1Department of Biological Regulation, Weizmann Institute of Science, 2Unit of Biological Services, Weizmann Institute of Science, 3Department of Diagnostic Imaging, Meir Medical Center, 4Pathology Department, Meir Medical Center
1Department of Biology, Centre for Vision Research, York University
Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel—University of Southern California
Traditional brain imaging techniques using MRI are very good at visualizing the gross structures of the brain. A structural brain image made with MRI provides high contrast of the borders between gray and white matter, and information about the size and shape of brain structures. However, these images do not detail the underlying structure and integrity of white matter networks in the brain, which consist of axon bundles that interconnect local and distant brain regions.
Diffusion MRI uses pulse sequences that are sensitive to the diffusion of water molecules. By measuring the direction of diffusion, it is possible to make inferences about the structure of white matter networks in the brain. Water molecules within an axon are constrained in their movements by the cell membrane; instead of randomly moving in every direction with equal probability (isotropic movement), they are more likely to move in certain directions, in parallel with the axon (anisotropic movement; Figure 1). Therefore, measures of diffusion anisotropy are thought to reflect properties of the white matter such as fiber density, axon thickness, and degree of myelination. One common measure is fractional anisotropy…
1Institute of Imaging Science, Vanderbilt University, 2Department of Radiology and Radiological Sciences, Vanderbilt University, 3Department of Biomedical Engineering, Vanderbilt University, 4Department of Molecular Physiology and Biophysics, Vanderbilt University, 5Department of Physical Medicine and Rehabilitation, Vanderbilt University, 6Department of Physics and Astronomy, Vanderbilt University
1Department of Neurology, University of Ulm
1Department of Neurosurgery, Medical College of Wisconsin, 2Department of Biomedical Engineering, Marquette University
1National Service of Neurosurgery, Centre Hospitalier de Luxembourg, 2University of Applied Sciences Trier, 3Internal Medicine, Erasmus Universiteit Rotterdam, 4Service of Neuroradiology, Centre Hospitalier de Luxembourg
1Providence VA Medical Center, Department of Psychiatry & Human Behavior, Alpert Medical School, Brown University, 2Department of Psychology, University of Georgia
1Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, 2Center of Medical Imaging and Computing, UCL, 3Department of Neurosurgery, National Hospital for Neurology and Neurosurgery
1Functional and Applied Biomechanics Section, Rehabilitation Medicine Department, Clinical Center, National Institutes of Health
Functional magnetic resonance imaging (fMRI) is a non-invasive neuroimaging technique used to investigate human brain function and cognition in both healthy individuals and populations with abnormal brain states. Functional MRI utilizes a magnetic resonance signal to detect changes in blood flow that are coupled to neuronal activation when a specific task is performed. This is possible because hemoglobin within the blood has different magnetic properties depending on whether or not it is bound to oxygen. When a certain task is performed, there is an influx of oxygenated blood to brain regions responsible for that function, and this influx can then be detected with specific MRI scan parameters. This phenomenon is termed the blood oxygen level ependent (BOLD) effect, and can be used to create maps of brain activity.
This video begins with a brief overview of how MRI and fMRI signal is obtained. Then, basic experimental design is reviewed, which involves first setting up a stimulus presentation that is specifically designed to test the function that will be mapped. Next, key steps involved in performing the fMRI scan are introduced, including subject safety and setting up at the scanner. Commonly used steps for data processing are then presented, including pre-processing and statistical analysis with the general linear …
1Department of Pediatrics, Division of Neurology, The Emory University School of Medicine