More Direct Way to Map Brain Activity Deemed Feasible
Magnetic resonance imaging (MRI) can be used to directly detect the electrical activity emitted by neurons, NIMH scientists and colleagues have demonstrated. Their findings suggest the feasibility of a more direct and reliable method of mapping brain activity through functional magnetic resonance imaging (fMRI) than has been available up to now. Currently, fMRI measures neuronal activity only indirectly by tracing the flow of oxygenated blood. Since the hardest working brain areas need more oxygen, this signal has been deemed a close approximation of neuronal activity, albeit with some mismatches.
In the new study, published online October 12, 2006 in the Proceedings of the National Academy of Sciences, NIMH physicists Natalia Petridou, Ph.D., Peter Bandettini, Ph.D., and colleagues eliminated the confounding effect of blood flow by scanning rat brain cultures devoid of blood vessels. These cultures nonetheless emitted bursts of neuronal activity. MRI readings of the ebb and flow of neuronal activity matched a direct, independent measure of neuronal electrical activity via EEG. Both the MRI and the EEG signals stopped when the researchers chemically blocked neuronal activity. This suggested that magnetic resonance signal changes were most likely due to the electrical discharges of neurons. The challenge that lies ahead will be to find a way to similarly separate electrical from blood flow signals in the living human brain, say the researchers.
Petridou N, Plenz D, Silva AC, Loew M, Bodurka J, Bandettini PA. Direct magnetic resonance detection of neuronal electrical activity. Proc Natl Acad Sci U S A. 2006 Oct 12; [Epub ahead of print]