sensation and perception Flashcards

1
Q

perception definition

A

Everything you see, feel, hear, taste, and smell is a product of the biological machinery inside your brain.

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2
Q

what are the four things humans sense?

A

light
chemicals
mechanical forces
temperature

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3
Q

what is the process of perception?

A

physical/”distal stimuli” -> input from the physical world -> (psychophysics) -> mental world/”proximal stimuli”

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4
Q

what are the qualities of empiricism?

A
  • knowledge comes from outside the mind
  • How are the brain and perception shaped by exposure to different environments?
  • The environment shapes the brain and our experience of the world
  • “Blank Slate” / Nurture argument
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5
Q

what are the qualities of rationalism?

A
  • certain fundamental principles drive/shape knowledge
  • What are the basic substrates and laws that drive perception?
  • Our brain’s architecture shapes and constrains experience
  • innate tendencies/ nature argument
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6
Q

how do we get from mental to physical world stimuli?

A
  1. Sample physical information
  2. Integrate and encode it in the brain
  3. Interpret and use it
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7
Q

what are the types of sensory receptors in humans?

A
  • photoreceptors sense light
  • chemoreceptors sense chemicals
  • mechanoreceptors sense mechanical forces
  • thermoreceptors sense temperature
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8
Q

what is visible light?

A

Visible light is electromagnetic radiation of 380-760nm, emitted by the sun, lightbulbs, etc

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9
Q

what information does light tell us?

A
  • Light energy is reflected and absorbed by surfaces around us.
  • This changes the properties of the light.
  • Light waves contain information about surfaces.
  • The brain extracts surface information from light
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10
Q

what is physical stimulus in the eye?

A

light waves reflected from the image pass through the cornea and enter the eye through the pupil. the lens focuses the light on the retina

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11
Q

what is sensation in the eye?

A

sensory receptors in the retina are called rods and cones and detect the light waves

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12
Q

what is transduction in the eye?

A

rod and cones convert light waves into signals and these signals are processed by ganglion cells which generate action potentials that are sent to the brain by the optic nerve

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13
Q

how do photoreceptors work?

A
  • When light hits a photopigment molecule, it splits
  • The split activates the photoreceptor cell – this is the moment of transduction from lightwave to neural impulse
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14
Q

what is photopigment depletion?

A
  • The pupil constricts and widens to control the amount of light coming in to optimize the sensitivity of the photoreceptors for the light conditions.
  • Photoreceptors are at the BACK of the eye so that photopigments can be readily replenished.
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15
Q

what are the qualities of rod cells?

A

response: slow
recovery: slow
acuity: low
sensitivity: high
location: peripheral retina
how many: 120 million
function: peripheral and low-light achromatic version
types: one type

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16
Q

properties of cone cells?

A

response: fast
recovery: fast
acuity: high
sensitivity: loq
location: central retina
types: 3 (L,M and S)
how many: 6 million
function: detailed, central, chromatic vision

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17
Q

what are the three types of cone cells?

A

Short (“blue”) peak at 440nm

Medium (“green”) peak at 540

Long (“red”) – peak at 570nm

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18
Q

what is colour blindness?

A

Most commonly: lose L/M differentiation (red/green colorblind)

  • Common in caucasian males(~5%)
  • X-linked genetic trait
  • Recently evolved

*Less commonly: lose S cones; ocular albinism; brain injury

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19
Q

what is the distribution of photoreceptors on the retina?

A
  • Cones are concentrated at the fovea.
  • Rods are fewer in the periphery, and increase towards the fovea, but there are no rods at the fovea.
  • Higher receptor density = higher perceptual acuity
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20
Q

what is the purpose of eye movements?

A
  • Bring new objects of interest to the fovea
  • Keep the eyes fixed when the head/body move
  • Prevent images from fading by shifting their position on the retina
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21
Q

what is the blind spot?

A

The blind spot corresponds to the place where the axons of 1.2 million retinal ganglion cells form the optic nerve

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22
Q

what is the importance of edges?

A
  • Signal the presence of an object or boundary (usually)
  • Blank spaces are unimportant (usually)
  • The visual system exaggerates edges, starting in the retina
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23
Q

what are the two types of retinal ganglion cells?

A

1) midget cells
2) parasol cells

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24
Q

what is the function of midget cells?

A

Midget Cells receive input from cones
* The number of cells they summarize is small
* They project to the parvocellular pathway: the pathway into the brain that carries high-acuity details

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25
Q

what is the function of parasol cells?

A

Parasol Cells receive input from rods
* The number of cells they summarize is large
* They project to the magnocellular pathway:the pathway into the brain that carries low-light peripheral vision, motion and contrast

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26
Q

what are receptive fields?

A
  • The place/type of stimulus that elicits a response in a given neuron
  • Neurons “respond” selectively to specific regions/stimuli, from sensory receptors all the way through to cortical brain areas.
  • “Respond” = change their firing rate (increasing OR decreasing)
  • Easier to map RFs at early stages (vision/touch) –becomes increasingly difficult the further into the system you go.
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27
Q

what are dark adaptation and Troxler?

A

Dark adaptation and Troxler fading reflect changes in sensitivity of the visual c

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28
Q

what happens when you physically deform a mechanoreceptor?

A

Physically deforming a mechanoreceptor causes ion channels to open, which causes the cell to fire.

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29
Q

what information do the mechanoreceptors involved in the pressure and stretch receptors in the skin provide?

A

Pressure and stretch receptors in the skin:
* Light touch
* Texture
* Stretch
* Pain

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30
Q

what information do the mechanoreceptors involved in the pressure and stretch receptors in the muscles, tendons and internal organs provide?

A
  • Body position
  • Body movement
  • Interoception
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31
Q

what information do the mechanoreceptors involve in the pressure and stretch receptors in the movement of hair cells in the inner ear?

A
  • inertia
  • gravity
  • hearing
32
Q

what are cutaneous mechanoreceptors? (sense of touch)

A
  • Multiple systems: light touch, firm pressure, vibration, pain, and skin stretch
  • All types respond to physical deformation
  • Receptors shapes are specialized for different types of pressure
33
Q

how is skin specialised?

A

1) high sensitivity to light touch
2) high acuity for texture

34
Q

what are the distribution of touch receptors?

A

*Touch the skin with one or two points.

*Gradually move the points closer together.At some point two will feel like one.

*This distance is the two-point-discrimination threshold.

*If two points stimulate two different receptors, you will feel two points. If two points stimulate only one receptor, you will
feel only one.

*Density of receptors in the skin is highest on the hands and face, lowest on the upper arm,calf, etc.

35
Q

what is haptic touch?

A

Haptic touch: exploring objects with your sub cutaneous mechanoreceptors

36
Q

what are examples of haptic touch?

A
  • Vibrations = roughness/texture
  • Position of fingers around object = shape
  • Skin stretch, tendon stretch = weight
37
Q

define proprioception, kinesthesis and interoception

A

Proprioception (body position)
kinesthesis (body movements)
interoception (body state)

38
Q

what are the functions of the stretch muscles?

A

Stretch receptors in muscles and tendons (spinal/brain stem): low-level control + perceptual input

stretch receptors in smooth muscle (e.g. lungs,bladder, stomach, bowels):low level (spinal/brainstem) control + perceptual input

39
Q

what is the purpose of the hair cells in the ear?

A
  • head motion perception(semicircular canals)
  • Gravity perception (inner ear)
  • Sound perception (cochlea)
40
Q

what is the function of Hair cells in the semicircular canals?

A

Hair cells in the semicircular canals:head motion/inertia

*Semicircular canals contain endolymph
*Acceleration and deceleration of head movement – endolymph movement lags behind the hair cells, causes them to bend
*Changes in viscosity of endolymph can interfere with perception

41
Q

Hair cells in the inner ear otolith organs

A
  • gravity
    *Inner ears contain the otolith organs
    *Gravity shifts the otoliths (small crystals) against hair cells
    *Provides sense of head position relative to upright
42
Q

what is the general function of the ear?

A

The function of the ear is to channel and amplify sound waves

43
Q

function of auditory hair cells?

A

Ion channels on adjacent hairs are connected by a “tip link”. Movement of the hair cells pulls the ion channels open,depolarizing (activating) the cell.

44
Q

what level db leads to hearing damage in the ear?

A

prolonged exposure to>85dB, or sudden exposure to 120-145dB

45
Q

what do the mechanoreceptors in the cochlea provide?

A
  • Loudness – amplitude of sound wave increases firing rate
  • Pitch – which part of the cochlea is activated
  • Timbre – composite frequencies –simultaneous activation of multiple locations on the cochlea
  • NOT Location – this comes from time and volume differences between the two ears (more on this later!
46
Q

what are the qualities of thermoreceptors?

A
  • Free nerve endings
  • At least four types:
  • Fast cold
  • Fast hot
  • Slow cold
  • Slow hot
  • Found in:
  • the skin
  • in the cornea (to trigger blinking)
  • In the brainstem (to regulate core temperature)
47
Q

how does skin sense temperature - slow system?

A
  • SLOW system comes from unmyelinated C-fibers
  • Myelin speeds up neural transmission, so unmyelinated nerves are slow (signals take a perceptible amount of time to get to the brain)
  • Adapt quickly
48
Q

how does skin sense temperature? - fast system

A
  • FAST system comes from A-delta-fibres
  • fast, extreme heat/cold
  • No adaptation
49
Q

how do chemoreceptors work?

A
  • Function like a “lock and key”:
  • specific classes of receptors are sensitive to specific molecule types.
  • Found in:
    a) tongue (gustation)
    b) nasal epithelium (olfaction)
    c) other locations in the body (heart,stomach)
50
Q

how does the tongue work?

A
  • Each of the papillae on the tongue contains multiple tastebuds
  • Each taste bud contains multiple chemoreceptors
  • Five (ish) receptor types: salty, sweet, bitter, sour, andsavory (AKA umami).
51
Q

What is the relationship between taste receptors and tastants?

A

sweet - sugars (calorie-dense foods)
umami - glutamate (protein-rich food)
salty - NaCl (electrolytes)
sour - Acid (fermented/unripe foods)
bitter - toxins, inedible substances

52
Q

what are the qualities of taste preferences?

A
  • Innate preferences (e.g. sweet over bitter)
  • Exposure to amniotic fluid and breast milk (flavor determined by maternal diet)
  • Exposure to flavours over lifespan
  • Genetic variability in taste bud types and numbers(“supertasters”, “nontasters”, e.g. Bartoshuk et al., 1994)
  • Perception of flavor is more than gustation alone
53
Q

what is ageusia

A
  • inability to taste
  • Temporary loss of taste is common.
  • Permanent ageusia is rare.Usually caused by nerve damage or deformity
54
Q

what is nasal epithelium?

A
  • smell/olfaction
  • Inhaling brings odorants to the nasal epithelium
  • Odorants bind to proteins in the cilia of the receptor cells and activate the cell
  • Each cell has only a single receptor type
55
Q

Axel and Buck 2004 Nobel Prize

A
  • There are ~1000 different odorant receptors, each one coded by a different gene
  • Genetic codes for olfaction receptors alone comprise 3% of our genes
56
Q

how do we localise smells?

A
  • Orthonasal vs. Retronasal – clear differences in perception/recognition
  • Left vs. Right nostril arrival times?
  • Scent tracking – better with two nostrils thanone
57
Q

what are pheromones?

A

Odorants to communicate and control conspecific behaviour

58
Q

do human pheromones exist?

A

– McClintock effect (controversial!)
– Lots of smell recognition/preference studies (are these really pheromones?)

59
Q

what is anosmia?

A

Loss of sense of smell
* Temporary loss due to inflammation / blockage is routine
* Permanent loss due to range of causes (congenital, head trauma, disease, aging) common (1-2% in young,>12% in elderly)

60
Q

what are chemoreceptors in the body?

A
  • CO2 and O2 sensitive chemoreceptors that sample blood leaving the heart and communicate with brain areas that control breathing rate
  • Chemoreceptors in the gastric system cause nausea and vomiting
61
Q

name the sensory receptors involved in the 5 senses

A
  • Vision: photoreceptors in the retina
  • Audition: mechanoreceptors in the cochlea
  • Smell: chemoreceptors in the nasal cavity
  • Taste: chemoreceptors in the tongue, nasal cavity, and digestive tract; plus mechanoreceptors and thermoreceptors on the tongue.
  • Touch/Somatosensation:
    – cutaneous mechanoreceptors for light touch, vibration, pain, stretch
    – cutaneous thermoreceptors for skin temperature
    – Haptic touch also involves mechanoreceptors in the muscles and tendons; input from the motor system
    – Proprioception, kinesthesis, gravity, nausea, bladder pressure, bowel pressure, hunger, satiety, body temperature (all independent systems)
62
Q

where does perception come from?

A

Perception comes from the brain
* Receptors are distributed and sendinput to the brain
* If they did not transmit to the brain,there would be no perception.
* Does your foot feel warmth? No – it comes from the brain!

63
Q

how is sensory input interpreted in the brain?

A
  • Vision, audition, and somatosensation all have a similar general architecture
  • Input goes through the thalamus first, and then to specialized areas in the cerebral cortex.
64
Q

what are the key components of the primary visual pathway?

A
  1. Optic Nerve
  2. Optic Chiasm
  3. Lateral Geniculate Nucleus(LGN), in the Thalamus
  4. Optic radiations
  5. Primary visual cortex (AKAstriate cortex, V
65
Q

what do axons of the retinal ganglion cells form?

A

Axons of the retinal ganglion cells form the optic nerve that leaves the eye

66
Q

Where do certain retinal genglion cell axons end up?

A

The retinal ganglion cells have long axons that end up in the LGN of the thalamus.

The axons coming from retinal ganglion cells in the nasal (inner) part of the retina cross over at the optic chiasm.

Axons coming from cells in the temporal (outer)part of the retina do not cross

67
Q

how is information from the left and right visual fields encoded?

A

Information in the left visual field goes to the right hemisphere.

Information in the right visual field goes to the left hemisphere.

68
Q

what is the lateral geniculate nucleas (LGN)

A

LGN has layers with different cell types, primarily:
* Parvocellular (“P” cells):
- receive input primarily fromcones/midget cells
- Pathway for high-acuity vision and color

  • Magnocellular (“M” cells):
  • receive input primarily from rods/parasol cells
  • Pathway for detecting contrast and motion, low-light vision
69
Q

what is the primary visual cortex?

A
  • Contains multiple detailed maps of visual space organized into layers
  • The left hemisphere contains maps of right visual field, and vice versa
  • The upper half contains maps of lower visual field, and vice-versa
  • The fovea is over-represented
70
Q

what information does the V1 contain?

A

Receptive fields:Each cell responds selectively to a region of the visual field.

Cells in V1 are also selective for:
– The orientation of edges in their RFs
– Color in that region (“blobs”)
– The left or right eye

71
Q

what happens when V1 is damaged?

A
  • Patient reports complete blindness in the part of space associated with the area that has been damaged.
  • But many of these patients can “guess” accurately about stimuli presented in their blind field.
  • This visual capacity in “blind” space is called blindsight
72
Q

what are the key components of the primary auditory pathway?

A
  1. Superior Olive (pons)
  2. Inferior colliculus (midbrain)
  3. Medial geniculate nucleus (MGN)in the thalamus
  4. Auditory cortex
73
Q

what is the superior olive?

A
  • Receives input from BOTH ears
  • Critical for detecting interaural time and volume differences
  • This gives us information about the location of sounds
74
Q

what is the inferior colliculus?

A
  • Primarily receives auditory input
  • Also receives somatosensory and visual input
  • Multisensory integration occurs here* Visual information constrains auditory localization(ventriloquist effect)
75
Q

what is the medial geniculate nucleus?

A
  • Right next to the lateral geniculate nucleus
  • Like the LGN, acts as a relay station on the way to primary auditory cortex.
  • Auditory input is heavily influenced by other modalities before it reaches the cortex