Tropes

futurity_sci_tech 00827.txt

#Dendrites are like minicomputers in your brain University of North carolina at Chapel hill rightoriginal Studyposted by Mark Derewicz-UNC on October 30 2013the branch-like projections of neurons called dendrites are not just passive wiring but act more like tiny computers multiplying the brain s processing power. uddenly it s as if the processing power of the brain is much greater than we had originally thoughtsays Spencer Smith an assistant professor in the University of North carolina at Chapel hill s School of medicine. His team s findings published in the journal Nature could change the way scientists think about longstanding scientific models of how neural circuitry functions in the brain while also helping researchers better understand neurological disorders. magine you re reverse engineering a piece of alien technology and what you thought was simple wiring turns out to be transistors that compute informationsmith says. hat s what this finding is like. The implications are exciting to think about. xons are where neurons conventionally generate electrical spikes but many of the same molecules that support axonal spikes are also present in the dendrites. Previous research using dissected brain tissue had demonstrated that dendrites can use those molecules to generate electrical spikes themselves but it was unclear whether normal brain activity involved those dendritic spikes. For example could dendritic spikes be involved in how we see? The answer Smith s team found is yes. Dendrites effectively act as mini-neural computers actively processing neuronal input signals themselves. Directly demonstrating this required a series of intricate experiments that took years and spanned two continents beginning in senior author Michael Hausser s lab at University college London and being completed after Smith and Ikuko Smith set up their own lab at the University of North carolina. They used patch-clamp electrophysiology to attach a microscopic glass pipette electrode filled with a physiological solution to a neuronal dendrite in the brain of a mouse. The idea was to directly istenin on the electrical signaling process. ttaching the pipette to a dendrite is tremendously technically challengingsmith says. ou can t approach the dendrite from any direction. And you can t see the dendrite. So you have to do this blind. t s like fishing if all you can see is the electrical trace of a fish. And you can t use bait. ou just go for it and see if you can hit a dendritehe adds. ost of the time you can t. ut Smith built his own two-photon microscope system to make things easier. Once the pipette was attached to a dendrite Smith s team took electrical recordings from individual dendrites within the brains of anesthetized and awake mice. As the mice viewed visual stimuli on a computer screen the researchers saw an unusual pattern of electrical signalsâ##bursts of spikesâ##in the dendrite. Smith s team then found that the dendritic spikes occurred selectively depending on the visual stimulus indicating that the dendrites processed information about what the animal was seeing. To provide visual evidence of their finding Smith s team filled neurons with calcium dye which provided an optical readout of spiking. This revealed that dendrites fired spikes while other parts of the neuron did not meaning that the spikes were the result of local processing within the dendrites. Study co-author Tiago Branco created a biophysical mathematical model of neurons and found that known mechanisms could support the dendritic spiking recorded electrically further validating the interpretation of the data. ll pointed the data to the same conclusionsmith says. he dendrites are not passive integrators of sensory-driven input; they seem to be a computational unit as well. is team plans to explore what this newly discovered dendritic role may play in brain circuitry and particularly in conditions like Timothy syndrome in which the integration of dendritic signals may go awry. Several fellowships and grants helped fund the project including support from the Wellcome Trust the European Research Council and Gatsby Charitable Foundation. Source: UNC-Chapel Hillyou are free to share this article under the Creative Commons Attribution-Noderivs 3. 0 Unported license C

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