Astrocyte-Neuron Lactate Shuttle and Hemodynamic Brain Scans Essay

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,... ...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