Eon'eo Cheong'gag Jang'ae Yeon'gu/Communication Sciences & Disorders · Sep 30, 2026
Age-Related Differences in Sentence Comprehension and Prefrontal Activation: A Functional Near-Infrared Spectroscopy (fNIRS) Study
By Kim J, 이은송, Moon GC et al.
Objectives: This study examined age-related differences in sentence comprehension by integrating behavioral performance and prefrontal cortical activation measured with functional near-infrared spectroscopy (fNIRS). Focusing on Korean sentence processing, which allows flexible word order through case marking, we investigated whether aging is associated with structure-specific syntactic deficits or with altered recruitment of prefrontal control resources that support sentence interpretation under increased processing demands. Methods: Younger (N=11) and older (N=10) Korean adults completed a picture–sentence matching task while fNIRS data were recorded. Sentence stimuli were systematically manipulated according to grammatical voice (active vs. passive) and word-order canonicity (canonical vs. noncanonical), yielding four sentence types. Behavioral measures included mean sentence comprehension scores and reaction times. Neural activity was indexed by changes in oxygenated hemoglobin (ΔHbO) within anatomically defined prefrontal subregions, including the frontopolar and orbitofrontal cortices. Results: Behaviorally, older adults demonstrated significantly lower comprehension scores and slower reaction times overall compared to younger adults. However, no significant Group×Sentence Type interactions were observed, indicating that age-related performance differences were not selectively tied to particular sentence structures. Hemodynamic analyses revealed a regionand condition-specific effect: younger adults showed greater task-evoked activation than older adults in the right orbitofrontal cortex during passive canonical sentence processing. No reliable age-related differences were observed in other prefrontal regions or sentence conditions. Conclusion: These findings suggest that age-related differences in sentence comprehension may reflect reduced efficiency in recruiting prefrontal control and regulatory mechanisms during sentence interpretation, rather than selective degradation of syntactic representations associated with specific grammatical structures.