Reserve and Reserve-building activities research: key challenges and future directions

Abstract

Background: The concept of Cognitive Reserve has great appeal and has led to an interesting and important body of research. We believe, however, that it is unnecessarily limited by 'habits' of measurement, nomenclature, and intra-disciplinary thinking.

Main body: A broader, more comprehensive way of conceptualizing Reserve is proposed that invokes a broader measurement approach, nomenclature that uses specific terms embedded in a theoretical model, and crosses disciplines.

Conclusion: Building on this comprehensive conceptualization, we will discuss fruitful directions for future research.

Keywords: Cognitive Reserve; Inter-disciplinary; Measurement; Neurological Reserve; Nomenclature theory; Quality of life; Reserve-building activities; Resilience; Tipping point.

Fig. 1

Cross-sectional relationships between components of Reserve and performance. This model provides a roadmap for the nomenclature and expected relationships among Reserve-related constructs at a specific point in time. Going counter-clockwise from left, “Genetic and inborn factors” refer to inborn or background determinants of brain function (e.g., single nucleotide polymorphisms). These factors are the only direct causes of (innate) Brain Reserve, which represents a subject’s potential brain structure (e.g., head size, intracranial volume, synapse count, Central Nervous System (CNS) structure). Regardless of a subject’s Brain Reserve, the subject’s Neuronal network function represents the present level of functioning of a subject (e.g., functional connectivity as measured by functional magnetic resonance imaging). Then the combination of a subject’s present Neuronal network function, Environmental Factors (e.g., socioeconomic adversity or advantage; stressful events) and Disease Burden (e.g., diagnosis, symptoms, treatment side effects, progressive disability) determine the subject’s Expected Performance on a task. Finally, the Difference between Observed and Expected Performance is impacted by the person’s Expected Performance, (acquired) Reserve and Reserve-Related Person Characteristics. Reserve and Reserve-Related Person Characteristics are each hypothesized to lead to larger differences between observed and expected performance, but through different mechanisms. Whereas Reserve relates specifically to compensatory or protective brain function, Reserve-related person characteristics refer to attitudes, values, or socio-emotional skills that are posited to enhance an individual’s resilience in the face of adversity and / or disease. Both Reserve and Reserve-related person characteristics are posited to be directly affected by the individual’s past- and current Reserve-Building Activities. Such activities are hypothesized to include a multidimensional array of activities that promote brain health, including cultural/intellectual pursuits, physical activity, social/community participation, spiritual/religious practices, and dietary/lifestyle habits

Fig. 2

Critical characteristics reflecting distance from tipping point. Loss of Reserve can be identified by early warning signs (i.e., slope, time to recovery, variance, and autocorrelation), and may explain different phenotypes of a disease (reprinted with permission from Wolters Kluwer from Olde Rikkert [: 605])