Department of Biomedical Engineering, Toyo University , Saitama , Japan.
Department of Health Sciences, Faculty of Human Life and Environment, Nara Women's University , Nara , Japan.
J Appl Physiol (1985). 2018 Jun 1;124(6):1413-1419. doi: 10.1152/japplphysiol.00909.2017. Epub 2018 Feb 8.
Changes in cerebral blood flow (CBF) subsequent to alterations in the partial pressures of oxygen and carbon dioxide can modify dynamic cerebral autoregulation (CA). While cognitive activity increases CBF, the extent to which it impacts CA remains to be established. In the present study we determined whether dynamic CA would decrease during a cognitive task and whether hypoxia would further compound impairment. Fourteen young healthy subjects performed a simple Go/No-go task during normoxia and hypoxia (inspired O fraction = 12%), and the corresponding relationship between mean arterial pressure (MAP) and mean middle cerebral artery blood velocity (MCA V) was examined. Dynamic CA and steady-state changes in MCA V in relation to changes in arterial pressure were evaluated with transfer function analysis. While MCA V increased during the cognitive activity ( P < 0.001), hypoxia did not cause any additional changes ( P = 0.804 vs. normoxia). Cognitive performance was also unaffected by hypoxia (reaction time, P = 0.712; error, P = 0.653). A decrease in the very low- and low-frequency phase shift (VLF and LF; P = 0.021 and P = 0.01) and an increase in LF gain were observed ( P = 0.037) during cognitive activity, implying impaired dynamic CA. While hypoxia also increased VLF gain ( P < 0.001), it failed to cause any additional modifications in dynamic CA. Collectively, our findings suggest that dynamic CA is impaired during cognitive activity independent of altered systemic O availability, although we acknowledge the interpretive complications associated with additional competing, albeit undefined, inputs that could potentially distort the MAP-MCA V relationship. NEW & NOTEWORTHY During normoxia, cognitive activity while increasing cerebral perfusion was shown to attenuate dynamic cerebral autoregulation (CA) yet failed to alter reaction time, thereby questioning its functional significance. No further changes were observed during hypoxia, suggesting that impaired dynamic CA occurs independently of altered systemic O availability. However, impaired dynamic CA may reflect a technical artifact, given the confounding influence of additional inputs that could potentially distort the mean arterial pressure-mean middle cerebral artery blood velocity relationship.
脑血流（CBF）在氧和二氧化碳分压变化后的变化可以改变动态脑自动调节（CA）。虽然认知活动增加了 CBF，但它对 CA 的影响程度仍有待确定。在本研究中，我们确定了认知任务期间是否会降低动态 CA，以及低氧是否会进一步加剧这种损害。14 名年轻健康受试者在常氧和低氧（吸入 O 分数为 12%）下进行简单的 Go/No-go 任务，并检查平均动脉压（MAP）和平均大脑中动脉血流速度（MCA V）之间的相应关系。通过传递函数分析评估了与动脉压变化相关的 MCA V 的动态 CA 和稳态变化。虽然在认知活动期间 MCA V 增加（P < 0.001），但低氧没有引起任何额外的变化（P = 0.804 与常氧相比）。低氧也没有影响认知表现（反应时间，P = 0.712；错误，P = 0.653）。在认知活动期间观察到非常低和低频率相移（VLF 和 LF；P = 0.021 和 P = 0.01）和 LF 增益增加（P = 0.037），表明动态 CA 受损。虽然低氧也增加了 VLF 增益（P < 0.001），但它没有引起动态 CA 的任何额外改变。总的来说，我们的研究结果表明，认知活动期间动态 CA 受损，尽管我们承认与可能扭曲 MAP-MCA V 关系的额外竞争但未定义的输入相关的解释性复杂性，但系统的 O 可用性发生改变，但未改变。然而，在低氧条件下，动态 CA 受损可能独立于系统 O 可用性的改变，这表明在改变系统 O 可用性的情况下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。这表明在改变系统 O 可用性的情况下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。这表明在改变系统 O 可用性的情况下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。这表明在改变系统 O 可用性的情况下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。
在低氧条件下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。在低氧条件下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。在低氧条件下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。在低氧条件下，认知活动会增加脑灌注，从而减轻动态 CA，但不能改变反应时间，这对其功能意义提出了质疑。
然而，在低氧条件下，动态 CA 的受损可能是由于技术上的人工制品造成的，因为可能会扭曲平均动脉压-平均大脑中动脉血流速度关系的额外输入的混杂影响。
