Mapping Brain-to-Spinal Cord Pathways for Motor Control

Summary: Researchers have created a 3D map tracking brain parts that connect to V1 cervical cells, which shape motor production. They made connections between these various” telephone operator” cells in the spinal cord by using a genetically modified influenza virus.

The map provides a framework for further investigation into engine power and behavior and demonstrates how brain signals control movement. This discovery provides insights into the neural networks that underlie activity and prepares the groundwork for research into motor disorders.

Important Information:

    Neurological Connections Visualized: A 3D map maps head regions sending signals to V1 cervical interneurons.

  • Advanced Tools: Genetically modified influenza virus and 3D scanning enabled accurate tracing of brain-to-spinal cable channels.
  • Motor Control Insights: The map identifies various pathways essential for shaping engine actions.

Origin: St Jude Children’s Research Hospital

Muscle movement is facilitated by the brain’s motor neurons, but these signals normally pass through vertebral interneurons before reaching their destination. It is unclear how the brain and this incredibly different group of” telephone controller” cells are related.

To solve this, researchers at St. Jude Children’s Research Hospital created a whole-brain map visualizing regions of the brain that send immediate sources to V1 interneurons, a group of cells needed for action.

The research made it possible for them to precisely track the origins of the various mental signals that these interneurons received. Credit: Neuroscience News

The resulting map and the three-dimensional interactive site that accompany it provide a framework for deeper understanding the anatomical makeup of the nervous system and how the brain and spinal cord interact with one another.

The findings were published now in&nbsp, Neuron. &nbsp,

” We have known for decades that the machine method is a distributed system, but the final output is through the cervical cord”, said related author&nbsp, Jay Bikoff, PhD, St. Jude&nbsp, Department of Developmental Neurobiology.

” There, you have motor cells which cause muscle contraction, but the motor neurons don’t operate in isolation. Their activity is sculpted by networks of molecularly and functionally diverse interneurons” .&nbsp,

resolving the connection between machine result and the brain

Although there have been significant advancements in understanding how different regions of the brain interact with various parts of motor power, the precise connection between these regions and particular spinal cord cells has been a blind place in the field. Cells are difficult to study, primarily because they come in hundreds of different, intermingled types. &nbsp,

” It’s equivalent to untangling a game of Christmas lights, except it’s more difficult given that what we’re trying to understand is the result of over 3 billion times of development”, said co-first artist Anand Kulkarni, PhD.

Although recent discoveries have demonstrated the existence of molecularly and developmentally distinct interneuron subclasses, much is still unknown about their function within neural communication.

Understanding how neural control of movement and behavior works is essential, according to Bikoff.

” We need to understand how the brain communicates these signals.”

The researchers used a genetically modified version of the rabies virus that is missing a crucial protein, the glycoprotein, from its surface to examine the connections between the brain and the spinal cord. This inhibited the virus’s ability to spread between neurons.

This basically left the virus at its source. The virus could make a single jump across synapses before getting stuck again by reintroducing this glycoprotein to a particular population of interneurons.

The researchers tracked the virus using a fluorescent tag. The researchers were able to identify which parts of the brain were linked to these interneurons by tracking where the virus travels.

3D map allows researchers to visualize connections

The researchers used this method to study a class of interneurons called V1 interneurons, which had previously been shown to have a significant influence on motor output. The research gave them the ability to precisely trace the brain’s multiple signals that these interneurons received. &nbsp,

” We’re only targeting the V1 interneurons, but these are actually a highly heterogenous group of neurons, so we thought,’ Let’s target as many of the V1s as we can and see what’s projecting to them,'” Bikoff said. &nbsp,

The researchers turned to serial two-photon tomography to visualize these neurons and generate&nbsp, a three-dimensional reference atlas. This method renders the brain as it exposes fluorescently labeled neurons in hundreds of micron-thick sections.

The researchers had the opportunity to accurately predict the network that links the spinal cord and the interneurons with which they communicate.

Researchers can look into the neural circuits that control movement by identifying how these structures interact with the spinal cord, and the accompanying web atlas will make the data freely accessible to everyone.

We now have a theoretical understanding of how some of the identified brain regions behave, explained Bikoff, but we can now make hypotheses about how these effects are mediated and what the potential role of the V1 interneurons might be. It will be very useful for the field as a hypothesis-generating engine”.

Authors and funding

The study’s first authors are Phillip Chapman and Anand Kulkarni, St. Jude. The study’s other authors are Alexandra Trevisan, Katie Han, Jennifer Hinton, Paulina Deltuvaite, Mary Patton, Lindsay Schwarz, and Stanislav Zakharenko, St. Jude, Lief Fenno, University of Texas at Austin, and Charu Ramakrishnan and Karl Deisseroth, Stanford University.

Funding: The study was supported by a grant from the National Institutes of Health ( R01NS123116 ), and ALSAC, the fundraising and awareness organization of St. Jude.

About this news from brain mapping research

Author: Chelsea Bryant
Source: St Jude Children’s Research Hospital
Contact: Chelsea Bryant – St Jude Children’s Research Hospital
Image: The image is credited to Neuroscience News

Original Research: Open access.
A brain-wide map of descending inputs onto spinal V1 interneurons” by&nbsp, Jay Bikoff et al. Neuron


Abstract

A brain-wide map of descending inputs onto spinal V1 interneurons

The coordinated activity of neural circuits that are distributed across various brain regions, which use descending motor pathways to send information to the spinal cord, causes motor output. The organizational mechanism by which supraspinal systems target distinct spinal motor circuit components is still a mystery.

Here, using viral transsynaptic tracing along with serial two-photon tomography, we have generated a whole-brain map of monosynaptic inputs to spinal V1 interneurons, a major inhibitory population involved in motor control.

We identified 26 distinct brain structures that directly innervate V1 interneurons, spanning medullary and pontine regions in the hindbrain as well as cortical, midbrain, cerebellar, and neuromodulatory systems. Moreover, we identified broad but biased input from supraspinal systems onto V1Foxp2&nbsp, and V1Pou6f2&nbsp, neuronal subsets.

These studies provide an anatomical foundation for understanding how supraspinal systems affect spinal motor circuits and reveal features of biased connectivity and convergence in descending inputs to molecularly distinct interneuron subsets.

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