The CRUNCH model does not account for load-dependent changes in visuospatial working memory in older adults

Numerous neuroimaging studies have shown that older adults tend to activate the brain to a greater extent than younger adults during the performance of a task. This is typically interpreted as evidence for cognitive compensation. The Compensation-Related Utilisation of Neural Circuits Hypothesis (CRUNCH) model is a highly influential model of compensation, and states that increased functional magnetic resonance imaging (fMRI) activity in older adults compared to younger adults should reverse at higher levels of task difficulty. Here, the CRUNCH model was tested using a visuospatial working memory paradigm. fMRI activity in older vs. younger adults was in the opposite direction to that predicted by the model. Given that the CRUNCH model is the predominant model of compensation, this result was surprising. These results were followed up with a systematic review of the CRUNCH in healthy ageing literature. A surprisingly small number of published studies (4) have tested the predictions of the CRUNCH model. Further experimental work is required to validate the CRUNCH model in cognitive ageing.