Sign language narrative reveals universal and modality-specific features of cortical timescale hierarchy

Area of Science:

• Neuroscience
• Linguistics
• Cognitive Science

Background:

• Human languages uniquely enable storytelling, engaging hierarchical neural processing from words to narratives.
• Neuroimaging studies show spoken language comprehension involves a neural time-scale hierarchy.
• Sign languages share features with spoken languages but use unique modality-specific elements (hands, face, space).

Purpose of the Study:

• To investigate which aspects of the language hierarchy are speech-specific versus modality-general.
• To examine neural processing of sign language narrative comprehension using naturalistic fMRI.
• To identify universal and modality-specific neural signatures in language processing.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used with native signers.
• Participants watched a sign language interpretation of a narrative and its scrambled versions.
• Naturalistic stimuli were employed to study brain activity during comprehension.

Main Results:

• Signed narratives synchronize hierarchical neural networks, similar to spoken language.
• A modality-invariant dissociation was found: frontotemporal regions track sentence structure, while the Default Mode Network tracks plot.
• New neural signatures for sign language were identified: superior parietal cortex for discourse timescales and ventral occipital cortex for word/sentence processing.

Conclusions:

• Signed narratives engage hierarchical neural networks, supporting modality-invariant aspects of language processing.
• The study identified novel neural correlates for sign language processing, including discourse-level and word/sentence-level tracking.
• These findings highlight both universal mechanisms and potential modality-specific adaptations in the neurobiology of language.