Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Jun 2006
ReviewDesign and analysis of fMRI studies with neurologically impaired patients.
Functional neuroimaging can be used to characterize two types of abnormality in patients with neurological deficits: abnormal functional segregation and abnormal functional integration. In this paper we consider the factors that influence the experimental design, analysis, and interpretation of such studies. With respect to experimental design, we emphasize that: 1) task selection is constrained to tasks the patient is able to perform correctly, and 2) the most sensitive designs entail presenting stimuli of the same type close together. ⋯ At the second level (between subjects), inference should be based on between-subjects variance. Provided that these and other constraints are met, deficits in functional segregation are indicated when activation in one or a set of regions is higher or lower in patients relative to control subjects. In contrast, deficits in functional integration are implied when the influence of one brain region on another is stronger or weaker in patients relative to control subjects.
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J Magn Reson Imaging · Jun 2006
ReviewPrinciples of magnetic resonance assessment of brain function.
MRI has advanced to being one of the major tools for the assessment of brain function. This review article examines the basic principles that underpin these measurements. The main emphasis is on the characteristics and detection of blood oxygen level dependent (BOLD) contrast. ⋯ The second section of the article deals with the imaging characteristics of BOLD in terms of the attainable spatial resolution and linear system characteristics. In the third section, practical BOLD imaging is examined for choice of pulse sequence, resolution, echo time (TE), repetition time (TR), and flip angle. The final section touches on other MRI approaches that are relevant to cognitive neuroimaging, in particular the measurement of blood flow, blood volume, resting state fluctuations in the BOLD signal, and measures of connectivity using diffusion tensor imaging and fiber-tracking.
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Over the past dozen years, the use of MRI techniques to map brain function (fMRI) has sparked a great deal of research. The ability of fMRI to image several different physiological processes concurrently (i.e., blood oxygenation, blood flow, metabolism) and noninvasively over large volumes make it the ideal choice for many different areas of neuroscience research in addition to countless applications in clinical settings. ⋯ There seems to be no foreseeable end in sight to the advancement of fMRI techniques and its subsequent use in basic research as well as in clinical settings. In this work, fMRI techniques and the ongoing development of existing techniques are discussed with implications for the future of fMRI.
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J Magn Reson Imaging · Jun 2006
ReviewThe clinical potential of functional magnetic resonance imaging.
Functional magnetic resonance imaging (fMRI) has had a huge impact on understanding the healthy human brain. To date it has had much less impact in clinical neuroscience or clinical practice. ⋯ Nevertheless, there are emerging applications for clinical fMRI, and as the field matures the number of applications is likely to grow. It seems certain that fMRI has an important role to play in helping us understand the mechanisms of neuropsychiatric diseases and in helping to identify effective therapeutic strategies.