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Chapter 12

Chapter 12 - study notes

Course Code
Matthias Niemeier

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What are formant? What are they good for? Acoustic energy in speech wave. Sound for
speech, they are peaks in frequency spectrum of that sound. Vowels are harmonic sounds
with regular intervals of frequency level. There are at least 3 peaks, formants. They are
good for distinguishing /b/ different vowels, help us perceive speech
Narrow definition of touch = sensations caused by mechanical displacements of skin
Tactile = adj form of touch (expanded def) = mechanical interaction includes perception of
temperature changes (thermal sensation), the sensation of pain (potentially damaged skin),
and internal sensations that inform us of positions and movements of our limbs in space.
Collectively these internal sensation = Kinesthesis (perception of position and movement
of our limbs in space) when they arise from muscles, tendons, and joints, and they are part
of a broader system known as proprioception (perception mediated by kinaesthetic and
vestibular system), which includes vestibular system as well. All these senses put together
is somatosensation = collective term for sensory signals from body
Purpose of touch = evolutionary, sense pain, temperature sensation enables us to seek or
create thermally safe environment. Mechanical sensations play important role in our
intimate sexual and reproductive activities and provide powerful means of communicating
our thoughts and emotions nonverbally. We also use touch to ID and manipulate objects
that cant be seen or heard. Our eyes and ears can perceive signals from objects far from
body, but we must almost always be in direct contact w/ object to perceive it by touch
(exception is vibration of jackhammer across street, temperature ie sun). Touch involves
action to a greater degree than any of our other senses
sense of touch housed in largest and heaviest of sense organs, skin weights 4 kg. 1.8 sq f.
touch receptors are embedded all over body, both hair(less) as well as in mouths, muscles,
tendons, joints
receptor units for touch embedded in both outer layer = epidermis and inner layer =
dermis (consisting of nutritive and connective tissues, within which lie mechanoreceptors
just as eye has rods and cones for receptors. Touch has multiple channels specialized info-
processing subsystems that each contribute to overall sense of touch. Ex when touch ice, we
feel temp, shape, texture
each type of receptors can be characterized by 3 attributes: 1) type of stimulation to which
receptor responds ex pressure, vibration, temp 2) size of receptive field receptors are

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activated when stimulation is applied to a particular area of body, which constitutes
receptors’ receptive field. Size of receptive field refers to extent of body area that elicits a
receptor response 3) rate of adaptation (fast vs slow) a fast adapting (FA) receptor
responds w/bursts of action potentials, first when its preferred stimulus is applied and then
again when it is removed. It not respond during steady state /b/ stimulus onset and offset.
But a slow adapting (SA) receptor remains active throughout period during which stimulus
is in contact w/ itz receptive field
Mechanoreceptors (tactile receptors) = sensory receptors that are responsive to
mechanical stimulation ie pressure, vibration, and movement. It consist of a nerve fiber and
an associated expanded ending. All tactile nerve fibers are called A-beta fiber which has
relatively wide diameters that permit very fast neural conduction. 4 populations of tactile
receptors that are found in hairless skin ie palm = meissner corpuscle, merkel cell
neurite complex, pacinian corpuscle, ruffini ending. In hairy skin there are 5 major
A-beta tactile receptors. Those mechanoreceptors and associated afferent fibers have
properties similar to those in hairless skin: 2 types are slowly adapting and 3 are fast
adapting. Tactile nerve fibers for various types are assumed to terminate in diff expanded
So skin 1st has epidermis layer then have dermis layer. The endings of meissner and merkel
receptors located at junction of epidermis and dermis, whereas pacinian and ruffini
receptors are in dermis and subcutis not included informal definition of skin
r Receptive
FeatureFunction Example
SAI (merkel)Small SlowSustained
downward pressure,
very low frequency
<5Hz. Spatial
n. Pattern
Reading Braille
SAII (ruffini)Large SlowSustained
downward pressure,
lateral skin stretch,
skin slip (low
sensitivity to
vibration across
Determine if
grasp is good.
Need more
than 1 SAII to
be stimulated
FAI (meissner) Small FastTemporal changes in
skin deformation (5-
If stimulated =
wobble, flutter.
Helps correct

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detection ur grip if coffee
cup is moving
ie vibration
FAII (pacinian)Large FastTemporal changes in
skin deformation
When object
first make
contact w/skin
or when object
u holding
another object.
A buzz
The mechanoreceptors work together to inform us about every individual object we touch.
Ex. Opening a door w/ key. feeling shape of your key in pocket = SAI and even maybe FAI.
Shaping your fingers to grasp key = SAII. Insert key to lock, your grip force increases so
that key not slip = FAI. FAII tells u when key has hit end of keyhole
In addition to tactile mechanoreceptors in skin, another type of mechanoreceptor lie within
muscles, tendons, and joints = kinaesthetic receptors. Play role in sensing where our limbs
are and wat kinds of movements were making.
Muscle spindle = sensory receptor located in muscle that sense its tension ex angle
formed by a limb at a joint. It conveys rate at which muscle fibers are changing in length
Lacking kinaesthetic senses ie cutaneous nerve damaged, relay completely on vision to tell
about positions of limbs in space, if lights turned off cant tie shoes, walk up or down stairs,
clap hand cuz no idea where hands, feet are
Thermoreceptors = sensory receptors that signal info about changes in skin temperature.
Located in both dermal and epidermal layers of skin. 2types: warmth fibers = fires when
temperature of skin surrounding the fibers rises, cold fibers = fire in response to
decreases in skin temperature, this out#s warmth fibers by ratio of about 30:1.
Normally skin is kept at 30-36 degree C, neither cold nor warmth fiber respond much while
skin temperature remains within this range. Thermoreceptors also kick into gear when we
make contact w/ an object that is warmer or colder than skin. Objects in environment
typically cooler than 30degreeC so it is usually cold fibers that tell us about object.
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