Mind scanners move in

February 28, 1997

Neuroscience is unravelling more about the functions of the brain. THE uncertainties of brain surgery could soon be overcome thanks to cutting-edge research at London University. Scientists at the Institute of Psychiatry, part of King's College, are pioneers in using magnetic resonance imaging not just to scan the brain's structure but also to investigate how an individual's brain functions.

Steve Williams, of the institute's neuro-imaging unit, says such imaging techniques have been used since the late 1970s to observe anatomy, but that only recently have people explored the idea of looking at brain function this way.

"We are the first group in Britain to use this technique regularly in a clinical environment. Other methods of looking at brain function have involved putting electrodes on a person's head or injecting them with radioactive material," he said. "These are obviously more dangerous methods and not ideal for young children or old people. Also, if you want to measure something serially there are only so many times you can do it safely."

The scanner at the institute is far less invasive. It works by taking a picture of blood oxygen status within the brain. To measure the parts of the brain involved in a specific function scientists ask a patient to lie in the scanner and perform a task such as speaking for 30 seconds, followed by a similar period of inactivity.

The process is repeated for five minutes, with the machine recording snapshot images of blood oxygen levels in the whole brain at intervals of three seconds. The resulting images are superimposed, with all the active images added together, and then all the inactive images totalled.

Two images appear, showing the relative distribution of blood oxygen in the brain dependent on whether someone is talking or remaining silent. Dr Williams explained: "Activity in an area of the brain results in more blood and oxygen flowing to that region. That gives a changed picture. The images reveal which hemisphere of that person's brain is, for example, language-dominant. You get information this way about deep structures as well as about those on the surface.

"In approximately 85 per cent of cases, if you are right-handed the left side of the brain is language dominant. If someone has a brain tumour and surgeons are having to remove tissue, it is important to make sure you are not removing the eloquent part of the brain responsible for language."

Such images are already being used to corroborate information about brain function which has been gained through other more invasive procedures. "The objective for the medium and long term is to find out, through this simple, non-invasive method, which parts of the brain surgeons should be avoiding while operating on an individual," said Dr Williams.

The institute also hopes to use the technology as a way of monitoring how best to treat patients recovering from strokes.

"If you are young, the plasticity of the brain allows some reorganisation. There are a number of different drugs in development that may speed up the recovery. We hope to use the machine to monitor, over time, the improvements in brain processes and function, to see what methods facilitate the greatest preservation of brain structure and function."

What happens to the brain when people hear alien voices in their heads is also being investigated by scientists at the institute. Peter Woodruff, at the department of psychological medicine, has found evidence to suggest that something very real is happening in the minds of people who repeatedly hallucinate. He has undertaken research using magnetic resonance imaging to map what happens in the patient's mind. Tests show that blood-flow in the part of the brain normally associated with hearing increases when the voices are present.

"During hallucinations we saw increased blood-flow in the part of the brain that normally perceives speech," said Dr Woodruff.

He has gone on to show that the areas in the brain activated during hallucinations are similar to areas activated when the patient, during a non-hallucinatory period, listens to taped speech. "When the patient is not hallucinating, playing the tape activates the area of the brain which normally responds to speech. The areas activated during auditory hallucinations overlap, though they are not exactly the same," he said.

Dr Woodruff found that when he played the taped speech to patients while they were hallucinating, he discovered that res-ponse to the speech was less than when he played it during a non-hallucinating period.

"It appears that there is a competitive process for areas of the brain which perceive speech between the external speech and the hallucinations," Dr Woodruff said. "We know that when a person is hallucinating, there is less capacity for the brain to respondto the external speech."

Please login or register to read this article

Register to continue

Get a month's unlimited access to THE content online. Just register and complete your career summary.

Registration is free and only takes a moment. Once registered you can read a total of 3 articles each month, plus:

  • Sign up for the editor's highlights
  • Receive World University Rankings news first
  • Get job alerts, shortlist jobs and save job searches
  • Participate in reader discussions and post comments

Have your say

Log in or register to post comments