Event-related optical signal (EROS) is a brain-scanning technique that uses
infrared light through
optical fibers to measure changes in optical properties of active areas of the
cerebral cortex. Whereas techniques such as
diffuse optical imaging (DOI) and
near-infrared spectroscopy (NIRS) measure optical absorption of haemoglobin, and thus are based on blood flow, EROS takes advantage of the scattering properties of the
neurons themselves, and thus provide a much more direct measure of cellular activity. EROS can pinpoint activity in the
brain within millimeters (spatially) and within milliseconds (temporally). Currently, its biggest limitation is the inability to detect activity more than a few centimeters deep, which thus limits this fast
optical imaging to the
cerebral cortex. EROS is a new, relatively inexpensive technique that is non-invasive to the test subject. It was developed at the
University of Illinois at Urbana-Champaign in the Cognitive Neuroimaging Laboratory of Dr. Gabriele Gratton and Dr. Monica Fabiani.