How your brain ages

Ageing is inevitable, but what can we do to keep our brains young and limber as long as possible? According to neurologist Etienne van der Walt, what's good for your heart is good for your head too. Here's why.

Life stages of the brain

"A human baby is born with roughly 100 billion brain cells," says Dr Etienne van der Walt, a clinical neurologist and founder of Cape Town-based Neurozone, a business that uses brain science to enhance human capacity. According to Van der Walt, to understand the mature brain you first need to understand how much the brain changes over a lifetime.

"The first thing a baby's brain does is to recognise the face of its mother, and shortly thereafter, its father. This is the first step in the creation of the 'social brain', which is a very human characteristic and one we all need if we are to survive in a community."

When we reach puberty, Van der Walt explains, the brain is intent on exploration of the world and the creation of identity: "This is why, as teenagers, our estimation of our own capability is so high and our calculation of risk so low."

As adults, our brains are optimally geared to gather knowledge and skills that ultimately lead to expertise. This is the foundation of experience. "And it is this," says Van der Walt, "which the world needs. Aged brains are brains with experience – and therefore wisdom – to share."

What is consistent across the different life stages of the brain is its cellular functioning: "Thoughts are physical and tangible," Van der Walt assures us. "They are the electrical impulses that travel through our neurons [brain cells] and along our synapses [the junctions between cells over which neurotransmitters send chemical messages]. Each of our neurons is connected to other brain cells by thousands of cellular extensions [dendrites]."

Running around the neuron's axon (main wire) is the myelin sheath, which is a form of insulation, much like the plastic around electrical wire, Van der Walt explains.

The adaptable brain

Neuroplasticity is the name given to our brain's ability to adapt, regenerate and re-arrange itself, not just throughout our lifetime, but also in the case of disease and injury. "This is the amazing power of the brain and what is responsible for the brain's ability to regenerate after a stroke, for example," explains Van der Walt.

It is now thought that diminishing neuroplasticity is the main cause of diminished brain function in ageing brains.

So what happens to our brains as we age? It is not that we lose brain cells over time, but rather that the functioning of the connections between our brain cells diminishes. To illustrate this point, Van der Walt displays two brain scans side by side. The first scan is of a healthy young adult's brain, and shows plump white and grey matter that fills the skull. The second scan shows an elderly brain in which the white and grey matter has shrunk, leaving visible gaps between the skull and the brain itself.

Van der Walt is quick to point out that both scans would be considered normal. "Then again," he says, "there is a difference between normal ageing and successful ageing."

As we grow older, we gradually lose brain function in four key areas: our senses become dulled, our working memory (the ability, for example, to remember a phone number long enough to dial it) becomes reduced, and both our retrieval of knowledge and our fluid intelligence (or reasoning speed) slows.

Oxygen: too much of a good thing?

"Oxygen," says Van der Walt, "will kill us all in the end."

While we literally depend on oxygen for every breath we take, the ever-ageing process of oxygen metabolism in our bodies can leave a residue of oxygen free radicals that cause damage to cells over time.

Oxidative stress is considered to play an important role in conditions such as dementia, motor neuron disease and other illnesses which affect brain function.

How then do we prevent or slow oxidative stress and its effects on the brain? According to Van der Walt, everything that is good for the heart is also good for the head. "There is a lot that we can do to help our brains age well," he says. "Ageing is inevitable, but it is important that we look after our brains. When we are old we need to be able to retrieve the knowledge and experience we have accumulated over a lifetime so that we can share our wisdom with the rest of the world."

Story by Ambre Nicolson.