Brain blood flow responds differently to pain and touch, mouse study finds
When the brain is stimulated, blood flow increases. For 30 years, functional magnetic resonance imaging (fMRI), one of the most powerful windows into the human brain, has operated on the basis of this connection. fMRI doesn't actually see neurons firing; it tracks changes in blood oxygenation.
A new study in mice challenges the traditional understanding of how the brain's blood flow responds to different sensations, such as pain and touch. Traditionally, functional magnetic resonance imaging (fMRI) has operated on the assumption that increased blood flow correlates with neural activity. However, researchers led by Ravi Rungta at the Université de Montréal discovered that this relationship is not straightforward.
While touch and pain triggered nearly identical neural activity in most layers of the mouse cortex, pain resulted in significantly lower blood flow—more than 50% less than touch. This discrepancy arises because the brain's blood supply is not uniform, with distinct arteriole networks feeding different cortical layers, and these networks react differently to stimuli.
The study, published in the journal Science, utilized advanced imaging techniques to observe blood flow in all six layers of the mouse cortex, revealing that the overall change in blood flow does not always align with neural activity. These findings suggest that blood vessels should be viewed as an active component of neural circuits rather than merely a delivery system.
Further research is needed to explore whether these distinct vascular networks also play a role in chronic pain and neurodegenerative diseases, conditions often associated with reduced blood flow in the deep layers of the cortex.
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