Astrocyte-neuron lactate shuttle and hemodynamic brain scansHemodynamic brain scans such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI ) have been of immense use in the fields of neuroscience to illuminate the components and modulation of brain function. However, these hemodynamic brain scans have proven useful without brain scientists truly understanding the mechanism by which they produce signals. Previously, it had been assumed without verification that the images produced by such techniques were the direct result of neuronal activity. However, new techniques for studying brain function have revealed that when astrocyte activity is inhibited, blood-dependent brain scanners do not work (Halber 2008). Furthermore, other studies have demonstrated that astrocytes display finely tuned responses to stimuli (Halber 2008) that can communicate with each other in networks via the propagation of calcium waves. In light of these new findings regarding astrocyte function and communication, their influence on hemodynamic brain scans would provide much insight into our current understanding of neuropathology and neuromodulation. General results of the influence of astrocytes on brain scans. PET and fMRI scans are blood-dependent brain scans. However, the mechanism by which each works differs from each other in the fundamental principle of blood flow that it measures. In fMRI, a measurement of the BOLD signal (dependent on the level of oxygen in the blood) is used, which is then translated into working images. PET scans require a labeled radioactive tracer that accumulates in areas of activation. These active areas are then expressed in imaging techniques that interpret the level of activation. However,...... middle of paper...... arch 2009. doi:10.1016/j.tins.2008.11.005MB. (June 20, 2008). Main role of astrocytes in the brain [Web journal article]. 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.1156120Segelken, R. (2004). CU laser microscopy technique settles debate over brain chemistry and could facilitate studies of Alzheimer's disease and stroke damage. Cornell Chronicle. Retrieved from http://www.news.cornell.edu/chronicle/04/7.1.04/astrocyte-neuron.htmlVaishnavi SN, Vlassenko AG, Rundle MM, Snyder AZ, Mintun MA, Raichle, ME (2010). Regional aerobic glycolysis in the human brain. Proc. Natl. Acad. Sci. United States SA.107, 17757-17762. doi: 10.1073/pnas.1010459107