Freeman affects neural activity with magnets

September 27, 2007 Neuroscientists, including UC Berkeley Professor of Vision Science and member of the Bioengineering Graduate Group Ralph Freeman, have for the first time measured the electrical activity of nerve cells and correlated it to changes in blood flow in response to transcranial magnetic stimulation (TMS), a noninvasive method to stimulate neurons in the brain. Their findings, reported in the Sept. 28 issue of the journal Science, could substantially improve the effectiveness of brain stimulation as a therapeutic and research tool. TMS works by generating magnetic pulses via a wire coil placed on top of the scalp. The pulses pass harmlessly through the skull and induce short, weak electrical currents that alter neural activity. "There are potentially limitless applications in both the treatment of clinical disorders as well as in fundamental research in neuroscience," said Elena Allen, a graduate student at UC Berkeley's Helen Wills Neuroscience Institute (HWNI) and co-lead author of the study. "For example, TMS could be used to help determine what parts of the brain are used in object recognition or speech comprehension. However, to develop effective applications of TMS, it is first necessary to determine basic information about how the technique works." TMS offers the opportunity to non-invasively and reversibly manipulate neural activity in a specific brain area, whereas other techniques for studying neural activity in humans, such as functional magnetic resonance imaging (fMRI) or electroencephalogram (EEG), only measure ongoing activity. "Using TMS is inherently challenging because its neural effects can be so variable," said Freeman, principal investigator of the study. "Fortunately, we can determine empirically what the end result is by making measurements with fMRI. This should be valuable to clinicians who must evaluate the effectiveness of a stimulation treatment. In turn, fMRI may serve as a guide to determine adjustments in treatment parameters." The study was also co-authored by Elena Allen and Brian Pasley, graduate students in the Helen Wills Neuroscience Institute, and Thang Duong, a graduate student in vision science. The National Eye Institute of the National Institutes of Health and the National Science Foundation helped support this research. Read the full story at the UC Berkeley NewsCenter .