A layered approach sharpens brain signals in optical imaging

Near-infrared spectroscopy, or fNIRS, offers a way to monitor brain activity without surgery or radiation by tracking changes in blood flow and oxygenation. Light sources placed on the scalp send near-infrared light into the head, and detectors measure the light that scatters back. Because this light must pass through the scalp and skull before reaching the brain, the measured signal always includes a mix of superficial and cerebral contributions. Separating those signals has long been a central challenge for fNIRS researchers.