A Double Challenge: Cerebral Blood Flow During Concurrent Breath-Hold and Motor Task

Motor activation and breath-holding probe complementary aspects of cerebrovascular function: the response to local neuronal demand and to a global vascular challenge. Combining them tests whether local perfusion responses remain supported when the cerebral circulation must also accommodate a systemic perturbation, potentially revealing constraints that either challenge alone would miss. We used arterial spin labelling (ASL) MRI to investigate whether concurrent breath-holding modifies the regional cerebral blood flow (CBF) response to motor activation. Fourteen healthy volunteers underwent pseudo-continuous ASL at 3T during sequential finger tapping with normal breathing, finger tapping during breath-holding, and breath-holding alone. Each condition included a resting baseline followed by eight 25-second task blocks interleaved with recovery. CBF responses were assessed using whole-brain voxelwise analyses and participant-specific primary motor cortex (M1) and supplementary motor area (SMA) regions. Baseline CBF was equivalent across conditions within predefined bounds of 10% either side. Motor-related perfusion increases remained detectable during concurrent breath-holding, but the mean M1 CBF increase was 26.5%, compared with 51.3% during normal breathing - a difference of 24.8 percentage points (p < 0.001). Corresponding SMA responses were 23.2% and 41.2%, although this difference was not statistically significant (p = 0.092). Breath-holding alone produced spatially heterogeneous responses, including regional CBF reductions. No significant global grey- or white-matter CBF changes from baseline were detected after correction for multiple comparisons. These findings demonstrate that a detectable motor perfusion response can coexist with substantial attenuation during a concurrent respiratory challenge, despite comparable resting perfusion. Combining global vascular and local neuronal challenges may reveal constraints on regional perfusion responses that are not apparent from either challenge alone, providing a framework for investigating cerebrovascular adaptability and its potential impairment in disease.