THE NEXT TIME you find yourself in a taxi, ask the driver to tell you about the last movie he watched. If he has a foggy recollection, you can always blame it on how his brain is wired.

It is not that taxi drivers have especially bad memories. Like everyone else, their brains are “wired” as a direct result of repeated behaviour and experiences and this can have interesting results.

A famous brain-imaging study by Dr Eleanor Maguire, formerly of University College Dublin and now at London City University, looked at a group of London taxi drivers and observed that parts of their brain literally grew due to their job.

“The study suspected that because these men had to get to know London streets like the back of their hand, parts of the brain responsible for this function might be larger than in the average person,” says Dr Richard Roche, lecturer in psychology at the National University of Ireland, Maynooth.

It was found that a part of the brain known as the posterior hippocampus was larger than average, especially in the right half or right hemisphere of the brain. Roche explains that as this area grew, it expanded into a nearby part of the brain.

“As a result, when these taxi drivers were asked to recall the plot of a film, they weren’t as accurate as the average person. There is a bit of a cost when you enhance a particular brain function and the neurons expand into another area,” Roche says.

This shows that the brain is not a hard-wired organ that is incapable of change. It is plastic and the wiring is changed slightly every time we perform a new thought or action, says Dr Kevin Mitchell, neurogeneticist at Trinity College Dublin.

Experience literally shapes the brain, says Mitchell. “The major function of the brain is to adapt itself to the environment, form memories of what has happened in the past and better predict the future. This happens at the level of brain cells connecting with each other.”

We know that neuroplasticity occurs early in development when the young brain is organising itself, says Dr Lorraine Boran, lecturer in cognitive psychology at Dublin City University.

This plasticity continues throughout our lives in response to learning, and also in the case of brain injury where rehabilitation focuses on compensation of lost function or maximising spared function, she says.

“Brain connections form and reform in response to our environment,” explains Boran.

In order to describe how connections are formed and fixed in the brain, Boran, Mitchell and Roche all use the mantra: cells that fire together wire together.

Roche says that the phrase “use it or lose it” also applies. He explains that one of the reasons that people seem to experience cognitive decline as they get older is because their brains aren’t getting the same workout as they used to.

“A lot of people get to retirement age and cognitively, they hang up their boots. Something as simple as reading can keep neurons firing.”

Dr Niall Pender is head of the department of psychology and principal clinical neuropsychologist at Beaumont Hospital. He works with a “memory clinic” that involves older people who are not suffering from cognitive decline such as vascular dementia but who are pre-empting this by getting involved in activities that will keep the brain as active as possible for as long as possible.

He explains that it’s not just crosswords or brainteasers that keep the mind active. Exercise and socialising and especially learning new skills keep neurons firing and create new neural pathways in the brain.

Forming new connections is the key to recovery in stroke patients and others who have suffered brain trauma of some sort, explains Pender. Borrowing an analogy from psychologist Barbara Wilson, he says we should think of the brain as a finely-tuned orchestra.

If the string section disappears there are two choices: the rest of the musicians can improvise and attempt to play the same piece of music or they can adapt the sheet music to work with the remaining orchestra.

Similarly, when sections of the brain are damaged or destroyed by an injury, this does not spell disaster. “The brain is very plastic and its capacity to recover from damage is vast,” says Roche. “This is contrary to what people thought until relatively recently. For a long time the received wisdom was that if you damaged your brain there wasn’t much you could do.”

“Use it or lose it” comes into play when the brain has been damaged, says Roche. “The more active your brain is pre-stroke, the more resilient it will be afterwards.”

How the brain is pre-wired also has a profound effect on how each individual processes information and approaches problems.

Mitchell says: “When the brain has developed in a different way the wiring is different than normal. This is most likely what happens in conditions such as autism and schizophrenia. “If that’s the case, you’re probably not going to be able to fix the problem itself but you can compensate,” he says.

With autism, there are some differences in areas of the brain that are wired to mediate social cues, explains Mitchell. People with autism can find it difficult to maintain eye contact. They may not look at people simply because their wiring means that they are not interested in looking at people.

Mitchell emphasises that because the brain is pre-wired to behave in a certain way does not mean this cannot be changed consciously. “It is possible for those with autism to compensate by learning social rules in an intellectual fashion.”

Despite all our current knowledge, we are still learning how the brain works, says Pender. There are many different parts and they all have a role to play – from keeping us breathing and waking to high-level executive skills and the parts that give us a sense of humour.

We also have to take into account elements of our genetic history and our environment. We are born with certain predispositions that help shape our personality and intelligence, and experience changes this further.

People often ask if some brains are wired better than others, says Mitchell. “Not better but they are certainly wired differently.”

Bad to the bone?

DO WE CHOOSE a life of crime or does it choose us? Dr Kevin Mitchell, neurogeneticist at the department of genetics in Trinity College Dublin, says that certain individuals are more likely to end up behind bars because of the way their brain is wired.

Psychopathic individuals in particular are estimated to make up 20 per cent of the prison population and are three to four times more likely to re-offend than the average criminal. They don’t respond particularly well to rehabilitation either.

The psychopath is defined by a particular personality profile, explains Mitchell. “They are superficially charming, egocentric, calculating, manipulative and have a deficit in what you might call moral reasoning or a conscience. “Someone with a psychopathic personality knows the difference between right and wrong but doesn’t feel it,” he adds.

Research in neuroscience and genetics has found that this behaviour is due to underlying structural differences in the brain.

The prefrontal cortex and the amygdala are parts of the brain that are responsible for impulse control and emotional responses such as empathy. In the brain of the psychopath these regions have been found to be reduced in size.

“When we are shown faces of other people expressing fear, a part of the brain known as the amygdala becomes active as we feel sympathy. This area does not activate in the brain of a psychopath,” Mitchell points out.

“Brain imaging shows that people classed as psychopathic don’t even show an emotional response to pain they might receive themselves such as an impending electric shock.”

Mitchell talks about a psychopath who was asked why he didn’t care if he caused pain to others. “He said he could sense pain as physical stimulus but it didn’t carry negative emotional weight. It was something to avoid but not in a visceral way. “Brain imaging would seem to support this clear disconnect between the intellectual and the emotional,” says Mitchell. Psychopathy may be the result of faulty brain wiring but it is not all that rare. It is estimated that about 1 per cent of the general population have this condition, so you’re probably on first-name terms with one.

Thankfully, most psychopaths aren’t like Dexter. “In fact, many do very well in jobs where these kinds of personality traits are seen as useful,” adds Mitchell.