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Building better brains is more than just about lifestyle

One popular view likens the brain to a muscle that must be trained to be fit. ‘Use it or lose it’ derives from this simple idea and is the basis of advice on how to stay mentally alert in old age and defy the effects of age-related mental decline—even dementia. When popular science is mixed with lifestyle journalism, it is not surprising that much uncomplicated advice is the retelling of a hackneyed tale. ‘Live a good life’, ‘all things in moderation’, ‘stay active, early to bed’ and ‘look after your health and everything will be alright’ all seem well-intended but hardly well-founded in fact. Stern stands well apart from, and shoulders above, any suspect tradition of health journalism. His investigations have poked and probed the brain’s capacity to make good the harm inflicted by trauma, disease or ageing. His factual reviews have made the concept of cognitive reserve accessible to the neuroscience and epidemiological communities to the point that, once his ideas are ingested, the enquiring mind will nurture each to its maturity as a testable hypothesis. Here, he has compiled a readable volume of short essays grouped around the theme of ‘cognitive reserve’. In an historical context, Stern’s ideas are not new; all can be traced to a sound understanding of human development, how pathology diminishes brain functions and how efficiency can be restored through healing and regeneration. In this compilation, Stern’s intention is to integrate some of the best and most recent data on the topic, an intention he fulfils admirably. The brain’s cognitive functions are based on co-ordinated interactions between very large numbers of neurons distributed within and between specialized brain areas. These ‘sub-specialized units’ present a considerable problem to modern clinical neuroscience. How are these units co-ordinated? How are their actions integrated? And, when one or more are damaged, how can they resume the same functions that were earlier established in a healthy co-ordinated brain? The self-organizing principle of cortical development was re-applied to explain how brain recovery from injury is influenced by experience and to suggest the likely neurobiological substrates of recovery following stroke or localized brain injury. These recovery processes differ in their long-term benefits for the individual and, importantly, the sources of difference are largely unknown. Although the example of stroke is widely cited, it remains uncertain how stroke lesions that are identical in nature and extent may cause lasting deficits in one individual whilst another person recovers completely. The sources of individual differences in brain functional responses to pathological change is thoughtfully explored in this volume in conditions other than stroke. Alzheimer’s disease, ageing, heart surgery, AIDS and trauma are explored but stroke, epilepsy, schizophrenia and autism could have easily been added to the problems investigated. All are of high clinical relevance and all provide tools to understand the brain’s resilience in the face of damage. Almost 40 years ago, the Newcastle team led by Martin Roth showed a close relationship between the density of senile plaques (typical of Alzheimer’s disease) and the degree of cognitive impairment present before death. This relationship fell someway short of exact agreement and the nature of discrepancies between plaque count and mental impairment attracted the attention of other neuropathologists. Twenty years later, Robert Katzmann showed that the duration of formal education could explain some of the discrepancy but his work was hampered by the limitations of his epidemiological data and difficulties encountered in adjusting for many other confounders. Stern provides contemporary accounts by talented clinical scientists to show how advances in methodology since Katzmann have made tractable the puzzle of cognitive reserve. Richards et al.