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Human Sense of Touch Consists of 16 Unique Types of Nerve Cells

The AHA! Team — Fri, 24 Jan 2025 07:50:08 +0000

Linköping University via EurekAlert! – No less than 16 different types of nerve cells have been identified by scientists in a new study on the human sense of touch. Comparisons between humans, mice and macaques show both similarities and significant differences. The study, a collaboration between researchers at Linköping University and Karolinska Institutet in Sweden and the University of Pennsylvania in the USA, has been published in Nature Neuroscience. “Our study provides a landscape view of the human sense of touch. As a next step, we want to make portraits of the different types of nerve cells we have identified,” says Håkan Olausson, Professor at Linköping University, about the study published in Nature Neuroscience. We perceive touch, temperature and pain through the somatic sensation system. A common understanding is that there is a specific type of nerve cell for each type of feeling, such as pain, pleasant touch, or cold. But the findings from the current study challenge that notion and show that bodily sensations are probably much more complicated than that. Much of the knowledge we have today about how the nervous system works comes from research on animals. But how big are the similarities between, for example, a mouse and a human? Many findings in animal studies have not been confirmed in human research. One reason for this may be that our understanding of how it works in humans is inadequate. The researchers behind the current study, therefore, wanted to create a detailed atlas of different types of nerve cells involved in human somatosensation and compare it with those of mice and macaques, a primate species. In the study, a research group at the University of Pennsylvania, led by Associate Professor Wenqin Luo, made detailed analyses of the genes used by individual nerve cells, so-called deep RNA sequencing. Nerve cells that had similar gene expression profiles were grouped together as one sensory nerve cell type. In this way, they identified 16 distinct types of nerve cells in humans. As the researchers analyse more cells, they will likely discover even more distinct types of sensory nerve cells. The nerve cell gene expression analyses provide a picture of what the cellular machinery looks like in the different cell types. The next question was how this relates to nerve cell function. If a nerve cell produces a protein that can detect heat, does that mean that the nerve cell responds to heat? The current study is the first to link gene expression in different types of nerve cells with their actual function. To investigate the function of nerve cells, a research group at Linköping University, led by Saad Nagi and Håkan Olausson, used a method that allows the researchers to listen to the nerve signalling in one nerve cell at a time. Using this method, called microneurography, the researchers can subject skin nerve cells in awake participants to temperature, touch or certain chemicals, and “listen in on” an individual nerve cell to find out if that particular nerve cell is reacting and sending signals to the brain. During these experiments, the researchers made discoveries that would not have been possible, had the mapping of the cellular machinery of different types of nerve cells not given them new ideas to test. One such discovery concerns a type of nerve cell that responds to pleasant touch. The researchers found that this cell type unexpectedly also reacts to heating and capsaicin, the substance that gives chili its heat. Reacting to capsaicin is typical of pain-sensing nerve cells, so it surprised the researchers that touch-sensing nerve cells 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 cannot be explained by what is known about the cell’s machinery and suggests that there is another mechanism for detection of cold, which has not yet been discovered. The authors speculate that these nerve cells form an integrated sensory pathway for 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. In this study, we see what type of proteins these nerve cells express as well as what kind of stimulation they can respond to, and now we can link it. It’s a huge step forward”, says Håkan Olausson. Another example is a type of very rapidly conducting pain-sensing nerve cell, which was found to respond to non-painful cooling and menthol. “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 we? Many of the 16 types of nerve cells that the researchers identified in the study are roughly similar between the species. The biggest difference the researchers found was in very rapidly conducting pain-sensing nerve cells that react to stimulation that can cause injury. These were first discovered in humans in 2019 by the same group at Linköping using microneurography. Compared to the mouse, humans have many more pain nerve cells of the type that send pain signals to the brain at high speed. Why this is so, the study cannot answer, but the researchers have a theory: “The fact that pain is signalled at a much higher velocity in humans compared to mice is probably just a reflection of body size. A mouse doesn’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 study is a collaboration between Patrik Ernfors’ research group at Karolinska Institutet, Wenqin Luo’s research group at the University of Pennsylvania and Håkan Olausson and Saad Nagi’s research group at Linköping University. 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. Article: Leveraging Deep Single-soma RNA Sequencing to Explore the Neural Basis of Human Somatosensation, Huasheng Yu, Saad S. Nagi, Dmitry Usoskin et al. (2024). Nature Neuroscience, published online November 4 2024, doi: 10.1038/s41593-024-01794-1 Journal Nature Neuroscience DOI 10.1038/s41593-024-01794-1 To read the original article click here.

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6 Strategies to Deescalate Intense Emotions In the Moment

AHA Publisher — Fri, 26 Aug 2022 07:00:57 +0000

Dr. Caroline Leaf – Stress is a normal part of life. We cannot escape it, but we can learn to manage and live with it. In this podcast (episode #407) and blog, I give you 6 tips to help deescalate turbulent emotional situations, reduce stress in the moment and build up your cognitive resilience: 1. Touch: The burgeoning field of research on healthy and appropriate touch highlights its scientific importance. Many studies have shown how touch promotes bonding, attachment, mental wellbeing and even physical health! How? Through research by neuroscientists like Edmund Rolls, we know that touch activates the orbitofrontal cortex, which is linked to feelings of reward and compassion. Dr. David Linden, professor of neuroscience at John Hopkins, says touch communicates “I am on your side”, while Dr. Dacher Keltner from Berkeley notes how appropriate touch is our primary language of compassion and primary means of spreading compassion. He argues that we are actually better at reading touch than we are at reading facial expressions! In another study by Jim Coan and Richard Davidson, participants laying in an fMRI brain scanner anticipating a painful blast of white noise showed heightened brain activity in regions associated with threat and stress. But participants whose romantic partner stroked their arm while they waited didn’t show this reaction at all. In this study, touch had essentially turned off the threat switch! The moral of the story? Lend a helping hand (or hug!), literally. 2. Express affection: Telling someone that you love them and letting them know how much they mean to you is powerful. It activates mirror neurons from nonverbal communication cues, while the words stimulate auditory cues of safety and reward, highlighting the recipient’s sense that “I am needed” and “I am important”. All this calms down the neurochemical chaos from toxic stress—love really is a kind of drug! In fact, when you express affection, it triggers dopamine in the other person as they hear your voice or see you, which also helps balance energy in the brain and helps that person feel calmer, enhancing their reward/incentive/bonus circuitry. Affection also releases oxytocin, which promotes bonding (those “warm, fuzzy feelings” we get when we are around someone we love), while activating the vagus nerve (which fires up the brain and body in a positive direction), and lowering cortisol (the stress hormone). So, never hesitate to tell someone you love and care for them, especially when they are stressed out! 3. Pet an animal: Animals are just the best! A number of studies have shown that a pet’s presence can lower blood pressure, relieve depression and anxiety, and moderate stress in the elderly largely by providing needed companionship. But the benefits of having a pet are not limited to a particular age group. Petting or stroking an animal activates the anterior cingulate cortex, the area responsible for emotional processing. This means that when we hug a dog, for example, the sensations stimulate positive feelings across the cingulate cortex and amygdala, which helps reduce toxic stress, lower our heart rate, reduce blood pressure, balance energy in the brain, and release surges of dopamine and serotonin, all of which help us feel better mentally and physically and manage stress in the moment. Even if you don’t have a pet, if you are in challenging place, try visiting a friend or family member that does have a pet, or even a petting zoo or farm! 4. Warm up: When you are very stressed, soak in a hot tub/Jacuzzi, take a long, hot shower, use a sauna or steam room, or drink a cup of hot tea, cocoa or coffee. Doing this can help: Relax your muscles Improve your circulation Stimulate the release of endorphins Lower cortisol Improve immune function Improve lung capacity Reduce anxiety and depression by increasing blood flow and oxygen to the brain Increase BDNF, a hormone necessary for memory formation and cognitive health Reduce inflammation and calm the nervous system Balance hormones like ACTH and cortisol Increase “feel good” neurotransmitters like serotonin 5. Prepare and share a meal with others: Sharing a meal with your loved ones helps maintain connection and bonding through a shared, fun and meaningful experience. No wonder Dr. Jeffrey Cummings from Cleveland has made it one of his three pillars of brain health! The familiar activity of eating together can calm down the stress response, boost mood, nourish the body and promote social connectedness, all of which are essential to a healthy brain and body. Shared meals also activate executive functions in the brain, exercising the mind and brain and making us better thinkers! Since it is a goal-directed activity that is fun, it can help develop organizational skills, problem-solving, and memory retrieval, all of which activate different regions in the brain and help increase overall cognitive health and resilience. 6. Help someone: We have all heard the phrase, “helping others helps yourself”. But this is more than just a popular saying. Research has shown how helping others, whether with our time, a physical gift or a monetary donation, improves overall mental and physical health and resilience. In one study, helping others was related to a 30% reduction of mortality in participants. This data, along with data from previous studies, actually suggests that “help given to others is a better predictor of health and well-being than indicators of social engagement or received social support”. When you reach out to the people in your community and lend a helping hand in any way you can, you not only make the external world a better place for everyone, but you also make your internal world a better place for you. Helping others can improve your overall health and longevity, your mood, your sense of purpose, your social connectedness and your sense of self, all of which contribute to a life worth living. To read the original article click here.

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Corona Means No Face Touching. Science Shows We Can’t Help It

AHA Publisher — Wed, 17 Jun 2020 07:00:01 +0000

Israel21c Staff – Throughout this whole corona crisis, we’ve been repeatedly told to avoid touching our faces so as not to transmit or catch the virus. But if you too have been unable to stop putting your hand to your face, it might be because you’re busy getting a sense of yourself. And you’re not alone. A study carried out by Weizmann Institute scientists that was recently published in the Royal Society journal Philosophical Transactions B suggested that humans touch their faces in order to self-smell, and that this self-smelling is a mechanism through which we manage to get a sense of self. Given that face-touching could be responsible for transferring nearly 25 percent of respiratory illnesses, the researchers set out to resolve while we still do so. Through an online questionnaire, they received 404 responses from 137 men and 260 women aged 19 to 74 across 19 countries, who provided a report on their sniffing habits. A whopping 94.31% of respondents reported sniffing their own hands. Meanwhile, an honest 91.58% said they did the same with their armpits. Combining the questionnaire results with other experiments and studies, the researches came to believe that while humans also sniff their hands to obtain information on other people they touched, we primarily do so to provide information on intrinsic sources. Some of the sniffing, they say, is conscious, and has to do with making sure we “don’t smell bad” or even to detect signs of disease. But on a subconscious level, they note, humans sniff themselves to form a sense of self. “We think that in sniffing our own body, we are subconsciously obtaining an external reflection and reassurance of self,” they wrote. “Given that mirrors have not been around since the dawn of humanity, a sense of self can likely be formed without one at hand. We propose that the path by which humans could have always observed themselves to get a notion of self is by olfaction.” In an apparent nod to our corona-stricken times, the study’s authors invited readers to take part in a personal, at-home experiment: next time you participate in an online meeting or seminar, they suggest, take your eyes off the speaker and check out the audience instead. Count how many people are touching their faces, specifically their noses, and you’ll see that a large amount of people are doing exactly that. Moreover, they add, you’ll be able to spot people sniffing. And no wonder, may we add — never-ending Zoom meetings most certainly have us reaching to check that we’re still all there. To read the original article click here. For more articles from Israel21c click here.

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Flexible Artificial Skin Shows Promise for Real-World Applications

AHA Publisher — Fri, 04 Oct 2019 07:00:16 +0000

Ecole Polytechnique Fédérale de Lausanne via News Medical Net – “This is the first time we have developed an entirely soft artificial skin where both sensors and actuators are integrated. This gives us closed-loop control, which means we can accurately and reliably modulate the vibratory stimulation felt by the user. This is ideal for wearable applications, such as for testing a patient’s proprioception in medical applications.” Just like our senses of hearing and vision, our sense of touch plays an important role in how we perceive and interact with the world around us. And technology capable of replicating our sense of touch – also known as haptic feedback – can greatly enhance human-computer and human-robot interfaces for applications such as medical rehabilitation and virtual reality. Scientists at EPFL’s Reconfigurable Robotics Lab (RRL), headed by Jamie Paik, and Laboratory for Soft Bioelectronic Interfaces (LSBI), headed by Stéphanie Lacour at the School of Engineering, have teamed up to develop a soft, flexible artificial skin made of silicone and electrodes. Both labs are part of the NCCR Robotics program. The skin’s system of soft sensors and actuators enable the artificial skin to conform to the exact shape of a wearer’s wrist, for example, and provide haptic feedback in the form of pressure and vibration. Strain sensors continuously measure the skin’s deformation so that the haptic feedback can be adjusted in real time to produce a sense of touch that’s as realistic as possible. The scientists’ work has just been published in Soft Robotics. Haptics Sandwiched Between Silicone Layers The artificial skin contains soft pneumatic actuators that form a membrane layer which can be inflated by pumping air into it. The actuators can be tuned to varying pressures and frequencies (up to 100 Hz, or 100 impulses per second). The skin vibrates when the membrane layer is inflated and deflated rapidly. A sensor layer sits on top of the membrane layer and contains soft electrodes made of a liquid-solid gallium mixture. These electrodes measure the skin’s deformation continuously and send the data to a microcontroller, which uses this feedback to fine-tune the sensation transmitted to the wearer in response to the wearer’s movements and changes in external factors. The artificial skin can be stretched up to four times its original length for up to a million cycles. That makes it particularly attractive for a number of real-world applications. For now the scientists have tested it on users’ fingers and are still making improvements to the technology. “The next step will be to develop a fully wearable prototype for applications in rehabilitation and virtual and augmented reality,” says Sonar. “The prototype will also be tested in neuroscientific studies, where it can be used to stimulate the human body while researchers study dynamic brain activity in magnetic resonance experiments.” To read the original article click here.

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