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Abstract

The relative contributions of excitation and inhibition to fMRI responses remain unknown. In principle, inhibition may increase or decrease fMRI signals depending on local circuitry. Negative BOLD signals and CBF decreases were shown for ring stimuli in primary visual cortex (V1). High-resolution fMRI can exploit the functional segregation in V1 to reveal differences between excitatory and inhibitory responses, including layer-specific differences. We measured high-resolution BOLD, CBV and CBF in macaque V1 and found laminar differences in the positive and negative fCBF responses, suggesting different neurovascular coupling mechanisms depending on the location within the cortical sheet.