High-denisty DOT system. High-denisty DOT system. (a) Schematic of the high-density imaging grid with 24 sources (red) and 28 detectors (blue). Measurement pairs are represented by green lines. We used first-, second-, third-, and fourth-nearest-neighbor pairs at source–detector separations of 13, 30, 40, and 48 mm, respectively. (b) Schematic showing the placement of the imaging grid over the visual cortex. (c) Detected light level vs. source–detector separation on a human subject averaged over 1 sec (≈10 image frames). All first-, second-, third-, and fourth-nearest-neighbor pairs were detected simultaneously and were well above the noise floor (dotted line). Benjamin W. Zeff et al. PNAS 2007;104:29:12169-12174 ©2007 by National Academy of Sciences