Optical imaging

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Optical imaging is a recent technique that gives cognitive neuroscientists the ability to simultaneously obtain information about the source of neural activity as well as its time course. In other words, it allows them to "see" neural activity and study the functioning of the brain.

In this method, a laser source of near infrared light is positioned on the scalp. Detectors composed of optic fiber bundles are located a few centimeters away from the light source. These detectors sense how the path of light is altered, either through absorption or scattering, as it traverses brain tissue.

This method can provide two types of information. First, it can be used to measure the absorption of light, which is related to concentration of chemicals in the brain. Second, it can measure the scattering of light, which is related to physiological characteristics such as the swelling of glia and neurons that are associated with neuronal firing. Important chemicals that this method can detect include hemoglobin and chytochromes.