A Double Challenge: Cerebral Blood Flow During Concurrent Breath-Hold and Motor Task
Background/Hypothesis: Challenging the brain with simultaneous global and local demands may reveal functional constraints not apparent with either challenge alone. Here, we combine breath-holding with a motor task to investigate how a global vascular challenge modifies the local neurovascular response. Methods: Fourteen healthy adults underwent arterial spin labelling magnetic resonance imaging during three conditions: finger tapping with normal breathing, 25-second inspiratory breath-holding, and finger tapping during breath-holding. Cerebral blood flow responses were assessed using whole brain voxelwise analyses and motor regions of interest. Results: In the primary motor cortex, the increase in cerebral blood flow relative to baseline was approximately halved during the combined breath-holding and motor task challenge compared with motor task alone (26.5% vs 51.3%; p<0.001). Supplementary motor area responses were also smaller (23.2% vs 41.2%), but the difference was not statistically significant (p=0.092). Regional perfusion reductions were less extensive during the combined challenge than during breath-holding alone. These regional effects occurred without significant global grey- or white-matter perfusion changes from baseline. Conclusion/Interpretation: Combining global and local challenges revealed constraints on task-evoked perfusion increases not apparent during motor activation alone. This approach could help assess whether impaired cerebrovascular reserve compromises the brains capacity to meet local functional demands.