Neural activity drives opposite changes in oxygenated and deoxygenated hemoglobin
Evidence
In response to neural activity in the brain, an increase in oxygenated blood is directed to the region, resulting in a drop in de-oxygenated blood. Thus HbO and HbR concentrations change in opposite directions in response to neural activity (Shah and Seghouane 2014 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 4273
Near infra-red (NIR) light (wavelengths 650-1000 nm) is relatively transparent to human tissues. The absorption spectra of oxygenated and de-oxygenated haemoglobin (HbO and HbR respectively) for NIR light differ in that HbO maximally absorbs light of longer wavelength (900-1000 nm) whereas HbR maximally absorbs light of shorter wavelength. These differential absorption spectra make it possible to separate out changes in the concentration of HbO and HbR. In response to neural activity in the brain, an increase in oxygenated blood is directed to the region, resulting in a drop in de-oxygenated blood. Thus HbO and HbR concentrations change in opposite directions in response to neural activity (Shah and Seghouane 2014 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 4281
Categorization
- DEFINE: Explains the hemodynamic basis of fNIRS measurement—the core physiology the reader wants.
- XREF: Relates to the reader’s broader interest in hearing physiology; the HbO/HbR hemodynamic contrast is the shared basis of fNIRS and fMRI BOLD imaging. — connects to: Oxygenated and deoxygenated haemoglobin absorb near-infrared light differently, enabling functional imaging; Brain activity drives opposing concentration changes in oxygenated and deoxygenated blood
- corroborated: 3 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 4273; Dijk, Pim van, Physiology, Psychoacoustics and…, 4281