Functional Magnetic Resonance Imaging (fMRI),which is one of the most exciting recent developments in biomedical magnetic resonance imaging, allows the non-invasive visualisation of human brain function(1).
Functional MRI is a measurement technique based on ultrafast MR imaging sequences that are sensitive to the physiological changes of cerebral blood flow (CBF) and cerebral blood volume (CBV).These allow the researcher to measure changes in brain function typically via increases or decreases in blood oxygenation during the scanning(2).
The detection of neural activation in fMRI relies on perturbations of the water magnetization that are associated with the hemodynamic change (3).
Advantage and Disadvantage of fMRI
One of the greater advantages of fMRI is the spatial resolution (millimeters), so we can say MR imaging has outstanding spatial resolution but has a short coming with respect to temporal resolution of less than a second (4).
EEG
Electroencephalography is a cheap non-invasive technique which has become widely used in studying brain activity to measure the electric potential differences on the scalp produced by the active cortical neurons (5).
Moreover, EEG provides a direct and real time measurement of neural activity. The temporal resolution is of the order of a few milliseconds, which allow rapid changes in cortical function to be followed. On the other hand the spatial resolution is relatively low (6, 7).
MEG
Magnetoencephalography (MEG) is a non invasive technique for studing neuronal activity in the brain. Unlike electrophysiological methods that depend on volume currents, MEG depends on the primary current (2, 8).
MEG is closely related to EEG. MEG is a more expensive method and provides be...
... middle of paper ...
...ram Recordings. Journal of Magnetic Resonance Imaging 27:607-616 (2008).
11-Karen J. Mullinger, Simultaneous EEG and fMRI at high fields. PhD Thesis 2008.
12-Matthew J. Brooks. Jiri Vrba, Karen J. Mullinger, Geroa Bjork Geirsdottir, Winston X. Yan, Claire M. Stevenson, Richard Bowtell, Petter G. Morris. Source Ilcalisation in concurrent EEG/fMRI: Application at 7T. NeuroImage 45(2009) 440-452.
13-Christos E. Vasios, Leonardo M. Angelone, Patrick L. Purdon, Jyki Ahveninen, John W. Belliveau, and Giorgio Bonmassar. EEG/(f)MRI measurements at 7 Tesla using a new EEG cap (''InkCap''). NeuroImage 33 (2006) 1082-1092.
14-Marcus A. Gray, Ludovico Minati, Neil A. Harrison, Peter J. Gianaros, Vitaly napadow, and Hugo D. Critchley. Physiological recording: Basic concepts and implemntation during functional magnetic resonance imaging. Neuroimage. 2009; 47(3-8): 1105-1115.
...owell, E. R., Thompson, P. M., & Toga, A. W. (2004). Mapping changes in the human cortex
Other testing procedures that are commonly employed, in order to gain a better visual image of the excitatory activity in the brain are the PET scan and the MRI. According to Kalat (2004), these methods are non-invasive, meaning that they don’t require the insertion of objects into the brain, yet they yield results that allow researchers to record brain activity. The PET scan (positron emission tomography) involves the researcher injecting a radioactive chemical into the patient’s body, which is then absorbed mainly by the brain’s most active cells. With the use of radioactive detectors, placed around the patient’s head, a map is produced that shows which areas of the brain are most active.
Rowland, L. P., ed. Merritt’s Textbook of Neurology. 7th ed. Lea and Febiger. Philadelphia: 1984.
[21] Shah, N.J., Marshall, J.C., Zafiris, O., Schwab, A., Zilles, K., Markowitsch, H.J., Fink, G.R., 2001. The neural correlates of person familiarity: a functional magnetic resonance imaging study with clinical implications. Brain 124, 804–815.
In persons suffering from epilepsy, the brain waves, electrical activity in the part of the brain called the cerebral cortex, have a characteristically abnormal rhythm produced by excessive electrical discharges in the nerve cells. Because these wave patterns differ markedly according to their specific source, a recording of the brain waves, known as an electroencephalogram (EEG) is important in the diagnosis and study of the disorder. Diagnosis also requires a thorough medical history describing seizure characteristics and frequency.
In normal sleeping patterns a person usually passes through five phases of sleep, the fifth being REM. The sleeping human passes cyclically through these five phases throughout a night's rest. These phases can be defined in electrical activity of the brain; much like the activity of the heart is often defined. The technique of measuring the electrical activity of the brain is call Electro-encephalogram, or EEG. When the electrical events of a person's brain are graphed on a electrical magnitude versus time axis the graph of a person who is in different stages of being asleep or awake appear to have different levels of electrical activity occurring in the brain. (See (14))
During the period November 2005-January 2009 a survey was conducted by Dr. Owen at the Medical Research Council Cognition and Brain Sciences in the United Kingdom. This clinical study was conducted on 54 patients that received severe brain injury’s 23 of them were in a vegetative state and 31 were in a minimally conscious state. This study main goals are to define the capacitance for a response to stimulation and to evaluate any available response through intervention to form communication using information from routine Magnetic Resonance Imaging (MRI). The investigators developed two different imagery tasks, motor and spatial imagery that the patients were going to perform while they were in the MRI scanner. In the motor imagery they were asked to imagine playing tennis where they hit
Alan Alda's fear of fMRI is re-arranging the hydrogen atoms on the brain. When re-arranging the hydrogen atom in the brain they use a magnetic field and it is same as the electrical field. It is true that they are disrupting the brain with the magnetic and electric field, but they are doing it in very subtle small ways. The
The diagnosis of epilepsy is usually made after the patient experiences a second unprovoked seizure (Leppik, 2002). Diagnosis is often difficult, however, since it is unlikely that the physician will actually see the patient experience and epileptic seizure, and therefore must rely heavily on patient’s history. An electroencephalography (EEG) is often used to examine the patient’s brain waves, and some forms of epilepsy can be revealed by a characteristic disturbance in electrical frequency (Bassick, 1993). The variations in frequency can take form as spikes or sharp waves (Fisher, 1995). The variations are divided into two groups, ictal electrograph abnormalities, which are disturbances resulting from seizure activity, and interictal electrograph abnormalities, or disturbances between seizures. The EEG can also give clues as to which region of the brain the disturbances arise from. Interictal temporal spikes will predict the side of seizure origin in 95% of patients if three times as ...
According to Russell Poldrack’s article, what fMRI can tell us is often overrated despite its powerful impact on the study of the human brain. fMRI is a useful technique that allows us to image brain activities by measuring blood flow in the brain. It expanded our understanding of mental disorders from a biological perspective and helped us understand structures and functions of the brain. However, there are several limitations on what neuroimaging can tell us because it is difficult to determine how our brain works or how we can diagnose and treat mental disorders from them.
The recent advances in non-invasive brain imaging, increased computational power, and advances in signal processing methods have heightened the research in this area. As we make progress in interpreting noninvasive brain signals in time we will begin to explore applications that go beyond treatment. But for now these noninvasive methods of estimating brain activity is still something to be cautious about since it only measures the brain’s blood, oxygen consumption, glucose utilization, and more. These measurements may not be accurate enough to figure out one person’s problem. The problem again might be internal and measuring only the obvious would not aid in figuring it all out.
The best way for someone to see the brain activity and how it is functioning to tell future decisions, is a PET scan. A PET scan is short for positron emission tomography which shows how the brain and tissues are working. It is a radioactive substances that tracks injuries or diseases within the brain. Another scan that can be used is an MRI. An MRI is short for magnetic resonance imaging which is a scan in the head to be able to see trauma to the brain which shows as bleeding or
S.A. Clark, T. A. (1988). Receptive fields in the body-surface map in adult cortex defined by temporally correlated inputs. Nature, 332.
Sullivan, S. J., Hammond-Tooke, G. D., Schneiders, A. G., Gray, A. R., & McCrory, P. (2012). The diagnostic accuracy of selected neurological tests. Journal of Clinical Neuroscience, 19. 423-427. doi:10.1016/j.jocn.2011.09.011
Antidepressant drugs are designed to correct the imbalance. Sutton believes that feedback between his brain machine and MRI pictures of the brain at work will provide more insight not only of depression and Alzheimer's, but of stroke, multiple sclerosis, and other disorders that affect large areas of the brain. In one experiment, he and his colleagues looked at pictures of brains while their owners did simple motor tasks, such as tapping their fingers in simple and complex patterns. As expected, they saw activity in small networks of cells located in brain areas that control movements.