How Reliable is CBF?

Why Cerebral Blood Flow?

CBF is required for cognition!

  • Neurons are high maintenance!
    • Brain consumes as much as 30% of all metabolic resources
  • Does not store any energy.
  • Tight control is necessary to feed the brain.
    • The neurovascular unit

How it's studied

  • To understand how neuronal activity is associated with NVC we have to measure both actual activity and vascular changes.
  • Can't do that in humans!

The Neurovascular Unit

  • Refers to the the neurons, astrocytes, pericytes, smooth muscle cells, and endothelial cells that control blood flow through a specific vascular bed.

Neurovascular Coupling

A more detailed view...

What makes CBF potentially unreliable?

Consider the pathway

  • Deep nuclei.
  • Vasoactives can be released by different pathways.
    • E.g. NA, ACh, NPY

Consider Brain State

  • Alert versus impaired
  • Cholinergic Activation?
  • Disease vs. Healthy
    • Alzheimers Disease
    • VCID (vascular cognitive impairment and dementia)
    • Stroke

So how reliable is it?

Have all fMRI studies been invalidated?

fMRI is quite reliable

  • Bullet One
  • Bullet Two
  • Bullet Three

Reliability

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Validity

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The real questions lie in how to interpret the data

References

https://www.morganclaypool.com/doi/abs/10.4199/C00005ED1V01Y200912ISP002

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