Simultaneous TMS and fMRI in spatial cognition research
Functional Magnetic Resonance Imaging (fMRI) is capable of visualizing in vivo associations between different cognitive functions and patterns of neural activity in the human brain, and has therefore developed into a popular and versatile tool in human neuroscience. A parallel and complimentary development, Transcranial Magnetic Stimulation (TMS) allows controlled manipulation of brain activity, with a quantifiable impact on behavior or cognition and is now a well established tool, particularly in cognitive studies, for inducing transient disruptions of neural activity non-invasively in conscious human volunteers (1). Over the past couple of years, this ability of actively interfering with neural processing during behavioral performance has been increasingly used for the investigation of causal brain-behavior relations in higher cognitive functions (2). Due to their complimentary contribution, the simultaneous combination of TMS with FMRI, however, promises to be of especially great value for our understanding of the human brain, as it provides the opportunity to stimulate brain circuits while simultaneously monitoring changes in brain activity and behavior. Such a multi-modal imaging approach could identify brain networks of functional relevance, and might allow for causal brain-behavior inferences across the entire brain. In my talk, I will present a short introduction into the methodological and technical challenges such a simultaneous combination creates, describe how to solve these challenges, and present first cognitive research studies combining TMS and fMRI for investigating the neurobiology of spatial cognition (3). (1) Sack, A. T. (2006). Transcranial magnetic stimulation, causal structure-function mapping and networks of functional relevance. Current Opinion in Neurobiology, 16, 593-599. (2) Sack, A. T., Camprodon, J. A., Pascual-Leone, A., & Goebel, R. (2005). The dynamics of inter-hemispheric compensatory processes in mental imagery. Science, 308 (5722), 702-704. (3) Sack, A. T., Kohler, A., Bestmann, S., Linden, D. E. J., Dechent, P., Goebel, R., & Baudewig, J. (2007). Imaging the brain activity changes underlying impaired visuospatial judgments: Simultaneous fMRI, TMS, and behavioral studies. Cerebral Cortex 17(12), 2841-2852.