Treatment studies We are currently engaged in testing the ability of transcranial direct current brain polarization to modulate brain activity and facilitate functions, particularly learning. We are currently testing a new technique for increasing the focality and predictability of the effect. In the process, we are validating a physical model for current distribution in the head and exploring individual differences in response. Neurophysiological probe studies We have successfully shown changes in the motor cortex response to transcranial magnetic stimulation (TMS) that are linked to the expectation of reward. We are currently studying how this response varies with expected reward value. Using magnetic resonance spectroscopy to explore how cortical gamma aminobutyric acid (GABA) concentration changes during rewarded behavior and looking for correlations between GABA levels and the response to TMS within individuals. We also plan to use theta-burst transcranial magnetic stimulation of the motor and premotor cortex to produce a temporary impairment on learning tasks, as a model for traumatic brain injury. We then see whether adding various forms of reward to the same tasks can overcome this temporary blockade. These investigations will also be carried out with the addition of functional MRI, to look for the effect of theta burst stimulation and reward on patterns of activation. In a study funded by the Center for Neuroscience and Regenerative Medicine at the Uniformed Services University of the Health Sciences, we are investigating the ability of near-infrared spectroscopy to detect activation of the frontal pole of the brain by a simple task, which has been previously validated using functional MRI. The goal is to provide a simple, computerized, portable, and robust system for detecting mild head injuries. The project is being piloted in healthy subjects and will shortly move to head injured patients. Collaborative work With support from a DARPA program on accelerated learning, we are collaborating with investigators at the MIND Institute at the University of New Mexico on using DC brain polarization to shorten the time required to attain behavioral and neuroimaging endpoints for expert status on learning tasks. In Phase I of this project, we have met DARPA 2X metrics for acceleration of threat detection learning. In Phase II we will deploy the technique in an ongoing military training program. In a collaboration with the Section on Biomedical Stochastic Physics, LIMB, NICHD, we are developing a novel system for diffuse optical tomography as a way of monitoring regional cortical blood flow in three dimensions without exposure to magnetic fields or cumbersome equipment.
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