Functional Role of NREM sleep oscillations in aging

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Aging is associated with important modifications in sleep including shorter sleep duration, shallower sleep and reductions in specific brain waves (or oscillations of the brain activity) such as slow-waves and spindles. Specific components of declarative memory consolidation (i.e. ability to recall explicitly facts and events) also decline significantly with normal aging. Importantly, slow-waves and spindles play an important role in reinforcing cerebral memory traces during sleep. The long-term objective of this research program is to understand the functional role of sleep oscillations in aging. Specifically, we will use a multi-modal approach to test the hypothesis that age-related changes in sleep oscillations are associated with changes in the ability of the brain to strengthen declarative memory. Our first specific objective is to localize on the cortex synchronous activity and evaluate how these cortical areas communicate together during sleep oscillations after learning a declarative memory task in young and older participants. We predict that synchrony during sleep oscillations will emerge from a broader and more connected set of cortical regions after learning, as compared to the control task. We also expect that these effects will be less pronounced in older participants and that performance on the retention of a declarative memory task in the morning will be associated to enhanced cortical communication during sleep oscillations. Our second specific objective is to evaluate the effects of inducing weak electric currents on specific areas on the scalp to induce sleep oscillations and enhance retention on a declarative memory task in young and older participants. We predict that compared to a control condition, sleep oscillations will be enhanced in the young and, in particular, in the older participants, which will improve the retention on a declarative memory task. The research program will provide crucial knowledge as to how age-related changes in sleep oscillations are associated with changes in brain plasticity. The development of a methodology to induce sleep oscillations provides an innovative causal approach to assess the role of sleep oscillations. In the spirit of the NSERC mandate, this research program will also stimulate the development of new methodology (electromagnetic neuroimaging) and advanced technological devices (wave-based neurostimulation). The overall objective is the enhancement of brain plasticity during sleep in specific populations which show sleep oscillations abnormalities (e.g. mild cognitive impairment and Parkinson disease).