scholarly journals Conference Report: Functional Magnetic Resonance Imaging for Beginners – A Review of the fMRI Experience IV, 13–14 May 2002, Natcher Conference Center, National Institutes of Health, Bethesda, MD

2002 ◽  
Vol 2 ◽  
pp. 1803-1807
Author(s):  
Daniel Caggiano ◽  
Mateus Joffily
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Conference Report ◽  
National Institutes Of Health ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
International Audience ◽  
Fmri Response ◽  
Imaging Mechanisms

The fourth fMRI Experience meeting was held at the Bethesda, Maryland campus of the National Institutes of Health on May 13thand 14th, 2002. The purpose of the meeting was to provide a platform for students working with functional magnetic resonance imaging (fMRI) to present their research to an international audience of peers. This year’s meeting featured special lectures from Dr. Leslie Ungerleider (“Imaging Mechanisms of Visual Attention”) and Dr. Daniel Weinberger (“Genetic Variation and fMRI Response”).

Ocular Dominance in Human V1 Demonstrated by Functional Magnetic Resonance Imaging

1997 ◽  
Vol 77 (5) ◽  
pp. 2780-2787 ◽  
Author(s):  
Ravi S. Menon ◽  
Seiji Ogawa ◽  
John P. Strupp ◽  
Kâmil Uǧurbil
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Ocular Dominance ◽  
Blood Oxygen Level Dependent ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Contrast Mechanism ◽  
Fmri Response ◽  
The Difference

Menon, Ravi S., Seiji Ogawa, John P. Strupp, and Kâmil Uǧurbil. Ocular dominance in human V1 demonstrated by functional magnetic resonance imaging. J. Neurophysiol. 77: 2780–2787, 1997. Very high resolution functional magnetic resonance imaging (fMRI) at a 4 Tesla (T) magnetic field was used to map ocular dominance regions in the human visual cortical layers using the blood oxygen level dependent (BOLD) contrast mechanism. The fMRI response from primary visual cortex (V1) exhibited a distribution of ocular dominance reminiscent of the single-cell recordings of Hubel and Wiesel. Pixels could be grouped into seven categories varying from left-only response to binocular-only response to right-only responses. Nonspecific responses were found in the MRI-visible draining veins as well as in the parenchyma. Although large vessel BOLD signals are easily detectable, regardless of field strength, they demonstrate a fMRI response to photic input that could not be used to distinguish ocular dominance. The difference in BOLD response between a region activated by one eye and that activated by the other is only 2.9% on average. This necessitates the use of a difference paradigm to visualize the regions of ocular dominance accurately. The data show that BOLD-based fMRI is sensitive to neuronal activity in cortical columns when using differential techniques, opening up the possibility of mapping specialized populations of neurons in humans that are not accessible to electrophysiological or other methods of invasive mapping.

scholarly journals Systems Analysis of Functional Magnetic Resonance Imaging Data Using a Physiologic Model of Venous Oxygenation

2001 ◽  
Vol 21 (5) ◽  
pp. 517-528 ◽  
Author(s):  
John H. Woo ◽  
Gasser M. Hathout
Keyword(s):  
Magnetic Resonance Imaging ◽  
Mathematical Model ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Linear Behavior ◽  
Fmri Response ◽  
Physiologic Model ◽  
Task Activation

The authors revisit a simple mathematical model, presented in previous work, that characterizes the response of cerebral venous oxygenation to changes in blood flow and oxygen consumption. This physiologically based model can qualitatively duplicate the results of several recent empirical studies in which other authors have tested the hypothesis of linearity in the functional magnetic resonance imaging (fMRI) response to task activation, in that the experimentally found nearly linear behavior of the system and also its subtle departures from linearity are both predicted by simulations of the model. The model is simple enough that its equations can be explicitly solved. Moreover, an amended model that incorporates a varying cerebral blood volume parameter is found to have similar if not better consistency with the empirical data; indeed, this “extended” model is shown to be solvable by the same differential equation as the authors' simple one, wherein the volume is fixed as a constant. These investigations lend further indirect support to the blood oxygen level-dependent hypothesis of venous deoxyhemoglobin as the primary mechanism for fMRI signal changes during task activation, as well as for the authors' simple system as a useful physiologic model thereof. Although the authors' mathematical model does not formally represent a linear system with respect to the flow input, its underlying linear character may help partially explain the “nearly” linear behavior of the fMRI response.

Functional Magnetic Resonance Imaging Measures of Blood Flow Patterns in the Human Auditory Cortex in Response to Sound

1998 ◽  
Vol 41 (3) ◽  
pp. 538-548 ◽  
Author(s):  
Sean C. Huckins ◽  
Christopher W. Turner ◽  
Karen A. Doherty ◽  
Michael M. Fonte ◽  
Nikolaus M. Szeverenyi
Keyword(s):  
Magnetic Resonance Imaging ◽  
Blood Flow ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Speech Stimuli ◽  
Complex Stimuli ◽  
Scanning Session ◽  
Auditory Research

Functional Magnetic Resonance Imaging (fMRI) holds exciting potential as a research and clinical tool for exploring the human auditory system. This noninvasive technique allows the measurement of discrete changes in cerebral cortical blood flow in response to sensory stimuli, allowing determination of precise neuroanatomical locations of the underlying brain parenchymal activity. Application of fMRI in auditory research, however, has been limited. One problem is that fMRI utilizing echo-planar imaging technology (EPI) generates intense noise that could potentially affect the results of auditory experiments. Also, issues relating to the reliability of fMRI for listeners with normal hearing need to be resolved before this technique can be used to study listeners with hearing loss. This preliminary study examines the feasibility of using fMRI in auditory research by performing a simple set of experiments to test the reliability of scanning parameters that use a high resolution and high signal-to-noise ratio unlike that presently reported in the literature. We used consonant-vowel (CV) speech stimuli to investigate whether or not we could observe reproducible and consistent changes in cortical blood flow in listeners during a single scanning session, across more than one scanning session, and in more than one listener. In addition, we wanted to determine if there were differences between CV speech and nonspeech complex stimuli across listeners. Our study shows reproducibility within and across listeners for CV speech stimuli. Results were reproducible for CV speech stimuli within fMRI scanning sessions for 5 out of 9 listeners and were reproducible for 6 out of 8 listeners across fMRI scanning sessions. Results of nonspeech complex stimuli across listeners showed activity in 4 out of 9 individuals tested.

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