Cellular rhythms help brain function at optimum levels

April 27th, 2009 - 3:40 pm ICT by IANS  

Washington, April 27 (IANS) Cells need to follow specific rhythms in order to keep the brain working at peak levels, according to a new study.
If these rhythms in nerve cells or neurons become irregular, they can trigger conditions like schizophrenia and autism.

“A unifying theme here is that of brain rhythms and ‘arrhythmias’ (irregular heartbeat),” said Karl Deisseroth, associate professor of bioengineering, psychiatry and behavioural sciences and study co-author of both papers at Stanford University Medical Centre (SUMC).

These findings suggest that like the cells that maintain regular heartbeats, certain brain cells also orchestrate oscillations (rhythms) governing behaviour of other cells guided by those rhythms.

Deisseroth’s team focussed on neurons in mice that produce a protein called parvalbumin. Some researchers have suspected that these neurons drive “gamma” brain waves oscillating at a frequency of 40 times a second (40 Hertz).

These waves are believed to affect information flow in the brain. This could never be proved because no one could selectively control the neurons and see the resulting effect on the information flow, or oscillations.

The potential link to disease comes from the fact that in autism the gamma oscillations appear to be present at the wrong intensity, while in schizophrenia there appear to be too few parvalbumin neurons.

“This has been a fundamental mystery. We have these cells that could be crucially involved in high-level, complex information processing and we see these oscillations that are happening, but people don’t really know how to put all this together,” Deisseroth said.

“But this is exactly the kind of thing now that we can address using optical methods.”

That’s because Desisseroth’s group has developed a technique, called optogenetics, in which specific cells can be genetically engineered to be controlled by pulses of visible light.

The team did this with parvalbumin neurons in mice and found that by exciting or inhibiting them, they could produce or suppress “gamma” waves and see a marked change in the “bit rate” or quantity of information flowing through brain circuits.

“What we found is that if you crank the parvalbumin neurons down, you see fewer of these 40-Hertz oscillations. If you crank them up you see more of these gamma oscillations,” Deisseroth said.

“That’s the first real proof that these neurons are indeed involved in generating these gamma brain waves.

“The final outcome of this is that parvalbumin neurons and gamma oscillations work together to enhance the flow of real information in the brain,” he said.

These findings were published online in Sunday edition of Nature along with a companion paper from MIT which Deisseroth and graduate student Feng Zhang co-authored.

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