Hemispheric interactions during the pre-attentive change detection of different acoustic features in speech and non-speech sounds

Human brain shows a functional hemispheric asymmetry for auditory processing. Different acoustic features activate the left and right hemispheres differently depending on their nature. In addition, speechness (speech vs. non-speech) may also influence the dominant hemisphere for processing the feature. Anomalous asymmetry for a certain acoustic feature, therefore, may provide a clue to identify the source of deteriorated speech perception. It was shown that dyslexic adults have an abnormal asymmetry of the efferent auditory pathways that may cause their difficulties in speech perception (e.g., voicing discrimination) (Jacquier, 2008). The present study examined the effects of the speechness (speech or non-speech) and the ear (left vs. right) of stimulation for pre-attentive change detection of four types of auditory features, using the mismatch negativity (MMN) as an index. Furthermore, speech and non-speech sounds were presented either alone (monaural condition) or in parallel (dichotic condition) to investigate possible interference effects.