Cerebrovascular physiology – article alert #90

Orthostatic tolerance and the brain

462- Impact of hypocapnia and cerebral perfusion on orthostatic tolerance – Lewis et al.

463- Phenylephrine Alteration of Cerebral Blood Flow During Orthostasis; Effect on N-Back Performance in Chronic Fatigue Syndrome – Medow et al.

Cerebral autoregulation

464- Does the static cerebral autoregulatory plateau have a finite slope in healthy preterm neonates? Toksvang and Berg

465- Dynamic cerebral autoregulation after bed rest: effects of volume loading and exercise countermeasures – Jeong et al.

466- Integrative physiological and computational approaches to understand autonomic control of cerebral autoregulation – Tan and Taylor

467- Arterial pressure above the upper cerebral autoregulation limit during cardiopulmonary bypass is associated with postoperative delirium – Hori et al.

468- Shoulder Surgery in the Beach Chair Position Is Associated with Diminished Cerebral Autoregulation but No Differences in Postoperative Cognition or Brain Injury Biomarker Levels Compared with Supine Positioning: The Anesthesia Patient Safety Foundation Beach Chair Study – Laflam et al.

Exercise and the brain

469- The effect of changes in cerebral blood flow on cognitive function during exercise – Ogoh et al.

470- Acute exercise stress reveals cerebrovascular benefits associated with moderate gains in cardiorespiratory fitness – Brugniaux et al.

Traumatic brain injury

471- Cerebrovascular regulation, exercise, and mild traumatic brain injury – Tan et al.

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5 thoughts on “Cerebrovascular physiology – article alert #90

  1. Interesting indeed. Do you think that the CBF changes in 469 would be enough expect changes in function on the Stroop test? I wonder if a different way to test this would have been to cause hypoperfusion or something to document deficits first, and then restore CBF to baseline levels and higher to see if there was improvement.
    462 is interesting as well. I think we have seen in orthostatic tolerance tests that the duration is often affected by cerebral blood flow. And symptoms vs. no symptoms associated with low CBF.
    Things to chew on!

    1. Thank you for your comments Jessica. I have some issues with Ogoh’s paper. I also asked myself if changes were enough for improvements in cognitive function measured by the Stroop test. Are you aware of a threshold needed (minimum change in CBF) to observe any change in executive function ? As for your suggestion (hypoperfusion followed by restoration of CBF), we would also need to know if the relationship between changes in CBF and executive function is comparable when blood flow increases vs. decreases…Finally, these results are for trained subjects…another question would be whether such a relative increase in CBF, but at lower absolute CBF, such as in older individuals/sick people, would lead to similar results (no impact on cognitive function)…

      As for the influence of the cerebrovascular function on orthostatic tolerance, we are working on a new manuscript at the moment…stay tuned 😉

  2. Hi guys,
    Really interesting paper. However, MCA velocity as a marker of global or regional CBF may be misleading when taken in isolation. As Wille et al. 2012 found increases in vertebral arteries during acute changes in blood gases http://www.ncbi.nlm.nih.gov/pubmed/22495584. Also, MCA diameter may not always remain stable (http://www.nature.com/jcbfm/journal/v31/n10/full/jcbfm201181a.html)

    I am not aware of any minimum threshold in CBF for a change in executive function.

    We found uncoupling of regional CBF delivery and executive cognitive performance during exercise. We found significant increases in regional haemoglobin (4.3%) and oxyhaemoglobin (3.8%) at rest during a participation in WCST to the dorsolateral (DLPFC). Performance in WCST was maintained for 35min. However, during a 20-km cycling TT, regional haemoglobin (8.3%) and oxyhaemoglobin (6.7%) again increased compared to rest but performance in WCST was impaired. We concluded this occurred due to the fact participants had to use similar cerebral areas in order to pace themselves over the 20-km. [soon to be published I hope!!]

    In the Ogoh et al. paper exercise did not need to be attended too. Simply meaning that they did not have to pace themselves, the intensity was fixed and the duration was known. Therefore cerebral areas associated with executive functions would be “available” for performance in the Stroop. It is interesting to consider where in the brain the increased CBF went! Would have been nice if fNIRS assessment of DLPFC was measured also.

    I agreed hypoperfusion followed by restoration would be an interesting approach.

    1. Thank you for your comments James. You highlight interesting points. I agree that, taking into consideration regional differences in CBF during exercise and in responses to changes in blood gases, I am sure that we’ll need to monitor more than one artery in future studies, not only the MCA…

      In regards to the MCA diameter issue, I am sure that you are aware of Coverdale et al. and Verbree et al. studies recently published in J Appl Physiol…? (See previous posts: https://physiologiste.wordpress.com/2014/10/29/article-alert-special-edition/ and https://physiologiste.wordpress.com/2014/12/03/interesting-podcast-over-at-journal-of-applied-physiology/)

      Your pacing issue is an interesting one as well! Looking forward to reading your soon to be published paper 😉

  3. Yer, I agree. It’s an interesting paper by Ogoh et al but I’m not sure the methodology was optimised to see an effect. They have utilised a situation in which, I think, cognitive performance is likely to be optimised (peak CBF related exercise intensity, exercise modality with low demand on cognitive resources, a participant group that it likely to already have good cerebrovascular health), so I’m not convinced there is much potential to improve cognitive performance further. It’s hard to measure changes in cognitive performance at the best of times anyway. The have a confounder in which its been shown numerous times that reaction time tends to improve within a single trial, even despite the best efforts to familiarise participants. This is perhaps the biggest issue. So the fact that the MCA reduces a bit is perhaps not enough to limit any particular performance outcome. As you and James will recognise, they are only getting a snapshot of one particular cerebral artery, and I’m not sure blood supply limitations are likely to be an issue in this scenario anyway.

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