In their quest to map the millions of neural highways and connections in the brain, researchers at the Allen Institute have made a significant step forward, unveiling a new high-resolution view of the wiring diagram of the mouse brain. Their study, which was published in the journal Nature, traced thousands of connections between brain areas and lays the groundwork for researchers to better understand how brain circuitry might go awry in diseases and disorders such as Alzheimer’s disease and schizophrenia.
The Allen Institute for Brain Science is a division of the Allen Institute, an independent, 501(c)(3) nonprofit medical research organization located in Seattle and is dedicated to accelerating the understanding of how the human brain works in health and disease. Using a big science approach, the Allen Institute generates useful public resources used by researchers and organizations around the globe, drives technological and analytical advances, and discovers fundamental brain properties through integration of experiments, modeling and theory. Launched in 2003 with a seed contribution from founder and philanthropist, the late Paul G. Allen, the Allen Institute is supported by a diversity of government, foundation and private funds to enable its projects.
The publicly available dataset resulting from approximately a thousand new experiments represents the most detailed map of connections in a mammalian brain to date, tracing neural wiring within and between the thalamus and cortex, the outermost shell of the mammalian brain that is responsible for higher level functions like memory, decision making, and understanding the world around us.
Sifting through the data, the researchers uncovered an underlying “org chart” of wiring among the different areas comprising these two structures, showing a defined order to the connections that are the underpinnings of what makes our brains tick.
Using a computational approach, the researchers found that different sections of the cortex and thalamus can be mapped into a hierarchy, much like a company’s org chart. Parts of the cortex that are specialized for information gathered via our senses, like vision and smell, are on the bottom rungs, and regions that handle more complicated input — like calling up a memory evoked by a familiar scent — sit at the top. Connections flow both up and down the brain’s org chart, but the connections moving up are different than those moving down. They also found that not all connections respect these hierarchical laws. There are hints that the human cortex uses the same organizational system, and a previous study led by Van Essen showed a similar hierarchy in visual regions of the primate brain.
“These connections are the primary way neurons communicate with each other. The elaborate and complicated networks in the brain, their different pathways and subsystems, process everything we see, our movements, memories and feelings.” … “Understanding the connectivity of the brain is fundamental for understanding how the brain works.” – Hongkui Zeng, Ph.D., Executive Director of Structured Science at the Allen Institute for Brain Science, a division of the Allen Institute, and senior author of the study
“This is another landmark, tour-de-force study from the Allen Institute for Brain Science that addresses fundamental issues of brain organization in the mouse.” … “The team has acquired, analyzed, and freely shared a vast amount of high-quality anatomical connectivity data, thereby providing the most extensive ‘meso-connectome’ description to date for the wiring of any mammalian brain.” – David Van Essen, Ph.D., Alumni Endowed Professor of Neuroscience at Washington University School of Medicine in St. Louis and a scientific advisor to the Allen Institute for Brain Science
“This is not a simple hierarchy, like a one-way sequence of ascending steps. There are a lot of connections which do not follow the strict hierarchical rules. But this tells us something about the likely flow of information in these parts of the mammalian brain.” … “The next step will be to look directly at how neurons pass information through their electrical activity to confirm that this pattern matters.” – Christof Koch, Ph.D., Chief Scientist and President of the Allen Institute for Brain Science and one of the study co-authors