A Picture Naming Task for Measuring Brain Activity with Functional MRI and Event-Related Potentials

M. E. Wagshul, A. Azizian, S. Fiore, M. S. Korgaonkar, C. J. Perkins, T. Watson, N. K. Squires Radiology, Stony Brook University, Stony Brook, NY, United States, Psychology, Stony Brook University, Stony Brook, NY, United States, Neurology, Stony Brook University, Stony Brook, NY, United States, Biomedical Engineering, Stony Brook University, Stony Brook, NY, United States Introduction Aphasia is a language-related disorder resulting from acquired damage to the language networks of the brain, often a result of a stroke-induced infarct. While many aphasic stroke patients undergo spontaneous recovery, clinical trails have demonstrated that late recovery is possible, especially when intensive speech therapy is used in conjunction with pharmaco-therapeutic agents. In order to understand the basis for this recovery, and thus to guide the development of new rehabilitation methods and drugs, it is critical to be able to study the functional changes which occurs in the brain over the course of the therapy. Functional MRI (fMRI) has been used to study the nature of functional activation in the brain under various language-related stimuli, and to study changes in the brain during therapy [1]. This tool can provide a key component in our understanding of how the brain rewires itself in the wake of a stroke-induced insult. At the same time, fMRI does not produce all of the key information about brain activation which may be needed. The BOLD technique, which serves as the standard for fMRI brain mapping, does not have the temporal resolution to distinguish between the rapid neural activation processes which occur as a result of a functional stimulus. For example, the early neural firing in the sensory cortex which is an obligatory response to sensory input is certainly different from the later firing which occurs during a semantic naming task. Event-related potentials (ERPs) [2], which utilize electrodes placed over the surface of the scalp to measure electrical activity, have the exact opposite spatio-temporal capabilities compared to fMRI. While an individual ERP electrode has the ability to record the temporal details of neural activity, the technology is not sophisticated enough to identify the precise location in the brain where that firing has occurred. Only crude localization, such as distinguishing between right and left hemisphere, is possible. The goal of this study was to design and test a language-related paradigm which could be used for both fMRI and ERP, so that the information from the two techniques could be combined to provide both detailed spatial and temporal information about functional activation in the brain during a simple language-related task.