Halai AD, Parkes LM, Welbourne SR. Dual-echo fMRI can detect activations in inferior temporal lobe during intelligible speech comprehension.
Neuroimage 2015;
122:214-21. [PMID:
26037055 PMCID:
PMC4627358 DOI:
10.1016/j.neuroimage.2015.05.067]
[Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 05/22/2015] [Accepted: 05/24/2015] [Indexed: 11/29/2022] Open
Abstract
The neural basis of speech comprehension has been investigated intensively during the past few decades. Incoming auditory signals are analysed for speech-like patterns and meaningful information can be extracted by mapping these sounds onto stored semantic representations. Investigation into the neural basis of speech comprehension has largely focused on the temporal lobe, in particular the superior and posterior regions. The ventral anterior temporal lobe (vATL), which includes the inferior temporal gyrus (ITG) and temporal fusiform gyrus (TFG) is consistently omitted in fMRI studies. In contrast, PET studies have shown the involvement of these ventral temporal regions. One crucial factor is the signal loss experienced using conventional echo planar imaging (EPI) for fMRI, at tissue interfaces such as the vATL. One method to overcome this signal loss is to employ a dual-echo EPI technique. The aim of this study was to use intelligible and unintelligible (spectrally rotated) sentences to determine if the vATL could be detected during a passive speech comprehension task using a dual-echo acquisition. A whole brain analysis for an intelligibility contrast showed bilateral superior temporal lobe activations and a cluster of activation within the left vATL. Converging evidence implicates the same ventral temporal regions during semantic processing tasks, which include language processing. The specific role of the ventral temporal region during intelligible speech processing cannot be determined from this data alone, but the converging evidence from PET, MEG, TMS and neuropsychology strongly suggest that it contains the stored semantic representations, which are activated by the speech decoding process.
Intelligible speech comprehension activates bilateral superior temporal lobe.
Critically, intelligibility also activates anterior inferior temporal lobe.
Phonological processing does not activate inferior temporal lobe.
fMRI results converge with existing PET, MEG and neuropsychology.
Anterior inferior temporal lobe is involved during speech comprehension.
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