Common neural substrates support speech and non-speech vocal tract gestures

Area of Science:

• Neuroscience
• Cognitive Science
• Speech Science

Background:

• The neural basis of speech production is debated, particularly regarding shared substrates with non-speech vocal tract gestures.
• Previous research has implicated specific brain regions in speech processing, but the extent of overlap with non-speech vocalizations remains unclear.

Purpose of the Study:

• To investigate whether producing non-speech vocal tract gestures engages the same neural regions as producing non-sense speech syllables.
• To compare brain activation patterns between speech and non-speech vocal production using functional magnetic resonance imaging (fMRI).

Main Methods:

• Blood-oxygen-level-dependent (BOLD) fMRI with a sparse sampling design was employed to capture brain activity during overt speech and non-speech vocal tract gesture production.
• Voxel-wise whole-brain analyses and region of interest (ROI) analyses focused on frontal and temporoparietal areas were conducted.
• Activation patterns for speech and non-speech conditions were directly compared.

Main Results:

• Significant overlap in brain activation was observed between speech and non-speech vocal tract gesture production.
• Non-speech gestures exhibited greater activation extent and amplitude in examined regions compared to speech.
• Both conditions demonstrated comparable leftward lateralization in activation for target perception and production.

Conclusions:

• The findings suggest that the left hemisphere's auditory dorsal stream plays a more generalized role in vocal tract gesture production, extending beyond speech.
• The neural mechanisms supporting speech production may encompass a broader range of vocal behaviors than previously assumed.
• This research refines our understanding of the neuroanatomy underlying human vocal communication.