We’ve looked at brain interfaces before (Emotiv Headset). This article looks at a different technique.

If you’ve ever happened to cover the end of a small flashlight with your thumb in a darkened room, you’ve probably noticed that your skin is remarkably transparent to red light. You may have also noticed a periodic darkening of your glowing thumb in synchrony with your heat beat. In broad strokes, that’s the principal by which the finger pulse monitors (plethysmographs) work. It works even better at near infrared wavelengths. Oxygenated blood and deoxygenated blood have maximum absorbances at different wavelengths. By alternating wavelengths, measuring the absorbance, and doing some math,  you can calculate the oxygen saturation of the blood. And that’s a pulse oximeter.

Researchers have long used blood flow in specific areas of the brain as an indicator of brain activity in that region. The principle is sound: increased neural activity requires lots of energy and oxygen, and that results in greater local blood flow. Researchers used to measure blood flow with magnetic sensors, but now use functional magnetic resonance imaging (fMRI) and similar imaging techniques, some of which measure glucose uptake more directly.

OK, now combine the two ideas and you might come up with something like Tom Chau, et al did at the University of Toronto. They used IR emitters and detectors to decode subjects’ preference for one beverage or another with 80% accuracy. It’s a start.

For more information:
www.sciencedaily.com/releases/2009/02/090210092730.htm
www.physorg.com/news153472589.html
www.crunchgear.com/2009/02/10/new-brain-scan-technique-uses-ir-detecting-headband
www.bioe.psu.edu/NMR/pdf_files/2005/enrico.pdf
www.bcs.rochester.edu/people/aslin/pdfs/Aslin_Mehler2005.pdf