New Method for Mapping Neural Circuits in Action Developed
How neurons communicate has been a subject of research for decades. Many facts have been established, like neurons communicate by sending signals also called nerve impulses, that the overall “firing” of neurons determines a person’s state of mind at each moment, and so on. But there has been no study that shows how exactly this neuronal “conversation” takes place, like when and where neurons establish connections.
Part of the problem is somewhat technical. Before, scientists studied neuronal response via electrodes, using one neuron at a time. But the thing is – the brain has billons of neurons which are anatomically arranged in circuits. The basic mechanisms underlying neural circuits are almost impossible to uncover unless scientists could actually record the activities of these neurons simultaneously.
New method facilitates mapping of neuronal conversations
The human brain is consists of 80 billion neurons that work together to receive incoming stimuli, interpret them, and send them out for action (response). The arrangement of this tightly-knit network remains to be a wonder as there is no way to identify it directly through a brain tissue. However, a group of scientists was able to develop a new method of mapping brain neurons, indicating which neuron transmits signal and at what time.
The team, led by Theo Geisel, Director at the Max Planck Institute for Dynamics and Self-Organisation, used data from an imaging method called fluorescence measurements. Such method makes use of specifically designed molecules that fluoresce when attached to calcium. According to the researchers, since the calcium concentration inside the neurons follows its electrical activity, it is possible to keep track of the activities of thousands of neurons simultaneously.
The problem was, neurons send and receive signals in a very fast manner that it’s difficult to observe how they respond to stimuli. However, Geisel and his team were able to develop an algorithm that makes it possible to obtain accurate information about the lines of connection in the neural network through the measured data obtained.
To test their theory, the researchers conducted an experiment using a neuronal network model. The aim of the experiment is to simulate the measured signals obtained through the method, including the effects of calcium dynamics and fluorescence measurements.
The team were able to see causal relationships within the neuronal network only in calmer phases. But in more active phases, it becomes very much difficult to map the flow of information as more and more neurons tend to join in the conversation.
The scientists believe that their method will make it possible to reconstruct neural networks without any specific assumptions regarding their makeup, and that their algorithm will permit neural circuit diagrams to be calculated on a broad scale – both in natural and cultivated networks.
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