Using MRI to study processes in the human brain

27 November 2014

On 29 October, Dr Ciara McCabe gave a fascinating talk on using MRI to study activities in different parts of the human brain in order to understand processes related to clinical depression.

Dr Ciara McCabe

Neuro imaging using MRI, she said, has “only been around” since the 1990s. The technology is typically able to record 36 to 40 slices of the brain, 3mm thick, in about two seconds, which it is now possible to reduce to 0.7s using a multiband technique. Blood is magnetically charged so more blood flow to a particular part of the brain shows up in these scans.

Everyone experiences periods of sadness and loss on occasion, but some people suffer from conditions such as anhedonia, which is the failure to obtain pleasure from activities or stimuli previously found to be rewarding. Researchers theorise that this may result from the breakdown in the brain’s reward system, involving the neurotransmitter dopamine.

Dr McCabe described a series of experiments where brain functions were studied in response to pleasurable stimuli – a chocolate drink and images of chocolate, and an unpleasant strawberry drink accompanied by images of rotten strawberries. It was, of course, important to make sure that the subjects used were people who found chocolate to be pleasant and the strawberry drink unpleasant. before starting.

The study showed there was a big difference in the ways that the brains of normal people showed an immediate and large response to the chocolate stimuli, whereas patients who were in remission from depression showed a reduced response to the chocolate, but a larger response to the strawberry drink. The samples were only 15 people each but the differences were large enough to make the studies statistically significant.

The team then studied a group of 25 young people in the age group 16 to 21 with a family history of clinical depression and again found much less response to the chocolate and much more response to the strawberry drink. The team is now studying 13 to 18 year olds.

Treatments, whether anti depressant medicines or psychological counselling only work in about 30 to 40% of cases, so the challenge now is to come up with better treatments.

The team has therefore been engaged in looking at the effects of drugs and combinations of drugs on groups of 15 people with 15 people on placebos. Some drugs seemed to have more effect than others. For example, Citalopram significantly reduced the lateral orbitofrontal responses to the aversive strawberry stimuli.

Research continues.

After the formal part of the talk, there was a lively discussion.