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    Study finds circuit that helps a brain decide

    To keep track of neural activity, as indicated by the flash of calcium-induced flash, the Flavel Institute invented a microscope that tracks worms as they move. To identify new circuits, they tracked the activity patterns of about 10 major neurons. Credits: Flavel Lab / MIT PIcower Institute

    MIT’s neuroscientist is C. We have discovered an elegant architecture of basic decision-making brain circuits that allow elegans worms to search for food and stop feasting when they find their source. This circuit, which can integrate multiple streams of sensory information, uses only a few major neurons to flexibly switch between them depending on environmental conditions while maintaining long-term behavior.

    “In the case of foraging worms, the decision to roam or live has a major impact on their survival.” Chief author Stephen Flavel said. “By studying how the brain controls this important decision-making process, we thought we could uncover the basic circuit elements that could be deployed in the brains of many animals.”

    Flavell said this approach of studying simple invertebrates to gain basic insights into how the brain works has a long tradition in neuroscience.For example, a study of how squid nerves propagate Electric impulse It has led to important insights that explain how brain cells fire in virtually all animals.

    An important component of the brain circuit identified by Flavell and colleagues may now seem simple as revealed, but it has never been so easy to find. NiJi, the lead author of Flavel’s lab postdoc, understood it using several advanced techniques, including one of the lab’s own inventions.The results of the work of her and her co-authors will be displayed in the journal eLife..

    Tracking thoughts

    C. elegans is a popular model in neuroscience because it has only 302 neurons and the “wiring diagram” or connectome is fully mapped. But even so, in addition to the very tight and overlapping interconnectivity between those neurons, the ability to signal each other through chemicals called neuromodulators, seeing Connectome, it is. It means that it is almost impossible to identify how to switch between different behavioral states.

    To identify the circuits that work in this network, Flavell’s lab worm As they move around, they constantly image the activity of neurons across the worm’s brain, as indicated by the flashes triggered by calcium. Ji used a scope to focus on 10 interconnected neurons involved in foraging and track patterns of neural activity associated with roaming or dwelling behavior.

    Ji and co-authors trained software that learns patterns very well so that they can predict worm behavior with 95% accuracy based on neural activity. Analysis revealed a quartet of neurons whose activity was particularly associated with roaming. Another important pattern was that the transition from roaming to cessation to retention always followed the activation of a neuron called NSM. Flavell’s lab previously sensed the presence of new food ingested by NSM and released a neuromodulator called serotonin to signal other neurons to slow down worms and make them live in the nutrient area. Was shown.

    Feast or feed: Research finds circuits that help the brain make decisions

    When AIA detects food odors, it sends that information into a mutually inhibitory loop between NSM and neurons expressing MOD-1 and PDF. If the worm is eating, the NSM will dominate and force a dwelling state. If the worm is not, it roams to find the cause of the food odor. Credits: Flavel Lab / MIT PIcower Institute

    Mutual antagonism

    After identifying activity patterns that change as the worm switches states, Ji began manipulating neurons in the circuit to understand how they interact. To confirm the role of the NSM as a trigger for residential conditions, Ji designed the NSM to be artificially activated by a flash of light (a technique called optogenetics). When she flashed the light, it settled the worm by blocking the activity of roaming-related neurons. Further experiments have shown that this inhibitory power depends on roaming neurons with inhibitory serotonin receptors called MOD-1. When Ji genetically knocked out the MOD-1 receptor, NSM was unable to suppress roaming behavior and immediately stopped attempting a lack of feedback.

    Similarly, Ji showed that when the worm was roaming, the roaming quartet was using the neuromodulator PDF to block the activity of the NSM. For example, optogenetic activation of PDF-expressing neurons suppressed NSM activity.

    In a normal worm, if the roaming quartet is active, the NSM is not active and vice versa. However, when Ji genetically knocks out the circuit elements that underlie this mutual suppression, both the roaming quartet and the NSM are activated at the same time, resulting in a strange state where the worm meanders at about half the roaming speed.

    Sensory input

    Therefore, through the ongoing battle for mutual restraint, roaming is maintained by the quartet and housing is maintained by the NSM, but the question remains. How does the worm decide to toggle the switch? To investigate, Ji et al. Programmed a machine learning algorithm to identify which neurons function upstream of a wider circuit to influence the tug of war between serotonin and PDF. This approach identified a neuron called AIA, which is known to integrate sensory information about food odors. AIA’s activities have covariated with some roaming Neuron Use NSM while roaming and when the dwelling begins.

    In other words, when activated by the odor of food, the AIA can use its input to drive either side of the mutual suppression circuit to switch between actions. Recalling that NSM can sense that the worm is actually eating, Ji and Flavell can guess what AIA and NSM have to do. If the worm smells food but doesn’t eat it, you need to roam further until it smells food. If the worm smells food and starts eating at the same time, the worm should continue to live there.

    “For foraging worms, food odors are important, but ambiguous sensory cues. AIA’s detects food odors and sends that information to these different downstream circuits in response to other incoming cues. The function allows animals to contextualize and adapt their odors. Foraging decisions. ” “If you’re looking for circuit elements that can work in larger brains, this stands out as a basic motif that may enable context-sensitive behavior.”


    Scientists use machine learning to predict odors based on worm brain activity


    For more information:
    Ni Ji et al, Neural Circuits for Flexible Control of Persistent Behavioral States, eLife (2021). DOI: 10.7554 / eLife.62889

    Journal information:
    eLife

    Quote: Feast or feed: Research has found a circuit that helps the brain make decisions (22 November 2021) 22 November 2021 https://medicalxpress.com/news/2021-11-feast- Obtained from forage-circuit-brain.html

    This document is subject to copyright. No part may be reproduced without written permission, except for fair transactions for personal investigation or research purposes. Content is provided for informational purposes only.

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