Blaise Frederic - Quantitative cerebral hemodynamic measures and physiological noise ... скачать в хорошем качестве

Blaise Frederic - Quantitative cerebral hemodynamic measures and physiological noise ...

Extracting quantitative cerebral hemodynamic measures and removing physiological noise from BOLD fMRI data using time delay processing BOLD fMRI data is affected by the oxygenation and volume of blood moving through the circulatory system. Because these properties are carried by the blood itself, fluctuations in these parameters arrive at different parts of the brain at different times. Time delay processing extracts hemodynamic information from BOLD fMRI data by characterizing the time delay between a regressor reflecting these parameters and the BOLD data throughout the brain. Global endogenous random variations of blood volume and oxygenation can be tracked as they pass through the highly perfused tissue of the brain through their effect on the BOLD signal by determining the strength and peak time delay of their cross correlation with regressors generated from near infrared spectroscopy (NIRS) data, or extracted from the BOLD data itself. Blood oxygenation can also be manipulated with a gas challenge to increase the SNR of the technique. Using this technique, BOLD data can be separated into global hemodynamic effects and local hemodynamic variations due to neuronal activity.