Nineteen
Eighty-Four by George Orwell
Odd choice, I know. Originally, I had planned on something more like this:
But as it happened I was reading 1984 while writing this piece and the quote in its context of lovers in impossible, desperate, and dehumanizing circumstances—of love as an act of rebellion, of love to remind them that they were still human, if only fleetingly so—seemed to capture the essence and intensity of the sense of touch: "Merely from feeling it he would have known it by sight."
Ask anyone who has seen 'All Quiet on the Western Front' to recall the most poignant scene from the film, and it will no doubt be this scene:
Movieclips via YouTube
It is not enough to simply see things with our eyes, or to hear things with our ears; no, something deep inside us drives our desire to touch, to connect.
Seeing is not believing. We do not believe something is real and true until the sense of touch sends the message to our brain telling us it is so, cue poor old doubting Saint Thomas:
What perhaps most differentiates the sense of touch from the other senses is that it is not only a source of commonality between humans as individuals (and as primates), but also between humans and the simplest organisms on earth.
HOW THE SENSE OF TOUCH IS PROCESSED IN OUR BODIES
Human skin is comprised of
millions of sensory receptors, including: [1][28]
- Thermoreceptors (temperature)
- Mechanoreceptors (movement/vibrations & pressure)
- Photoreceptors (light)
- Nociceptors (pain)
- Chemoreceptors (chemicals)
The skin's four main mechanoreceptors are: [37]
- Pacinian corpuscles
- Meissner's corpuscles
- Merkel's discs
- Ruffini endings
- Sensory receptors are each associated with nerve fibers (eg: A-beta, A-delta & C fibers). [30] [see Table 1]
- When the sensory receptors in the skin are stimulated, they send electrical pulses to these nerve fibers, which then relay the pulses to the spinal cord. [28][30]
- From the spinal cord the pulses travel to the brain which translates the electrical signal. [28][30]
- From here the waters get a bit murky, but in 2011 researchers working with transgenic mice identified a group of neurons in the brain’s neocortex with a dedicated, “sub-network of connections that enable them to communicate with one another and amplify the information they are receiving from the stimulus.” [15]
Table 1: Touch Fibers [38-40]
Type of Nerve Fiber
|
Myelinated
|
Conduction Speed
m/s
|
Information Carried by Fiber
|
A-beta
(5 sub-types)
|
yes
|
35 - 90
|
|
A-delta
|
yes
|
5 - 40
|
|
C
|
no
|
0.5 - 2
|
|
| |||
|
 |
Source: Pleasant to the Touch / The Scientist / September 1, 2012 |
 |
| A cortical sensory homunculus |
Areas of the body with greater or more complex sensory or motor connections are represented as larger in the homunculus, those with fewer or less complex connections are represented as smaller.
For instance, there is a large area of cortex devoted to sensation in the hands, as compared to the back. The resulting image is that of a distorted human body, with disproportionately huge hands, lips, and face. [16][24]
For instance, there is a large area of cortex devoted to sensation in the hands, as compared to the back. The resulting image is that of a distorted human body, with disproportionately huge hands, lips, and face. [16][24]
MORE ON HOW TOUCH IS PROCESSED
- Research published in 2012, found that the frequency of skin vibrations also has a role in tactile perception: [20]
When we run our fingers over a surface, the frequency of vibrations produced in the skin produce corresponding oscillations in nerves, which, in turn, convey specific messages about texture to the brain. (Think trying to find a light switch in the dark.)
- Research published in the journal Cell (2011) using genetically engineered mice to investigate how touch is processed in the skin and nervous system found that each C-type low-threshold mechanosensory receptor branches, “to send projections to as many as 30 different hair follicles.”
- Three different hair types, thick and long (or guard hairs), short, and fine, are evenly spaced throughout the skin of mice and are associated with a different and specific set of nerve endings:
“The nerves connecting each patch of skin containing one guard hair and other associated smaller hairs line up in columns in the spinal cord—neighboring columns correspond to neighboring patches of skin." [25]
The researchers, "estimate that there are about 3,000 to 5,000 columns in the spinal cord, with each column accounting for 100 to 150 hair follicles." [25]
 |
How Touch is Processed: Nerve cells stretch from the spinal cord to hair follicle cells, allowing detection of different levels of touch sensation. [25] Image Credit: David Ginty lab |
DIFFERENT TOUCH SYSTEMS: [23]
Discriminative Touch System:
Involved in sensing the location, movement and strength of touch.
Emotional Touch System:
Conveys information to the posterior insula, a part of the brain implicated in
the process of social bonding.
- Nerve fibers involved in social touch detect touch frequencies that are slow and gentle. [26]
- These nerve fibers are abundant in the parts of the body we instinctively touch for comfort or to show affection. [26]
THE ACUITY OF OUR SENSE OF TOUCH LESSENS WITH AGE
- Studies have shown a decline in passive tactile spatial acuity (the ability to resolve the fine spatial details of an object pressed against the skin) with age. [34-36]
- This decline is attributed to the gradual loss of touch, pain and temperature receptors that occurs as we age. [23]
CROSS-MODEL PLASTICITY
- Researchers have found that adult animals with hearing loss will re-route the sense of touch into the hearing parts of the brain. [17]
(I believe Lance Kerwin attempted similar research in the 70’s. … apologies, any excuse for a James at 15 reference.)
- Many studies have shown that tactile spatial acuity is enhanced among blind individuals compared to sighted individuals of the same age. [8–13][19]
- However, a McMaster University study found that blind individuals who could read Braille had greater sensitivity in their reading finger than non-Braille readers among blind study participants.
- This suggests that the heavier the reliance upon our fingertips, the greater our tactile acuity. [19]
TACTILE ILLUSIONS
Tactile illusions exploit the sense of touch. [4]
One example is the cutaneous rabbit illusion, in which a sequence of taps at two separated skin locations results in the perception that intervening skin regions were also tapped. [5]
Another is the Pinocchio illusion: [16]
“Researchers have found that if they vibrate the tendon of the biceps, many people report feeling that their forearm is getting longer, their hand drifting ever further from their elbow. And if they are told to touch the forefinger of the vibrated arm to the tip of their nose, they feel as though their nose was lengthening, too.”
THE PLASTICITY OF BODY PERCEPTION
- Studies of monkeys learning to use a rake to obtain distant objects have found that multisensory brain cells began to respond to objects appearing anywhere along the length of the rake, suggesting the brain represented the rake as actually being part of the hand. [31]
“If you look towards your hand in a darkened room and see it illuminated by a bright flash, an afterimage of your hand remains after the flash. If you then move your hand, the afterimage changes, though no actual visual signal is present.”
EVER WONDER WHY WE CAN'T TICKLE OURSELVES?
- Brain scientists at University College London have pinpointed the cerebellum as the part of the brain that prevents us from self-tickling.
- The cerebellum can distinguish expected sensations from unexpected sensations.
- Because our brain anticipates this contact from the hands and prepares itself for it, the feeling of unease and panic is removed, and thus the body no longer responds the same as it would if someone else were to tickle us.
- For more on this, click on the link to view the video by HowStuffWorks Why Can't You Tickle Yourself?
TOUCH & FIRST IMPRESSIONS
In the 2008 paper, Experiencing
Physical Warmth Promotes Interpersonal Warmth, researchers found: [27]
- "Participants who briefly held a cup of hot (versus iced) coffee judged a target person as having a “warmer” personality (generous, caring)."
- "Participants holding a hot (versus cold) therapeutic pad were more likely to choose a gift for a friend instead of for themselves."
PROSTHETIC RESEARCH
- In the video below, the man is wearing a prosthetic hand that restores sensation via three small electrodes implanted on the peripheral nerves of the residual limb.
- He then uses the prosthetic hand to pick up and remove stems from cherries while blindfolded.
- With the sensation off, 9 out of 15 cherries were damaged. With the sensation on, 1 out of 15 cherries was damaged. [21]
DTSciVids
- Researchers in South Korea and the United States have created a stretchable artificial skin that can register heat, pressure and moisture. The artificial skin is also embedded with heated elements to maintain warmth. [22]
VOA News
6 MORE INTERESTING POINTS
ABOUT THE SENSE OF TOUCH
- Somatosensation, a fancy name for the sense of touch, also plays an important role in proprioception, which is fancy name for the self-awareness of the relative positions of neighbouring body parts, and of the effort required for their movement. [15][41] (Think trying to touch your nose with your eyes closed.)
- Photoreceptors detect potentially damaging ultraviolet radiation, inducing increased production of melanin by melanocytes. [14]
- Astereognosis is the inability of an individual to identify an object by touch alone. [2][3]
- Patients in a deep vegetative coma will show skin responsiveness when touched. [16]
- Pain asymbolics (individuals who lack the emotional pain system mentioned above) are aware that pain is occurring, but are not sensitive to the pain. It is in effect, pain without unpleasantness. [26]
- Your sense of touch is the first sense to develop inside of the womb. [28]
***
FIN
REFERENCES
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[15] INTERNATIONAL
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<www.sciencedaily.com/releases/2009/12/091215173017.htm>.
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esciencenews.com in Psychology &
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[37] https://en.wikipedia.org/wiki/Mechanoreceptor
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1984 QUOTATION
Orwell, George (2014-05-06). The Collected
Works of George Orwell: Nineteen Eighty-Four, Animal Farm, Down an (Kindle
Locations 25692-25694). HarperCollins Canada. Kindle Edition.
ADDITIONAL RESOURCES
IMAGE CREDITS
Still of
John Hurt and Suzanna Hamilton in Nineteen Eighty-Four (1984) / December
22, 2010 © 1984 Metro-Goldwyn-Mayer Studios Inc. All Rights Reserved. Nineteen Eighty-Four at Amazon
"Creación de Adám" by Michelangelo -
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"Caravaggio - The Incredulity of Saint
Thomas" by Original uploader was Dante Alighieri at en.wikipedia -
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"Mikrofoto.de-volvox-4" by Frank Fox - http://www.mikro-foto.de. Licensed under CC BY-SA 3.0 de via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Mikrofoto.de-volvox-4.jpg#/media/File:Mikrofoto.de-volvox-4.jpg
"Creation poster" by Source. Licensed under Fair use via Wikipedia - https://en.wikipedia.org/wiki/File:Creation_poster.jpg#/media/File:Creation_poster.jpg
"Blausen 0809 Skin TactileReceptors"
by BruceBlaus. When using this image in external sources it can be cited as:Blausen.com
staff. "Blausen gallery 2014". Wikiversity Journal of Medicine.
DOI:10.15347/wjm/2014.010. ISSN 20018762. - Own work. Licensed under CC BY 3.0
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“Interpreting Touch” Image from the article Pleasant
to the Touch / The Scientist / September 1, 2012
"1421 Sensory Homunculus" by OpenStax
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http://cnx.org/content/col11496/1.6/, Jun 19, 2013.. Licensed under CC BY 3.0
via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:1421_Sensory_Homunculus.jpg#/media/File:1421_Sensory_Homunculus.jpg
‘How Touch is Processed’ Image by David Ginty
lab, via Touching
a nerve: How every hair in skin feels touch and how it all gets to the brain
/ www.sciencedaily.com
