Brain complexity: synapse controls (Introduction)

by David Turell , Monday, October 26, 2015, 13:03 (3316 days ago) @ dhw

The connections can be modulated and modified with feedback controls. In other words the circuitry is not fixed:-http://www.the-scientist.com//?articles.view/articleNo/44061/title/Circuit-Dynamo/-"With Abbott, Marder's lab developed the “dynamic clamp,” a method that uses a computer to introduce a conductance—the ease with which an electric current can pass through a circuit—into neurons to model their behavior. They also worked out the negative-feedback system within neurons that allows for changes in parameters while maintaining their normal function. “We were building models and they were fragile. We would change a parameter, and the model would crash. I kept saying that the cells don't crash all the time, so how do cells balance their number of ion channels? What we came up with is a very simple way of thinking about this.”-"The bigger picture. “The big themes that have come from the STG model, and partly from our lab, are that neuronal circuits are multiply modulated, that modulators reconfigure circuits, and that there have to be pretty simple global regulatory mechanisms that help neurons maintain stable electrical activity despite the fact that their ion channels—the proteins in the cell membranes that carry out electrical signaling—are being constantly replaced.”-"For the last 10 years, Marder's lab has been working to understand the extent of variability within individual nervous systems that still allows the systems to remain stable. “For quite a long time, people thought that all nervous systems had to be very tightly tuned,” she says. “And what we are seeing is that, actually, they can be quite variable and change over time and still work well enough because there is a lot of degeneracy in the way circuits are constructed.”-***-"Greatest hits: -• Discovered that acetylcholine acts as a neurotransmitter in the crustacean stomatogastric ganglion (STG), where it functions as both an excitatory and an inhibitory signal
• Among the first to describe neuromodulators that acted differently than neurotransmitters, resulting in long-lasting effects on neuronal circuits
• Determined that neurons are robust, maintaining their electrical activity patterns despite the turnover of channels and other changes
• With colleagues, developed the “dynamic clamp,” a neurophysiological method that can finely manipulate nerve cells and simulate neuronal and muscle systems using computer-adjusted parameters
• Showed that there are multiple sets of parameters in neurons and networks that can produce similar output patterns."-Comment: Not your average computer