Monday, 8 March 2010

The Neuropsychology of ‘Brain Training’ and Cognitive Reserve

Many 'brain exercise' products have been marketed in recent years, promising to help people stay mentally fit as they age, and even help prevent dementia. However, a systematic review by Pap, Walsh and Snyder (2009) found no good evidence that brain training will either prevent or slow down mental deterioration in healthy older adults.

Mild memory problems are part and parcel of getting older, but more moderate and severe memory problems and cognitive dysfunction are often indicative of a dementia. Alzheimer's disease is the most common type of dementia, followed by vascular dementia. We know that unhealthy lifestyles including smoking, drinking and unbalanced high fat diets can increase our risk. We also know that genes play a role, and that neuro-traumatic events such as strokes or head injury can increase the risk of developing dementia. But many people wonder what they can do to lower their risk.

Pap, Walsh and Snyder (2009) found 10 good-quality studies that looked at cognitive training in healthy elderly people. When they pooled the studies' results, they found that training led to small improvements in specific tasks related to the training. However, they found no evidence that this prevented or slowed the onset of dementia. That's not to say that brain exercises don't have the potential to help, but researchers say that better-designed studies are needed to find out. Part of the problem with the studies so far is that they didn't assess people for very long. So they couldn't say what long-term effects the training might have had on people's risk of dementia. The studies also mainly looked at how well people performed tasks that were closely tied to their training and nothing else. To meaningfully explore the connection between brain training and dementia, studies would need to look at overall brain function as well as people's performance on tasks in everyday life.

Bold claims made by commercial computer games should be interpreted with an element of cynicism until better research is conducted. Scientists do know however, that there is clear evidence that physical exercise and a balanced diet can delay the progress of dementia significantly. Although the preventative effects of both of these factors is thought to be modest.

Cognitive reserve is valuable way of conceptualising one’s vulnerability to dementia and prognosis. The term cognitive reserve describes the mind's resilience to neuropathological damage of the brain. In the first study of its kind in Katzman et al. published findings from post-mortem examinations on 137 elderly persons unexpectedly revealed that there was a discrepancy between the degree of Alzheimer’s disease neuropathology and the clinical manifestations of the disease. This is to say that some participants whose brains had extensive Alzheimer’s disease pathology, clinically had no or very little manifestations of the disease. Furthermore, the study showed that these persons had higher brain weights and greater number of neurons as compared to age-matched controls. The investigators speculated with two possible explanations for this phenomenon: these people may have had incipient Alzheimer's disease but somehow avoided the loss of large numbers of neurons, or alternatively, started with larger brains and more neurons and thus might be said to have had a greater ‘reserve’. This is the first time this term is used in the literature in this context.

The study sparked off interest in this area and to try to confirm these initial findings further studies were done. Higher reserve was found to provide a greater threshold before clinical deficit appears. Neuronoal density rather than brain size appear to be significant in high cognitive reserve individuals. Moreover, genetics again appear to play a part. Childhood cognition, educational attainment, and adult occupation all contribute to cognitive reserve independently. The strongest association in this study was found with childhood cognition. However, cognitive reserve is somewhat of a double edged sword, as it is believed that people with high reserve go undiagnosed until neuronal damage is severe, then rapid decline ensues.

Pap KV, Walsh SJ, Snyder PJ. Immediate and delayed effects of cognitive interventions in healthy elderly: A review of current literature and future directions. Alzheimer's & Dementia. 2009; 5: 50-60.

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