Campaigners say it also adds weight to their calls for newer anti-psychotic drugs to be made more available to patients in the wake of concerns about rationing.

The new research suggests risperidone - one of a number of recent anti-psychotic treatments - improves activity at the front of the brain.

Scientists used brain imaging techniques to track how the drug acted on the prefrontal cortex, which is thought to control human thought processes.

Older schizophrenia drugs have been shown to control some of the thought processes associated with the condition, such as halluncinations and delusions.

But many have side effects, including a Parkinson's disease-like syndrome.

Side effects

Newer drugs like risperidone reduce apathy and social withdrawal, improve patients' ability to think clearly and rarely have severe side effects.

However, until now there have been no studies on humans of how the drugs work on the brain.

In an article in the US magazine, the Proceedings of the National Academy of Science, researchers from the University of Cambridge and the Institute of Psychiatry in London provide the first proof that substituting risperidone for the older drugs increases frontal lobe activity in schizophrenics who were asked to perform a memory-related task.

The researchers also found risperidone was slightly more effective at improving patients' health and memory.

They used functional magnetic resonance imaging, a technique for taking repeated "snapshots" of the brain over time.

These snapshots reveal changes in blood flow and oxygen levels and reflect activity in different parts of the brain.

The researchers believe their findings may open up new avenues for investigation into schizophrenia treatments and will mean doctors will be able to map how different drugs affect an individual's brain.

Rationing

Cliff Prior, chief executive of the National Schizophrenia Fellowship welcomed the new research and said it boosted calls for newer schizophrenia drugs to be made more available.

The organisation has expressed concerns that the drugs are being rationed by the NHS because they tend to be more expensive than older treatments.

Mr Prior said: "It is encouraging to see research which focuses more on people's quality of life than symptom control alone. 

When NICE [the National Institue for Clinical Excellence] evaluates treatments for schizophrenia the views of the real 'experts', people prescribed anti-psychotics, must be the focal point. 

"Many people taking older drugs complain of heavy sedation.   Given the choice, treatments which cause less of this problem are very welcome."