Elementary neural processing units that tile the mouse brain

November 6, 2017, RIKEN
Credit: RIKEN

A hexagonal lattice organizes major cell types in the cerebral cortex, researchers in Japan have discovered. The pattern repeats across the brain, with similar cells synchronizing their activity in 'microcolumns', which could represent an essential computational unit in the brain.

The neocortex, the convoluted structure that covers much of the mammalian like a sheet and controls motor actions, language, and sensing, is more than just a tangle of gray and white matter. Precision wiring connects cortical areas, but regular, repeating modules that could underlie neural information processing brain-wide have not been observed. "We think we have found a functional unit of the cortex, a repeating 'processor' across which the brain's computation is distributed, like in parallel computers," says Toshihiko Hosoya, research team leader at the RIKEN Brain Science Institute. His group's study, more than 10 years in the making, was published in Science on November 3.

"The concept of columns in the brain is not entirely new," observes Hosoya, referring to orientation and ocular dominance columns found in the visual cortices of monkeys and cats. "What is new is finding neurons organized in columns across multiple brain areas. Our results suggest that the same functional units could underlie very different types of brain functions, from sensory perception to motor control."

Technical advances in brain imaging facilitated the identification of microcolumns. Repeating roughly every 40 microns, such tiny columns may be missed because of the way brains are experimentally processed. "The angle and thickness of a brain slice are very important, and the direction of a column can change even within a single slice, which could be the reason why they weren't noticed before," says Hosoya. Using 3-D anatomical methods, including two-photon imaging and cell-type-specific labeling, the researchers found that columns are arranged hexagonally in layer V of the cortex. This is a major output layer with two distinct pyramidal cell types that are comparatively large, sparse, and easily labeled. Microcolumns contained only one or the other cell type, and neural activity within each column was also synchronized. Hosoya's group is currently investigating whether other cortical layers also contain microcolumns, as well as whether this architecture is separate from or subsumes known visual cortical columns in other species—given that microcolumns show similar response properties.

As for why the columns are arranged hexagonally, "it may just reflect the most efficient way to pack them together," says Hosoya. "However, in all the mice we studied, the hexagons were oriented the same way with respect to the brain's surface. If it was just about packing, they could be oriented randomly, but we didn't see that. This conserved directionality may suggest that the lattice evolved as an efficient solution for diverse brain processes." The cortical circuit—the metaphor borrowed from computers to explain how the wiring of neurons realizes information processing—has long been a holy grail in neuroscience. "In computers, a modular architecture can determine how the computation is executed, and many parallel computation models have a hexagonal structure," Hosoya notes. "Now we have some evidence that small identical computational units—microcolumn modules—underlie the architecture of the cortical circuit, at least in layer V."

One suggestion is that fundamentally understanding one elementary unit can reveal the whole brain's activity, says Hosoya. "Since we identified microcolumns across different brain regions, the same underlying computation may serve completely different functions. It's exciting to think that by understanding 10 or so neurons in one microcolumn, we could actually explain the activity of the 15 billion neurons of the neocortex."

Explore further: Confirmation of repeated patterns of neurons indicates stereotypical organization throughout brain's cerebral cortex

More information: Hisato Maruoka et al. Lattice system of functionally distinct cell types in the neocortex, Science (2017). DOI: 10.1126/science.aam6125

Related Stories

Confirmation of repeated patterns of neurons indicates stereotypical organization throughout brain's cerebral cortex

May 11, 2012
Neurons are arranged in periodic patterns that repeat over large distances in two areas of the cerebral cortex, suggesting that the entire cerebral cortex has a stereotyped organization, reports a team of researchers led ...

3D models of neuronal networks reveal organizational principles of sensory cortex

May 5, 2015
Researchers at the Max Planck Institute for Biological Cybernetics (Germany), VU University Amsterdam (Netherlands) and Max Planck Florida Institute for Neuroscience (USA) succeed in reconstructing the neuronal networks that ...

Researchers discover an essential genetic mechanism of cerebral cortex development

September 19, 2013
The cerebral cortex is the most complex and vital structure in our brain. It is the nerve centre for those "higher" functions that characterise our species, such as language and abstract thought. The nerve cells – or neurons ...

Faulty DNA repair depresses neural development

August 31, 2017
DNA is the computer code that programs every event in the body. Despite the importance of DNA fidelity, as the body develops, cells grow and replicate, DNA is constantly turned over. This repeated process can compromise the ...

Study describes changes to structural brain networks after radiotherapy for brain tumors

June 26, 2017
Researchers compared the thickness of brain cortex in patients with brain tumors before and after radiation therapy was applied and found significant dose-dependent changes in the structural properties of cortical neural ...

Recommended for you

How does brain structure influence performance on language tasks?

October 17, 2018
The architecture of each person's brain is unique, and differences may influence how quickly people can complete various cognitive tasks.

Regulating microglial activity may reduce inflammation in neurodegenerative diseases

October 17, 2018
A group of Massachusetts General Hospital (MGH) investigators is proposing that targeting immune checkpoints—molecules that regulate the activity of the immune system—in immune cells called microglia could reduce the ...

New imaging tool captures how sound moves through the chinchilla ear

October 17, 2018
Researchers have developed a new device that can be used to visualize how sound-induced vibrations travel through the ear. The technology is providing new insight into how the ear receives and processes sound waves and, with ...

Sensory perception is not a one-way street

October 17, 2018
When we interact with the world, such as when we reach out to touch an object, the brain actively changes incoming sensory signals based on anticipation. This so-called 'sensory gating' has now been investigated by neuroscientists ...

Environmental factors may trigger onset of multiple sclerosis

October 16, 2018
A new Tel Aviv University study finds that certain environmental conditions may precipitate structural changes that take place in myelin sheaths in the onset of multiple sclerosis (MS). Myelin sheaths are the "insulating ...

Cesarean-born mice show altered patterns of brain development, study finds

October 15, 2018
Cesarean-born mice show altered patterns of cell death across the brain, exhibiting greater nerve cell death than vaginally delivered mice in at least one brain area, a finding by Georgia State University researchers that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.