Scans show cocaine users have ‘lower brain activity’

THE comparison between the scans are stark.

The first scan is that of people who don’t take cocaine. It shows two large bright red areas in parts of the brain responsible for impulse behaviour. In contrast, the second and third set of images, are of problem cocaine users. It shows much smaller areas highlighted in red. Trinity College Dublin researcher Dr Hugh Garavan said this shows lower brain activity in these parts of the brain among cocaine users.

A final scan Dr Garavan shows is for a part of the brain responsible for monitoring behaviour. This allows a person to assess the riskiness of their behaviour. The sophisticated machine at the Institute of Neuroscience at Trinity College Dublin is a functional magnetic resonance imaging (fMRI), which Dr Garavan said is the country’s only research-dedicated machine. The scan measures blood flow, which is an indirect measure of neural activity.

“If neurons start to fire, you get increased blood flow to those regions. If you are doing a task, you can identify what brain regions show a change in blood flow,” he said.

This is then converted into coloured computer maps of the brain. The areas showing greatest brain activity are bigger and brighter, with cooler regions suggesting lower brain activity. “Those who are impulsive are less active, which suggests that the brain centre is not working as well. The implication is they are less able to regulate their behaviour,” he said.

The fMRI scan has analysed test results of more than 50 dependent cocaine users in the US.

Dr Garavan has links with universities there, where it is possible for researchers to recruit drug users and, as in this case, give them cocaine produced and administered at a hospital. This is followed by computer tests aimed at measuring impulse control. This group is then compared with that of a controlled group of non-users. The research has attracted international attention and Dr Garavan presented results last week to The Royal Society, the British national academy of science. He said most of the research on addiction focused on the reward centres of the brain. “We’re interested in the cognitive dimension, how we control our behaviour, whether what we are doing is risky and what we’re finding is that cocaine users seem to be compromised in the brain regions important for assessing risks and regulating behaviour.”

He said it wasn’t clear yet whether this was a consequence of cocaine use or a pre-existing condition people had.

He said the research might partly explain why only a minority of recreational cocaine users end up becoming hooked.

Dr Garavan said they were now researching abstinence among ex-users: “What happens if you give it up, do the brain differences correct? Can we predict who’s likely to become an addict, who’s likely to relapse and successfully quit?”

He said the research may also guide treatment programmes for addicts.