In new research published today by Nature Methods, scientists from the Hebrew University and Harvard University have announced a “Neuronal Positioning System” (NPS) that maps the circuitry of the brain, similar to how a Global Positioning System (GPS) receiver triangulates one’s location on the planet.
For more than a century, neuroscientists have tried to uncover the structure of the brain’s neuronal circuits in order to better understand how the brain works. These brain circuits, which perform functions such as processing information and triggering reflexes, are comprised of nervous system cells called neurons that work together to carry out a specialized function. Neurons send the messages to other neurons, or to target tissues such as skin and muscle that they innervate, via specialized wire-like processes called axons.
While numerous scientific consortiums have advanced our understanding of neuronal organization, the available mapping techniques remain imperfect.
Now, scientists from Dr. Alex Binshtok's laboratory at the Hebrew University’s Faculty of Medicine and Dr. Jeff Lichtman's laboratory at Harvard University have described a method to map the location of the axonal branches (“arbors”) of many individual neurons simultaneously, at the resolution of individual axons. Thus, by “seeing” many axons in the same preparation, it becomes possible to understand how specific neurons in one region are wired to other neuronal types and other regions.
This new approach makes it possible to learn about organizational principles of neuronal networks that would otherwise be difficult or impossible to study.
The research was conducted by Dr. Shlomo Tsuriel, a postdoctoral fellow from Dr. Alex Binshtok’s lab and the study’s lead author, with help from student Sagi Gudes, under the guidance of Dr. Binshtok at the Hebrew University’s Faculty of Medicine (Department of Medical Neurobiology at the Institute for Medical Research Israel Canada) and at The Edmond and Lily Safra Center for Brain Sciences. The research was conducted in collaboration with Dr. Jeff Lichtman from Harvard University’s Center for Brain Science and Department of Molecular and Cellular Biology.
Instead of trying to trace entire neurons all the way from the axon tips to the cell body, Dr. Tsuriel labeled only the cell body, but in a way that indicates the locations of its axonal branches. To that end, he used multiple injections in overlapping regions of a target tissue, with three or more differently colored retrograde tracers.
This approach is in some ways analogous to the principle used in a Global Positioning System (GPS) receiver, which uses distances from three or more satellites to triangulate its position. For this reason the new technique was called “Neuronal Positioning System” (NPS).
The description of this new method is presented today in Nature Methods as “Multispectral labeling technique to map many neighboring axonal projections in the same tissue” (Advance Online Publication, doi:10.1038/nmeth.3367).
According to Hebrew University’s Dr. Alex Binshtok: “The new method that we developed allows us to answer a ‘big question’ in neuroscience about the organizational principles of neuronal circuits…I believe many scientists will find the NPS approach useful to help them answer the question of how the brain works.”
Support for the research came from the Humans Frontiers Science Foundation, European Research Council (ERC) under the European Union’s Seventh Framework Programme, US National Institute of Mental Health and US National Institutes of Health.
Posted April 27, 2015