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Archive - Dec 29, 2014

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Scientific First: Optogenetics Captures Neuronal Transmission in Live Mammalian Brain

Neurons, the cells of the nervous system, communicate by transmitting chemical signals to each other through junctions called synapses. This "synaptic transmission" is critical for the brain and the spinal cord to quickly process the huge amount of incoming stimuli and generate outgoing signals. However, studying synaptic transmission in living animals is very difficult, and researchers have to use artificial conditions that don't capture the real-life environment of neurons. Now, EPFL (Ecole Polytechnique Federale de Lausanne) scientists in Switzerland have observed and measured synaptic transmission in a live animal for the first time, using a new approach that combines genetics with the physics of light. Their breakthrough work was published online on December 24, 2014 in an open-access artic le in Neuron. Drs. Aurélie Pala and Carl Petersen at EPFL's Brain Mind Institute used a novel technique called "optogenetics" that has been making significant inroads in the field of neuroscience in the past ten years. This method uses light to precisely control the activity of specific neurons in living, even moving, animals in real time. Such precision is critical in being able to study the hundreds of different neuron types, and understand higher brain functions such as thought, behavior, language, memory - or even mental disorders. Optogenetics works by inserting the gene of a light-sensitive protein into live neurons, from a single cell to an entire family of cells. The genetically modified neurons then produce the light-sensitive protein, which positions itself on the outside of the cell, on the membrane. There, it acts as an electrical channel - something like a gate. When light is shone on the neuron, the channel opens up and allows electrical ions to flow into the cell, a bit like a battery being charged by a solar cell.

Dominant Ant Genus Evolved Twice—Once in New World, Once in Old World

About one tenth of the world's ants are close relatives; they all belong to just one genus out of 323, called Pheidole. "If you go into any tropical forest and take a stroll, you will step on one of these ants," says Okinawa Institute of Science and Technology Graduate University's Professor Evan Economo. Pheidole fill niches in ecosystems ranging from rainforests to deserts. Yet until now, researchers have never had a global perspective of how the many species of Pheidole evolved and spread across the Earth. Dr. Economo, researchers in the Biodiversity and Biocomplexity Unit, and colleagues at the University of Michigan compared gene sequences from 300 species of Pheidole from around the world. They used these sequences to construct a tree that shows when and where each species evolved into new species. At the same time, in a parallel effort, they scoured the academic literature, museums around the world, and large databases to aggregate data on where all 1,200 or so Pheidole species live on Earth, creating a range map for each species. Their results, published online on November 26, 2014 in an open-access article in the Proceedings of the Royal Society Series B, suggest that Pheidole evolved the same way twice, once to take over the New World, and then again to take over the Old World. Dr. Economo began this project by selecting sample ants to represent each Pheidole species. The team then sequenced the DNA of the sample ants to determine genetic similarities between species, and computationally reconstruct the "family tree" of Pheidole species, providing a history of how they evolved. This may seem like a lot of effort for a group of seemingly inconsequential creatures, but in fact many ecologists use ants to better understand evolution and the terrestrial ecosystems ants inhabit.