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Poster D1, Friday, August 17, 4:45 – 6:30 pm, Room 2000AB

How does functional connectivity between domain-general and language networks relate to sentence comprehension? A resting-state fMRI study in older adults

Megan C. Fitzhugh1, Leslie C. Baxter2, Corianne Rogalsky1;1Arizona State University, 2Barrow Neurological Institute & St. Joseph’s Hospital and Medical Center

As many as one-third of older adults without dementia experience difficulties understanding conversations in their everyday lives. While comprehending speech in quiet environments or with simple sentence structures remains relatively preserved in older adults, their ability to comprehend speech in noisy environments or with more complex sentence structures can be reduced, and not fully explained by hearing loss. Research in older adults suggests that as we age, the traditionally-defined left-lateralized frontotemporal language network may not be sufficient to process relatively complex or degraded speech, requiring additional domain-general resources to maintain a sufficient level of comprehension. Such resources include the cingulo-opercular and frontoparietal brain networks associated with selective attention and working memory, respectively. Yet the degree to which these networks can support language comprehension in challenging situations remains unclear. The present study examines how functional connectivity between domain-general brain networks and the language network are related to difficult sentence comprehension performance in older adults. Twenty adults aged 60 to 80 years completed the experimental protocol. Participants were all native English-speaking, right-handed, and without cognitive impairment as measured by the Mini-Mental Status Examination. Participants completed a sentence-picture matching task with six conditions: sentences varied by two types of sentence structure (canonical and noncanonical word order) and three types of masker (multispeaker babble, broadband noise, or none). The canonical sentences presented without a masker served as a control condition to which performance in the other conditions was compared. Accuracy and reaction times were recorded. A 10-minute resting-state fMRI scan, pure tone audiometry, and several cognitive and psycholinguistic measures were obtained. The CONN Toolbox using SPM12 functions (http://www.nitrc.org/projects/conn) was used to preprocess the resting-state fMRI data and compute functional connectivity measures between the networks of interest (frontoparietal, cingulo-opercular, and language networks). Multiple regression models were then used to determine the relationship between functional connectivity measures and sentence comprehension performance in each condition. Age, hearing status, and vocabulary and processing speed measures were included in the models as covariates. Accuracy in the sentence comprehension conditions was not significantly related to any of the functional connectivity measures. However, reaction time results reveal: (1) reaction time in multispeaker babble was significantly positively correlated with functional connectivity between the cingulo-opercular and language networks and (2) reaction time for noncanonical sentences was significantly positively correlated with the functional connectivity between the frontoparietal and language networks. These initial results suggest that increased effort in comprehending challenging sentences (defined as longer reaction times) in older adults is related to greater network connectivity between the language network and specific domain-general networks, and that the cingulo-opercular and frontotemporal networks contribute to difficult sentence comprehension in unique ways. Future studies are needed to determine if these increased functional connectivities between domain-general and language networks reflect compensatory mechanisms in older adults, and to further characterize the distinct contributions of the frontoparietal and cingulo-opercular networks to sentence comprehension.

Topic Area: Control, Selection, and Executive Processes

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