Glioma Infiltration of Posterior Perisylvian Language Areas Disrupts Functional Responses in the Left Precentral Gyrus

Introduction: The dual speech coordination model asserts that there are two separate but interacting regions in the left precentral gyrus which coordinate speech production–the dorsal precentral speech area (dPCSA) and ventral PCSA (vPCSA). The dPCSA integrates auditory feedback for vocal pitch control and prosody, while the vPCSA integrates tactile and proprioceptive feedback for syllabic and phonetic articulation. Lesions to structures upstream from precentral speech coordination centers should down-regulate functional MRI (fMRI) responses in these regions. We hypothesized that: (1) Lesions to auditory processing supported by the posterior superior temporal gyrus would disrupt fMRI responses in the dPCSA when participants repeat sentences and hum melodies, and that (2) Lesions to somatosensory processing supported by the anterior left inferior parietal lobe would disrupt fMRI responses in the vPCSA when repeating sentences, but not when humming melodies.

Methods: Sixty-six pre-operative participants with left hemisphere lesions performed a speech and melody repetition task while undergoing fMRI. On every trial, they were presented with a sentence (“the boy stopped to tie his shoes”) or piano melody; they were instructed to listen to and repeat the stimulus after a rehearsal period.

Results: We find supporting evidence for both hypotheses: (1) Participants with lesions to the left posterior superior temporal gyrus had weaker fMRI responses in the dPCSA when repeating sentences and when humming melodies, and (2) Participants with lesions to the left inferior parietal lobule had weaker fMRI responses in the vPCSA when repeating sentences but not when humming melodies.

Conclusion : We provide causal lesion evidence to demonstrate language pathway specific disruptions to processing in the dominant precentral gyrus. Our results support the emerging dual speech coordination model, highlighting distinct but complementary roles for the dPCSA and vPCSA in integrating auditory and proprioceptive feedback for laryngeal and phonoarticulatory coordination.