Resting-State Connectivity in Acute and Subacute Poststroke Aphasia: A Functional Near-Infrared Spectroscopy Pilot Study

Abstract

Background:

Understanding how brain function and language skills change during early (acute and subacute) stroke phases is critical for maximizing patient recovery, yet functional neuroimaging studies of early aphasia are scarce. In this pilot study, we used functional near-infrared spectroscopy (fNIRS) to investigate how resting-state functional connectivity (rs-FC) in early aphasia differs from neurologically healthy adults and is related to language deficits.

Materials and Methods:

Twenty individuals with aphasia (12 acute and 8 subacute phase) and 15 healthy controls underwent rs-fNIRS imaging with a 46-channel montage centered over bilateral perisylvian language areas. FC was computed using a prewhitening, autoregressive Pearson correlation routine applied to preprocessed oxyhemoglobin (HbO) data. Connections were classified as left intra-, right intra-, or interhemispheric. We then compared rs-FC between groups by connection type and examined Spearman correlations between rs-FC averages and language measures within patients.

Results:

Participants in the acute phase had significantly reduced global rs-FC across all HbO-based connections compared to healthy controls. No significant differences were found in rs-FC between controls and patients in the subacute phase. Controlling for days since stroke, stronger right intra- and interhemispheric rs-FC was related to milder aphasia across all patients. Exploratory correlations revealed that relationships between language measures and rs-FC differed between acute and subacute patient groups.

Conclusion:

This study provides preliminary evidence that fNIRS-based rs-FC measures may be a viable metric to index the early impacts of stroke in people with aphasia.

Impact statement

Questions regarding the nature of neural recovery in early poststroke aphasia mostly remain unanswered, largely due to the shortage of functional imaging studies in this population. Logistical challenges of magnetic resonance imaging are central barriers to early stroke imaging. Functional near-infrared spectroscopy (fNIRS) is a promising alternative as it is relatively inexpensive and portable. Resting-state functional connectivity (rs-FC) provides an avenue to avoid the confounds of task demands and difficulties inherent in task-based imaging studies. The importance of this pilot study lies in its first-ever application of fNIRS-based rs-FC to investigate brain–behavior relationships in acute and subacute aphasia.