Comprehension of degraded speech sounds with m-sequence modulation: An fMRI study

In a recent electroencephalography (EEG) study (Takeichi et al., 2007a). we developed a new technique for assessing speech comprehension using speech degraded by in-sequence modulation and found a correlation peak with a 400-ms delay. This peak depended oil the comprehensibility of the modulated speech sounds Here we report the results of a functional magnetic resonance imaging (fMRI) experiment comparable to out previous EEG experiment. We examined brain areas related to verbal comprehension of the modulated speech Sound to examine which neural system processes this modulated speech A non-integer. alternating-block factorial design was used with 23 Japanese-speaking participants, with time reversal and m-sequence modulation as factors A main effect of time reversal was found in the left temporal cortex along the superior temporal sulcus (BA21 and BA39). left precentral gyrus (BA6) and right inferior temporal gyrus (BA21) A main effect of modulation was found in the left postcential gyrus (BA43) and the right medial frontal gyn (BA6) as an increase by modulation and in the left temporal cortex (BA21, 39), parahippocampal gyrus (BA34), posterior cingulate (BA23). caudate and thalamus and right SUpeiior temporal gyrUS (BA38) as a decrease by modulation. Ail interaction effect associated specifically with non-modulated speech Was found in the left frontal gyrUS (BA47), left occipital cortex in the COMM (BA18), left precuneus (BA7, 31). i ight precuneus (BA31) and right thalamus (forward>reverse) The other interaction effect associated specifically with modulation of speech sound was found in the inferior frontal gyrUS in the opercular area (BA44) (forward>reverse). Estimated scalp projection of the component correlation function (Cao et a], 2002) for the corresponding EEG data (Takeichi et al. 2007a, showed leftward dominance Hence, activities in the superior temporal sulcus (BA21 and BA39). which are commonly observed for speech processing. as well as left precentral gyrus (BA6) and left inferior frontal gyrUS in the opercular area (BA44) is suggested to contribute to the comprehension-related EEG signal. (C) 2009 Elsevier Inc All rights reserved