Scientists Reveal Detailed Map of Brain of Adult Fly
SAN FRANCISCO, CA – July 27, 2018
A group of American scientists has managed to make a detailed map of the brain of an adult fly Drosophila melanogaster.
Drosophila melanogaster has a rich repertoire of innate and learned behaviors. Its 100,000-neuron brain is a large but tractable target for comprehensive neural circuit mapping. Only electron microscopy (EM) enables complete, unbiased mapping of synaptic connectivity; however, the fly brain is too large for conventional EM. Scientists from several US Universities have developed a custom high-throughput EM platform and imaged the entire brain of an adult female fly at synaptic resolution. To validate the dataset, they traced brain-spanning circuitry involving the mushroom body (MB), which has been extensively studied for its role in learning. All inputs to Kenyon cells (KCs), the intrinsic neurons of the MB, were mapped, revealing a previously unknown cell type, postsynaptic partners of KC dendrites, and unexpected clustering of olfactory projection neurons. These reconstructions show that this freely available EM volume supports mapping of brain-spanning circuits, which will significantly accelerate Drosophila neuroscience.
So, they contribute a complete EM volume of an adult female Drosophila brain for free use by the research community. Validation reconstructions demonstrated the reliable tracing of local and long-range connectivity, revealing both known and new elements in the MB circuitry underlying associative learning and recall. The researchers conclude this volume is suitable for tracing brain-spanning neuronal circuits at synaptic resolution. Reconstructions of the neurons reported here are included in a preconfigured, downloadable tracing environment to serve as entry points for further investigation.
Now, as some commentators rightly note, they can try to write a full-fledged fly simulator. But some experts useful of such a simulator will be limited. They give mainly two reasons for this. First is that the interconnection between neurons is not only electrical but also chemical. Accordingly, it is impossible to create a model based solely on an electric signal. And second, every neuron every day creates three new connection tiers and destroys the old ones. In simple terms, to create a similar computer model, it is necessary to physically solder three new contacts each of the 100,000 neurons every day.