A recent study has shown rapid MRI signals in response to whisker pad stimulation in mice that track electrical activity. We used rapid, high SNR imaging at 7 T to look for a possible direct effect of visual stimulation on MRI signal in human visual cortex. Two rapid stimulation protocols and variation of T1-weighting failed to generate observable signal changes above the 0.01% detection threshold, well below the previously reported effect size of 0.15%. This confirms the well-established difficulty in developing more direct measures of neuronal activity than available with BOLD-fMRI.
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