Summary: Researchers compared the 16 different types of nerve cells found in mice and macaques to those found in humans, revealing both shared and distinctive characteristics. The research uncovers unanticipated complexities in how brain cells respond to stimuli, implying a visual system that combines various kinds of sensations.
Importantly, some nerve cells that sense contact also respond to heat and cooling, demonstrating a complex process for processing pleasurable sensations. This research provides insight into the differences in human nerve signaling throughout evolution, especially in terms of the rate of human pain response.
Findings may help us understand visual control and pain management more fully. Further study may reveal even more body types and broaden our understanding of visual nerve pathways.
Important Facts:
- There are sixteen different types of visual nerve cells with sophisticated response profiles that have been found in humans.
- Some touch-related brain cells even respond to problems and temperature, hard previous assumptions.
- In humans, quick pain-signaling nerve cells are more common and quickly than in mice, perhaps as a result of body size.
Origin: Linkoping University
In a recent research on the individual sense of touch, researchers have identified no less than 16 different types of muscle tissue. Comparisons between people, animals and chimps show both connections and significant variations.
The study, which was co-authored by academics at Linköping University, Karolinska Institutet in Sweden, and the University of Pennsylvania in the USA, has been published in Nature Science.
Our research provides a panoramic view of how people perceive the mortal sense of touch. As a second stage, we want to create photographs of the different types of brain cell we have identified”, says Håkan Olausson, Professor at Linköping University, about the study published in , Nature Science.
Touch, heat, and pain are all influenced by the bodily experience system. A typical understanding is that there is a certain type of brain cell for each type of feeling, like as soreness, comfortable feel, or cold.
However, the results of the current study concern that assumption and demonstrate that bodily sensations are probably many more complex than that.
Much of the studies on pets has led to the development of our current understanding of how the nervous system operates. But how large are the similarities between, for instance, a keyboard and a man?
Some studies from pet studies have not been confirmed by human studies. This could be due to our limited understanding of how it functions in people, for example.
So, the authors of the current study wanted to compile a detailed map of the various nerve cell types used in primal somatosensation in order to compare the results of mice and macaques.
In the study, a study group at the University of Pennsylvania, led by Associate Professor Wenqin Luo, made precise analyses of the genes used by individual muscle cells, so-called strong RNA scanning.
Nerve cells with similar gene expression patterns were combined into one sensory nerve body type. In this way, they identified 16 different types of nerve tissue in humans. The researchers ‘ ability to identify even more distinct sensory nerve cells as they conduct more cell analysis.
The gene expression evaluations of brain cell genes provide a snapshot of how the biological machinery functions among the various cell types. How does this relate to nerve cell work, the second inquiry was. Does the presence of a peptide that can detect heat indicate that the brain body is responding to temperature?
The present study is the first to link the real function of different types of brain cells with gene expression.
A research team at Linköping University, led by Saad Nagi and Hkan Olausson, used a technique that allows the researchers to listen to the brain signaling in one brain cell at a time to evaluate the work of muscle tissue.
Using this method, called microneurography, the researchers may issue body nerve cells in sleepy participants to heat, contact or certain chemicals, and “listen in on” an adult nerve cell to find out if that special nerve cell is reacting and sending signals to the brain.
The researchers made discoveries during these experiments that would not have been possible had they not had had the ability to map the cellular machinery of the various nerve cell types. A type of nerve cell that responds to pleasant touch is one of the findings.
The researchers discovered that this cell type unsurprisingly responds to capsaicin, the substance that heats chili, and other factors. Capsaicin reacts to touch-sensing nerve cells, which is typical of pain-sensing nerve cells. It surprised the researchers to learn that touch-sensing nerve cells also responded to such stimulation.
Further, this nerve cell type also responded to cooling, even though it does not produce the only protein so far known to signal cold perception. This finding does not fit into the description of what is known about the cell’s machinery, and suggests that there is a different way to detect cold that has not yet been discovered.
The authors speculate that these nerve cells combine to create a sensory pathway that produces pleasant sensations.
” For ten years, we’ve been listening to the nerve signals from these nerve cells, but we had no idea about their molecular characteristics.
We can now link the information we have in this study with what kind of proteins these nerve cells express as well as what kind of stimulation they can respond to. It’s a huge step forward”, says Håkan Olausson.
Another type of pain-sensing nerve cell, which responds to non-painful cooling and menthol, is an example.
” There’s a common perception that nerve cells are very specific – that one type of nerve cell detects cold, another senses a certain vibration frequency, and a third reacts to pressure, and so on. It’s often talked about in those terms. But we see that it’s a lot more complicated than that,” says Saad Nagi, Associate Professor at Linköping University.
And what about the comparison between mice, macaques and humans? How similar are our personalities? The researchers found that the species characteristics of many of the 16 different types of nerve cells are essentially similar. The researchers discovered that nerve cells that could be injured by pain-sensing nerve cells were conducting very quickly.
These were first discovered in humans in 2019 by the same group at Linköping using microneurography. Humans have many more pain nerve cells than mice, of the type that send pain signals to the brain at high speeds. Why this is so, the study cannot answer, but the researchers have a theory:
The fact that humans communicate pain much more quickly than mice does is probably just a reflection of body size. A mouse does n’t require such rapid nerve signalling.
” But in humans, the distances are greater, and the signals need to be sent to the brain more rapidly, otherwise, you’d be injured before you even react and withdraw”, says Håkan Olausson.
The research was carried out in collaboration with the Karolinska Institutet research group, Wenqin Luo’s research group at the University of Pennsylvania, and Hkan Olausson and Saad Nagi’s research group at Linköping University.
Funding: Financial support for the study was provided by the National Institutes of Health, the Swedish Research Council, ALF Grants Region Östergötland, and the Knut and Alice Wallenberg Foundation.
About this news about sensory neuroscience research
Author: Karin Söderlund Leifler
Source: Linkoping University
Contact: Karin Söderlund Leifler – Linkoping University
Image: The image is credited to Neuroscience News
Original Research: Open access.
” Leveraging Deep Single-soma RNA Sequencing to Explore the Neural Basis of Human Somatosensation” by Håkan Olausson et al. Nature Neuroscience
Abstract
Leveraging Deep Single-soma RNA Sequencing to Explore the Neural Basis of Human Somatosensation
Homogeneous dorsal root ganglion ( DRG ) neurons contribute to the versatility of somatosensation. However, soma transcriptomes of individual human ( h ) DRG neurons—critical information to decipher their functions—are lacking due to technical difficulties.
In this study, we isolated somata from individual hDRG neurons and conducted deep RNA sequencing ( RNA-seq ) to detect, on average, over 9, 000 unique genes per neuron, and we identified 16 neuronal types.
These findings were supported and verified by RNAscope in situ hybridization and spatial transcriptomics. Cross-species analyses revealed differences between potential pain-sensing neurons and the presence of human-specific neuronal types.
Molecular-profile-informed microneurography recordings revealed temperature-sensing properties across human sensory afferent types.
In summary, by employing single-soma deep RNA-seq and spatial transcriptomics, we generated an hDRG neuron atlas, which provides insights into human somatosensory physiology and serves as a foundation for translational work.
