Neural Plasticity and Cognitive Reserve
Zahra Bardai, BSc, MD, CCFP, MHSc, FCFP, Community Family Physician, Lecturer, University of Toronto, Assistant Clinical Professor (Adjunct), Department of Family Medicine, McMaster University, Hamilton, ON.
Abstract
Neural plasticity in the context of normal aging and dementia can be evaluated on a number of levels. Traditionally there has been much focus on cellular dysfunction, which is evidenced by the plaques and tangles that are the hallmarks of Alzheimer type dementia. Now, more than ever, there is an emerging spotlight on the preservation of functional levels despite failing cognition be it from normal aging, mild cognitive impairment (MCI) or diagnosed dementia. Neural plasticity can be viewed as the complex interaction between the neurons' electrical, biochemical and physical structure and the individual's behavioural, psychological and sociological activities.1 This article will briefly review the neurobiology of cognition and the sequence of events that lead to its demise. The remainder of this review concentrates on tangible, evidence based strategies to uphold clinical cognition through the aging process.
Keywords: neural plasticity, aging, dementia, cognition, neurons.
…there were neurons in her head, not far from her ears, that were being strangled to death, too quietly for her to hear them. Some would argue that things were going so insidiously wrong that the neurons themselves initiated events that would lead to their own destruction. Whether it was molecular murder or cellular suicide, they were unable to warn her of what was happening before they died.
-Still Alice
Lisa Genova
Cellular Neural Plasticity
Memory, even in its simplest depiction, is a complex process involving multiple structures in the brain as well as the use of key neurotransmitters. Using a time classification structure, memory can be divided into very short term, short term and long-term memory. It can further be subdivided into explicit (conscious recollection), episodic (temporal recollection), semantic (conceptualized paradigms), implicit (unconscious recollection), perceptual (symbolic imaging), procedural (habitual rules), associative (operative conditioning), non-associative (stimulus sensitization), and operational or working memory.2,3 The basic mechanics of memory formation in the above domains involves the exposure to information or experiences and their subsequent transfer, storage and retrieval from memory. The part of the brain responsible for this function is comprised primarily of the hippocampus and amygdala. There is also significant interplay of these limbic structures with the prefrontal cortex and the entorhinal/parahippocampal cortexes of the medial temporal lobe. Added to this is the role of neurotransmitters (NT), particularly acetylcholine, and the muscarinic and nicotinic receptors that modulate NT pathways.