Local hemodynamic changes that accompany changes in brain activity cause local magnetic resonance imaging (MRI) signal changes. Functional MRI (fMRI) is the name used for the group of MRI techniques used to detect these changes to map human brain activation. In this dissertation, eight studies were carried out which included the dissection of activation–induced MRI signal change components and characterization of their correlation with the magnitude, timing, and extent of neuronal activation and subsequent hemodynamic events; post processing method development; and fMRI applications. Study one involved the characterization of activation–induced signal change locations, dynamics, and magnitudes using echo–planar imaging (EPI) sequences with combinations of different hemodynamic sensitizations. Study two involved the development and implementation of correlation and Fourier analysis for robust brain activation image creation.

Cerebrovascular reactivity, suppression of neuronal activity,

Simultaneously acquired EEG and BOLD (Blood Oxygenation level dependent contrast) MRI allowed to study on line the neurophysiological changes in rat brain during epileptic seizures. MRI and EEG data were acquired with a specially designed high quality MR RF-antenna with incorporated non-invasive carbon EEG electrodes. The problem of severe pollution of the EEG data due to MR gradient switching during simultaneous EEG/MRI acquisitions was solved by a specially designed automated effective filtering algorithm. We measured continuously EEG data, and T 2 * -weighted coronal MRI sections of rat brain before and after the injection of pentetrazol (43mg/(kg body weight) PTZ; convulsive dose 97%), an epilepsy inductor. In this way, we could correlate the abnormalities in the EEG traces, with changes in the MRI BOLD signal intensities. Immediately after PTZ induction and before epileptic discharges were observed on the EEG traces, the cortex displayed an increase in BOLD signal intensity (inc...