Interferometric near-infrared spectroscopy (iNIRS) noninvasively measures the optical and dynamical properties of the human brain in vivo. However, iNIRS uses single-mode fibers, which reduces the detected light throughput. Here, we demonstrate the parallel interferometric near-infrared spectroscopy (πNIRS) to overcome this limitation. In πNIRS we use multi-mode fibers for light collection and a high-speed, two-dimensional camera for light detection. With more than 8000 parallel channels, we can sense the cerebral blood flow and absorption changes with only 2-10 msec integration time (~100-500x faster than conventional iNIRS). This capability enabled us to monitor prefrontal cortex activation in humans in vivo.
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