Ch 5 Sensation and Preception Flashcards
1
Q
Sensation and Perception
A
- Animals evolved to make use of
movement to approach fitness
opportunities and avoid threats - The body transforms energy from
the world into information to guide
us in these movements - Sensationis the detection of
environmental stimuli by bodies - Perceptionis the recognition and
identification of a sensory stimulus
2
Q
Types of Sensations and Stimuli
A
Smell,Taste,Hearing,Touch,Vision,
3
Q
Thresholds are Limits of the Senses
A
- Sensation relies on receptors cells being
able to transduce energies from the
world into electrochemical nerve signals - Signal detection theory forms a basis
for analyzing stimulus detection - hits, misses, false alarms, correct responses
- Absolute threshold is the least amount
of energy that we can detect for a
specific sense - Just noticeable difference (JND)
describes the amount of energy change
required to be detected
4
Q
Weber-Fechner’s Law
A
- Psychophysicists in the 1800s
established that the relationship
between stimulus magnitude and
perception is not linear - Fechner’s law describes our
experienced sensations as
proportional to the logarithm of
the stimulus magnitude - Ψ = k log(S)
5
Q
Steven’s Power Law
A
- However, not all sensations work
the same way… - Many decades later in 1957,
Stanley Stevens systematically
tested this relationship with
many types of stimuli - This led to a more general form
called Stevens’ power law: - Ψ(I) = kIa
- a is an exponent that changes
depending on the type of stimulus
6
Q
Processing Sensory Information
A
- Information flows through networks
in our nervous system - Two general directions stand out:
- Bottom-upinformation processing:
- From the senses to “higher” regions or
layers of the brain - Top-downinformation processing:
- From higher regions or layers of the
brain to lower regions or layers - Much of our conscious experience
is a combination of sensory
information with our expectations
about what “should” be sensed - Based on prior learned experiences
7
Q
The Chemical Senses: Smell
A
- The chemical senses are the most evolutionarily
ancient of all the senses - Receptors in single cells can detect molecules in the
environment for chemoattraction& chemorepulsion - In multicellular animals like us, odorants in the air
trigger responses in olfactory receptor neurons - The receptor neurons send signals (action
potentials) to the olfactory bulb, which relays
them to the brain - Humans have a relatively weak sense of smell, but
we can still detect a drop of perfume diffused in a
lecture hall like this one
8
Q
The Chemical Senses: Taste
A
- Taste works somewhat like smell
- Tastantsare molecules that trigger
responses in taste receptor cells that
make up taste buds in the tongue - Taste buds with specific compositions
are found on papillae - There are five types of taste receptor
cells, specialized for: - Sweet, salt, umami, sour, bitter
- Axons that make up the gustatory
nerves send taste information to brain
9
Q
The Tactile Senses (Somatosensation)
A
- Touch is a mechanical and thermal
sense that results from many
receptor cells in the skin… - Pain and temperature
: - Free nerve endings
- Fine touch and pressure
: - Meissner’s corpuscle (touch)
- Merkel’s disc (fine touch)
- Ruffini’s ending (joint movement)
- Pacinian corpuscle (vibration)
- Hair receptors (flutter, steady touch)
10
Q
The Tactile Senses (Somatosensation)
A
- Touch and pain sensations
detected by receptor cells in skin
are sent to dorsal spinal cord - From there they ascend to the
brainstem and then to thalamus - The thalamus integrates signals
with other senses and passes
somatosensory signals to the
postcentral gyrus (parietal lobe) - Also called
cortex
primary somatosensory
(S1); recall the homunculus
11
Q
The Auditory Sense: Hearing
A
- Hearing is a type of mechanical sense
that transduces pressure changes in a
medium - Compression and expansion of molecules
(water, air, etc.) - Sound waves vary in terms of:
- Frequency(measured in Hz)
- Perceived as pitch changes
- Amplitude(measured in pascals)
- Perceived as loudness changes (dB)
- Phase(measured in radians)
- Requires two ears for sound localization
- The wavelength of a sound is the length
of one cycle of a pressure wave
12
Q
The Auditory Sense: Hearing
A
- Sound first enters the outer ear
- Pinnaeand ear canals
- It then vibrates the tympanic membrane
(ear drum) and ossicles of the middle ear - Maleus, incus, stapes
- The oval window vibrates, causing fluid
pressure changes in the basilar membrane
of the cochlea - Receptor hair cells (stereocilia) in the
basilar membrane turn that pressure into
action potentials (nerve signals) - Signals are sent to the brainstem and then
to the thalamus and finally to primary
auditory cortex (A1) in the temporal lobe
13
Q
The Vestibular Sense: Balance
A
- Our sense of balance (or rather
head position) is inferred from
the detection of fluid changes by
cilia within semicircular canals - Found adjacent to the cochlea
- Information sent to the brainstem,
thalamus, and parietal cortex - Three axes for directionality
- Pitch, yaw, & roll
- One semicircular canal for each
direction in 3D space
14
Q
Vision: The Eye
A
- Eyes have evolved many times in
animals, with most vertebrates
having a common structure - A pupil that varies in size
depending on lighting conditions - A flexible lens that focuses light
from different distal focal points - A retina containing photoreceptor
cells that transduce light - Rods
- Cones
15
Q
Vision: The Retina
A
- Rodsare primarily used in dark light
conditions and are more concentrated in the
retinal periphery - Conesare primarily used in bright light
conditions and are concentrated in the
retinal fovea - Also used for colour vision
- The fovea is the centre of our visual field (the
focus point) and generates the highest image
resolution - Photoreceptors send converging signals to
bipolar cells, which send converging signals
to ganglion cells - Ganglion cell axons form the optic nerve
- A blind spot exists nerve leaves the eyes
