Cognitive resilience/reserve: Myth or reality? A review of definitions and measurement methods

Abstract

Introduction: This review examines the concept of cognitive reserve (CR) in relation to brain aging, particularly in the context of dementia and its early stages. CR refers to an individual's ability to maintain or regain cognitive function despite brain aging, damage, or disease. Various factors, including education, occupation complexity, leisure activities, and genetics are believed to influence CR.

Methods: We revised the literature in the context of CR. A total of 842 articles were identified, then we rigorously assessed the relevance of articles based on titles and abstracts, employing a systematic approach to eliminate studies that did not align with our research objectives.

Results: We evaluate-also in a critical way-the methods commonly used to define and measure CR, including sociobehavioral proxies, neuroimaging, and electrophysiological and genetic measures. The challenges and limitations of these measures are discussed, emphasizing the need for more targeted research to improve the understanding, definition, and measurement of CR.

Conclusions: The review underscores the significance of comprehending CR in the context of both normal and pathological brain aging and emphasizes the importance of further research to identify and enhance this protective factor for cognitive preservation in both healthy and neurologically impaired older individuals.

Highlights: This review examines the concept of cognitive reserve in brain aging, in the context of dementia and its early stages. We have evaluated the methods commonly used to define and measure cognitive reserve. Sociobehavioral proxies, neuroimaging, and electrophysiological and genetic measures are discussed. The review emphasizes the importance of further research to identify and enhance this protective factor for cognitive preservation.

Keywords: EEG; brain networks; brain reserve; cognitive reserve; cognitive resilience; fMRI; neural reserve.

FIGURE 1

Proxies of cognitive reserve (CR). Comprehensive representation of factors contributing to CR, quantifiable through various elements including genetic and sociobehavioral factors, proxies derived from brain imaging measurements, and electrophysiological measures from EEG/MEG. A novel perspective, detailed in the manuscript, introduces the concept of network analysis and graphs as a new framework for understanding CR. EEG, electroencephalography; MEG, magnetoencephalography; MRI, magnetic resonance imaging; PET, positron emission tomography.

FIGURE 2

Implementation of cognitive reserve. Schematic illustration depicting the subdivision of reserve into cognitive reserve (CR) and brain reserve. CR encompasses neural processes, manifesting as neural reserve and neural compensation. Neural reserve refers to the brain's inherent capacity to optimize performance and withstand pathology, while neural compensation involves adaptive mechanisms that counteract cognitive decline.

FIGURE 3

The concepts of efficiency and capacity. Neural activity increases with increasing task demands with two different efficiencies and capacities. In particular, neural activity increases with increasing task demands at two different rates representing low and high efficiency. Additionally, neural activity increases with increasing task demands to two different maximum levels. Once neural activity reaches this high or low‐capacity limit, even greater task demands do not cause further changes.