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May 2013: mini-NIRS for Brain Activity Measurement

Friday, May 31, 2013

May 2013: mini-NIRS for Brain Activity Measurement

Modern imaging technologies that allow glimpses into the brain’s activity require bulky nuclear magnetic resonance scanners and are thus limited to laboratory use.

Researchers from the Bernstein Focus Neurotechnology Berlin and the Berlin-based company NIRx are developing an alternative, portable method of near infrared spectroscopy (NIRS), the mini-NIRS.

As in EEG, NIRS technology assesses the brain from the skull’s surface. But while EEG directly measures voltage changes caused by neuronal activity, NIRS provides clues about the brain’s metabolism by measuring transmitted light which is related to neuronal activity. Depending on the amount of blood and oxygen level in the brain, a detector measures how much of the infrared-sourced light has passed through the brain’s tissue.

While functional magnetic resonance imaging also measures blood oxygenation, NIRS is smaller and less expensive to use, without any interferences caused by electromagnetic fields or muscle contractions.

To test the mini-NIRS’ real life application, volunteers were equipped with a wearable cap that integrates 20 miniaturized light detectors and emitters. The light is produced and measured directly on the skull. The electronics for the data registration, which consist of a thick paperback-sized interface and a laptop, fit into a backpack wire-connected to the cap. Even under distractive conditions, the participants could reliably extract motor control signals for the hand movement from the brain’s contralateral motor center. “In some subjects, we could even relate individual hand movements to the NIRS signals,” said Christoph Schmitz, CEO of NIRx and head of the study. The use of mini-NIRS could enhance brain-computer interfaces, with which, for instance, enable paralyzed patients to control technical devices.

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Activation of motor cortex measured with mini-NIRS in downtown Berlin. Image: © NIRx