Frequency-domain measurements of changes of optical pathlength during spreading depression in a rodent brain model

Michael B. Maris; Avraham Mayevsky; Eva Marie Sevick; Britton Chance

doi:10.1117/12.44185

1 May 1991 Frequency-domain measurements of changes of optical pathlength during spreading depression in a rodent brain model

Michael B. Maris, Avraham Mayevsky, Eva Marie Sevick, Britton Chance

Author Affiliations +

Proceedings Volume 1431, Time-Resolved Spectroscopy and Imaging of Tissues; (1991) https://doi.org/10.1117/12.44185
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Previously, we have shown that time-resolved spectroscopy can monitor changes in the distribution of photon migration pathlengths which are reflective of the changes in the tissue absorption due primarily to oxygenated or deoxygenated hemoglobin. In this study, we have monitored mean photon migration pathlengths in the frequency domain in the rodent brain insulted by hypoxia, ischemia and spreading depression (SD) using phase modulated spectroscopy (PMS). This technique consisted of monitoring light which emerged from the exposed rodent skull at 8 mm form an incident light source of 754 nm and 816 nm whose intensity was modulated at 220 MHz. The changes in phase-shift, (theta), of the emergent light with respect to the incident light are reflective of the photon pathlengths and hemoglobin absorbance. A multiprobe assembly holding PMS source fiber, nicotinamide dinucleotide (NADH) fluorometric probe, electrocortigraph (ECoG) electrodes, and doppler blood flow probe was placed on the rodent brain to simultaneously monitor brain metabolism, electrical cortical activity (ECoG) and blood flow. The PMS detector fiber was placed 8 mm posterior to the multiprobe assembly. Correlations between changes in intracellular deoxygenation (NADH) and hemoglobin deoxygenation as measured by PMS changes at 754 nm and 816 nm during hypoxia, and ischemia were found. The depolarization phase of spreading depression resulted in a similar increase at both 754 nm and 816 nm. We attribute this result to vasoconstriction and/or the decrease of extracellular space due to water shift in the rodent brain.

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Michael B. Maris, Avraham Mayevsky, Eva Marie Sevick, and Britton Chance "Frequency-domain measurements of changes of optical pathlength during spreading depression in a rodent brain model", Proc. SPIE 1431, Time-Resolved Spectroscopy and Imaging of Tissues, (1 May 1991); https://doi.org/10.1117/12.44185

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