A Single Bout of Intermittent Hypoxia Increases Cerebral Blood Flow and Supports an Executive Function Benefit.

Alternating between brief normoxic and hypoxic intervals (i.e., intermittent hypoxia: IH) increases cerebrovascular dilation, cerebral blood flow (CBF), and O₂ extraction. Some work has shown that the physiological adaptations arising from multiple IH sessions improve brain health and executive function (EF)-a finding linked to a post-intervention improvement in cortical hemodynamics. Here, we provide a first demonstration of whether the physiological changes associated with a single IH session provide a transient post-intervention EF benefit. Healthy young adults (N = 24) completed an IH protocol entailing 12 alternating 5-min normoxic (P_ETO₂ = 100 mmHg) and hypoxic (P_ETO₂ = 50 mmHg) intervals that were normocapnic and isocapnic, and on a separate day completed a time-matched normoxic control protocol. Prior to (T0), and immediately (T1) and 30 min (T2) following each protocol, EF was assessed via the antisaccade task. Antisaccades require a goal-directed eye movement (i.e., saccade) mirror-symmetrical to a target and provide the resolution to detect subtle EF changes. As expected, hypoxic intervals decreased arterial and cerebral tissue O₂ saturation and increased CBF as estimated via near-infrared spectroscopy and transcranial Doppler ultrasound (ps < 0.001). In turn, antisaccade reaction times (RT) did not differ between T0 and T1 (p = 0.29); however, at T2 a reliable RT reduction was observed (p = 0.004). Notably, cortical hemodynamic changes during the hypoxic intervals did not correlate with the antisaccade RT benefit observed at T2 (ps > 0.17). Thus, a single bout of IH provided a transient post-intervention EF "boost" that was not linked to a unitary physiological adaptation to a reduced O₂ environment.