{"id":1055,"date":"2020-06-15T11:56:06","date_gmt":"2020-06-15T15:56:06","guid":{"rendered":"http:\/\/pressbooks.library.upei.ca\/upeiintropsychology\/chapter\/tactile-sensation\/"},"modified":"2020-06-16T13:04:32","modified_gmt":"2020-06-16T17:04:32","slug":"touch","status":"publish","type":"chapter","link":"https:\/\/pressbooks.library.upei.ca\/upeiintropsychology\/chapter\/touch\/","title":{"raw":"Touch","rendered":"Touch"},"content":{"raw":"
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Who doesn\u2019t love the softness of an old t-shirt or the smoothness of a clean shave? Who actually enjoys having sand in their swimsuit? Our skin, the body\u2019s largest organ, provides us\u00a0with all sorts of information, such as whether something is smooth or bumpy, hot or cold, or even if it\u2019s painful. Somatosensation<\/strong><\/a>\u2014which includes our ability to sense touch, temperature and pain\u2014transduces physical stimuli, such as fuzzy velvet or scalding water, into electrical potentials that can be processed by the brain.<\/p>\r\n\r\n

T<\/span>actile sensation<\/h2>\r\n

Tactile<\/em> stimuli<\/em>\u2014those that are associated with texture\u2014are transduced by special receptors in the skin called mechanoreceptors<\/strong><\/a>. Just like photoreceptors in the eye and auditory hair cells in the ear, these allow for the conversion of one kind of energy into a form the brain can understand.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"385\"]\"image\" Figure 5. A drawing of the somatosensory cortex in the brain and the areas in the human body that correspond to it - they are drawn in proportion to the most sensitive or the most innervated parts of the\u00a0body.[\/caption]\r\n

After tactile stimuli are converted by mechanoreceptors, information is sent through the thalamus to the primary <\/strong>somatosensory <\/strong>cortex<\/strong><\/a>for further processing. This region of the cortex is organized in a somatotopic <\/strong>map <\/strong><\/a>where different regions are sized based on the sensitivity of specific parts on the opposite side of the body (Penfield & Rasmussen, 1950<\/a>). Put simply, various areas of the skin, such as lips and fingertips, are more sensitive than others, such as shoulders or ankles. This sensitivity can be represented with the distorted proportions of the human body shown in Figure 5.<\/p>\r\n\r\n<\/div>\r\n

Pain<\/h2>\r\n\u00a0<\/strong>Most people, if asked, would love to get rid of pain (nociception<\/strong><\/a>), because the sensation is very unpleasant and doesn\u2019t appear to have obvious value. But the perception of pain is our body\u2019s way of sending us a signal that something is wrong and needs our attention. Without pain, how would we know when we are accidentally touching a hot stove, or that we should rest a strained arm after a hard workout?\r\n

Phantom limbs<\/h2>\r\nRecords of people experiencing phantom limbs <\/strong><\/a>after amputations have been around for centuries (Mitchell, 1871<\/a>). As the name suggests, people with a phantom limb have the sensations such as itching seemingly coming from their missing limb. A phantom limb can also involve phantom limb pain<\/strong><\/a>, sometimes described as the muscles of the missing limb uncomfortably clenching. While the mechanisms underlying these phenomena are not fully understood, there is evidence to support that the damaged nerves from the amputation site are still sending information to the brain (Weinstein, 1998<\/a>) and that the brain is reacting to this information (Ramachandran & Rogers-Ramachandran, 2000<\/a>). There is an interesting treatment for the alleviation of phantom limb pain that works by tricking the brain, using a special mirror box to create a visual representation of the missing limb. The technique allows the patient to manipulate this representation into a more comfortable position (Ramachandran & Rogers-Ramachandran, 1996<\/a>).\r\n
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<\/p>\r\n\r\n<\/div>","rendered":"

\n

Who doesn\u2019t love the softness of an old t-shirt or the smoothness of a clean shave? Who actually enjoys having sand in their swimsuit? Our skin, the body\u2019s largest organ, provides us\u00a0with all sorts of information, such as whether something is smooth or bumpy, hot or cold, or even if it\u2019s painful. Somatosensation<\/strong><\/a>\u2014which includes our ability to sense touch, temperature and pain\u2014transduces physical stimuli, such as fuzzy velvet or scalding water, into electrical potentials that can be processed by the brain.<\/p>\n

T<\/span>actile sensation<\/h2>\n

Tactile<\/em> stimuli<\/em>\u2014those that are associated with texture\u2014are transduced by special receptors in the skin called mechanoreceptors<\/strong><\/a>. Just like photoreceptors in the eye and auditory hair cells in the ear, these allow for the conversion of one kind of energy into a form the brain can understand.<\/p>\n

\"image\"
Figure 5. A drawing of the somatosensory cortex in the brain and the areas in the human body that correspond to it – they are drawn in proportion to the most sensitive or the most innervated parts of the\u00a0body.<\/figcaption><\/figure>\n

After tactile stimuli are converted by mechanoreceptors, information is sent through the thalamus to the primary <\/strong>somatosensory <\/strong>cortex<\/strong><\/a>for further processing. This region of the cortex is organized in a somatotopic <\/strong>map <\/strong><\/a>where different regions are sized based on the sensitivity of specific parts on the opposite side of the body (Penfield & Rasmussen, 1950<\/a>). Put simply, various areas of the skin, such as lips and fingertips, are more sensitive than others, such as shoulders or ankles. This sensitivity can be represented with the distorted proportions of the human body shown in Figure 5.<\/p>\n<\/div>\n

Pain<\/h2>\n

\u00a0<\/strong>Most people, if asked, would love to get rid of pain (nociception<\/strong><\/a>), because the sensation is very unpleasant and doesn\u2019t appear to have obvious value. But the perception of pain is our body\u2019s way of sending us a signal that something is wrong and needs our attention. Without pain, how would we know when we are accidentally touching a hot stove, or that we should rest a strained arm after a hard workout?<\/p>\n

Phantom limbs<\/h2>\n

Records of people experiencing phantom limbs <\/strong><\/a>after amputations have been around for centuries (Mitchell, 1871<\/a>). As the name suggests, people with a phantom limb have the sensations such as itching seemingly coming from their missing limb. A phantom limb can also involve phantom limb pain<\/strong><\/a>, sometimes described as the muscles of the missing limb uncomfortably clenching. While the mechanisms underlying these phenomena are not fully understood, there is evidence to support that the damaged nerves from the amputation site are still sending information to the brain (Weinstein, 1998<\/a>) and that the brain is reacting to this information (Ramachandran & Rogers-Ramachandran, 2000<\/a>). There is an interesting treatment for the alleviation of phantom limb pain that works by tricking the brain, using a special mirror box to create a visual representation of the missing limb. The technique allows the patient to manipulate this representation into a more comfortable position (Ramachandran & Rogers-Ramachandran, 1996<\/a>).<\/p>\n

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