Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The brain: with all its cells and their connections

08.08.2013
Scientists succeed in the complete reconstruction of a piece of retina

Decoding the essence of being – understanding the brain and all its connections, that is Connectomics. Scientists from the Max Planck Institutes for Medical Research in Heidelberg, of Neurobiology in Martinsried near Munich, and the Massachusetts Institute of Technology (MIT) now made an important step in this direction:


950 neurons in a block of mouse retina, reconstructed from serial block-face electron microscopy data by more than 200 undergraduate students. Spheres indicate the cell bodies (ganglion cells: blue, amacrine cells: green, bipolar cells: orange, photoreceptors: gray). “Skeleton” reconstructions of all neurons appear as web between the cell body layers. Black/white background shows the final connectivity matrix (the “connectome”) between the 950 neurons.

© Julia Kuhl, Winfried Denk; Helmstaedter et al., 2013; (c) Max Planck Institute for Medical Research, Heidelberg, Germany


950 neurons reconstructed in a block of mouse retina, imaged using serial block-face electron microscopy (gray images). Spheres indicate cell bodies (red, ganglion cells, green, amacrine cells).

© Fabian Isensee, Julia Kuhl; Helmstaedter et al., 2013; © Max Planck Institute for Medical Research, Heidelberg, Germany

After analyzing data for four years, aided by about 200 undergraduate students, the scientists created a precise diagram of all nerve cells and their connections in a piece of mouse retina. Although representing only a small fraction of the brain, this diagram already revealed a new cell type and circuit motifs that may help to understand the reactions of certain retinal cells.

The human brain contains about 100 billion nerve cells, each of which is in contact with thousands of other cells. Scientists have long speculated that the essence of our being, our emotions, thoughts and memories, are all based on those contacts. How can we decode the mysteries hidden in these connections? ”Even a tiny cube of brain tissue contains thousands of cells and many millions of connections“, says Moritz Helmstaedter, first author of the study now published in Nature. Helmstaedter now leads his own research group at the Max Planck Institute of Neurobiology in Martinsried.

Undeterred by those numbers, the neurobiologists accepted the challenge and now report a first step in this direction. Together with their American collaborators, the Max Planck researchers describe how they mapped all neurons and their connections in a piece of mouse retina.

Even though the cube of retina was only a tenth of a millimetre on a side, it contained around 1000 neurons and more than half a million contacts between them. “We needed about a month to acquire the data and four years to analyse them” says Helmstaedter. The reason for this long time is the extensive analysis needed to extract the wiring from electron-microscope images of brain tissue. Extremely thin neuronal processes needed to be followed over long distances, without missing any of the multitudes of connections between them. Current computer algorithms are very useful in this process but often not reliable enough. Humans are thus still needed to make the decision whether a neuronal “wire” branches or not. In the current study it took 20,000 hours alone to make those decisions. To analyse an entire mouse brain in this way would require several billion hours of human attention.

The retina does not merely transform images into electrical signals. It separates and filters the image information before transmitting it to the brain. The network of neurons in this small neurocomputer is accordingly complex. While mapping this network the scientists encountered a novel type of cell, belonging to the class of bipolar cells, but with an as yet unknown function. Motifs elsewhere in the connection diagram might explain why some of the retinal cells respond to a stimulus in the way they do. “These results show that we are on the right path, even though we analysed only about one tenth of a percent of the entire mouse retina”, says Helmstaedter. He is convinced, as are many other neurobiologists, that mapping and decoding the connectome will revolutionize brain research.

“Our goal is to map and understand the connectome of an entire mouse brain“, says Winfried Denk, who is currently in the process of moving his laboratory from the Heidelberg institute to Martinsried. How realistic is such an ambitious goal, given that the analysis of a miniscule piece of retina already took four years? The entire brain is 200,000 times larger, but Denk doesn’t seem too worried: ”I'm confident that we can scale up the automated imaging process, the serial-block face electron microscopy, that we used for the piece of retina in such a way that we can image an entire mouse brain. Yet we may end up imaging continuously for a year or two.“ However, Denk also concedes that there is currently no realistic way to analyse the data. ”Except, of course, someone gives us the tens of billions of dollars to pay for the necessary manpower.“

Helmstaedter has a different idea – he and his group are counting on help from the internet community: “We work on launching the online game Brainflight this year, which will allow internet users all over the world to fly along nerves cells while collecting points. Their choices of flight paths will help us to identify the real connections between neurons." Modern algorithms are often based on machine-learning and thus get better the more training data they are given. The brainflight-data will therefore also help with the development of enhanced data-analysis algorithms for the computer.

Contact

Dr. Moritz Helmstaedter
Max Planck Institute of Neurobiology, Martinsried
Phone: +49 89 8578-3690
Email: mhelmstaedter@­neuro.mpg.de
Prof. Dr. Winfried Denk
Max Planck Institute for Medical Research, Heidelberg
Phone: +49 6221 486-335
Fax: +49 6221 486-325
Email: denk@­mpimf-heidelberg.mpg.de
Dr. Stefanie Merker
Max Planck Institute of Neurobiology, Martinsried
Phone: +49 89 8578-3514
Email: merker@­neuro.mpg.de
Original publication
Moritz Helmstaedter, Kevin L. Briggman, Srinivas C. Turaga, Viren Jain, H. Sebastian Seung, & Winfried Denk
Connectomic reconstruction of the inner plexiform layer in the mouse retina
Nature, 8 August 2013

Dr. Moritz Helmstaedter | Max-Planck-Institute
Further information:
http://www.mpg.de/7491772/connectome-retina

More articles from Life Sciences:

nachricht Unique genome architectures after fertilisation in single-cell embryos
30.03.2017 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

'On-off switch' brings researchers a step closer to potential HIV vaccine

30.03.2017 | Health and Medicine

Penn studies find promise for innovations in liquid biopsies

30.03.2017 | Health and Medicine

An LED-based device for imaging radiation induced skin damage

30.03.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>