Authors: Ellen Clarke
Studying complex neuronal networks is critical to understanding how the brain functions. Researchers from the Allen Institute for Brain Science (WA, USA), Harvard Medical School (MA, USA) and Neuro-Electronics Research Flanders (Leuven, Belgium) have successfully published the largest network to date of connections between cortical neurons. The study will help to enhance understanding of how networks in the brain are organized.
“This is a culmination of a research program that began almost ten years ago. Brain networks are too large and complex to understand piecemeal, so we utilized high-throughput techniques to collect huge data sets of brain activity and brain wiring,” explained R. Clay Reid, Senior Investigator at the Allen Institute for Brain Science. “But we are finding that the effort is absolutely worthwhile and that we are learning a tremendous amount about the structure of networks in the brain, and ultimately how the brain’s structure is linked to its function.”
“For decades, researchers have studied brain activity and wiring in isolation, unable to link the two,” commented Vincent Bonin, Principal Investigator at Neuro-Electronics Research Flanders. “What we have achieved is to bridge these two realms with unprecedented detail, linking electrical activity in neurons with the nanoscale synaptic connections they make with one another.”
Lee and Bonin utilized a mouse model to identify cortical neurons that responded to visual stimuli, including vertical and horizontal bars on a screen. Lee captured millions of detailed images of cells and synapses in ultra-thin slices of brain, which were reconstructed in three dimensions. A team of annotators traced single neurons through the 3D images and located connections between individual neurons.
The study provided the first direct evidence to support the idea that neurons that carry out similar functions are more likely to be connected to each other. In addition, those connections are larger, despite the fact that they are tangled with many other neurons that perform different functions.
“Part of what makes this study unique is the combination of functional imaging and detailed microscopy,” explained Reid. “The microscopic data is of unprecedented scale and detail. We gain some very powerful knowledge by first learning what function a particular neuron performs, and then seeing how it connects with neurons that do similar or dissimilar things.”
Similar methods will be utilized on a project with the Allen Institute for Brain Science, Baylor College of Medicine (TX, USA), and Princeton University (NJ, USA), which will analyze larger brain segments. Data from the present study will also be available for other researchers to utilize in future projects.
Source: Allen Institute press release