The brain's circuit diagram: New method facilitates the mapping of connections between neurons
October 18, 2012 in Neuroscience
Calcium fluorescence measurements show the activity of neurons (left). From this, the scientists can deduce how the neurons are connected with each other (right). Credit: MPI for Dynamics and Self-Organization
(Medical Xpress)—The human brain accomplishes its remarkable feats through the interplay of an unimaginable number of neurons that are interconnected in complex networks. A team of scientists has now developed a method for decoding neural circuit diagrams. Using measurements of total neuronal activity, they can determine the probability that two neurons are connected with each other.
The human brain consists of around 80 billion neurons, none of which lives or functions in isolation. The neurons form a tight-knit network that they use to exchange signals with each other. The arrangement of the connections between the neurons is far from arbitrary, and understanding which neurons connect with each other promises to provide valuable information about how the brain works. At this point, identifying the connection network directly from the tissue structure is practically impossible, even in cell cultures with only a few thousand neurons. In contrast, there are currently well-developed methods for recording dynamic neuronal activity patterns. Such patterns indicate which neuron transmitted a signal at what time, making them a kind of neuronal conversation log. The Göttingen-based team headed by Theo Geisel, Director at the Max Planck Institute for Dynamics and Self-Organization, has now made use of these activity patterns.
The scientists use data from so-called calcium fluorescence measurements that were recorded in collaboration with the University of Barcelona. This imaging method uses specially tailored molecules placed in a cell that fluoresce when they bind calcium. Since the calcium concentration inside a neuron follows its electrical activity, it is possible to record the activity of thousands of neurons simultaneously - whether in a cell culture or in the living brain. However, the speed of the communication is too high to directly observe directly how an impulse is "fired" sand thus tease apart whether a connection is direct or takes places across several stations. By taking into account these difficulties, the algorithm developed in Theo Geisel's team makes it possible to obtain from the measured data remarkably precise information about the lines of connection in the neural network.
"Our method is based on a concept known as transfer entropy," explains Olav Stetter from the Max Planck Institute in Göttingen, lead author of the now published article. Transfer entropy is a measure used in information theory to quantify directed information flows. In other words, it is possible to calculate how probable it is that the signal from a particular neuron would result in activity in another. "Using transfer entropy, we developed a robust method that can reliably distinguish between true causal relationships and those that only appear to exist but resulted from indirect connections or measurement errors," says Stetter.
The scientists initially applied their new method to simulated calcium fluorescence experiments. They used a neuronal network model to simulate the measured signals including realistic effects of calcium dynamics and fluorescence measurements. As the scientists show, the causal relationships in the network are time variable and dependent on the state of the network activity. Only in calmer phases with relatively low activity did the causal relationships coincide with the actual structure of the network. The researchers in Göttingen were able to use this fact for their predictions. In more active phases so many neurons are simultaneously participating in the neuronal conversation that it is no longer easily possible to trace the path of information.
In the present article, they also examined real neurons. The analysis with the new method revealed an unusual concentration of connections surrounding individual cells. The researchers are optimistic that their method can be used on a broad class of systems: "Our method makes it possible to reconstruct neural networks without any specific assumptions regarding their makeup. Rather, we take a data-driven approach," explains Demian Battaglia.
The scientists hope that their algorithm will permit neural circuit diagrams to be calculated on a broad scale, in both cultivated and natural networks. The collected information from a number of different neural networks may then help researchers understand when and where neurons create connections, and which criteria they use to select their partners.
More information: Olav Stetter, Demian Battaglia, Jordi Soriano, Theo Geisel. Model-free Reconstruction of Excitatory Neuronal Connectivity from Calcium Imaging Signals. PLoS Computational Biology, 8(8): e1002653 (23 August 2012) doi:10.1371/journal.pcbi.1002653
Journal reference:
PLoS Computational Biology
Provided by
Max Planck Society
-
New statistical method provides way to analyze synchronized neural activity in animals
Aug 03, 2012 |
not rated yet |
0
-
Researchers connect neurons to computers to decipher the enigmatic code of neuronal circuits
Jul 12, 2011 |
not rated yet |
0
-
Out of mind in a matter of seconds: How fast neuronal networks delete sensory information
Jan 24, 2011 |
not rated yet |
0
-
Deeper insight in the activity of cortical cells
Jul 12, 2011 |
not rated yet |
0
-
Brain cell networks recreated with new view of activity behind memory formation
May 25, 2011 |
not rated yet |
0
-
Motion perception revisited: High Phi effect challenges established motion perception assumptions
Apr 23, 2013 |
3 / 5 (2) |
2
-
Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update)
Apr 02, 2013 |
4.5 / 5 (11) |
5
-
The visual system as economist: Neural resource allocation in visual adaptation
Mar 30, 2013 |
5 / 5 (2) |
9
-
Separate lives: Neuronal and organismal lifespans decoupled
Mar 27, 2013 |
4.9 / 5 (8) |
0
-
Sizing things up: The evolutionary neurobiology of scale invariance
Feb 28, 2013 |
4.8 / 5 (10) |
14
-
Why is zone 1 in liver more prone to ischemic injury?
May 23, 2013
-
How can there be villous adenoma in colon, if there are no villi there
May 22, 2013
-
How can there be a term called "intestinal metaplasia" of stomach
May 21, 2013
-
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013
-
If you became brain-dead, would you want them to pull the plug?
May 17, 2013
-
MRI bill question
May 15, 2013
- More from Physics Forums - Medical Sciences
More news stories
New neuron formation could increase capacity for new learning, at the expense of old memories
New research presented today shows that formation of new neurons in the hippocampus - a brain region known for its importance in learning and remembering - could cause forgetting of old memories by causing a reorganization ...
Neuroscience
May 24, 2013 |
4 / 5 (4) |
0
Help at hand for people with schizophrenia
How can healthy people who hear voices help schizophrenics? Finding the answer for this is at the centre of research conducted at the University of Bergen.
Neuroscience
May 24, 2013 |
4 / 5 (2) |
2
Japanese research organizations contribute to Human Brain Project
One of the major frontiers of modern science is a comprehensive understanding of the human brain and its functions to guide the development of new technologies in information and communication. In a major announcement for ...
Neuroscience
May 24, 2013 |
3.7 / 5 (3) |
0
Controlling mood through the motions of mitochondria
(Medical Xpress)—Regulating the distribution of power in neurons is done by a system that makes the national electric grid look simple by comparison. Each neuron has several thousand mitochondria confined ...
Neuroscience
May 23, 2013 |
4.9 / 5 (9) |
0
|
Brain uses internal 'average voice' prototype to identify who is talking
(Medical Xpress)—The human brain is able to identify individuals' voices by comparing them against an internal 'average voice' prototype, according to neuroscientists.
Neuroscience
May 23, 2013 |
3.7 / 5 (3) |
3
|
First drug to improve heart failure mortality in over a decade
Coenzyme Q10 decreases all cause mortality by half, according to the results of a multicentre randomised double blind trial presented today at Heart Failure 2013 congress. It is the first drug to improve heart failure mortality ...
Heart failure accelerates male 'menopause'
Heart failure accelerates the aging process and brings on early andropausal syndrome (AS), according to research presented today at the Heart Failure Congress 2013. AS, also referred to as male 'menopause', was four times ...
Hormone levels may provide key to understanding psychological disorders in women
Women at a particular stage in their monthly menstrual cycle may be more vulnerable to some of the psychological side-effects associated with stressful experiences, according to a study from UCL.
Feds fight morning-after pill age ruling in NY
(AP)—Department of Justice lawyers have again asked a federal appeals court in New York to delay lifting age restrictions and prescription requirements on an emergency contraceptive popularly known as the morning-after ...
Death highest in heart failure patients admitted in January, on Friday, and overnight
Mortality and length of stay are highest in heart failure patients admitted in January, on Friday, and overnight, according to research presented today at the Heart Failure Congress 2013. The analysis of nearly 1 million ...
Researchers identify first drug targets in childhood genetic tumor disorder
Two mutations central to the development of infantile myofibromatosis (IM)—a disorder characterized by multiple tumors involving the skin, bone, and soft tissue—may provide new therapeutic targets, according to researchers ...
Oct 18, 2012
Rank: not rated yet
Bad news for lateralization of function.
Congratulations to all involve.