Language-Related Brain Activation in Cognitive Decline and Aging: An fNIRS-Based Literature Review

This study aimed to compare the changes in language function and activated brain in normal aging and cognitive decline groups using functional near-infrared spectroscopy (fNIRS). PubMed was searched through October 2025 using keywords related to fNIRS, aging, cognitive decline, and language function/task. A total of 52 studies were selected based on exclusion criteria. 1) Most studies conducted comparisons between young adult and normal elderly groups, between the normal cognitive group and cognitive decline group. 2) The verbal fluency task was the predominant expressive task; lower cognitive status was generally associated with reduced language performance and cortical activation. In comprehension tasks, young adults showed equal or better performance than normal aging adults, but the latter group showed greater neural activation. And 3) the most frequent activation and inter-group differentiation were observed in the frontal lobe, particularly within the inferior frontal cortex (included Broca’s area), dorsolateral prefrontal cortex, and the frontopolar cortex. fNIRS-based analysis of language-related hemodynamic responses in normal aging and cognitive impairment suggests a correlation between language function and brain activation, offering a scientific basis for future assessment and intervention.