Previous research has found distinct brain activity differences between older and younger adults that correlate with cognitive performance. Older adults tend to show an increase in brain activity and demonstrate over-recruitment of bilateral brain regions compared to younger adults, which allows them to perform at a comparable level to younger adults at low task loads (Compensation-Related Utilization of Neural Circuits Hypothesis or CRUNCH model). This additional brain activity may be a form of neural compensation. However, others have observed compensatory brain activity during more difficult tasks, highlighting discrepancies in the literature. The main objective of the present study is to examine age-related differences in bilateral prefrontal (PFC) and right parietal lobe activity using functional near-infrared spectroscopy (fNIRS) (21 channels, 25 Hz, Brite, Artinis) while participants completed visuospatial working memory N-back tasks of increasing cognitive load (1-back, 2-back, and 3-back), thus testing the CRUNCH model. Twenty-four healthy younger (18-25 years) and 25 older (65-91 years) adults took part in the study. The results show older adults had higher error rates to target and were slower during the N-back tasks (p < .05). Age-related brain activity differences were observed between older and younger adults. Older adults demonstrated increased bilateral brain activation compared to younger adults, especially during the 2-back task. Behavioural differences were
also observed between age groups, with older adults showing lower accuracy (Pr) at higher loads (i.e., 2-back, and 3-back) but performed similar to younger adults at low loads (i.e., 1-back). The results of our study do not support the CRUNCH model nor the compensation view, but rather align with the Neural Inefficiency model, where older adults exhibit increased bilateral brain activity but show reduced task-related performance.
