Physical and mental exercises protect memory by rewiring the brain

Prior to these findings, published today in Molecular Psychiatry, researchers hadn’t pinpointed what changes in brain biology – collectively known as neuroplasticity – could explain their cognitive effectiveness.

“What we have shown for the first time is that physical and cognitive exercise led to different kinds of benefits in cognition in older people, and these are based upon distinct neurobiological mechanisms,” said Associate Professor Michael Valenzuela, from the University of Sydney's Brain and Mind Centre.

“The trial shows that resistance and cognitive training can be used to target different brain mechanisms – changes that together can help combat the effects of aging and Alzheimer’s disease.”

The study was a randomised control trial of 100 non-depressed older individuals (average age 70 years) who were at high risk of future dementia. Individuals were randomised (like the toss of a coin) to one of four training groups in which they completed two types of supervised centre-based training per session (physical and cognitive), twice per week, for a total of 6 months. Each session lasted 90 minutes and comprised either:

• Resistance exercise and computerised cognitive training
• Resistance exercise and a placebo computerised training (watching nature videos)
• Brain  training and a placebo exercise program (seated stretching/calisthenics)
• Placebo physical exercise and placebo cognitive training

The researchers found that resistance exercise led to structural brain plasticity, specifically, a thickening of grey matter in the ‘posterior cingulate’ cortex, a key integrating part of the brain that is affected early in Alzheimer's disease. By contrast, the control group underwent a small shrinkage in posterior cingulate grey matter.

Importantly, this plastic change was linked to global cognitive benefits as measured by the Alzheimer’s disease Assessment Scale-Cognitive scale. This is one of the most commonly used scales in dementia drug trials and differentiates between normal cognition, mild impairment and dementia.

In parallel, the researchers found that their brain training program strengthened connectivity between the brain’s memory centre (the hippocampus) and the frontal lobe – changes that specifically protected against memory decline as seen in the control group.

“Given the alarming predictions for dementia over the coming decades, this information should help design more effective dementia prevention strategies as well as contribute to their clinical and community implementation.”

This Study of Mental Activity and Resistance Training (SMART) was funded by the National Health and Medical Research Council (NHMRC) of Australia Dementia Research Grant, Project Grant ID No. 512672 from 2008 to 2011