Spotlight Research: Neural Correlates of Discourse Production in Individuals with Aphasia

Figure a) fNIRS probe design overlayed on template cortex with markers indicating channel data averaged to create an ROI.

Figure b) fNIRS probe sensitivity with warmer colors indicating higher sensitivity to cortex

Boston University PhD Graduate Dr. Emily J Braun Presents her Thesis: Neural Correlates of Discourse Production in Individuals with Aphasia

Dr. Emily J Braun’s thesis was titled Behavioral and Neural Evaluation of Discourse Production in Neurotypical Individuals and Individuals With Aphasia. This project analyzed the complex nature of discourse to address the gap in research caused by studies focusing on word-level tasks. Her study evaluated brain activity during longer speaking tasks such as answering conversational questions in individuals with and without aphasia using a technology called functional near-infrared spectroscopy (fNIRS). fNIRS allows us to evaluate brain activity while individuals are sitting upright and naturally conversing with people. This technology opens the door to evaluating brain activity for everyday speaking tasks in people with aphasia.

The study found greater brain activity in key language regions for language formulation tasks in long form conversation-like situations, as compared to short repetitive tasks such as repeating sentences or counting aloud. The results showed apparent differences between healthy individuals and individuals with aphasia.

In her dissertation, Dr. Emily J. Braun explained her experiments and results

“The first experiment evaluated cortical activity and behavioral response quality during a computer-based simulated conversation. Results of this experiment showed greater left frontotemporal cortical activity (frontal regions and temporal regions of the brain) while answering questions as compared to a control condition (sentence repetition) in healthy individuals, suggestive of activation of a left-lateralized language network for this discourse-level formulation task. The second experiment evaluated cortical activity and behavioral response quality during a task where participants watched videos and explained what they watched. Results of this experiment showed greater bilateral frontotemporal cortical activity during the experimental condition (narrative production) as compared to a control condition (counting aloud) in all three groups. The third experiment evaluated cortical activity while answering conversational questions from a conversation partner. Preliminary results of this experiment show greater cortical activity during the experimental condition (answering questions) as compared to the control condition (sentence repetition) in both left and right hemisphere frontotemporal regions.” 

The results of these experiments showed patterns that suggest a difference in areas of the brain that are used to support discourse and complex cognitive tasks, versus repetitive short form tasks. Dr. Braun’s research was made possible with the use of fNIRS technology, which is not yet widely used to evaluate brain activity in people with aphasia. The results of this study show that fNIRS is a promising tool for understanding brain function for real-world tasks after stroke.

For more information on this project, see the Boston University Neurophotonics Center website

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