Astrocyte-Neuron Lactate Shuttle and Hemodynamic Brain Scans
Hemodynamic brain scans such as Positron Emission Tomography (PET) and functional Magnetic Resonance Imaging (fMRI) have been of immense utility in the neuroscience fields in illuminating the components and modulation of brain function. However, these hemodynamic brain scans have afforded utility without brain scientists truly understanding the mechanism by which they produce signals. Previously, it had been accepted without verification that the images produced by such techniques were direct results of neuronal activity. However, new techniques in studying brain function have revealed that when astrocyte activity is inhibited, hemodependent brain scans do not function (Halber 2008). Additionally, other studies have demonstrated that astrocytes display finely tuned responses to stimuli (Halber 2008) which are amenable to communication with each other in networks via calcium-wave propagation. In light of these new findings in regards to astrocyte function and communication, their influence on hemodynamic brain scans would offer much lucidity to our current understanding of neuropathology and neuromodulation.
General Findings of Astrocytic Influence on Brain Scans
Both PET and fMRI scans are hemodependent brain scans. However, the mechanism by which each works do differ from each other by which fundamental principle of blood flow they measure. In fMRI, a BOLD-signal (blood-oxygen-level-dependent) measurement is utilized which is then translated into working images. PET scans require a radioactive labeled tracer which accumulates in areas of activation. These active areas are then expressed in imaging techniques that interpret the level of activation. However,...
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...arch 2009. doi:10.1016/j.tins.2008.11.005
Mo. (2008, June 20). Starring role in the brain for astrocytes [Web log post]. Retrieved from http://scienceblogs.com/neurophilosophy/2008/06/astrocytes_starring_role_in_the_brain.php
Schummers, J., Yu, H., & Sur, M. (2008). Tuned responses of astrocytes and their influence on hemodynamic signals in the visual cortex. Science, 320, 1638-1643.
doi: 10.1126/science.1156120
Segelken, R. (2004). CU laser microscopy technique settles brain chemistry debate, could aid studies of Alzheimer’s, stroke damage. Cornell Chronicle. Retrieved from http://www.news.cornell.edu/chronicle/04/7.1.04/astrocyte-neuron.html
Vaishnavi S.N., Vlassenko A.G., Rundle M.M., Snyder A.Z., Mintun M.A., Raichle, M.E.,
(2010). Regional aerobic glycolysis in the human brain. Proc. Natl. Acad. Sci. U SA.
107, 17757–17762. doi: 10.1073/pnas.1010459107
Astrocytes are star-shaped glial cells in the brain and spinal cord. They are the most abundant cell of the human brain. Astrocytes provide neurons with metabolic support, control local blood flow, and regulate the maintenance of synapses. They are a critical part of normal neural functioning. (3)
Positron Emission Tomography is a scanning technique that allows us to measure in detail the functioning of distinct areas of the human brain while the patient is comfortable, conscious and alert. PET represents a type of functional imaging, unlike X-rays or CT scans, which show only structural details within the brain. The differences between these types of imaging don’t end there.
In the last 20 years ago, there was a brain scientists that believed that neurons communicated to each other, they represented thoughts, and that glia were kind of like a stucco and mortar holding the house together. They were also considered simple insulators for neuron communication. There is a few of types of glial cells, but recently scientists have begun to focus on a particular type of glial cell it is called the astrocyte; it’s an abundant in the cortex. As you go up the evolutionary ladder, astrocytes in the cortex increase in size and number, with humans having the most astrocytes and also the biggest. Scientists also discovered that astrocytes communicate to themselves in the cortex and they are also capable of sending information to neurons. Astrocytes are also the adult stem cell in the brain and control blood flow to regions of brain activity.
Hemineglect is present when there is damage to the dorsal/ where visual pathway in the brain which leads from the occipital lobe of the brain to the parietal lobe. The ‘where visual pathway’ is concerned with constructing three dimensional representations of the environment and helps our brain to navigate where things...
Even if optogenetics remains as purely a research tool and does not give rise to beneficial effects directly in our species, it has still offered humans an unparalleled look into the function and dysfunction of the nervous system. Optogenetics has been adopted in laboratories around the world and enabled scientists to increase or decrease the activity of exclusive brain expanses on command. Great insight has been obtained through the use of this research tool and a great deal more
The detection of neural activation in fMRI relies on perturbations of the water magnetization that are associated with the hemodynamic change (3).
Kanske, P., Heissler, J., Schönfelder, S., Forneck, J., & Wessa, M. (2013). Neural correlates of
Neuroimaging is a multidiscipline science and experts from the field of psychology, statistics, physics and physiology all contribute to its further development (Poldrack et al., 2007). In the last 20 years the imaging techniques developed from single proton emission tomography (SPET) to positron emission tomography (PET) and finally to functional magnetic resonance imaging (fMRI) (Page, 2006). Their applications are numerous in experimental and cognitive psychology. However, at one level they can constitute another dependent variable (brain activity) as a response to an independent variable (stimulus manipulation) and at the other level, understanding the structure and processes of the brain can shed light on ‘normal’ cognitive functioning (Kaye, 2010). Therefore, this essay will argue that imaging techniques not only tell us about the brain structure but also try to explain its cognitive functions. Two non-invasive imaging techniques will be put forward, namely, electroencephalogram (EEG) that measures electrical activity and gives excellent temporal resolution and fMRI that is based on changes in blood supply and provides excellent spatial resolution. The claim will be evaluated in the light of their basic assumptions, methodology and contribution to examining the brain function. Relevant evidence of studies with healthy adults will be provided. Finally, technologies that can only show the brain structure will be introduced.
Neuroscience refers to “the scientific study of the nervous system” It has been responsible for breakthroughs involving molecular, cellular, developmental, and medical aspects of human behaviors. Various organizations such as the “International society for neurochemistry” and the “European Brain and behavior Society” exist today to further the study of the nervous system and expand human understanding of medical and psychological ailments. The actual study of the nervous system dates all the way back to ancient Egypt where surgeons would drill holes into the human skull in order to alleviate a variety of aliments. The second half of the 20th century furthered the study of neuroscience via advancements in Molecular biology, and electrophysiology. These advancements are currently being used to study potential solutions to diseases such as (ALS) amyotrophic lateral sclerosis, strokes, and brain trauma. This research is funded by credible organizations such as the (NIH) National Institute of Health and the “National S...
As a future graduate student, my goal is to contribute to scientific discoveries that will uncover the mysteries of the human brain using rigorous experimental methods and state of the art research and imaging techniques. While humanity has studied the intricacies of the ocean and the vast expanses of space, we are humbled because we know less about the frontier that exists within us than the one that exists beyond us.
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
Rowland, L. P., ed. Merritt’s Textbook of Neurology. 7th ed. Lea and Febiger. Philadelphia: 1984.
Other problems with using these noninvasive imaging methods of only few changes of variables in the brain’s activity are that maybe the problem does not reside in the blood, oxygen intake, or glucose utilization. It may be in other factors that we do not observe that is causing the trouble. By being limited to these estimations of brain activity does not really make our effort of correcting the problem that successful.
Culter, Mary Ann, Joanne Dombrowski, Michael Doughtery, Paula Henderson, and Laura McNicholas. “The brain: understanding nuerobiology. The brain-lesson1-What does this part of the brain do?” NIH publication, Mar.20120.21.Apr.2014.
The technologies used by the researchers range from functional magnetic resonance imaging (fMRI) that measures the changes in the different parts of the brain, to Steady state topography (SST) an...