2011 November 01 Tuesday
Highly Connected Upper Class Parts Of Brain Identified

Well connected parts of the brain form a sort of insiders club where the rest of the brain is less well connected. Like brain like society?

BLOOMINGTON, Ind. -- Just as the Occupy Wall Street movement has brought more attention to financial disparities between the haves and have-nots in American society, researchers from Indiana University and the University Medical Center Utrecht in The Netherlands are highlighting the disproportionate influence of so called "Rich Clubs" within the human brain.

Not all regions of the brain, they say, are created equal.

"We've known for a while that the brain has some regions that are 'rich' in the sense of being highly connected to many other parts of the brain," said Olaf Sporns, professor in the Department of Psychological and Brain Sciences in IU's College of Arts and Sciences. "It now turns out that these regions are not only individually rich, they are forming a 'rich club.' They are strongly linked to each other, exchanging information and collaborating."

Is part of your brain trying to protest? Is it trying to do a sit-down strike against other parts? Which parts of your brain win out in power struggles? Do some parts of your brain get their desires satisfied while other parts go wanting?

Think about it this way: When it becomes possible to connect brains to each other with elaborate embedded interfaces is there any doubt that not all parts of the brain will be connected up into virtual realms? I'm thinking the frontal cortex will make sure it is well connected and other parts of the brain will get short shrift.

By Randall Parker    2011 November 01 10:16 PM   Entry Permalink | Comments (12)
2011 February 03 Thursday
Electric Fields Speed Neural Communication

The standard model for how neurons transmit messages involves a wave of depolarization due to ions flowing thru channels in neuron membranes. Then when the wave of depolarization reaches a synapse neurotransmitters are released to travel across a gap from the axon and bind to a receptors of the dendrite of a different neuron on the other side of the gap. But some Caltech researchers believe that electrical fields generated by neurons also impinge upon other neurons and alter their behavior.

Pasadena, Calif.—The brain—awake and sleeping—is awash in electrical activity, and not just from the individual pings of single neurons communicating with each other. In fact, the brain is enveloped in countless overlapping electric fields, generated by the neural circuits of scores of communicating neurons. The fields were once thought to be an "epiphenomenon, a 'bug' of sorts, occurring during neural communication," says neuroscientist Costas Anastassiou, a postdoctoral scholar in biology at the California Institute of Technology (Caltech).

New work by Anastassiou and his colleagues, however, suggests that the fields do much more—and that they may, in fact, represent an additional form of neural communication.

This has a couple of interesting implications. First off, signaling via electrical fields would speed up neural communications. Atoms and molecules move much more slowly than electrical fields.

Second, alterations in electrical fields due to, say, cell phones or electric motors or other sources of electro-magnetic radiation have a much higher chance of altering cognitive processes if those neurons accept signals via variations in electric fields.

"In other words," says Anastassiou, the lead author of a paper about the work appearing in the journal Nature Neuroscience, "while active neurons give rise to extracellular fields, the same fields feed back to the neurons and alter their behavior," even though the neurons are not physically connected—a phenomenon known as ephaptic coupling. "So far, neural communication has been thought to occur at localized machines, termed synapses. Our work suggests an additional means of neural communication through the extracellular space independent of synapses."

Hundreds of millions of years of evolution produced a lot of design optimizations for the brain.

As Stephen Smith's lab at Stanford showed last fall the human mind is already stunning in its complexity measured only by considering neural synapses.

In particular, the cerebral cortex — a thin layer of tissue on the brain’s surface — is a thicket of prolifically branching neurons. “In a human, there are more than 125 trillion synapses just in the cerebral cortex alone,” said Smith. That’s roughly equal to the number of stars in 1,500 Milky Way galaxies, he noted.

...

Observed in this manner, the brain’s overall complexity is almost beyond belief, said Smith. “One synapse, by itself, is more like a microprocessor —with both memory-storage and information-processing elements — than a mere on/off switch. In fact, one synapse may contain on the order of 1,000 molecular-scale switches. A single human brain has more switches than all the computers and routers and Internet connections on Earth,” he said.

My guess is that the quantity of information that flows across synapses is many times the amount that flows via electric fields. Synapses localize information flow and therefore allow larger total quantities of information to be transmitted and stored.

By Randall Parker    2011 February 03 10:24 PM   Entry Permalink | Comments (0)
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