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Scientists shed light on brain activity

17 Jun 2002

A new non-invasive infrared spectroscopy technique to study brain activity will make skull surgery history.

Scientists at the University of Illinois, US, have pioneered a non-invasive diagnostic tool that can monitor changes at the brain's surface. Based on near-infrared spectroscopy, the technique looks set to replace more complicated and expensive methods such as magnetic resonance imaging (MRI) and positron emission tomography.

Enrico Gratton and his colleagues' technique measures brain activity by tracking the flow of blood and oxygen consumption in the brain. "Whenever a region of the brain is activated, for example directing a movement in a finger, that part of the brain uses more oxygen," explained Gratton.

The technique works by sending light from near-infrared laser diodes along optical fibers to a person's head. On penetrating the skull, the light enters regions of different blood and oxygen levels and is scattered. Using detectors to collect and examine the levels of scattered light, the scientists can map portions of the brain and extract information about its activity.

"By measuring scattering in this way, we can also determine where the neurons are firing," said Gratton. "This means we can simultaneously detect blood profusion and neural activity."

To validate their technique, the scientists measured haemoglobin oxygen concentrations with MRI, today's "gold standard" in brain studies, and their near-infrared spectroscopy. "Both methods were used to generate maps of the brain's motor cortex during a period of simulation by finger motion and rest," said Gratton. The scientists found that each technique produced similar results and are now keen to put it into practice.

"[Near-infrared spectroscopy] could be used to find hematomas in children and also to monitor recovering stroke patients on a daily or even hourly basis," added Gratton. "This would be impractical with MRI."

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