Bring Up Touch—How do we perceive tactile stimuli

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From all senses that we develop, touch is the first one to form. During pregnancy, fetuses will begin developing feelings of sensations on their faces at week 8. Yet, the nose and the lips will be responsible for processing nearly all sensations. A month later, feelings on the palms and soles will develop, and if we wait for an additional five weeks (week 17), the abdomen will start sensing too. Interestingly, our brain will devote a majority of its attention to those parts especially. It is relatively easy to test this. Try prodding someone else’s back, with their consent, and ask them to evaluate how far two prods are from each other. Then do the same again, but this time over their palm. Were the results similar? Hopefully, the palms results should be unquestionably more accurate than the back results. This effect is possible through the bulkier number of neuronal endings found on the skin of our palms compared to those on our back.

Speaking of neuronal endings, we cannot avoid talking about the many specialized sensory neurons that form the somatosensory neural pathways, which get completed by the middle of the third trimester. From this point on, the baby will feel a more integral range of feelings. Each specialized sensory neuron has, on its endings, receptors that are enabling the perception of different sensations. Mechanoreceptors will provide detection for pressure, light touch, tearing or vibration. Thermoreceptors are sensitive to temperature changes. Chemoreceptors will detect chemical changes, and nociceptors are responsible for transmitting pain signals. It is intriguing to note that pain is the last sensation to develop and appear through the formation of totally different pathways (read https://bringupscience.com/2021/01/23/bring-up-pain-2/ for more). In sum, all specific tactile inputs have distinct neurons responsible for their detections. This statement also applies to touch in social interactions. As opposed to ordinary touch, the tap that we receive on the back of our shoulder, as praise, elicits an emotional response. This particular tactile sensation makes up what we now describe as social or emotional touch. It recruits a different somatosensory system than the one involved in conventional touch.

A piece of evidence supporting the idea that social touch involves the activation of different pathways comes from studying people affected by primary sensory neuropathy. Individuals affected by this disorder are known to display touch blindness, i.e. they cannot feel any tactile input coming from neither their hands nor their bodies. They are even incapable of reading braille, where each letter corresponds to a dot pattern, and all dots are embossed. This adaptation, commonly, grants people who cannot read solely based on their sight the ability to read through touch. Thus as already mentioned, individuals affected by this neuropathy cannot read, nor can they feel the object coming in contact with their skin. However, they strangely can feel a touch from another person and attribute it an emotional value. They, indeed, can feel the gentle touch of someone stroking their arm and communicate that the touch felt pleasant. However, this theory is currently based on anecdotal evidence only, and thus we shouldn’t jump to any conclusion just yet.

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Even if social touch turns out to have no different pathways than conventional touch, it would be reasonable to keep in mind the importance of its impact anyway. Indeed, some orphan children, who grew up in an orphanage, received so little social-emotional interaction that it hampered their growth dramatically and, in some instances, even led to death. I should disclose that customarily the orphanage staff was conveying proper treatments with absolutely no intention of neglect. Unfortunately, they were often too few and could honestly not care for more than the children’s most basic needs. Those needs were thought, at that moment, to be strictly drinking, feeding, sleeping and occasional physical activity. As long as these aspects were all taken care of, they genuinely believe that they tended well. Only now we know that social touch is amongst those basic needs. The lack of it will downright kill a kid. Current studies have demonstrated that social touch enables growth hormone release and will stimulate the immune system. Researchers have found similar findings to support the reciprocal, i.e. that a lack of social touch hinders growth hormone release and cripples the immune system. Moreover, children who were unfortunate enough to have been placed in such an institution were found at an elevated risk to develop behavioural, social and psychological problems.

Additionally, social touch occupies such a meaningful place in our life that, as a result, we may mistakenly associate general tactile inputs to our impression of a person. To illustrate this idea, let us consider this well-known experiment conducted by social psychologists. The psychologist asked the volunteers to describe their first impressions of a stranger. Every subject of the study had the same task, to relay their general impression. The only difference between all the volunteers was the drink they were holding while meeting this other person: Half held a cold drink and the rest a hot drink. We would all think that the beverages they were holding should have no impact on their impression of another individual, but that is not what happened. Curiously, people holding the hot drinks described their new acquaintance as “warmer”; the inverse was also true for the cold drink volunteers. Another experiment tried a different approach through evaluation of the same resume but on two differently weighed clipboards. It seemed that the resume attached to the heavier clipboard made the candidate seem more serious and competent than the individual whose resume was attached to the lighter clipboard.

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Despite social touch playing an integral role in our life, it is not the only factor that can interfere with our touch perception. Emotions play a considerable role in how we interpret touch or pain. The feeling we bear in a particular moment (good/bad mood, relaxed/scared, rested/tired, etc.) may considerably impact how we will perceive that tap on our back. The same tap may feel like an assault or an encouragement, depending on your emotion at the time. If you hate the person, you might think of that tap as an assault, but if that person is a friend, then you could have perceived it as an encouragement. Additionally, when we feel happy, pain does not seem as terrible as when we are sad or depressed. We can only say that touch and emotions are in a very intricate relationship, indeed.

Now, I cannot write about touch without talking about tickles. I honestly find them somewhat intriguing since no one has yet to come with an irrefutable explanation as to why we feel them. There are many theories, however. My favourite one introduces tickles as an evolutionary mechanism that leads to more capable offspring. Tickles are, in the simplest terms, the results of neuronal overexcitation. We, as adults, can feel tickles in only our most sensitive areas, but as a kid, that surface can be as great as the entire space occupied by your skin. Sadly, our sensitivity, as we are ageing, seems to decline progressively. The duality of tickles (being felt as both unpleasant and pleasant) supposedly serves as both an incentive to protect the sensitive areas and encourage wrestling and fighting. Those two consequences force offspring to prepare and practise both their offensive and defensive strategies to better cope with inevitable future threats. It seems such a no-brainer that the more you practise, the better you become, and this is why I genuinely value this idea.

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Bring Up Biophilia—What makes us particularly attracted to nature

No one can dismiss the amazing feeling we get after spending some time in nature. We instantly feel relaxed and reinvigorated. Some might attribute this effect to time spent far away from work, and even though they could be correct, it is not the whole picture. Biophilia is a relatively new concept that brought the…

Bring Up Blood—How our oxygen gets carried throughout our body

Good evening my dearest followers, Please, take a moment to enjoy this excerpt for my newest post (Bring Up Blood). We could most certainly not live without blood. It is absolutely essential for the survival of our most distant limbs and organs. Even though almost all of our respiration is thanks to our respiratory organs,…

Bring Up Fibromyalgia – When pain becomes an everyday occurence

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 I woke up this morning feeling normal. My brain was working properly, my body didn’t ache, and I did not feel one bit tired. But why am I fricking telling you this? Isn’t it normal? As in everyone should be feeling like this, right? I would be very happy to tell you that it’s truly routine, but I unfortunately don’t have this pleasure. What usually happens goes a bit more like the following: I wake up tired, most likely caused by my insomnia, my brain is foggy, and I start feeling some painful impulses in my body. All of this is triggered by a chronic muscular pain syndrome (CMPS) which could one day become fibromyalgia. The explanation behind the uncertainty resides in how I fulfill the diagnosis, or more accurately how I do not.

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Two years ago, I decided to schedule an appointment with my family physician to discuss some issues that concerned me. The main one was the almost sudden emergence of pain in parts of my body. It was always very localized, never widespread like a headache or a cramp. It felt like a burst of sharp electrical firing in places such as the side of my foot, my hip, the palm of my hand, the inside of my elbow, etc. I would describe the feeling to never spread more than one centimetre wide. The absence of reasonable explanation for the pain was making me worry.

After examination, my family physician concluded that it didn’t meet all the criteria necessary for a fibromyalgia diagnosis. Although she explained that the situation could develop further and worsen. If that is the case, there would be a strong chance that my condition would fulfill the last required criteria for fibromyalgia. She encouraged me to include physical stretching in my daily routine and to do some research (knowing that I am a trained physiologist) on CMPS and fibromyalgia. From her suggestion, I did some research. It was not only to familiarize myself with those disorders, but also to find more ways to help reduce the pain caused by CMPS. As for stretching, I am not proud to say that I didn’t follow her recommendation very strictly. I do stretch, but I am sadly not doing it every day. Most often it’s because I forget, or I don’t feel like it. However, the main reason is that it annoys me. I find it so boring that I feel it’s such an effortful job. I know, I know! I need it, but let’s just say that at this point I became really good at finding excuses for myself in order to avoid it.

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Turns out that the idea of stretching is not that far-fetched. All the research papers examined were praising its benefit in treating fibromyalgia cases. So, I am probably really doing myself some important disfavour by not enforcing the practice. The reasoning behind its efficiency is however unclear. We actually have no clue what might cause the symptoms seen in fibromyalgia. There are only theories. Some people support that it’s triggered by an overexcitation of the glutamatergic neuronal pathways, others support that it’s caused by communication issues between the hypothalamus and the pituitary gland. Even if we don’t know what is at the root of the disorder, researchers are all agreeing on one thing. Fibromyalgia is a centralized disorder, which means that the central nervous system is at fault. By central nervous system I mean everything ranging from the spinal cord to the brain. This central nervous system is being oversensitive, and we yet do not understand why.

I know! You get it! Both fibromyalgia and CMPS are causing pain (read Bring Up Pain, for more information). Here’s a twist, though, it’s doing way more than messing up with your body, it’s also messing up with your head. The constant sleep disturbances and memory dysfunctions are probably my biggest troubles. As I mentioned at the very beginning, I do experience insomnia which has become more and more regular in the last few years. Usually, as soon as I would feel insomnia settling in, I would grab some melatonin which would consistently improve my sleeping capabilities. However, starting two months ago, I began experiencing insomnia every night and this lasted for a bit more than three consecutive weeks. From that moment on, melatonin would not seem to be working anymore. In the best course of action, I could fall asleep by midnight (I usually go to sleep around 9:30 p.m.-10 p.m.) and at worst, by 4 a.m. That means I got on average a good 6–7 hours of sleep every night, which doesn’t sound that bad. That’s if we’re not considering that a good night’s sleep, in my case, usually lasts 9–10 hours. This means that, by the third week, I was in a clear sleep deficit state.

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Being sleep deprived does nothing good on the brain. It also seemed to worsen the memory dysfunction and the fatigue aspects of CMPS. Useless to say that trying to finish up my Master of Science in Physiology was challenging. For example, it took me two attempts to pass the mandatory course exams. The memory deficits were affecting me worse probably because I had learnt to strongly rely on it through many years spent in school. This has led me to develop severe performance anxiety that was best displayed in public speaking scenes. This was gut-wrenching since I loved public speaking, and still do actually despite the trouble. I would have taken twice, or even thrice, as much pain if it had meant retrieving my memory function and avoiding performance anxiety altogether. Now, I can’t even talk without stumbling on my words. It makes it seem as if I have no mastery of what I am introducing, and this genuinely pains me.

Oh well! I didn’t mean to be a drag. As far as I know, there is so much more you can learn about chronic pain syndromes and fibromyalgia. It is gaining awareness, but still, many ignore its impacts. This was my story and is by no means a complete overview of the chronic pain disorders. This was, however, a fair representation about my own experience with the disorder. I realize that my case is very mild, but some of you might not be as fortunate and thus my compassion goes to you. It is not easy for anyone to have to deal with such an awful situation, but luckily, we can find solace in knowing that we are not going through this alone. 

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Let’s also be conscious that there are quite a handful of promising treatments right now. There is much to be happy about. Additionally, if you really take care of yourself, you can seriously have some control over how worse it can get. That be yoga, meditation, stretching, antidepressants, marijuana (yes, that is correct!), acupuncture, diet change or others, it’s all yours to explore. I personally prefer yoga, meditation and diet change, or more specifically intermittent fasting (See Bring Up Intermittent Fasting). Despite not having had the pleasure to try acupuncture yet, I would definitely like to give it a shot someday.

I thank you infinitely for reading this post and if you would like to know more about the mysteries that surround us, please join my subscription list to keep up with my newest content. If you have any questions, please add them to the comment section and I’ll make sure to answer as soon as humanly possible.

Bring Up Pain – Where all of this hurt comes from

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I hurt myself constantly and I am certain you do too. I am so clumsy, though I am not sure why. Maybe I try to hurry up a bit too much, I hate wasting time by lingering on any task for too long. So, for example, I often end up hitting my big toe on one of the corners of the bed base trying to get out of bed in a hurry or cutting myself on a razor haphazardly left in the bathroom drawer when trying to find my eye cream. Other than hurtful to my ego, those experiences hurtful to my body, which leads to pain. Pain is always taken for granted. You are hardly waking up every morning dreading the idea that you’ll eventually experience it, but when it does finally happen you are neither surprise. Pain is experienced by most of us, but despite its universality, very few understand how it works. Actually, can someone please tell me what the heck is pain and how can I fricking get rid of it?

It took me many years of undergraduate studies and then graduate studies to finally understand its main mechanisms, which I will now share with you. I hope that by the end of this article, you not only come to understand pain, but to appreciate it for its complexity and its vital necessity. 

When you think about pain, probably you are thinking about it the same way I did before starting my post-secondary studies. I thought pain was the result of injury. You break your skin; it hurts. You hit your foot; it hurts. You fall; it hurts. You get my point. But that doesn’t explain the headache you got last week, nor does it explain the heartburn you got last time you ate greasy food. It’s easy to point fingers at possible culprits for our pain, but it’s not really clear why it causes the pain in the first place. Why does not drinking enough water causes me headaches?

So, let’s break everything into small steps. The very first thing your body does is feeling things, this is called perception. But when the body perceives something that may be hurtful to you, it becomes known as nociception. The body can sense things that are called stimuli (plural of stimulus) which is a fancy word for sensations. Those stimuli can be of thermal (heat or cold), mechanical (pressure or tension), or chemical (inflammation or toxins) nature. Then considering our example giving earlier, hitting my big toe, and cutting myself led to nociception of a stimulus of mechanical nature. As for the headache and the heartburn, it was from chemical nature. For the headache, there was probably not enough oxygen and for the heartburn, too much acid. 

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Now let’s look at this nociception closer. The changes are perceived by some detectors that we call pain receptors, or more specifically nociceptors. Those nociceptors can differ greatly from each other. They can have different endings which make them able to detect specific types of stimulus or they can also vary in size. The latter will influence how fast the nerve will carry the signal to the brain. It’s this difference in size that makes you sense two pain waves. For example, when you hit your toe. You first grab your toe, but it really was a few seconds after you grabbed it that the intense and sharp sensation started kicking in. This is because the large nerves carried the information related to location and nature of the pain faster than the smaller nerves. It’s those smaller nerves that were responsible to carry the information related to the intensity and emotional nature of the pain and is delayed. This whole process that we just went through is called transduction. 

After transduction there is conduction, which is for us step 2. This step explains how the signal is actually sent to the brain. It will probably not be any news to you, the signal is carried by nerves, or neurons. All these neurons are organized into something that resembles a family tree. In your family tree there are your siblings, your cousins and obviously yourself. All of them serve as an analogy for the first-order neuron or most commonly called primary afferents. As suspected, they stem from wherever you can feel (skin, ears, organs, etc.), and they end at the spinal cord. In your family tree, there are also your parents, your aunts, and your uncles. Those are like the second-order neurons, there are generally fewer than the previous group. They are located in your spinal cord. Then, you have your grandparents. Those are like the third-order neurons and are present from the end of your spinal cord to your brain. Simple, isn’t it? 

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After the signal has reached through all the three levels of neurons and finally the brain, then there is transmission. Transmission refers to the mechanism to which all different information will be sent to their appropriate processing section. Then an output signal will be produced and will be modulated depending on its intensity and its relevance. If the intensity is too much and is not relevant, the signal may be tuned down, or reciprocally up if the situation is reversed. So that makes up two steps: Transmission and Modulation.

The very last step is Perception, and it relates not to the initial perception we introduced when we talked about transduction, but to the final products that leads to a reaction. It is at that moment you grab your toe

So, if I try to summarize everything, first you feel; secondly, the signal goes through three levels of neuron up to the brain; thirdly, the signal is interpreted by the brain; fourthly, the signal is tuned by the brain and lastly it is sent back to the appropriate location to create a reaction. Normally, it takes all those steps to induce pain, but there are some cases where the pain seems to appear out of thin air. That pain is often said to be neuropathic. Where signals are generated in the absence of stimulus detection which is common in chronic muscular diseases. 

Reversely, there is another disease that leads to the inability to generate pain. Doesn’t that sound wonderful, right? People affected by congenital insensitivity to pain with anhidrosis (CIPA) would disagree. Pain is a protective mechanism that forces you to have a reaction when faced to a potentially harmful stimulus. Without pain, most people with CIPA will die before the age of 25. They usually end up burning themselves seriously, biting off their tongues or scratching to the bone, which could eventually lead to infection, which can also lead to death. These are only examples of things that may happen to you without the ability to generate pain. Pain is so important since it is there to avoid putting yourself under unnecessary harm. 

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Pain can also be split into two categories: acute and chronic. We talk about acute pain when dealing with a situation that is sudden and ephemeral (that doesn’t last in time). In contrast, we talk about chronic pain when it’s persistent in time, usually more than three months. So all previously mentioned pain examples were actually all acute, apart from chronic muscular disease. It’s neuropathic nature which tends to be difficult to treat, renders it a chronic disorder. Fibromyalgia is a good example for this, to learn more read Bring Up Fibromyalgia. 

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Now to avoid pain you have different strategies. You can simply take some analgesics like acetaminophen (Tylenol) or ibuprofen (Advil), and if the pain is really intense, morphine. There is also the placebo effect that is really strong in helping face pain. Grabbing your foot when you hit it also greatly helps since it creates some natural inhibition of the pain through a process called the gate control theory. Mindfulness has also been shown to be helpful by redirecting our attention to external stimuli. Obsessing over our pain is detrimental. At best, it blocks the downregulation of the pain and at worst it promotes its upregulation.

Now that you know where pain comes from, my advice to you is to accept it, to cherish it, to listen to it and to respond to it with kindness. Pain is a necessary evil that is an intricate part of life. Whenever you feel pain, remember that you are living, and most important, that you are living science. 

I thank you infinitely for reading this post and if you would like to know more about the mysteries that surround us, please join my subscription list to keep up with my newest content. If you have any questions, please add them to the comment section and I’ll make sure to answer as soon as humanly possible.