Temporal lobe regions engaged during normal speech comprehension

J. T. Crinion, M. A. Lambon-Ralph, E. A. Warburton, D. Howard, R. J. S. Wise
2003 Brain  
Processing of speech is obligatory. Thus, during normal speech comprehension, the listener is aware of the overall meaning of the speaker's utterance without the need to direct attention to individual linguistic and paralinguistic (intonational, prosodic, etc.) features contained within the speech signal. However, most functional neuroimaging studies of speech perception have used metalinguistic tasks that required the subjects to attend to speci®c features of the stimuli. Such tasks have
more » ... ed a forced-choice decision and a motor response from the subjects, which will engage frontal systems and may include unpredictable top-down modulation of the signals observed in one or more of the temporal lobe neural systems engaged during speech perception. This study contrasted the implicit comprehension of simple narrative speech with listening to reversed versions of the narratives: the latter are as acoustically complex as speech but are unintelligible in terms of both linguistic and paralinguistic information. The result demonstrated that normal comprehension, free of task demands that do not form part of everyday discourse, engages regions distributed between the two temporal lobes, more widely on the left. In particular, comprehension is dependent on anterolateral and ventral left temporal regions, as suggested by observations on patients with semantic dementia, as well as posterior regions described in studies on aphasic stroke patients. The only frontal contribution was con®ned to the ventrolateral left prefrontal cortex, compatible with observations that comprehension of simple speech is preserved in patients with left posterior frontal infarction. Abbreviations: FG = fusiform gyrus; fMRI = functional MRI; IFG = inferior frontal gyrus; IPL = inferior parietal lobe; PAC = primary auditory cortex; SPMs = statistical parametric maps; STS = superior temporal sulcus; STG = superior temporal gyrus; T+ = the six subjects in this group were asked to identify, at the end of each scan, whether there were two or three different narrators in each story and reversed story; T± = the 11 subjects in this group were asked to listen closely to the stimuli but there was no explicit task demand. with the clinical literature on so-called word deafness (an agnosia for speech associated with little, if any, impairment of Brain 126(5) ã Guarantors of Brain 2003; all rights reserved
doi:10.1093/brain/awg104 pmid:12690058 fatcat:ddhqtpgk3fdffdgpzx2iecjh2u