Neurobiologists program a neural network for analyzing the brain's wiring

February 28, 2017

How does consciousness arise? Researchers suspect that the answer to this question lies in the connections between neurons. Unfortunately, however, little is known about the wiring of the brain. This is due also to a problem of time: tracking down connections in collected data would require man-hours amounting to many lifetimes, as no computer has been able to identify the neural cell contacts reliably enough up to now. Scientists from the Max Planck Institute of Neurobiology in Martinsried plan to change this with the help of artificial intelligence. They have trained several artificial neural networks and thereby enabled the vastly accelerated reconstruction of neural circuits.

Neurons need company. Individually, these cells can achieve little, however when they join forces neurons form a powerful network which controls our behaviour, among other things. As part of this process, the cells exchange information via their contact points, the synapses. Information about which neurons are connected to each other when and where is crucial to our understanding of basic brain functions and superordinate processes like learning, memory, consciousness and disorders of the nervous system. Researchers suspect that the key to all of this lies in the wiring of the approximately 100 billion cells in the human brain.

To be able to use this key, the connectome, that is every single neuron in the brain with its thousands of contacts and partner cells, must be mapped. Only a few years ago, the prospect of achieving this seemed unattainable. However, the scientists in the Electrons – Photons – Neurons Department of the Max Planck Institute of Neurobiology refuse to be deterred by the notion that something seems "unattainable". Hence, over the past few years, they have developed and improved staining and microscopy methods which can be used to transform brain tissue samples into high-resolution, three-dimensional . Their latest microscope, which is being used by the Department as a prototype, scans the surface of a sample with 91 electron beams in parallel before exposing the next sample level. Compared to the previous model, this increases the data acquisition rate by a factor of over 50. As a result an entire mouse brain could be mapped in just a few years rather than decades.

Although it is now possible to decompose a piece of brain tissue into billions of pixels, the analysis of these images takes many years. This is due to the fact that the standard computer algorithms are often too inaccurate to reliably trace the ' wafer-thin projections over long distances and to identify the synapses. For this reason, people still have to spend hours in front of computer screens identifying the synapses in the piles of images generated by the electron microscope.

Training for neural networks

However the Max Planck scientists led by Jörgen Kornfeld have now overcome this obstacle with the help of . These algorithms can learn from examples and experience and make generalizations based on this knowledge. They are already applied very successfully in image process and pattern recognition today. "So it was not a big stretch to conceive of using an artificial network for the analysis of a real neural network," says study leader Jörgen Kornfeld. Nonetheless, it was not quite as simple as it sounds. For months the scientists worked on training and testing so-called Convolutional Neural Networks to recognize cell extensions, cell components and synapses and to distinguish them from each other.

Following a brief training phase, the resulting SyConn network can now identify these structures autonomously and extremely reliably. Its use on data from the songbird brain showed that SyConn is so reliable that there is no need for humans to check for errors. "This is absolutely fantastic as we did not expect to achieve such a low error rate," says Kornfeld with obvious delight at the success of SyConn, which forms part of his doctoral study. And he has every reason to be delighted as the newly developed will relieve neurobiologists of many thousands of hours of monotonous work in the future. As a result, they will also reduce the time needed to decode the connectome and, perhaps also, the consciousness, by many years.

Explore further: A high-performance, low-energy artificial synapse for neural network computing

More information: Automated synaptic connectivity inference for volume electron microscopy. Nature Methods, online 27 February, 2017 DOI: 10.1038/nmeth.4206

Related Stories

A high-performance, low-energy artificial synapse for neural network computing

February 21, 2017
For all the improvements in computer technology over the years, we still struggle to recreate the low-energy, elegant processing of the human brain. Now, researchers at Stanford University and Sandia National Laboratories ...

Scientists discover new mechanism of how brain networks form

December 26, 2016
Scientists have discovered that networks of inhibitory brain cells or neurons develop through a mechanism opposite to the one followed by excitatory networks. Excitatory neurons sculpt and refine maps of the external world ...

Staining method brings the reconstruction of all nerve cells and their connections within reach (Update)

April 14, 2015
It is widely believed that learning is based on changes in the connections between nerve cells. Knowing the interconnections of nerve cells would considerably aid understanding of how the brain works. Scientists have pursued ...

Rabies viruses reveal wiring in transparent brains

January 19, 2017
Scientists under the leadership of the University of Bonn have harnessed rabies viruses for assessing the connectivity of nerve cell transplants: coupled with a green fluorescent protein, the viruses show where replacement ...

Making connections in the eye: Wiring diagram of retinal neurons is first step toward mapping the human brain

August 7, 2013
The human brain has 100 billion neurons, connected to each other in networks that allow us to interpret the world around us, plan for the future, and control our actions and movements. MIT neuroscientist Sebastian Seung wants ...

Recommended for you

Highly precise wiring in the cerebral cortex

September 21, 2017
Our brains house extremely complex neuronal circuits whose detailed structures are still largely unknown. This is especially true for the cerebral cortex of mammals, where, among other things, vision, thoughts or spatial ...

Faulty cell signaling derails cerebral cortex development, could it lead to autism?

September 20, 2017
As the embryonic brain develops, an incredibly complex cascade of cellular events occur, starting with progenitors - the originating cells that generate neurons and spur proper cortex development. If this cascade malfunctions ...

Research redefines proteins' role in the development of spinal sensory cells

September 19, 2017
A recent study led by Samantha Butler at the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA has overturned a common belief about how a certain class of proteins in the spinal cord regulate ...

The brain at work: Spotting half-hidden objects

September 19, 2017
How does a driver's brain realize that a stop sign is behind a bush when only a red edge is showing? Or how can a monkey suspect that the yellow sliver in the leaves is a round piece of fruit?

Team discovers how to train damaging inflammatory cells to promote repair after stroke

September 19, 2017
White blood cells called neutrophils are like soldiers in your body that form in the bone marrow and at the first sign of microbial attack, head for the site of injury just as fast as they can to neutralize invading bacteria ...

Epileptic seizures show long-distance effects

September 19, 2017
The area in which an epileptic seizure starts in the brain, may be small but it reaches other parts of the brain at distances of over ten centimeters. That distant activity, in turn, influences the epileptic core, according ...

0 comments

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.