Doctors can now view brain processes in real time. Geoff Watts reports.
A study of brain function in a group of schizophrenic patients has revealed why a newer anti-psychotic drug is more effective than its older counterparts. It has also shown that the theory underpinning the use of these drugs is broadly correct. Reporting his findings, Tonmoy Sharma of the Institute of Psychiatry says that he and his group "have been able to show for the first time that deterioration in brain function in schizophrenia is not irreversible".
To assess the effect of medication, psychiatrists usually look for alterations in their patients' mood and behaviour. But these things are difficult to measure precisely and objectively, and they reveal nothing of how and why a drug works. With the advent of functional brain scanning, psychiatrists could begin to watch the organ in action and compare it in health and in disease.
However, the original scanning techniques required an injection of a radioactive isotope, so limiting the frequency with which they could be repeated. The invention of functional magnetic resonance imaging (fMRI) gave doctors a non-invasive method that can be repeated as often as required.
Some of the older anti-psychotic drugs such as haloperidol have been around for decades. Newer and more expensive alternatives, notably risperidone, seem to be more effective at dealing with disordered thought processes and other symptoms of schizophrenia. But there has been little hard evidence of where they work in the brain or what exactly they do. Sharma's team scanned a group of schizophrenic patients receiving older anti-psychotics, then switched them to haloperidol. Six weeks later, the patients were scanned again. By revealing the bloodflow in different areas of the brain, fMRI measures the activity in those areas. All scans were carried out while the subjects were performing a simple test of their working memory - failures of this type of memory being a feature of schizophrenia. "The main difference that we saw after the patients had switched to risperidone was an increase in activity in the pre-frontal cortex," says psychopharmacologist Garry Honey. "There have been theoretical models that these drugs work by increasing activity in this region. This study is the first direct evidence for that activation."
Commenting on the findings, Sharma says that they are heartening for people with schizophrenia. "We were surprised that the improvement was so marked and that function seemed to come back online and to resemble normal brain activity."
Schizpohrenia is not the only condition in which Sharma and his group intend to use fMRI. They are also interested in sexual arousal. They plan to show neutral or sexually stimulating images to people while their brains are being scanned. Although the work has been done using normal subjects, the aim is to study sexual deviance. "What we want to do is define the brain regions that are involved in sexual arousal. Once you have identified those regions, you may have an objective measure of arousal that can be applied to sexual offenders," says Honey.
In this, as in other socially deviant or psychiatric conditions, fMRI offers a potentially useful way of following the progress of disease and monitoring the effectiveness of drug and other treatments. With so few means available to them for studying cognitive and other events as they happen, psychiatrists and neuroscientists will be queuing up to use this most promising window on the brain.