Investigating human brain functions in real-time

Abstract

In recent years, the technique known as functional magnetic resonance imaging (fMRI) has played a significant role in the study of the functions of the human brain. The technique is based on blood oxygenation level dependent (BOLD) signal, which gives an indirect measure of the neuronal activities within the brain. A typical fMRI session usually involves several thousands of MR image data acquired as individual slices with spatial resolution of a few millimeters and sampled at around one image volume per three to six seconds. In most cases, there is a need to preprocess the acquired images to remove unwanted signals such as head motion and other physiological noise. The signal intensity of each volume element (voxel) is then analyzed to determine whether it is affected by the behavioral performance of the subject during the experiment. The result of the analysis is the activation map, which indicates regions in the brain that are activated when the subject performed the specified task. In other words, activation maps are "windows" where we can see what part of the brain is involved when we think, smell, feel, taste, or move. The computational demand, however, is usually very high that most fMRI experiments are analyzed offline and the results become available only several hours or days after the experiment. This motivated the development of real-time functional MRI, a technique used for the immediate analysis of fMRI data with results available within seconds after data acquisition.