Psychology
Functional Magnetic Resonance
Functional Magnetic Resonance Imaging (fMRI) is a neuroimaging technique that measures brain activity by detecting changes in blood flow. It is commonly used in psychology to study cognitive processes, emotions, and behavior. By providing detailed images of brain function, fMRI helps researchers understand how different regions of the brain are involved in various mental processes.
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11 Key excerpts on "Functional Magnetic Resonance"
eBook - ePubAdvanced MR Neuroimaging
From Theory to Clinical Practice
- Ioannis Tsougos(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
7 Functional Magnetic Resonance Imaging (fMRI) 7.1 Introduction Focus Point • Indirect measurement of neural activity, based on hemodynamic changes. • Oxyhemoglobin is diamagnetic, while deoxyhemoglobin is paramagnetic. • Following neuronal activity, there is an increase of oxygenated blood delivery, increasing oxyhemoglobin, therefore increasing the MR signal. • Paradigm design for fMRI is challenging. • Temporal resolution is limited by hemodynamic response. • Need for cooperative patients. • High magnetic fields (≥3 T) are preferable. • Resting state fMRI is a recent concept. 7.1.1 What Is Functional Magnetic Resonance Imaging (fMRI) of the Brain? Functional Magnetic Resonance imaging (fMRI) is a neuroimaging procedure performed in the MRI scanner to evaluate functional brain activity, basically by detecting changes associated with blood flow during specific stimuli. In that sense, the term “functional” may be considered misleading since the procedure actually provides an indirect measurement of neural activity, relying on the fact that cerebral blood flow and neuronal activation may be linked. Although fMRI is indeed one of the most recently applied methods of neuroimaging, the basic idea behind the technique is quite old. That is, if brain activity requires blood flow, it may be possible to estimate it by measuring changes in blood flow. Interestingly, William James in The Principles of Psychology, a monumental text in the history of psychology published in 1890, mentioned an Italian scientist named Angelo Mosso who performed an experiment in the late 1800s by observing the patient on a delicately balanced table, which could tip downward either at the head or the foot if the weight of either end was increased. Theoretically, any emotional or intellectual activity of the subject would redistribute the blood flow and change the table’s balance
eBook - PDF- Joseph V. Hajnal, Derek L.G. Hill, Joseph V. Hajnal, Derek L.G. Hill(Authors)
- 2001(Publication Date)
- CRC Press(Publisher)
196 8.5 Conclusion .................................................................................................. 197 References ............................................................................................. 197 8.1 Introduction to fMRI Functional Magnetic Resonance imaging, or fMRI, is a noninvasive imaging technique used to investigate physiological function. It is most commonly used to study brain function by measuring blood oxygenation level, although other organs (e.g., kidneys) and other quantities (e.g., perfusion) can be studied. This chapter concentrates on using fMRI for blood oxygenation-related imaging of the brain, as image registration has become an indispensible part of the analysis of these data for research and clinical purposes. 184 Medical Image Registration fMRI allows the experimenter to determine which parts of the brain are activated by different types of sensory stimulation, motor activity, or cogni-tive activity. For instance, fMRI can be used to study responses related to visual or auditory stimulation, the movement of a subject’s fingers, or the imagined rotation of 3D objects. The subject in an fMRI experiment will lie within the magnet, and a partic-ular form of stimulation is applied or task performed. For example, the subject may wear special glasses so that pictures can be shown during the experiment. Then, MR images of the subject’s brain are taken, starting with a single high resolution scan. This is used later as an anatomical substrate for overlaying the brain areas which were activated by the stimulus. Next, a series of low res-olution scans (the raw functional images) are taken, one every few seconds; normally, 100 or more such scans are obtained. During some of these scans, the stimulus (in this case the moving picture) will be presented, and during others the stimulus will be absent. These images are sensitive to changes in blood flow and or blood oxygenation in the brain caused by brain activity.
- Darin D. Dougherty, Scott L. Rauch, Jerrold F. Rosenbaum, Darin D. Dougherty, Scott L. Rauch, Jerrold F. Rosenbaum(Authors)
- 2008(Publication Date)
- American Psychiatric Association Publishing(Publisher)
93 4 Functional Magnetic Resonance Imaging Robert L. Savoy, Ph.D. Randy L. Gollub, M.D., Ph.D. The tremendous advances in noninvasive brain-imag- ing technology described in this volume have the po- tential to aid clinicians in the diagnosis of psychiatric illness and to guide and monitor treatment of psychiat- ric disease. Several attributes of Functional Magnetic Resonance imaging (fMRI) suggest that this particular imaging modality will be critically important to the re- alization of this potential. These attributes include safety, reliability, and high spatial and relatively high temporal resolution across the entire brain. One criti- cally important consequence of these attributes is that it is feasible for subjects to be imaged repeatedly over time, thus greatly expanding the range of longitudinal study designs that can directly assess the pathophysi- ology of psychiatric symptoms. The power of fMRI to reveal information about the function of the brain is greatly increased by integrating fMRI data collected during an experimental paradigm with data collected during an identical paradigm with other imaging tools that have greater temporal resolution, such as electro- encephalography (EEG) or magnetoencephalography (MEG)—a strategy known as multimodal integration. These attributes of fMRI allow the clinician-scientist to probe, in awake, active human subjects, the complex neuronal systems that form the substrate for normal and disordered cognition, emotion, and behavior. fMRI uses no ionizing radiation, and there are no other known harmful effects of imaging performed within U.S. Food and Drug Administration (FDA)–approved guidelines; thus, fMRI can be repeated safely with indi- vidual subjects over time.
- Jill Jegerski, Bill VanPatten(Authors)
- 2013(Publication Date)
- Routledge(Publisher)
Functional Magnetic Resonance Imaging (fMRI) Aaron J. NewmanHistory of the Method
Functional Magnetic Resonance imaging (fMRI) celebrated its twentieth birthday in 2012 (Kwong et al., 1992; Ogawa et al., 1992). In this time, it has become the most widely-used technique for noninvasively investigating human brain activity in vivo.1 The first publications showing noninvasive measurement of human brain activity were preceded by more than 100 years of observation and research. In 1890, the physiologists Roy and Sherrington demonstrated that brain volume increased when the peripheral nerves of animals were electrically stimulated, leading them to posit “… the existence of an automatic mechanism by which the blood-supply of any part of the cerebral tissue is varied in accordance with the activity of the chemical changes which underlie the functional action of that part” (Roy & Sherrington, 1890, p. 105). Another key observation was published by Pauling and Coryell in 1936—that hemoglobin, the molecule in our blood that transports oxygen, has different magnetic properties depending on whether it is bound to oxygen (oxyhemoglobin—Hb) or not (deoxyhemoglobin—dHb). Hb is magnetically neutral, while dHb is paramagnetic , meaning that it has weak magnetic properties and will be attracted to a magnetic field. Work in chemistry and physics led to the development of the nuclear magnetic resonance (NMR) technique in the 1970s, which led soon after to the MRI, which uses strong magnetic fields, for in vivo medical imaging. Ogawa, Lee, Kay, and Tank (1990) published work showing that a particular type ofMRI image, called T2*-weighted, was sensitive to the amount of oxygen in the brain. Blood vessels in the brains of rats that were breathing room air appeared much darker in the MRI images than when the rats were breathing pure oxygen. This provided a potential intrinsic contrast
eBook - PDF- Marie T. Banich, Rebecca J. Compton(Authors)
- 2018(Publication Date)
- Cambridge University Press(Publisher)
As can be seen, the data obtained is over a wide spatial area of cortex (from de la Vega et al., 2014). (B) Shown here for comparison is the size of the region of brain tissue (depicted in blue) from which a single measurement can be obtained with more standard measures of brain function, in this case Functional Magnetic Resonance imaging (fMRI). (A) (B) Chapter 3 Methods 80 scientists to examine changes in the brain over time, such as those that occur with learning, and allow clinicians to observe changes occurring during the course of recovery or as a result of treatment regimens. A fourth advantage of fMRI is that it provides a measure of brain activity over seconds rather than minutes as is the case with PET. Finally, the precision of scans obtained from fMRI enables us to examine brain–behavior relationships in individuals, which makes fMRI particularly useful for clinical interventions such as neurosurgery (e.g., Matthews et al., 2006). Task-Based Approaches The original approach used in fMRI, which still accounts for the majority of studies today, is to examine brain activity in fMRI during the performance of a task. Such studies require a special set-up so that information can be conveyed to the par- ticipants and so their responses can be recorded. The typical items of equipment used in a cognitive psychology laboratory cannot be used because they contain metal. Rather all computer and electronic equipment for the study must be located outside the scanner room, in the control room. Special fiber optic or nonferrous metal must be used in all equipment in the scanner room and to link to equipment in the control room. Figure 3.8 shows a typical set-up for a functional neuroimaging study.
- Nick Van Bruggen, Timothy P.L. Roberts, Nick Van Bruggen, Timothy P.L. Roberts(Authors)
- 2002(Publication Date)
- CRC Press(Publisher)
The real breakthrough for functional brain imaging was the Þ rst application of nuclear magnetic resonance (NMR) imaging for functional activation studies. In the Þ rst investigation by Bel-liveau et al., 5 increases in blood ß ow and volume were recorded in the visual cortex during visual stimulation with the NMR contrast agent GdDTPA in 1990. The most common Functional Magnetic Resonance imaging (fMRI) technique, blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) followed in 1991 6 and led to an astounding evolution and expansion of cognitive science. Despite this rapid development, we must remember that many functional imag-ing methods are only indirect indicators of the brain activity, i.e., recording the hemodynamic response to a stimulus. Their correct interpretation depends on the intact coupling of brain activity and the induced metabolic or hemodynamic change. The situation is even more complex with the BOLD technique because the BOLD signal change is based on an increase in blood ß ow that is overproportional compared to the increase of oxygen consumption during functional activation. It must be emphasized, therefore, that the conclusions drawn from BOLD fMRI data are valid only when and if the coupling mechanisms are kept intact. The large amount of data acquired by different imaging modalities con Þ rms the robustness of this coupling of electrical activity and blood ß ow response in the healthy brain. However, the situation may be different in disease states. Coupling is achieved by the interaction of a complex system of biochemical and neurogenic mediators that are subject to pathological interference and may modulate both the effect of functional activation on metabolism and the response of blood ß ow to the change in metabolic activity. Knowledge of such disturbances is vital to understanding the coupling mechanisms and interpreting activation studies under clinical conditions.
eBook - ePub- (Author)
- 2011(Publication Date)
- Academic Press(Publisher)
This chapter reviews the key contributions of Functional Magnetic Resonance imaging (fMRI) to our understanding of human cognition and its various disorders. Following a brief introduction on fMRI methodology, the application of fMRI to elucidate the neural mechanisms underlying some core aspects of human cognition (language, praxis, spatial cognition, memory) is illustrated. The convergence (and divergence) of functional imaging and neurological data from patients with lesions of the central nervous system is then reviewed. Special emphasis is placed on how this informs our knowledge of the pathophysiology of disorders of cognition and neurological disease before the use of robust fMRI paradigms in presurgical patient evaluation and the planning of neurosurgical approaches to, for example, brain tumors (i.e., neuronavigation) is illustrated. Thereafter, the application of fMRI in developing novel approaches to the treatment of patients with neurological and neuropsychological deficits is highlighted. The chapter demonstrates the powerful potential of applying fMRI in both a clinical and a more research-oriented environment and its promising perspective to deliver new insights into neurological diseases and their treatment in the years to come. The chapter finishes by highlighting two particularly promising areas: human pharmacological fMRI and studies that link genotypic and phenotypic information. These intriguing new research avenues allow mapping of modulatory effects of pharmacological agents on large-scale neural systems supporting cognitive functions. The data enable inferences with reference to pharmacodynamics, specific neurotransmitters supporting specific cognitive operations, and most recently, changes in neurophysiological drug effects associated with genetic variations.Functional imaging of the human brain today is largely using fMRI because 1.5 or 3 tesla (T) MRI scanners are universally available. Furthermore, the techniques for determining which parts of the brain are activated (e.g., when moving a finger or making a decision) are easy to implement in a standard clinical environment. Human “brain mapping” is achieved by setting up the MRI scanner in a way that it detects changes in the regional distribution of blood flow to tissue with higher oxygen demand due to increased neural activity. There are different methods to achieve this; the most common technique uses the blood oxygenation level-dependent (BOLD) effect [1
eBook - PDFFunctional Magnetic Resonance Imaging
Advanced Neuroimaging Applications
- Rakesh Sharma(Author)
- 2012(Publication Date)
- IntechOpen(Publisher)
Exp Brain Res. 127, pp.371–381. Functional Magnetic Resonance Imaging – Advanced Neuroimaging Applications 76 McDonald, C.R., Thesen, T., Carlson, C., Blumberg, M., Girard, H.M., Trong,netrpunya, A., Sherfey, J.S., Devinsky, O., Kuzniecky, R., Dolye, W.K., Cash, S.S., Leonard M.K., Hagler, D.J. Jr, Dale, A.M., Halgren, E. (2010)Multimodal imaging of repetition priming: Using fMRI, MEG, and intracranial EEG to reveal spatiotemporal profiles of word processing. Neuroimage. 53,2, pp.707-17. Meinzer, M., Harnish, S., Conway, T., Crosson, B. (2011) Recent developments in functional and structural imaging of aphasia recovery after stroke. Aphasiology , 25,3, pp.271-290. Meyer, F.G. (2003) Wavelet-based estimation of a semiparametric generalized linear model of fMRI time-series. IEEE Trans Med Imaging. 22, pp.315–22. Miki, A., Liu, G.T., Englander, S.A., Raz, J., van Erp, T.G., Modestino, E.J., Liu, C.J., Haselgrove, J.C. (2001) Reproducibility of visual activation during checkerboard stimulation in Functional Magnetic Resonance imaging at 4 Tesla. Jpn J Ophthalmol. 45, pp.151–5. Minati, L., Grisoli, M., Bruzzone, M.G. (2007) MR spectroscopy, functional MRI, and diffusion-tensor imaging in the aging brain: a conceptual review. J Geriatr Psychiatry Neurol. 20,1, pp.3-21. Morales-Chacón, L. (2001) Magnetic resonance spectroscopy and Functional Magnetic Resonance images: non-invasive alternatives for identifying epileptogenic foci. Rev Neurol. 32,3, pp.234-6. Moutoussis, K., Zeki, S. (2004) The Chronoarchitecture of the Human Brain: Functional Anatomy Based on Natural Brain Dynamics and the Principle of Functional Independence. In: Frackowiak RSJ, Friston KJ, Frith CD, Dolan RJ, Price CJ, Jeki S, Ashburner J, Penny W, editor. Human Brain Function. Chapter 13. Elsevier Academic Press, London, pp. 201–229. Müller, H.P., Kassubek, J. (2007) Multimodal Imaging in Neurology: Special Focus on MRI Applications and MEG. Synthesis Lectures on Biomedical Engineering, 2,1, pp.1-75.
eBook - PDF- Joseph D. Bronzino, Donald R. Peterson, Joseph D. Bronzino, Donald R. Peterson(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
6 -1 6.1 Introduction Functional imaging is typically conducted in an effort to understand the activity in a given brain region in terms of its relationship to a particular behavioral state, or its interactions with inputs from another region’s activity. The advances in noninvasive functional brain monitoring technologies provide opportunities to accurately examine the living brains of large groups of subjects over long periods of time, with little impact on their well-being. Neurophysiological and neuroimaging technologies have con-tributed much to our understanding of normative brain function, as well as to our understanding of the neural underpinnings of various neurological and psychiatric disorders. Commonly employed techniques such as electroencephalography (EEG), event-related brain potentials (ERPs), magnetoencephalography (MEG), positron emission tomography (PET), single-positron emission computed tomography (SPECT), and Functional Magnetic Resonance imaging (fMRI), have dramatically increased our understanding of a broad range of brain disorders. Nevertheless, there is still much unknown about these syndromes. This is due, in large part, to the inherent complexity of the neurobiological substrates of these disorders and of the mind itself. In addition, each of the research methods used to study brain function and its disorders have methodological strengths as well as their own inherent limitations. These limitations place con-straints on our ability to fully explicate the neural basis of neurological and psychiatric disorders both inside and outside of the laboratory setting, and to use the information gleaned from laboratory studies 6 Functional Optical Brain Imaging Meltem Izzetoglu Drexel University 6.1 Introduction ...................................................................................... 6 -1 6.2 Working Principles ...........................................................................
eBook - PDF- Stanley Finger, Francois Boller, Kenneth L. Tyler(Authors)
- 2009(Publication Date)
- Elsevier(Publisher)
One criticism of this approach has been that the time necessary to press a key after a decision to do so has been made is affected by the nature of the decision process itself. By implication, the nature of the processes underly-ing the key press, in this example, might have been altered. Although this issue (known in cognitive science jargon as the assumption of pure insertion ) has been the subject of continuing discussion in cognitive psychology, it finds its resolution in functional brain imaging, where changes in any process are directly signaled by changes in observable brain states. Events occurring in the brain are not hidden from the investigator, as in the purely cognitive experi-ments. Careful analysis of the changes in the functional images reveals whether processes (e.g., specific cognitive decisions) can be added or removed without affecting ongoing processes (e.g., motor processes). Processing areas of the brain that become inactive during the course of a particular cognitive paradigm are seen as reductions in functional activity (see Raichle and Mintun, 2006). While changes of this sort are hidden from the view of the cognitive scientist, they become obvious when brain imaging is employed. MAGNETIC RESONANCE IMAGING (MRI) Instrumentation Yet another technology emerged contemporaneously with PET and CT. This was magnetic resonance ima-ging (MRI). MRI is based upon a set of physical prin-ciples associated with the behavior of hydrogen atoms or protons in a magnetic field. When placed in a strong THE ORIGINS OF FUNCTIONAL BRAIN IMAGING IN HUMANS 263 magnet field, protons, as well as some other nuclei, behave like tiny bar magnets that would be expected to line up in parallel with the magnet field. When these protons are disturbed from their equilibrium state by radio frequency pulses, a voltage is induced in a recei-ver coil that can be characterized by its change in mag-nitude over time.
eBook - PDF- Ross J. Roeser, Michael Valente, Holly Hosford-Dunn(Authors)
- 2011(Publication Date)
- Thieme(Publisher)
Other fMRI Techniques Other fMRI techniques are termed perfusion fMRI . These tech-niques, which measure cerebral blood flow, include bolus tracking, which requires the injection of a magnetic compound such as gadolinium, and spin labeling (Moseley et al, 1996). They are somewhat limited in that they are either invasive (bo-lus tracking), which limits the number of times an individual may be scanned without risk of kidney damage, or more time consuming (spin labeling). However, spin labeling can provide highly accurate results when only a specific area of the cortex is being examined. Two other techniques, not technically considered func-tional imaging but utilizing MRI, will undoubtedly play an increasing role in studies of audition. These are diffusion tensor imaging and MR spectroscopy. In diffusion tensor imaging, white matter tracts may be followed and identi-fied. Thus, auditory pathways below the cortex may be studied. In MR spectroscopy, analysis is made of the chemi-cal composition of the brain tissue in the area being exam-ined. The concentration of particular chemical compounds in an area of the brain gives an indication of the health of the tissue in that area. This technique may have potential for determining the effects of auditory deprivation or stim-ulation in auditory areas of the brain, including the cortex. ♦ Magnetoencephalography General Principles Of all the functional imaging techniques, MEG provides the most direct assessment of neural events, detecting the tiny magnetic signals generated directly from traveling current along activated neurons. 8 Functional Brain Imaging 145 • The presence of activation on an fMRI scan provides evidence of some viable function in a particular area of the cortex. Pearl • Some would argue that MEG is more valid than fMRI because it directly measures neural activity, whereas fMRI does this indirectly by assessing regions of increased blood flow.
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