Non-Invasive Brain Stimulation

   To evaluate brain-behavior relationships, my research often favors a class of neuroscientific experimental techniques known as non-invasive brain stimulation. These techniques involve the use of methods that present no more than minimal risk to participants and are capable of stimulating either wide range or focal change in cortical activity. To answer lobe- or hemisphere-based questions of perception and cognition, we use transcranial direct current stimulation (tDCS). tDCS is a safe and affordable method for exciting (anodal) or inhibiting (cathodal) areas of the cortex. Using this technique, we are presently investigating exciting new questions about the brain regions involved in perception and spatial cognition. For example, we are presently investigating the lateralization of frontal cortex involvement in causal decision-making and the role of the right parietal cortex in the perception of spatial configurations. A second method of non-invasive brain stimulation used in my research is cold pressor stimulation (CPS). CPS involves immersing the foot in 0-2 degree Celsius water for 50 seconds. This technique has been shown to influence electrophysiological markers of arousal, like the P50 ERP (Woods et al., 2011), and invoke a wide range of cortical and subcortical activation (e.g., the postcentral gyrus; the frontal gyri; anterior insula; anterior cingulate gyrus; occipital and temporal cortices; the thalamus; the hypothalamus; amygdala; hippocampus; cerebellar cortex; and pontine areas). As arousal is a critical component for conscious perception (Llinas, 1998), understanding how changes in arousal influence behavior provides important insight into many questions of perception and cognition. This technique for manipulating arousal has proven effective at treating visual neglect after stroke (Woods et al., 2004 & 2012), improving performance on tasks of visual perception in healthy participants (Woods et al., 2009, 2010, & in press), and as a probe for the integrity of subcortical arousal systems in both healthy adults and patients (Woods et al, 2004, 2011, & 2012). Furthermore, few non-invasive methods have the ability to induce such wide range activation of cortical and subcortical regions. Thus, my research program uses the powerful, yet non-invasive techniques of tDCS and CPS to investigate brain-behavior relationships.

Relevant publications

Woods, A.J., Philbeck, J.W., Wirtz, P. Hyper-arousal decreases human visual thresholds. PLoS ONE, 4(8): e61415. doi: 10.1371/journal.pone.0061415. [PDF]

Woods, A.J., Chatterjee, A., Kranjec, A., Bikson, M., Minhaus, P., Hamilton, R. Space, time, and causal inference: a tDCS study. Annual Meeting of the Society for Neuroscience, in press.

Kessler, S., Woods, A.J., Minhas, P., Rosen, A., Bikson, M. Dose response relationships and safety parameters for transcranial direct current stimulation in children. Annals of Child Neurology, in press.

Minhas, P., Bikson, M., Woods, A.J., Rosen, A., Kessler, S. Transcranial direct current stimulation in the pediatric versus adult brain: A computational modeling study. IEEE Xplore, in press, accepted May 2012. [PDF]

Woods, A.J., Mennemeier, M., Garcia-Rill, E., Huitt, T., Chelette, K. C., McCullough, G., Munn, T., Brown, G., Kiser, T. S. (2012). Improvement in arousal, visual neglect, and perception of stimulus intensity following cold pressor stimulation. Neurocase, 18: 115-122. [PDF]

Woods, A.J., Philbeck, J.W., Chelette, K., Skinner, R.D., Garcia-Rill, E., and Mennemeier, M. (2011). Cold pressor stimulation diminishes P50 amplitude in normal subjects. Acta Neurobiologiae Experimentalis, 71: 348-358. [PDF]

Woods, A.J., & Philbeck, J.W. (2010). When does cortical arousal influence performance on visual perception tasks? Journal of Vision, 10(7): 84. [abstract]

Woods, A.J., Philbeck, J.W., Chelette, K., Skinner R., Garcia-Rill, E., Chichka, D., Potolicchio, S., & Mennemeier, M. (2009). Cortical arousal influences early but not late visual perception. Journal of Vision, 9(8), 1113. [abstract]

Mennemeier, M. S., Chelette, K. C., Woods, A. J., Hudson, J., Dewi, E., Taylor-Cooke, P.A., Wallace, T., & Skinner, R. D. (2007). The P50 ERP is sensitive to arousal states in both neglect and normal subjects. Journal of the International Neuropsychological Society, in press. [abstract]

Woods, A. J., Mennemeier, M., Garcia-Rill, E., Meythaler, J., Mark, V. W., Jewell, G. R., & Murphy, H. (2006). Bias in magnitude estimation following left hemisphere injury. Neuropsychologia, 44, 1406-1412. [PDF]

Woods, A. J., Jewell, G. R., Fisk, G., Tipton, S., Dowler, R., & Mennemeier, M. (2004). Caloric stimulation in neglect: not just for the vestibular system anymore. Journal of the International Neuropsychological Society, 10, 92. [abstract]