The Brain: The Story of You

by David Eagleman

When the team began their research, they expected to find a clear-cut link between cognitive decline and the three diseases that are the most common causes of dementia: Alzheimer’s, stroke and Parkinson’s. Instead, here’s what they found: having brain tissue that was being riddled with the ravages of Alzheimer’s disease didn’t necessarily mean a person would experience cognitive problems. Some people were dying with a full-blown Alzheimer’s pathology without having cognitive loss. What was going on? The team went back to their substantial data sets for clues. Bennett found that psychological and experiential factors determined whether there was loss of cognition. Specifically, cognitive exercise – that is, activity that keeps the brain active, like crosswords, reading, driving, learning new skills, and having responsibilities – was protective. So were social activity, social networks and interactions, and physical activity. On the flip side, they found that negative psychological factors like loneliness, anxiety, depression, and proneness to psychological distress were related to more rapid cognitive decline. Positive traits like conscientiousness, purpose in life, and keeping busy were protective. The participants with diseased neural tissue – but no cognitive symptoms – have built up what is known as “cognitive reserve”. As areas of brain tissue have degenerated, other areas have been well exercised, and therefore have compensated or taken over those functions. The more ...