Noninvasive assessment of changes in cytochrome-c oxidase oxidation in human subjects during visual stimulation

In this study the authors used a whole-spectrum near-infrared spectroscopy approach to noninvasively assess changes in hemoglobin oxygenation and cyto chrorne-c oxidase redox state (Cyt-Ox) in the occipital cortex during visua l stimulation. The system uses a white light sourer (halogen lamp). The lig ht reflected from the subject's head is spectrally resolved by a spectrogra ph and dispersed on a cooled charge-coupled device camera. The authors show ed the following using this approach: (1) Changes in cerebral hemoglobin ox ygenation (increase in concentration of oxygenated hemoglobin, decrease in concentration of deoxygenated hemoglobin) in the human occipital cortex dur ing visual stimulation can be assessed quantitatively. (2) The spectral cha nges during functional activation cannot be completely explained by changes in hemoglobin oxygenation solely; Cyt-Ox has to be included in the analysi s. Only if Cyt-Ox is considered can the spectral changes in response to inc reased brain activity be explained. (3) Cytochrome-c oxidase in the occipit al cortex of human subjects is transiently oxidized during visual stimulati on. This allows us to measure vascular and intracellular energy status simu ltaneously.