CHAPTER 14
The Cutaneous
Senses
CHAPTER CONTENTS VL The Virtual Lab icons direct you to specific anima-
tions and videos designed to help you visualize what
Overview of the Cutaneous System you are reading about. Virtual Labs are listed at the end
The Skin of the chapter, keyed to the page on which they appear,
Mechanoreceptors and can be accessed through Psychology CourseMate.
Pathways From Skin to Cortex
The Somatosensory Cortex
The Plasticity of Cortical Body Maps
Perceiving Details
Receptor Mechanisms for Tactile Acuity Some Questions We Will Consider:
Cortical Mechanisms for Tactile Acuity
■ Are there specialized receptors in the skin for sensing different
Perceiving Vibration
tactile qualities? (p. 338)
Perceiving Texture ■ What is the most sensitive part of the body? (p. 343)
Perceiving Objects ■ Is it possible to reduce pain with your thoughts? (p. 355)
Identifying Objects by Haptic Exploration
The Physiology of Tactile Object Perception
W
Pain hen asked which sense they would choose to lose
Questioning the Direct Pathway Model of Pain if they had to lose either vision, hearing, or touch
The Gate Control Model some people pick touch. This is understandabl
Cognition and Pain given the high value we place on seeing and hearing, but mak
The Brain and Pain ing a decision to lose the sense of touch would be a seriou
SOMETHING TO CONSIDER: The Effect of mistake. Although people who are blind or deaf can get along
Observing Touch and Pain in Others quite well, people with a rare condition that results in losing
the ability to feel sensations though the skin often suffer con
Think About It
stant bruises, burns, and broken bones in the absence of th
warnings provided by touch and pain (Melzack & Wall, 1988
Rollman, 1991; Wall & Melzack, 1994).
But losing the sense of touch does more than
increase the chance of injury. It also makes it difficult to
When we touch something or are touched, receptors in the interact with the environment because of the loss of feed
▲
skin provide information about what is happening to the skin back from the skin that accompanies many actions. As I typ
and about the object contacting the skin. These fingers are this, I hit my computer keys with just the right amount o
sensing the cell phone’s shape and the quality of its surface.
As the person enters a number, texts, or searches the Internet,
force, because I can feel pressure when my fingers hit th
receptors in the skin provide information that helps the person keys. Without this feedback, typing and other actions tha
apply the right amount of pressure. In this chapter, we describe receive feedback from touch would become much more dif
perceptions associated with stimulation of the skin, focusing ficult. Experiments in which subjects have had their hand
on various qualities of touch, and also consider pain, which temporarily anesthetized have shown that the resulting
involves stimulation of the skin and other processes as well.
loss of feeling causes them to apply much more force than
Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
,necessary when carrying out tasks with their fingers and When we recognize that the perceptions we experi-
hands (Avenanti et al., 2005; Monzée et al., 2003). ence through our skin are crucial for carrying out everyday
A particularly dramatic case that involved losing the activities, protecting ourselves from injury, and motivat-
ability to sense with the skin, as well as the closely related ing sexual activity, we can see that these perceptions are
ability to sense the movement and positions of the limbs, is crucial to our survival and to the survival of our species.
that of Ian Waterman, a 17-year-old apprentice butcher, who In fact, we could make a good case for the idea that percep-
in May 1971 contracted what at first appeared to be a rou- tions felt through the skin and that enable us to sense the
tine case of the flu (Cole, 1995; Robles-De-La-Torre, 2006). positions and movements of our limbs are more important
He anticipated returning to work after recovering; however, for survival than those provided by vision and hearing. We
instead of improving, his condition worsened, with an initial begin our consideration of the cutaneous senses by focusing
tingling sensation in his limbs becoming a total loss of the on the skin.
ability to feel touch below the neck. Ian’s doctors, who were
initially baffled by his condition, eventually determined that
Overview of the Cutaneous
an autoimmune reaction had destroyed most of the neurons
that transmitted signals from his skin, joints, tendons, and
muscles to his brain. The loss of the ability to feel skin sen-
sations meant that Ian couldn’t feel his body when lying in System
bed, which resulted in a frightening floating sensation, and
he often used inappropriate force when grasping objects— In this section we will describe some basic facts about
sometimes gripping too tightly, and sometimes dropping the anatomy and functioning of the various parts of the
objects because he hadn’t gripped tightly enough. cutaneous system.
As difficult as losing sensations from his skin made Ian’s
life, destruction of the nerves from his muscles, tendons, and
joints caused an even more serious problem. The destruc- The Skin
tion of these nerves eliminated Ian’s ability to sense the Comel (1953) called the skin the “monumental facade of the
position of his arms, legs, and body. This is something we human body” for good reason. It is the heaviest organ in
take for granted. When you close your eyes, you can tell the human body, and, if not the largest (the surface areas
where your hands and legs are relative to each other and to of the gastrointestinal tract and of the alveoli of the lungs
your body. But Ian had lost this ability, so even though he exceed the surface area of the skin), it is certainly the most
could move, because the nerves conducting signals from his obvious, especially in humans, whose skin is not obscured by
brain to his muscles were unaffected, he avoided moving, fur or large amounts of hair (Montagna & Parakkal, 1974).
because not knowing where his limbs were made it difficult In addition to its warning function, the skin also prevents
to control them. body fluids from escaping and at the same time protects us
Eventually, after many years of practice, Ian was able by keeping bacteria, chemical agents, and dirt from penetrat-
to sit, stand, and even carry out movements and tasks such ing our bodies. Skin maintains the integrity of what’s inside
as writing. Ian was able to do these things not because his and protects us from what’s outside, but it also provides us
sensory nerves had recovered (they remained irreversibly with information about the various stimuli that contact it.
damaged), but because he had learned to use his sense of The sun’s rays heat our skin, and we feel warmth; a pinprick
vision to constantly monitor the positions of his limbs and is painful; and when someone touches us, we experience
body. Imagine, for a moment, what it would be like to have to pressure or other sensations.
constantly look at your hands, arms, legs, and body, so you Our main experience with the skin is its visible surface,
could tell where they were and make the necessary muscular which is actually a layer of tough dead skin cells. (Try stick-
adjustments to maintain your posture and carry out actions. ing a piece of cellophane tape onto your palm and pulling
Ian described the extreme and constant effort needed to it off. The material that sticks to the tape is dead skin cells.)
do this as making his life like “running a daily marathon” This layer of dead cells is part of the outer layer of skin,
(Cole, 1995). which is called the epidermis. Below the epidermis is another
Ian’s problems were caused by a breakdown of his layer, called the dermis (Figure 14.1). Within the skin are
somatosensory system, which includes (1) the cutaneous mechanoreceptors, receptors that respond to mechanical
senses, which are responsible for perceptions such as touch stimulation such as pressure, stretching, and vibration. VL
and pain that are usually caused by stimulation of the skin; (2)
proprioception, the ability to sense the position of the body
and limbs; and (3) kinesthesis, the ability to sense the move-
ment of the body and limbs. In this chapter we will focus Mechanoreceptors
on the cutaneous senses, which are important not only for Many of the tactile perceptions that we feel from stim-
activities like grasping objects and protecting against damage ulation of the skin can be traced to the four types of
to the skin, but also for motivating sexual activity. (Another mechanoreceptors that are located in the epidermis and
reason picking touch as the sense to lose would be a mistake.) the dermis. We can distinguish between these receptors
338 CHAPTER 14 The Cutaneous Senses
Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
, Merkel receptors (SA1) Meissner corpuscle (RA1)
Small receptive fields
Epidermis
Fires to Fires to
continuous pressure “on” and “off”
Perception Perception
Dermis
• Handgrip
• Fine details
control
Figure 14.1 A cross section of glabrous (without hairs or projections) skin, showing the layers of the skin
and the structure, firing properties, and perceptions associated with the Merkel receptor (SA1) and Meissner
corpuscle (RA1)—two mechanoreceptors near the surface of the skin. © Cengage Learning
by their distinctive structures and by how fibers associ- with perceiving stretching of the skin, the Pacinian corpuscl
ated with the receptors respond to stimulation. Slowly with sensing rapid vibrations and fine texture.1
adapting (SA) receptors respond with prolonged firing
to continued pressure. Rapidly adapting (RA) receptors
respond with bursts of firing just at the onset and offset of Pathways From Skin to Cortex
a pressure stimulus.
Two mechanoreceptors, the Merkel receptor (SA1) and The receptors for the other senses are localized in one area—
the Meissner corpuscle (RA1), are located close to the sur- the eye (vision), the ear (hearing), the nose (olfaction), and
face of the skin, near the epidermis. Because they are located the mouth (taste)—but cutaneous receptors in the skin ar
close to the surface, these receptors have small receptive distributed over the whole body. This wide distribution, plu
fields; a cutaneous receptive field is the area of skin which, when the fact that signals must reach the brain before stimula
stimulated, influences the firing of the neuron. tion of the skin can be perceived, creates a travel situation
Figure 14.1 shows the structure and firing of these we might call “journey of the long-distance nerve impulses,
receptors in response to a pressure stimulus that is presented especially for signals that must travel from the fingertips o
and then removed (blue line). The nerve fiber associated with toes to the brain.
the slowly adapting Merkel receptor fires continuously, as Signals from all over the body are conducted from
long as the stimulus is on; the nerve fiber associated with the skin to the spinal cord, which consists of 31 segments
the rapidly adapting Meissner corpuscle fires only when the each of which receives signals through a bundle called th
stimulus is first applied and when it is removed. The type dorsal root (Figure 14.3). After the signals enter the spina
of perception associated with the Merkel receptor is sensing cord, nerve fibers transmit them to the brain along two
fine details, and with the Meissner corpuscle, controlling major pathways: the medial lemniscal pathway and th
handgrip. spinothalamic pathway. The lemniscal pathway has larg
The other two mechanoreceptors, the Ruffini cylinder fibers that carry signals related to sensing the positions o
(SA2) and the Pacinian corpuscle (RA2 or PC), are located
deeper in the skin (Figure 14.2), so they have larger receptive
1
fields. The Ruffini cylinder responds continuously to stimula- Although Michael Paré and coworkers (2002) have reported that there are
no Ruffini receptors in the finger pads of monkeys, Ruffini cylinders are
tion, and the Pacinian corpuscle responds when the stimulus still included in most lists of glabrous (nonhairy) skin receptors, so they are
is applied and removed. The Ruffini cylinder is associated included here.
Overview of the Cutaneous System 339
Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
The Cutaneous
Senses
CHAPTER CONTENTS VL The Virtual Lab icons direct you to specific anima-
tions and videos designed to help you visualize what
Overview of the Cutaneous System you are reading about. Virtual Labs are listed at the end
The Skin of the chapter, keyed to the page on which they appear,
Mechanoreceptors and can be accessed through Psychology CourseMate.
Pathways From Skin to Cortex
The Somatosensory Cortex
The Plasticity of Cortical Body Maps
Perceiving Details
Receptor Mechanisms for Tactile Acuity Some Questions We Will Consider:
Cortical Mechanisms for Tactile Acuity
■ Are there specialized receptors in the skin for sensing different
Perceiving Vibration
tactile qualities? (p. 338)
Perceiving Texture ■ What is the most sensitive part of the body? (p. 343)
Perceiving Objects ■ Is it possible to reduce pain with your thoughts? (p. 355)
Identifying Objects by Haptic Exploration
The Physiology of Tactile Object Perception
W
Pain hen asked which sense they would choose to lose
Questioning the Direct Pathway Model of Pain if they had to lose either vision, hearing, or touch
The Gate Control Model some people pick touch. This is understandabl
Cognition and Pain given the high value we place on seeing and hearing, but mak
The Brain and Pain ing a decision to lose the sense of touch would be a seriou
SOMETHING TO CONSIDER: The Effect of mistake. Although people who are blind or deaf can get along
Observing Touch and Pain in Others quite well, people with a rare condition that results in losing
the ability to feel sensations though the skin often suffer con
Think About It
stant bruises, burns, and broken bones in the absence of th
warnings provided by touch and pain (Melzack & Wall, 1988
Rollman, 1991; Wall & Melzack, 1994).
But losing the sense of touch does more than
increase the chance of injury. It also makes it difficult to
When we touch something or are touched, receptors in the interact with the environment because of the loss of feed
▲
skin provide information about what is happening to the skin back from the skin that accompanies many actions. As I typ
and about the object contacting the skin. These fingers are this, I hit my computer keys with just the right amount o
sensing the cell phone’s shape and the quality of its surface.
As the person enters a number, texts, or searches the Internet,
force, because I can feel pressure when my fingers hit th
receptors in the skin provide information that helps the person keys. Without this feedback, typing and other actions tha
apply the right amount of pressure. In this chapter, we describe receive feedback from touch would become much more dif
perceptions associated with stimulation of the skin, focusing ficult. Experiments in which subjects have had their hand
on various qualities of touch, and also consider pain, which temporarily anesthetized have shown that the resulting
involves stimulation of the skin and other processes as well.
loss of feeling causes them to apply much more force than
Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
,necessary when carrying out tasks with their fingers and When we recognize that the perceptions we experi-
hands (Avenanti et al., 2005; Monzée et al., 2003). ence through our skin are crucial for carrying out everyday
A particularly dramatic case that involved losing the activities, protecting ourselves from injury, and motivat-
ability to sense with the skin, as well as the closely related ing sexual activity, we can see that these perceptions are
ability to sense the movement and positions of the limbs, is crucial to our survival and to the survival of our species.
that of Ian Waterman, a 17-year-old apprentice butcher, who In fact, we could make a good case for the idea that percep-
in May 1971 contracted what at first appeared to be a rou- tions felt through the skin and that enable us to sense the
tine case of the flu (Cole, 1995; Robles-De-La-Torre, 2006). positions and movements of our limbs are more important
He anticipated returning to work after recovering; however, for survival than those provided by vision and hearing. We
instead of improving, his condition worsened, with an initial begin our consideration of the cutaneous senses by focusing
tingling sensation in his limbs becoming a total loss of the on the skin.
ability to feel touch below the neck. Ian’s doctors, who were
initially baffled by his condition, eventually determined that
Overview of the Cutaneous
an autoimmune reaction had destroyed most of the neurons
that transmitted signals from his skin, joints, tendons, and
muscles to his brain. The loss of the ability to feel skin sen-
sations meant that Ian couldn’t feel his body when lying in System
bed, which resulted in a frightening floating sensation, and
he often used inappropriate force when grasping objects— In this section we will describe some basic facts about
sometimes gripping too tightly, and sometimes dropping the anatomy and functioning of the various parts of the
objects because he hadn’t gripped tightly enough. cutaneous system.
As difficult as losing sensations from his skin made Ian’s
life, destruction of the nerves from his muscles, tendons, and
joints caused an even more serious problem. The destruc- The Skin
tion of these nerves eliminated Ian’s ability to sense the Comel (1953) called the skin the “monumental facade of the
position of his arms, legs, and body. This is something we human body” for good reason. It is the heaviest organ in
take for granted. When you close your eyes, you can tell the human body, and, if not the largest (the surface areas
where your hands and legs are relative to each other and to of the gastrointestinal tract and of the alveoli of the lungs
your body. But Ian had lost this ability, so even though he exceed the surface area of the skin), it is certainly the most
could move, because the nerves conducting signals from his obvious, especially in humans, whose skin is not obscured by
brain to his muscles were unaffected, he avoided moving, fur or large amounts of hair (Montagna & Parakkal, 1974).
because not knowing where his limbs were made it difficult In addition to its warning function, the skin also prevents
to control them. body fluids from escaping and at the same time protects us
Eventually, after many years of practice, Ian was able by keeping bacteria, chemical agents, and dirt from penetrat-
to sit, stand, and even carry out movements and tasks such ing our bodies. Skin maintains the integrity of what’s inside
as writing. Ian was able to do these things not because his and protects us from what’s outside, but it also provides us
sensory nerves had recovered (they remained irreversibly with information about the various stimuli that contact it.
damaged), but because he had learned to use his sense of The sun’s rays heat our skin, and we feel warmth; a pinprick
vision to constantly monitor the positions of his limbs and is painful; and when someone touches us, we experience
body. Imagine, for a moment, what it would be like to have to pressure or other sensations.
constantly look at your hands, arms, legs, and body, so you Our main experience with the skin is its visible surface,
could tell where they were and make the necessary muscular which is actually a layer of tough dead skin cells. (Try stick-
adjustments to maintain your posture and carry out actions. ing a piece of cellophane tape onto your palm and pulling
Ian described the extreme and constant effort needed to it off. The material that sticks to the tape is dead skin cells.)
do this as making his life like “running a daily marathon” This layer of dead cells is part of the outer layer of skin,
(Cole, 1995). which is called the epidermis. Below the epidermis is another
Ian’s problems were caused by a breakdown of his layer, called the dermis (Figure 14.1). Within the skin are
somatosensory system, which includes (1) the cutaneous mechanoreceptors, receptors that respond to mechanical
senses, which are responsible for perceptions such as touch stimulation such as pressure, stretching, and vibration. VL
and pain that are usually caused by stimulation of the skin; (2)
proprioception, the ability to sense the position of the body
and limbs; and (3) kinesthesis, the ability to sense the move-
ment of the body and limbs. In this chapter we will focus Mechanoreceptors
on the cutaneous senses, which are important not only for Many of the tactile perceptions that we feel from stim-
activities like grasping objects and protecting against damage ulation of the skin can be traced to the four types of
to the skin, but also for motivating sexual activity. (Another mechanoreceptors that are located in the epidermis and
reason picking touch as the sense to lose would be a mistake.) the dermis. We can distinguish between these receptors
338 CHAPTER 14 The Cutaneous Senses
Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
, Merkel receptors (SA1) Meissner corpuscle (RA1)
Small receptive fields
Epidermis
Fires to Fires to
continuous pressure “on” and “off”
Perception Perception
Dermis
• Handgrip
• Fine details
control
Figure 14.1 A cross section of glabrous (without hairs or projections) skin, showing the layers of the skin
and the structure, firing properties, and perceptions associated with the Merkel receptor (SA1) and Meissner
corpuscle (RA1)—two mechanoreceptors near the surface of the skin. © Cengage Learning
by their distinctive structures and by how fibers associ- with perceiving stretching of the skin, the Pacinian corpuscl
ated with the receptors respond to stimulation. Slowly with sensing rapid vibrations and fine texture.1
adapting (SA) receptors respond with prolonged firing
to continued pressure. Rapidly adapting (RA) receptors
respond with bursts of firing just at the onset and offset of Pathways From Skin to Cortex
a pressure stimulus.
Two mechanoreceptors, the Merkel receptor (SA1) and The receptors for the other senses are localized in one area—
the Meissner corpuscle (RA1), are located close to the sur- the eye (vision), the ear (hearing), the nose (olfaction), and
face of the skin, near the epidermis. Because they are located the mouth (taste)—but cutaneous receptors in the skin ar
close to the surface, these receptors have small receptive distributed over the whole body. This wide distribution, plu
fields; a cutaneous receptive field is the area of skin which, when the fact that signals must reach the brain before stimula
stimulated, influences the firing of the neuron. tion of the skin can be perceived, creates a travel situation
Figure 14.1 shows the structure and firing of these we might call “journey of the long-distance nerve impulses,
receptors in response to a pressure stimulus that is presented especially for signals that must travel from the fingertips o
and then removed (blue line). The nerve fiber associated with toes to the brain.
the slowly adapting Merkel receptor fires continuously, as Signals from all over the body are conducted from
long as the stimulus is on; the nerve fiber associated with the skin to the spinal cord, which consists of 31 segments
the rapidly adapting Meissner corpuscle fires only when the each of which receives signals through a bundle called th
stimulus is first applied and when it is removed. The type dorsal root (Figure 14.3). After the signals enter the spina
of perception associated with the Merkel receptor is sensing cord, nerve fibers transmit them to the brain along two
fine details, and with the Meissner corpuscle, controlling major pathways: the medial lemniscal pathway and th
handgrip. spinothalamic pathway. The lemniscal pathway has larg
The other two mechanoreceptors, the Ruffini cylinder fibers that carry signals related to sensing the positions o
(SA2) and the Pacinian corpuscle (RA2 or PC), are located
deeper in the skin (Figure 14.2), so they have larger receptive
1
fields. The Ruffini cylinder responds continuously to stimula- Although Michael Paré and coworkers (2002) have reported that there are
no Ruffini receptors in the finger pads of monkeys, Ruffini cylinders are
tion, and the Pacinian corpuscle responds when the stimulus still included in most lists of glabrous (nonhairy) skin receptors, so they are
is applied and removed. The Ruffini cylinder is associated included here.
Overview of the Cutaneous System 339
Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
