Let Your Brain Do The Walking
Dr Paul Batman talks about physical activity and mental health. He looks at the impact exercise has on the hippocampus and overall brain function.
As a teacher, I always prided myself on knowing the names of every student in all my classes. I learned very early in my teaching career that knowing a student’s name was a very powerful motivator. I was told that the most important possession a person owns is their name and to be recognised by name is a sign of respect and interest. What is it about people that makes us remember them? Is it their appearance, their clothing, their facial expressions, the way they talk ...?
The part of the brain responsible for memory is the hippocampus, located on the innermost fold of the temporal lobe just under the temple. Names of people, machines, animals, etc. are stored in this temporal lobe of the brain.
The hippocampus is important for making new memories in the present and not in the past. Alzheimer’s disease affects the hippocampus, initially causing those in the early stages of the illness to forget things that happen in the moment, while still remembering things from the past. In old age, the hippocampus starts to shrink, increasing the risk of dementia or memory loss. Even in older people who don’t suffer from dementia, it will still shrink approximately 1-2% per year, eventually causing some memory loss1.
The hippocampus is also an important site in the development of mental illness such as depression, schizophrenia and bi-polar as it appears to start shrinking.
The hippocampus is also directly affected by estrogen, by increasing the density of the nerve synapses responsible for nervous activity that can delay the onset of memory loss.
In a 12-month study, a physical activity group increased their hippocampus volume by 2%, offsetting its deterioration associated with ageing. However, the improvement was not universal as the anterior hippocampus was the only section of the brain’s temporal lobe that showed improvement, suggesting that physical activity does not influence all regions of the brain at the same rate.
Changes to the front of the hippocampus resulted in an increase in a specific brain protein that is responsible for nerve cell growth, assisting with memory retention.1
Consistent physical activity over the 12 months also increased blood flow to the brain with fitter people presenting with greater hippocampus volume, critical for memory retention, adjusting to an environment and performing complex tasks. Moderate-intensity physical activity might specifically stem the decline in areas of the hippocampus that tend to deteriorate the fastest in older adulthood.
In general, physical activity can increase the volume of the hippocampus, increase the brain protein that is responsible for cell growth and increase short-term memory retention.
Universally, exercise programmes have focused on making the cardiovascular system healthier to combat heart disease and improve general health. New information is emerging suggesting that the heart can be instrumental to brain health to an extent that has not been previously realised.
Professor Jonathan Stone reports that there are five possible cardiovascular contributors to age-related memory loss and dementia that have not been previously identified.
These are the heart, brain, aorta, small vessels supplying the brain and, lastly, time2.
The heart is a very trainable organ that responds extensively to physical activity. It beats 60 to 70 times per minute, with an approximate volume of 50-60 millilitres of blood per beat. In 60 seconds, it pumps about five to six litres of blood carrying oxygen around the body, while also transporting carbon dioxide to the lungs for removal.
In a rested state, the heart pumps 35 million beats per year, equivalent to two to three billion beats in a lifetime. During intense exercise, the heart can pump 150-200 beats per minute with a volume of blood up to 200 millilitres per beat, equivalent to a cardiac output of 30-40 litres of blood per minute.
For the brain to function optimally, the heart must pump oxygen and nutrients to the smallest blood vessels that surround and feed it, and it is now regarded as potentially significant in improving brain health. Conversely, as heart function deteriorates, so does brain health.
Age-related memory loss and dementia has previously been regarded as an old person’s disease. However, there is now a growing awareness that it might have its roots in childhood and a sedentary lifestyle,
provoking an interest in inactivity and brain health In a landmark study examining the effect that sedentary behaviour has on brain function, Dr Catherine Kotz injected a neurochemical called Orexin into half of her rodent subjects, while the other half received just a water injection3. In other animal studies, it was found that without Orexin animals were always falling asleep. The results of this study showed that the rats injected with Orexin moved considerably more than those injected with the water, confirming Dr Kotz’s theory that there are specific neurochemicals that can control activity patterns.
To investigate this further, another researcher – Dr Colleen Novak – studied the brain networks and chemicals responsible for sitting in a chair or moving. Dr Novak mated multi-generational obese rats with obese rats, and lean rats with lean rats, and discovered that the obese rats did not have the ability to initiate movement4.
Irrespective of the types and amounts of neurochemicals, these animals did not have the wiring in the brain to respond to the injected chemicals and so remained sedentary. Alternatively, when the brain of the lean rats was injected, their movement became almost uncontrollable. The lean rats were bred to move, while the obese rats were bred to sit.
She also discovered that the muscle of the moving rats was different to the muscles of the sedentary rats, as was the signalling to the brain. The sedentary sitters did not respond the same way. Their muscles were trained to be sedentary and, as such, the signal to move was stopped. Obese rats tended to be less sensitive and unresponsive to moving signals from either the muscles or the brain. Their muscles were trained to sit while the other lean rats were trained to move, suggesting they were more sensitive to moving neurochemicals and had a stronger feedback loop from the muscles to the brain. It could be that the movers’ brains were hardwired to move. She also discovered that the muscle of the moving rats was different to the muscles of the sedentary rats, as was the signalling to the brain. The sedentary sitters did not respond the same way.
Their muscles were trained to be sedentary and, as such, the signal to move was stopped. Obese rats tended to be less sensitive and unresponsive to moving signals from either the muscles or the brain. Their muscles were trained to sit while the other lean rats were trained to move, suggesting they were more sensitive to moving neurochemicals and had a stronger feedback loop from the muscles to the brain. It could be that the movers’ brains were hardwired to move. While we are the product of our DNA, the environment that we exist in still influences our physiological function. It is common knowledge that a brain must be kept active to maintain its optimal function. This neuroplasticity allows the brain to change with its environment. As with other organs of the body, if the brain is not stimulated it will eventually turn off and become as dormant as the lifestyle it leads.
People leading sedentary lives have a brain that will form a sedentary structure, due to its interaction with its inactive environment leading to a sedentary lifestyle. Just as a muscle adapts to movement, so will the brain. Chronically inactive people are faced with a double-edged sword. They have a brain that is not responsive to the neurochemicals for movement and have muscles that are trained to sit that do not send feedback signals to the brain to get them moving. As the need to move is further eliminated, our brains will form to create a more sedentary lifestyle that can contribute to increased memory loss and, potentially, mental illness.
Reference
F I T P R O S E P T/ O C T 2 0 2 2
https://www.yumpu.com/en/document/read/67193939/september-october-2022-fitpro-magazine