The Nonvisual Senses
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Fig. 19.1 The physical properties of waves.
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Memorize Fig. 19.2
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The outer ears funnels sound waves to the eardrum.
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The bones of the middle ear amplify and relay the eardrum's vibrations through the oval window into the
fluid-filled cochlea.
The resulting pressure changes in the cochlear fluid
cause the basilar membrane to ripple, bending the hair
cells on its surface.
Hair cell movements trigger impulses at the base of
the nerve cells, whose approx. 30,000 fibres converge
to form the auditory nerve.
Fig. 19.3 We evolved in a much quieter world.
The Nonvisual Senses
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Nerve deafness can be partially restored with a cochlear
impant.
The device translates sounds into electrical signals that,
wired into the cochlear nerves, convey information about
sound to the brain.
Klinke 1999: Cochlear implants given to deaf kittens and
human infants seem to trigger an awakening of the
pertinent brain areas.
If installed as preschoolers, users can become proficients
in oral communication.
The implants in adults will not enable normal hearing if
their brain never learned to process sound during
childhood.
The Nonvisual Senses
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Loudness is perceived by the number of cochlear hair
cells that are stimluted.
Pitch is perceived as a combination:
Place theory links pitch with the location of stimulation of
the cochlear membrane.
Frequency theory: the rate of nerve impulses travelling up
the auditory nerve matches the frequency of the tone.
Volley principle: Neural cells can alternate firing. By firing
in rapid succession, they can achieve a combined
frequency above 1000 Herze (waves / second).
Volley for high pitch, frequency for low pitch, and a
combination for middle pitches.
The just noticeable difference for two sound sources is
.000027 seconds.
The Nonvisual Senses
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Touch: We have basically four senses of touch: pressure,
warmth, cold, and pain.
There is no one type of receptor that triggers pain. Instead
there are different nociceptor --sensory receptors the
detect hurtful temperatures, pressure and certain
chemicals. Fig. 19.6
Wall, 1965. Gate-control theory: The spinal cord contains
small nerve fibres that conduct most pain signals, and
larger fibres that conduct most other sensory signals.
When tissue is injured, the small fibres activate, you feel
pain. Large fibre activity (such as massage) closes the
gate.
Zubieta, 2003: A gene that boosts the availability of
endorphins can make the brain less responsive to pain.
The Nonvisual Senses
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Phantom limb sensations: where the brain misinterprets
spontaneous central nervous system activity, such as
sending a right thumb protruding out of your upper lip.
Tinnitus: A ringing-in-the-ears due to cochlea damage.
Non-threatening hallucinations as a side effect of
glaucoma, cataracts, diabetes or macular degeneration
(death of cells in the fovea).
Psychological influences: Kahneman, 1999: we prefer
longer trials, with more overall pain, but less pain at the
end; this is the 'taper off' effect.
Social-Cultural influences: Symbaluk 1997: We perceive
more pain if others around us do.
Fig. 19.7
The Nonvisual Senses
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Controlling Pain: The placebo effect. Scott, 2007. Fake
pain-killing chemicals cause brain to activate an area that
releases pain-killing endorphins.
Kaptchuk 2006: Fake acupunture does the same thing, all
the way to side effects.
Edward, 2009. Distraction (dissociation) counting
backward by 3s.
Virtual reality works even better, immersion in a 3d world
reduces the brain's pain-related activities.
Fig. 19.8
The Nonvisual Senses
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Taste. We have five basic taste sensations, based on
receptors on our tongues. Table 19.1
A very quick taste will alter the temporal lobe of your
brain. Kelling & Halpern, 1983.
Plassmann, 2008: Being told that a wine costs $90 rather
than its real price of $10 made it taste better and triggered
more activity in the brain area that responds to pleasant
sensations.
Embodied cognition. Figure 19.9 When hard-of-hearing
listeners see an animated face forming the words being
spoken at the other end of the phone line, the words
become easier to understand.
Kayser, 2007. A weak flicker of light that is barely
perceptible beomes more visible when accompanied by a
short burst of sound.
The Nonvisual Senses
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Smell: Fig. 19.10
Miller, 2004, Buck & Axel 1991: There are 350 receptor
proteins that recognize particular odor molecules. This is
the 'key-and-lock' model of smell.
The combination of olfactory receptors, activating different
neural patterns, that allow fine distinctions.
Herz, 2001. The attractiveness of smells depends on
learned associations.
Fig. 19.12 Information from the taste buds travels to an
area between the frontal and temporal lobes, registering
in an area not far from the sense of smell area, which
interacts with taste.
The brain's smell circuitry interacts with memory storage.
The Nonvisual Senses
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Kinesthesis is the sense of body position and movement.
Vestibular sense monitors your head and body position
and movement.
Anatomically, this is the semicircular canals, and the
vestibular sacs.
Messages are sent to the cerebellum, enabling you to
consciously sense movement and maintain balance.