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. Author manuscript; available in PMC: 2011 Apr 18.
Published in final edited form as: J Neuropsychiatry Clin Neurosci. 2010 Fall;22(4):iv–360. doi: 10.1176/appi.neuropsych.22.4.iv

Figure 2.

Figure 2

In the near-infrared range the major light-absorbing chromophores in tissue are water (gold), hemoglobin (oxyhemoglobin, pink; deoxyhemoglobin, blue), and cytochrome oxidase (green). Light penetrates tissue most deeply at wavelengths between ~700 –900 nm (gray band). Measurements are made at several wavelengths in order to be differentially sensitive to changes in oxyhemoglobin and deoxyhemoglobin. Measurement at an isobestic point (arrow), a wavelength equally sensitive to both, is sensitive to changes in total hemoglobin concentration.