Cortical Neurodynamics and Age-Related Memory Function

Below find referenced an interesting view of age-related changes in brain function and memory. As is true throughout the aging body and brain, the higher level changes produced in these intricate systems are far more complex than the few forms of cellular and tissue damage thought to cause aging. Simple damage and a complex system inevitably leads to complex outcomes, but that doesn't necessarily mean it is as hard to fix the damage as it is to understand the system. Consider rust in an ornate, many-legged, load-bearing iron structure as an analogy. Rust is easily dealt with, but it would be hard to try to model or predict exactly the ways in which the structure will weaken and fail over time.

The relatively random spiking times of individual neurons provide a source of noise in the brain. We show how this noise interacting with altered depth in the basins of attraction of networks involved in short-term memory, attention, and episodic memory provide an approach to understanding some of the cognitive changes in normal aging. The effects of the neurobiological changes in aging that are considered include reduced synaptic modification and maintenance during learning produced in part through reduced acetylcholine in normal aging, reduced dopamine which reduces NMDA-receptor mediated effects, reduced noradrenaline which increases cAMP and thus shunts excitatory synaptic inputs, and the effects of a reduction in acetylcholine in increasing spike frequency adaptation.

Using integrate-and-fire simulations of an attractor network implementing memory recall and short-term memory, it is shown that all these changes associated with aging reduce the firing rates of the excitatory neurons, which in turn reduce the depth of the basins of attraction, resulting in a much decreased probability in maintaining in short-term memory what has been recalled from the attractor network. This stochastic dynamics approach opens up new ways to understand and potentially treat the effects of normal aging on memory and cognitive functions.

Link: http://dx.doi.org/10.1016/j.nlm.2014.12.003

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