The Experts below are selected from a list of 339105 Experts worldwide ranked by ideXlab platform
Marcus E Raichle - One of the best experts on this subject based on the ideXlab platform.
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The restless Brain: how intrinsic activity organizes Brain Function
Philosophical transactions of the Royal Society of London. Series B Biological sciences, 2015Co-Authors: Marcus E RaichleAbstract:Traditionally studies of Brain Function have focused on task-evoked responses. By their very nature such experiments tacitly encourage a reflexive view of Brain Function. While such an approach has been remarkably productive at all levels of neuroscience, it ignores the alternative possibility that Brain Functions are mainly intrinsic and ongoing, involving information processing for interpreting, responding to and predicting environmental demands. I suggest that the latter view best captures the essence of Brain Function, a position that accords well with the allocation of the Brain's energy resources, its limited access to sensory information and a dynamic, intrinsic Functional organization. The nature of this intrinsic activity, which exhibits a surprising level of organization with dimensions of both space and time, is revealed in the ongoing activity of the Brain and its metabolism. As we look to the future, understanding the nature of this intrinsic activity will require integrating knowledge from cognitive and systems neuroscience with cellular and molecular neuroscience where ion channels, receptors, components of signal transduction and metabolic pathways are all in a constant state of flux. The reward for doing so will be a much better understanding of human behaviour in health and disease.
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Two views of Brain Function
Trends in cognitive sciences, 2010Co-Authors: Marcus E RaichleAbstract:Traditionally studies of Brain Function have focused on task-evoked responses. By their very nature, such experiments tacitly encourage a reflexive view of Brain Function. Although such an approach has been remarkably productive, it ignores the alternative possibility that Brain Functions are mainly intrinsic, involving information processing for interpreting, responding to and predicting environmental demands. Here I argue that the latter view best captures the essence of Brain Function, a position that accords well with the allocation of the Brain's energy resources. Recognizing the importance of intrinsic activity will require integrating knowledge from cognitive and systems neuroscience with cellular and molecular neuroscience where ion channels, receptors, components of signal transduction and metabolic pathways are all in a constant state of flux.
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A default mode of Brain Function.
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Marcus E Raichle, A. Z. Snyder, A M Macleod, W.j. Powers, Debra A. Gusnard, Gordon L ShulmanAbstract:A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human Brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human Brain in terms of the Brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the Brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with Functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the Brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and Functional MRI. These decreases suggest the existence of an organized, baseline default mode of Brain Function that is suspended during specific goal-directed behaviors.
Gordon L Shulman - One of the best experts on this subject based on the ideXlab platform.
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A default mode of Brain Function.
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Marcus E Raichle, A. Z. Snyder, A M Macleod, W.j. Powers, Debra A. Gusnard, Gordon L ShulmanAbstract:A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human Brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human Brain in terms of the Brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the Brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with Functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the Brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and Functional MRI. These decreases suggest the existence of an organized, baseline default mode of Brain Function that is suspended during specific goal-directed behaviors.
Peter Fransson - One of the best experts on this subject based on the ideXlab platform.
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spontaneous low frequency bold signal fluctuations an fmri investigation of the resting state default mode of Brain Function hypothesis
Human Brain Mapping, 2005Co-Authors: Peter FranssonAbstract:Recent neuroimaging studies have lead to the proposal that rest is characterized by an organized, baseline level of activity, a default mode of Brain Function that is suspended during specific goal-oriented mental activity. Previous studies have shown that the primary Function subserved by the default mode is that of an introspectively oriented, self-referential mode of mental activity. The default mode of Brain Function hypothesis is readdressed from the perspective of the presence of low-frequency blood oxygenation level-dependent (BOLD) Functional magnetic resonance imaging (fMRI) signal changes (0.012-0.1 Hz) in the resting Brain. The results show that the Brain during rest is not tonically active in a single mode of Brain Function. Rather, the findings presented here suggest that the Brain recurrently toggles between an introspectively oriented mode (default mode) and a state-of-mind that tentatively might be interpreted as an extrospectively oriented mode that involves a readiness and alertness to changes in the external and internal environment.
A. Z. Snyder - One of the best experts on this subject based on the ideXlab platform.
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A default mode of Brain Function.
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Marcus E Raichle, A. Z. Snyder, A M Macleod, W.j. Powers, Debra A. Gusnard, Gordon L ShulmanAbstract:A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human Brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human Brain in terms of the Brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the Brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with Functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the Brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and Functional MRI. These decreases suggest the existence of an organized, baseline default mode of Brain Function that is suspended during specific goal-directed behaviors.
A M Macleod - One of the best experts on this subject based on the ideXlab platform.
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A default mode of Brain Function.
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Marcus E Raichle, A. Z. Snyder, A M Macleod, W.j. Powers, Debra A. Gusnard, Gordon L ShulmanAbstract:A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human Brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human Brain in terms of the Brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the Brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with Functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the Brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and Functional MRI. These decreases suggest the existence of an organized, baseline default mode of Brain Function that is suspended during specific goal-directed behaviors.