Neurocognitive Aging and Brain Signal Complexity

Abstract

Brain organization can be appreciated across multiple spatial and temporal scales, where each scale affects the other in the emergent functions that we appreciate as cognition. As a complex adaptive system, the interplay of these scales in the brain represents the information that ultimately supports what we think and do. The dynamics of these multiscale operations can be quantified with measures of complexity, which are sensitive to the balance between information that is coded in local cell populations and that captured in the network interactions between populations. This local vs. global balance has its foundation in the structural connectivity of the brain, which is then realized through the dynamics of cell populations and their ensuing interactions with other populations. Considering brain function and cognition in this way enables a different perspective on the changes in cognitive function in aging.\n\nOur initial work examined changes in brain signal complexity from childhood to adulthood. Across two independent studies, we observed an overall increase in signal complexity with maturation, which also correlated with more stable and accurate cognitive performance. There was some suggestion that the maximal change occurs in medial posterior cortical areas, which have been considered \"network hubs\" of the brain. In extending to study to healthy aging, we observed a scale dependent change in brain complexity across three independent studies. Healthy aging brings a shift in local/global balance, where more information is coded in local dynamics and less in global interactions. This balance is associated with better cognitive performance, and interestingly in a more active lifestyle. It also seems that the lack of this shift in local/global balance is predictive of worse cognitive performance and potentially predictive of additional decline indicative of dementia.