A functional dissociation of the left frontal regions that contribute to single word production tasks
Date
2021
Type:
Article
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Abstract
Controversy surrounds the interpretation of higher activation for pseudoword compared to word reading in the left precentral gyrus and pars opercularis. Specifically,
does activation in these regions reflect: (1) the demands on sublexical assembly of articulatory codes, or (2) retrieval effort because the combinations of articulatory
codes are unfamiliar? Using fMRI, in 84 neurologically intact participants, we addressed this issue by comparing reading and repetition of words (W) and pseudowords
(P) to naming objects (O) from pictures or sounds. As objects do not provide sublexical articulatory cues, we hypothesis that retrieval effort will be greater for object
naming than word repetition/reading (which benefits from both lexical and sublexical cues); while the demands on sublexical assembly will be higher for pseudoword
production than object naming.
We found that activation was: (i) highest for pseudoword reading [P>O&W in the visual modality] in the anterior part of the ventral precentral gyrus bordering the
precentral sulcus (vPCg/vPCs), consistent with the sublexical assembly of articulatory codes; but (ii) as high for object naming as pseudoword production [P&O>W]
in dorsal precentral gyrus (dPCg) and the left inferior frontal junction (IFJ), consistent with retrieval demands and cognitive control.
In addition, we dissociate the response properties of vPCg/vPCs, dPCg and IFJ from other left frontal lobe regions that are activated during single word speech
production. Specifically, in both auditory and visual modalities: a central part of vPCg (head and face area) was more activated for verbal than nonverbal stimuli
[P&W>O]; and the pars orbitalis and inferior frontal sulcus were most activated during object naming [O>W&P]. Our findings help to resolve a previous discrepancy
in the literature, dissociate three functionally distinct parts of the precentral gyrus, and refine our knowledge of the functional anatomy of speech production in the
left frontal lobe.
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Citation
Ekert JO, Lorca-Puls DL, Gajardo-Vidal A, Crinion JT, Hope TMH, Green DW, Price CJ. A functional dissociation of the left frontal regions that contribute to single word production tasks. Neuroimage. 2021 Dec 15;245:118734. doi: 10.1016/j.neuroimage.2021.118734. Epub 2021 Nov 16. PMID: 34793955; PMCID: PMC8752962.
Keywords
Reading, Pattern Recognition, Visual, Physiology, Brain Mapping