An experiment conducted in the BBC Television series Alternative Medicine: The Evidence (BBC TWO, 9.00pm, Tuesday 24 January 2006) - presented by scientist Professor Kathy Sykes from Bristol University - shows acupuncture has a powerful and measurable effect on the human brain.

The effect is surprising, because scientists have previously predicted that parts of the cortex would be activated during acupuncture.

This unique experiment suggests that, on the contrary, parts of the brain, beyond the cortex, are actually deactivated.

The first programme in the three part series brings together a group of leading scientists including neuro-scientist Mark Lythgoe (UCL); neuro-physiologist Dr Aziz Asghar (Hull York Medical School); physician in clinical research Dr George Lewith (Southampton University); and acupuncturist Dr Hugh McPherson (University of York).

Together they devise a rigorous scientific test to assess the neurological effect of acupuncture.

Volunteers were subjected to a process acupuncturists call 'deep needling' and the findings were compared with a control group undergoing 'superficial needling'.

'Deep needling' involves having needles inserted approximately one centimetre into the back of the hand at a well known acupuncture point and the needles are then rotated by the practitioner until the effect acupuncturists call de chi (pronounced "duh chee") is experienced - the subjects feeling a dull, achy or tingling sensation.

Those undergoing 'superficial needling' have needles only inserted approximately one millimetre into a similar point.

During these two procedures the volunteers underwent brain scans to see what, if any, effect there was in the brain.

In the programme, when the results of the scans are analysed, the scientists discover that 'superficial needling' results in activation of the motor areas of the cortex, a normal response to touch or pain.

With 'deep needling' and de chi, a deeper part of the brain is affected.

This is within what is often known as the limbic system and, surprisingly, this part of the brain is deactivated with 'deep needling'.

Professor Sykes says: "The particular area of the brain where MRI shows deactivation during acupuncture is part of the 'pain matrix' which is involved in the perception of pain – it helps someone 'decide' whether something is painful or not, so it could be that acupuncture in some ways changes a person's pain perception."

The most up-to-date functional magnetic resonance imager (MRI) at York University was used - MRI is a relatively new technology that measures the changes in blood flow that result from brain activity.

Neuroscientists are more familiar with interventions causing activations and this result seems to support anecdotal accounts of acupuncture - and some experimental studies - which indicate that the therapy is particularly effective in the management of pain.

Professor Sykes goes on: "I'm just thrilled that we managed to do a real scientific experiment, shaped and run by scientists and run by acupuncturists together, where we found something quite unexpected; that acupuncture is having a measurable effect on the human brain."

In Alternative Medicine: The Evidence, Professor Kathy Sykes examines three forms of alternative medicine – acupuncture, healing and herbalism – to see if there is any scientific evidence for their effectiveness.

In the first programme on acupuncture, in addition to this neuroscience study, she travels to the United States and China where acupuncture is routinely used alongside conventional medicine in hospitals.

In China she witnesses a conscious patient undergoing open-heart surgery with acupuncture being used without general anaesthetic.