Sophisticated brain imaging has never been able to directly image the activity of neurons (namely, fMRI and PET scans). Instead, the realization that active neurons caused increased blood flow to occur in the vicinity allowed researchers to develop the techniques that could more easily monitor the flow activity. As blood flow increased in a region of the brain, then the neurons in the area must also be screaming with increased activity.
But, neurons do not have a direct connection to blood vessels and blood flow in the brain.
The correlation between active neurons and the resulting blood flow changes has just now been directly realized by a team at MIT who used two-photon excitation microscopydeveloped by the lab of Watt Webb at Cornell University. They found that another very common cell that composes about 1/2 of all brain cells, called an astrocyte which directly affects blood flow and is electrically quite unlike the neuron, instead reacts to non-electrical stimuli from surrounding cells.
This is a rather significant discovery and further research will lead to a deeper understanding of how our complex neural networks function and how they stay alive in our heads.
MIT unlocks mystery behind brain imaging :: PhysOrg.com June 19, 2008
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“Tuned Responses of Astrocytes and Their Influence on Hemodynamic Signals in the Visual Cortex”
James Schummers, Hongbo Yu, and Mriganka Sur
Science 20 June 2008: 1638-1643.
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Movies of visually evoked responses of neurons and astrocytes [ view ]
About Mriganka Sur at MIT
Picower Institute for Learning and Memory at Massachusetts Institute of Technology
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