Sustained hypoxia attenuates CBF and BOLD activation in visual cortex

To assess how hypoxia impacts neurovascular coupling, we examined the CBF/BOLD responses to visual activation following 2-days sustained hypoxia. Following hypoxia, the fractional change in response to the stimulus in both BOLD and CBF decreased by 50%. The reduced BOLD response can be explained by the reduction of the fractional CBF response alone, suggesting that other influences (baseline deoxyhemoglobin, coupling of the flow and metabolism responses, or cerebral blood volume responses) are essentially self-canceling. The absolute CBF during the stimulus was similar in both normoxia and hypoxia. The reduced fractional CBF response was due to increased baseline CBF during hypoxia.

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