Negative BOLD responses (NBRs) in the rat visual cortex (VC) are reported, for the first time, upon high frequency visual stimulation. So far, in rats, only an attenuation of the positive BOLD response (PBR) in VC had been reported with increase of the stimulus frequency up to 10-12Hz1,2. Here, experiments with very high sensitivity thanks to a cryoprobe operating at 9.4T, reveal NBRs in VC and how they are modulated by hyperoxia (already reported for PBRs3,4). Results suggest the possibility that the neurovascular couplings operating under PBRs and NBRs might not be the same.
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