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Abstract #0725

What Is the Ultimate Sensitivity of fMRI: Does the Whole Brain Activate?

Javier Gonzalez-Castillo1, Ziad S. Saad2, Handwerker Daniel1, Peter Bandettini1

1Section on Functional Imaging Methods, NIMH, NIH, Bethesda, MD, United States; 2Scientific and Statistical Computing Core, NIMH, NIH, Bethesda, MD, United States

Over the last 20 years fMRI have emphasized a localizationist view of brain function showing only a handful of regions responding to task/stimulation. Here, using 9 hours of functional data/subject, we challenge that view with evidence that, at high TSNR, fMRI activations extent beyond areas of primary relationship to the task; and that task-correlated signal changes appear in over 90% of the brain for a visual stimulation + attention-control task. Moreover, we show that responses vary greatly across regions; and that whole-brain parcellations based on response differences produce functionally meaningful clusters that are symmetrical across hemispheres and reproducible across subjects.