Reserve mechanisms in neurodegenerative diseases: from bench to bedside and back again

In the course of neurodegenerative disorders there are several mechanisms that may counteract the pathological process, mitigating the clinical manifestations of the disease. Usually referred as cognitive reserve hypothesis, this theoretical framework posits that individuals with enriched cognitive status (i.e. with higher educational and occupational levels and higher individual social achievement) may cope better with the occurrence of cognitive decline by a more efficient recruitment of neural networks sustaining higher-level functions. Cognitive reserve was initially studied in Alzheimer's disease, but this concept has been soon after extended also to other neurodegenerative disorders, such as Frontotemporal Dementia, Parkinson's disease, and Huntington's disease, suggesting a general applicability of cortical plasticity phenomena in contrasting neurodegeneration. The neural underpinnings of these dynamic compensatory mechanisms open the possibility for strategic interventions based on environmental approaches. In this continuously growing field, the aim of the present review is to explore new acquisitions, derived from basic research and clinical grounds, on cognitive reserve mechanisms and the potential application as novel therapeutic targets in neurodegenerative diseases.