Introducing the brain: how information flows (Introduction)

by David Turell , Thursday, November 02, 2023, 23:28 (385 days ago) @ David Turell

Electric and molecular signals at synapses:

https://medicalxpress.com/news/2023-11-unraveling-mysteries-brain-worm.html

"...a team of neuroscientists and physicists at Princeton University are helping to shine a clarifying light on how information flows in the brain by studying, of all things, the brain of a very small but ubiquitous worm known as Caenorhabditis elegans. The details of the experiment are chronicled in a recent issue of Nature. The team consisted of Francesco Randi, Sophie Dvali and Anuj Sharma and was led by Andrew Leifer, a neuroscientist and physicist.

"'Brains are exciting and mysterious," said Leifer. "Our team is interested in the question of how collections of neurons process information and generate action."

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:The worm is approximately one millimeter in length and is found in many bacteria-rich environments. Especially pertinent to the current study is the fact that the organism has a nervous system of only 302 neurons in its entire body, 188 of which reside in its brain.
"By contrast, a human brain has hundreds of billions of neurons," said Leifer. "So, these worms are much simpler to study. In fact, these worms are excellent for experimentation because they strike just the right balance between simplicity and complexity."

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"An additional advantage in using C. elegans in laboratory experiments is that the worm is transparent, and in certain cases, its tissue has been genetically engineered to be light sensitive. This area of research is known as optogenetics, and it has revolutionized many aspects of experimentation in biological neuroscience.

"Instead of the more conventional system of using an electrode to deliver a current into a neuron and thereby stimulate a response, the optogenetic technique involves using light-sensitive proteins from certain organisms and implanting those cells in another organism so that researchers can control an organism's behavior or responses using light signals

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"These optical tools allowed Leifer's team to begin the painstaking task of understanding how information flows through the worm's brain. The goal was to understand how signals flow directly through the worm's entire brain, so each neuron had to be measured. This involved isolating one neuron at a time, shining a light on it so that it was activated, and then observing how the other neurons responded.

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"'We concluded that in many cases, many molecular details that you can't see from the wiring diagram are actually very important for predicting how the network should respond," said Leifer.

"The researchers suggest that there is a form of signaling—part of the "molecular details that you can't see"—that does not progress along neural wires. Leifer and his group characterized these as "wireless signals." Although wireless signaling is well known among neuroscientists, it has largely been underappreciated for studying neural dynamics because it had often thought to be a process that occurs very slowly.

"Wireless signaling is a form of signaling by which a neuron releases molecules, called neuropeptides, into the extracellular space—or "extracellular milieu"—between neurons. These chemicals diffuse and bind to other neurons even if there is no physical connection between them."

Comment: an elegant study confirming that signaling is both electric and molecular. What is not known is a black box: how do neurons know how to develop new connected axons to other neurons to handle new mental activity?