/ 18 July 2014

It’s all in your head

On a neurological level
On a neurological level

The addicted brain
Society has (hopefully) moved away from a moral and legal view of addiction – that it is a sin or a crime freely chosen by the individual who needs to repent or should be punished.

“The modern view,” says Dr Volker Hitzeroth, a practising psychiatrist and lecturer at Stellenbosch University, “is that addicts are patients – they are sick and deserve treatment.”

On a neurological level, addiction can be seen in the brain’s common reward pathways, he says. “All drugs of abuse, whether they are cocaine, cannabis or alcohol, affect the dopamine in this pathway.”

Dopamine, a neurotransmitter, makes you feel good when it is released in your brain. But many things make people feel good – a tasty meal, your favourite song, sex – so what is the difference between a drug and normal happy-making behaviour?

“With normal behaviours, there is a lower peak of dopamine [the amount moving through these neural pathways] and the brain is exposed to the hormone for a longer period of time,” Hitzeroth says.

“With drugs, there is a higher peak for a shorter period of time.”

There are also certain individuals who are more susceptible to addiction: brain imaging studies have shown that the prefrontal cortex (which is in the front of the brain, just above the ­eyeballs, and is responsible for rationalising and decision-making processes) is “impaired or dysfunctional to some degree in drug users”.

This part of the brain is the last to develop in adolescents, which is why they are usually the most vulnerable to addiction.

Habitual drug use over long periods of time changes the brain’s structure. This means that, for addicts, it is not just about “getting clean”.

“You’ve got to look after your recovery for a long time. It doesn’t stop the day you finish your detox – your brain has changed,” Hitzeroth says.


Same brain, different goals
“The brain performs for us at its best,” says Etienne van der Walt, neuroscientist and founder of Cape Town-based company Neurozone, which focuses on applied brain science.

“In each life phase, the brain operates in a different way with the same aim: survival.”

For a young brain, the aim is to develop optimally, but a 75-year-old brain has a different goal.

“From middle age and older, the brain’s major function is to impart all this wisdom, knowledge and expertise that you’ve built up [during a lifetime],” Van der Walt says.

And there are physical changes: the brain becomes smaller as gaps in the grey matter reduce.

“We used to think that [it got smaller] because you lose neurons, but that is not the case,” he says.

Humans can continue to grow and regrow brain cells throughout their lives. But their connections change: “The brain starts to reduce its connecting points, its synapses [which connect brain cells to each other]”, which naturally reduces its functions.

“We believe that this is not necessarily an indicator of disfunction, but of altered function.”

Van der Walt says that there are a number of things people can do to ensure that their brain remains healthy as they get older, particular if you are middle-aged:

First, sleep more than six hours a night, preferably between seven and nine hours.

Second, don’t stress (although this is easier said than done).

Although he lists nutrition as the third important factor, he believes “it plays less of a role than chronic stress”.

Four, exercise and don’t be ­sedentary, which also helps to reduce stress.


The battle of the sexes begins in the womb
Professor Mark Solms, professor of neurophysiology at the University of Cape Town, takes great pains to preface his comments on the differences between men and women’s brains: “What I’m talking about is not ideology,” he says

“There are basic factual differences, which certainly exist and are very well documented in all primate species.”

In the womb, human babies initially have female bodies, but boy fetuses have an XY chromosome and girls have an XX chromosome.

This XY chromosome starts a genetic cascade that will set the boy baby on a different growth path to the girl, namely the creation of a molecule called TDF (the testis-determining factor), which turns the baby’s gonads into testes. Without this TDF, the gonads become ovaries.

“Every other difference flows from that difference,” he says.

The testes produce a first wave of testosterone at the end of the first trimester of pregnancy, and the fetus’s body and brain will become larger.

At the end of the second trimester there is another tranche of testosterone and this causes the baby’s brain to become “masculinised”, Solms says.

This results in physical differences between men, and women’s brains. In women, the corpus callosum (a band of fibre that joins the two hemispheres of the brain together) is larger, and this has been associated with better linguistic ability: baby girls talk earlier and better than boys.

The smaller corpus callosum in young boys has been linked to ­better spatial abilities. Solms stops in his explanations to reiterate that this is what is seen on average: “Any individual female might be more spatially aware than a man or vice versa, but this is the average.”

There is also the amygdala, linked to memory formation, decision-making and emotional responses, which is more active in men. This results in men and male children on average being more active and aggressive than females.

On the other hand, women have a larger anterior cingulate gyrus, which has been associated with empathy and pro-social behaviour.

The masculinisation of the brain can be interrupted by a number of mechanisms, including stress in the pregnant mother, and there are also genetic variants determining the extent of masculinisation.

The series of lectures was organised jointly by the University of Cape Town’s Centre for Open Learning (COL) and the ComaCare Trust.  The ComaCare Trust is a non-profit organisation dedicated to the care of coma patients in South Africa. The lectures were organised as part of its Heads Up programme, and as part of the COL’s Summer School Extension Programme.