SPATIAL SPECIFICITY OF HIGH-RESOLUTION, SPIN-ECHO BOLD AND CBF FMRI AT 7T

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In his letter, Dr. Duyn expresses concerns regarding the spatial specificity of our spin-echo (SE) BOLD and CBFbased functional mapping signals (1) because of inherent T*2 weighting in EPI images, blood contributions to SE BOLD, and BOLD effects in CBF-based fMRI. Detailed verification or discussion of these points was beyond the scope of our article (1), since it was submitted as a Note (although published as a Communication) addressing technical issues of high-resolution SE BOLD and CBF fMRI in humans at 4 and 7 T where EPI confronts major diffi- culties. Consequently, our remarks on the spatial specificity of fMRI were based on animal studies at high fields (2,3). However, the issues voiced by Dr. Duyn were indeed mentioned in the original article (1), and were fully dealt with in two articles published shortly afterwards (4,5). Our responses to Dr. Duyn?s three points are summarized below.