#neural circuits

[bodyalive]

Ulrike Rosenbach (b.1943) Performance ‘Glauben Sie nicht, dass ich eine Amazone bin’ (Don’t Believe I’m Amazon) 1976, Foto Klaus vom Bruch

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“As we awaken from sleep, our consciousness undergoes a radical transformation composed of dramatic adjustments in neural processes. Some neural circuits go quiet while others come online. The entire orchestration of the symphony of mind unfolds like changes in a music score, and while there is no single, master conductor, the decentralized process does have hot spots of top-down modulation linked by connections built over evolutionary time. These "command centers,” for lack of a more accurate but succinct term, do one thing really well: They create our sense of self, our sense of being a protagonist in a continuously unfolding nonlinear narrative through which we can travel again and again in our memories and plan possible and even impossible futures.“

- Antonio Damasio Self Comes to Mind

[dreaminginthedeepsouth]

“As we awaken from sleep, our consciousness undergoes a radical transformation composed of dramatic adjustments in neural processes. Some neural circuits go quiet while others come online. The entire orchestration of the symphony of mind unfolds like changes in a music score, and while there is no single, master conductor, the decentralized process does have hot spots of top-down modulation linked by connections built over evolutionary time.

These "command centers,” for lack of a more accurate but succinct term, do one thing really well: They create our sense of self, our sense of being a protagonist in a continuously unfolding nonlinear narrative through which we can travel again and again in our memories and plan possible and even impossible futures.“

- Antonio Damasio Self Comes to Mind

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Fly by Wire

As part of an ongoing endeavour to completely map neural circuits underlying behaviour, here is presented a connectome [neuron wiring diagram] resource of the entire ventral nerve cord of a male fruit fly

Read the published research article here

Image from work by Shin-ya Takemura and colleagues

Janelia Research Campus, Howard Hughes Medical Institute, VA, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife (reviewed preprint), May 2024

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Axon Ax-off

Like trees growing in the wild, the branches or axons of our nerve cells reach out as they develop. In the optic tract of a zebrafish, some branches of these retinal ganglion cells are ‘pruned’ to guide the accurate shape of circuits behind its eyes. Like snipping at a bonsai tree (although about 1000 times smaller), cells on one side of the tract (highlighted in red) send signals that help to cut off stray axons of cells on the other side (blue), leaving grouped or 'sorted' neurons behind (seen on the right). Researchers using CRISPR/Cas9 technology block the activity of ones of the genes involved, gpc3, leaving the optic tract in a disorganised unpruned state (left and middle). Insight into this molecular tree surgery might influence therapies for the human brain, which also uses a form of gpc3 – offering a helping hand in shaping neural circuits that develop errant branches.

Written by John Ankers

Image from work by Olivia Spead, Trevor Moreland and Cory J. Weaver, and colleagues

Department of Biological Sciences, University of South Carolina, Columbia, SC, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Cell Reports, February 2023

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Pushing Boutons

Our brain cells, or neurons, form circuits to store our memories and process thoughts. They connect up at synapses – junctions where they exchange chemical messages. Brain injuries often destroy this fragile architecture, so here researchers investigate how transplanting healthy neurons might help to heal these complex wounds. A high-powered microscope focuses at different depths in a wounded mouse brain, watching as a transplanted cell (highlighted in turquoise) reaches out. It develops structures ready to form synapses – tiny ‘boutons’ (bright dots) along some of its outstretched branches. But after traumatic brain injury neighbouring neurons react too strongly–forming too many connections that may overwhelm the neurons, leading to seizures, and then pruning too many away as the brain tries to correct itself. The next challenge is to find the right balance of neighbourly signals to restore a healthy community of neurons to recovering brains.

Written by John Ankers

Video from work by Sofia Grade and colleagues

Institute of Stem Cell Research, Helmholtz Center Munich, German Center for Environmental Health, Neuherberg, Germany

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Science Advances, June 2022

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Micro Expression

Gene expression involves two key stages: transcribing a section of DNA into an mRNA molecule, then translating that into a protein. The process is modulated by sophisticated regulatory systems, including microRNAs (or miRNAs), small segments of RNA that bind to mRNAs to inactivate them. miRNAs are known to be crucial for development, but identifying their specific roles is complicated. In the spinal cord, distinct types of neurons (shown in different colours in this cross-section from a mouse) are distinguished by the genes they express, and miRNAs are involved in this differentiation. In mice, recent research found that the loss of six miRNAs, the Mi34/449 group, alters the pattern of gene expression in spinal cord neurons, affecting their neural circuits. Mice lacking Mi34/449 also have external symptoms, such as unusual posture and greater heat sensitivity, providing an example of how miRNAs can help define cell populations, with far-reaching consequences for behaviour.

Written by Emmanuelle Briolat

Image from work by Shih-Hsin Chang and colleagues

Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, March 2021

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Connecting with Chimpanzees

Chimpanzees, along with bonobos, are our closest living relatives and share nearly 99% of our DNA. Despite this relatively small genetic difference, humans behave differently from apes. However, research on human and chimp brains is difficult, as many research techniques cause harm and are unethical. To discover more about what underpins these differences, researchers have used a new non-invasive scanning technology to build the first ever comprehensive atlas of brain connections in humans (bottom left), chimps (top) and macaque monkeys (bottom right). By comparing how different parts of the brain are wired together in these three species, scientists can start to pick out key regions that we share with chimps, as well as areas that might underpin distinctive human traits. This atlas has been made freely available to the scientific community to spark further research into the question of what makes a human a human and a chimp a chimp.

Written by Kat Arney

Image from work by Katherine L. Bryant and colleagues

Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in PLOS Biology, December 2020

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Simple Minds

The human brain, with billions of components and connections, is a unique wonder more complex than we can comprehend. Other animal brains are remarkably similar, even in much simpler organisms like fruit flies. With just a fraction of the complexity, the fruit fly brain accomplishes many key activities essential for life, so is a useful model to study the fundamentals of our own brain. Much is already known, but details on each region’s overall activity are unclear because most studies have focussed on isolated areas. A new approach has created a complete map of the central region, of 24,000 neurons, by combining countless microscopically-thin slices to generate a 3D guide (pictured, with each cell coloured artificially). The researchers have shared this ‘connectome’ freely online, hoping other teams will use the model to reveal secrets that might translate to our own brain, explaining how and why things sometimes go wrong.

Written by Anthony Lewis

Image by The FlyEM team, Janelia Research Campus, Howard Hughes Medical Institute (HHMI)

Research by Louis K Scheffer, C Shan Xu, Michal Januszewski, Zhiyuan Lu, Shin-ya Takemura, Kenneth J Hayworth, Gary B Huang and Kazunori Shinomiya, and colleagues, Janelia Research Campus, HHMI, Ashburn, VA, USA

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, September 2020

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