortical hierarchy.