Roles of ventral versus dorsal pathways in language production: An awake language mapping study

Area of Science:

• Neuroscience
• Cognitive Science
• Neurolinguistics

Background:

• Human language processing involves distinct dorsal and ventral streams in the left hemisphere.
• The precise functional division between these streams (e.g., motor vs. semantic, sequential vs. combinatorial) remains debated.

Purpose of the Study:

• To investigate the distinct roles of the dorsal and ventral language pathways in sentence generation and semantic processing.
• To determine if dorsal pathways are critical for sequential ordering and ventral pathways for semantic dependencies.

Main Methods:

• Direct cortical stimulation and subcortical resection during awake language mapping in 17 neurosurgical patients.
• Utilized a sentence generation (SG) task and a picture-word interference (PWI) task to assess sequential and semantic processing.
• Analyzed diffusion imaging connectivity maps seeded in tumor sites to correlate with functional deficits.

Main Results:

• Increased errors in the SG task compared to the PWI task were observed during subcortical testing in the dorsal stream territory.
• High error rates in both SG and PWI tasks occurred in the ventral stream territory.
• Tumor locations associated with dorsal stream connectivity correlated with higher SG than PWI errors, and vice versa for the ventral stream.

Conclusions:

• Provides evidence that dorsal pathways are essential for organizing words sequentially for sentence generation.
• Suggests ventral pathways are critical for processing semantic dependencies, independent of sequential order.
• Highlights the functional specialization of dorsal and ventral language streams based on fiber tract disruption.