Maximal aerobic capacity (MAC) has been associated with preserved neural tissue or brain maintenance (BM) in healthy older adults, including the hippocampus. Amnestic mild cognitive impairment (aMCI) is considered a prodromal stage of Alzheimer's disease. While aMCI is characterized by hippocampal deterioration, the MAC-hippocampal relationship in these patients is not well understood. In contrast to healthy individuals, neurocognitive protective effects in neurodegenerative populations have been associated with mechanisms of cognitive reserve (CR) altering the neuropathology-cognition relationship. We investigated the MAC-hippocampal relationship in aMCI (n = 29) from the perspectives of BM and CR mechanistic models with structural MRI and a memory fMRI paradigm using both group-level (higher-fit patients vs. lower-fit patients) and individual level (continuous correlation) approaches. While MAC was associated with smaller hippocampal volume, contradicting the BM model, higher-fit patients demonstrated statistically significant lower correlation between hippocampal volume and memory performance compared with the lower-fit patients, supporting the model of CR. In addition, while there was no difference in brain activity between the groups during low cognitive demand (encoding of familiar stimuli), higher MAC level was associated with increased cortical and sub-cortical activation during increased cognitive demand (encoding of novel stimuli) and also with bilateral hippocampal activity even when controlling for hippocampal volume, suggesting for an independent effect of MAC. Our results suggest that MAC may be associated with hippocampal-related cognitive reserve in aMCI through altering the relationship between hippocampal-related structural deterioration and cognitive function. In addition, MAC was found to be associated with increased capacity to recruit neural resources during increased cognitive demands.
Bibliographical noteFunding Information:
We thank the following people: Dr. Dafna Ben Bashat and Dr. Moran Artzi for help with planning of the acquisition sequences, Dr. Noa Bregman for her help with participant recruitment, and Dr. Yuval Nir for his thoughtful advice. The study has been funded from the grants of the National Institute of Psychobiology in Israel (NIPI) and Israel Science Foundation (ISF) provided to YL. The funding sources had no involvement in the conduction of the research.
© 2020 Wiley Periodicals LLC.
- cardiorespiratory fitness
- cognitive reserve
- mild cognitive impairment
ASJC Scopus subject areas
- Cognitive Neuroscience