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

Protein found to be key component in irregularly excited brain cells

July 17, 2018
In a new study in mice, researchers have identified a key protein involved in the irregular brain cell activity seen in autism spectrum disorders and epilepsy. The protein, p53, is well-known in cancer biology as a tumor ...

New drug target for remyelination in MS is identified

July 17, 2018
Remyelination, the spontaneous regeneration of the fatty insulator in the brain that keeps neurons communicating, has long been seen as crucial to the next big advance in treating multiple sclerosis (MS). However, a lack ...

Artificial neural networks now able to help reveal a brain's structure

July 17, 2018
The function of the brain is based on the connections between nerve cells. In order to map these connections and to create the connectome, the "wiring diagram" of a brain, neurobiologists capture images of the brain with ...

Convergence of synaptic signals is mediated by a protein critical for learning and memory

July 16, 2018
Inside the brain, is a complex symphony of perfectly coordinated signaling. Hundreds of different molecules amplify, modify and carry information from tiny synaptic compartments all the way through the entire length of a ...

Synapse-specific plasticity governs the identity of overlapping memory traces

July 16, 2018
Memories are formed through long-term changes in synaptic efficacy, a process known as synaptic plasticity, and are stored in the brain in specific neuronal ensembles called engram cells, which are activated during corresponding ...

'Concussion pill' shows promise in pre-clinical pilot study

July 16, 2018
In 2016, funded by a $16 million grant from Scythian, the multidisciplinary Miller School team embarked on a five-year study to examine the effects of combining CBD (a cannabinoid derivative of hemp) with an NMDA antagonist ...


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.