Lecture 1: Sensation Vs Perception

Question 1

What is the difference between sensation and perception

Answer 1

1. Sensation: real /collection of information
2. Perception: interpretation of reality based on individual
3. Pathway of sensation to perception:
   3a. Sensory stimulus->sensory receptors->neural impulses->interpretation

Question 2

Psychophysics

Answer 2

1. Attempts to quantify the relationship between sensation and perception
2. Has 3 elements
   2a. Simple responses by the subject
   2b. Extensive data collection from each subject
   2c. Precise manipulation of experimental stimuli

Question 3

Top down vs bottom up processing

Answer 3

1. Top down (old situations): uses prior knowledge/experience to influences answers which can lead to bias (ex: pattern recognition)
2. Bottom up processing (new situations): perception is created by sensory stimuli, is data driven and happens in real time
3. Need both to be effective

Question 4

Perceptual organization

Answer 4

1. When the brain makes inferences to organize sensory information from vision (in the form of electromagnetic waves)

Question 5

Perceptual organization: depth perception: Binocular cues

Answer 5

1. Depth perception that requires 2 eyes
2. Types
   2a. Retinal disparity: 2 retina each make a slightly different image (due to coming in from different angles), eyes compare these images creating depth perception
   2b. Convergence: when we focus on an image, we cross our eyes slightly (greater convergence for closer images): our brain registers how much our eyes turn in which tells us how close the image is

Question 6

Perceptual organization: depth perception: Monocular cues

Answer 6

1. Relative size: larger images look closer
2. Relative height: objects higher look distant
3. Overlap/interposition: object overlapped in front=looks closer
4. Shading/contour: darker(contour)= closer , lighter(shaded)=farther
5. Motion parallax: more distant objects move slower as we pass them

Question 7

Perceptual organization: Subjective Constancy

Answer 7

1. Subjective constancy: people assume size, Color and shape of things remains constant
   1a. Size constancy: perception that object has a fixed size regardless of the size of its in the retina
   1b. Color constancy: perception that object doesn’t change colour
   1c. Shape constancy: perception that object has a fixed shape, no matter its position (ex: closed vs open door)

Question 8

Perceptual organization: Gestalts grouping principles: main principles

Answer 8

1. Emergence: we put things into patterns without realizing it
2. Reification: perception has more information than sensation (abstract is perceived as real)
3. Invariance: simple objects are perceived in the same way regardless of their direction, rotation, scale etc.
4. Multistability: tendency for ambiguous perceptual experiences to alternate in unstable fashion

Question 9

Perceptual organization: Gestalts basic principles

Answer 9

1. Figure ground: multistability/ Humans organize their perceptions into figures and backgrounds
2. Pragnanz: Brain interprets images in the simplest manner possible
3. Law of proximity: close=grouped
4. Law of similarity: similar=grouped
5. Law of closure: gaps=closed
6. Law of continuity: aligned objects=continue behind obstructions (weird lines)
7. Law of symmetry: objects create symmetry
8. Law of past experience: objects based on past experience
9. Law of common fate: objects that move together=grouped
10. Law of common region: objects in same region=grouped
11. Law of parallelism: objects aligned parallel to one another=grouped
12. Law of connectedness: objects connected=grouped

Question 10

Sensory processing: Absolute threshold of sensation

Answer 10

1. Definition: Minimal intensity of stimulus that is detected (detected 50% of the time)
2. Subliminal stimulus: stimulus below absolute threshold
   2a. has no effect on conscious perception, but still affects brain activity

Question 11

Sensory processing: Just noticeable difference (JND)

Answer 11

1. Definition: the smallest noticeable difference in intensity of a stimulus while its being experienced
2. Webers law=K=(^I)/I
   2a. ^I: just noticeable difference
   2b. I: first stimulus
3. Higher intensity of original sound, the greater the difference needed to notice it

Question 12

Signal detection theory (SDT)

Answer 12

1. How individuals differentiate signals (important stimuli) from a noise (unimportant stimulus)
2. 4 possibilities
   2a. Hit (good): correct identification of signal
   2b. Miss: identification of signal as noise
   2c. False alarm: identification of noise as signal
   2d. Correct rejection (good): identification of noise

Question 13

Unbiased SDT in histogram

Answer 13

1. If put noise and signals in a histogram:
   1a. Criterion in middle: unbiased criterion
   1b. Anything less intense than criterion=no response
   1c. Anything more intense than criterion=response

Question 14

Biased SDT histogram

Answer 14

1. Conservative/+/strict: move criterion to right (histograms shift to left)
   1a. Reduce hit/false alarms: good if brave/thirsty
   1b. Increase miss/correct rejection: bad bc likely to get eaten
   1c. Increases specificity: positive identification is more likely correct
   1d. Conservative strategy: prefers correct rejection over hits
2. Liberal/-/relaxed: move criterion to left
   2a. Increase hit/false alarm
   2b. Decrease miss/correct rejection
   2c. Increases sensitivity: negative identification is more likely correct
   2d. Liberal strategy: prefer hits over correct rejection

Question 15

Sensory Receptor types

Answer 15

1. Free nerve ending : dendrites embedded in tissues
2. Encapsulated endings: dendrites encapsulated by connective tissue that enhances their sensitivity
3. Receptor cell: distinct cells (not neurons) that activate neurons. Each kind of receptor cell is designed to recieve and transducer a specific type of physical stimulus

Question 16

Sensory Receptor location

Answer 16

1. Exteroceptor: located near external environment (skin)
2. Interoceptors: located internally (organs sensing blood pressure)
3. Proprioceptor: located in moving body part because they sense position and movement (muscle movement)

Question 17

Sensory Receptor functions

Answer 17

1. Mechanoreceptors: touch such as pressure, distraction or vibration
   1a. Pacinian corpuscles: vibration and heavy touch
   1b. Meissner corpuscles: light touch
2. Thermoreceptors: temperature change
3. Nociceptors: pain
4. Photoreceptors: light
5. Chemoreceptors: taste, small, blood chemistry

Question 18

Transient receptor potential (TRP) channels

Answer 18

1. Receptors that respond to pain and changes in temperature
2. TRP channels are located on the surfaces of Nociceptors and thermoreceptors: if damaged by a stimulus they undergo conformational changes which activate action potentials that travel 3 types of nerve fibres
   2a. AB (A-beta) nerve fibres: high diameter, thick myelination, fastest signal conduction
   2b. A-delta nerve fibers: medium all
   2c. C nerve fibers: smallest, unmyelinated, slowest conduction speed

Question 19

Tonic vs phasic receptors

Answer 19

1. Tonic receptors: when receptors adapt slowly to stimuli and fire as long as stimulus is present
2. Phasic receptor: quickly adapt to stimuli and dire when intensity or rate of stimulus changes

Question 20

Primary somatosensory cortex (PSC)

Answer 20

1. Sensory receptors->primary somatosensory cortex (PSC) in post central gyrus of parietal lobe
2. Homounculus: representation of how much space different areas of the body take up in PSC

Question 21

Sensory adaptation

Answer 21

1. Occur in response to short continuous exposure to stimuli
2. Temporary

Question 22

Structure of eye

Answer 22

1. Path of light:
   1a. Cornea->anterior chamber->lens->vitreous chamber->retina->fovea
2. Assisting parts:
   2a. anterior chamber & posterior chamber: filled with aqueous humor (nutrients, maintains inocular pressure) from ciliary bodys leaked out of the canal of Schlemm
   2b. Accommodation: ciliary muscle contract=lens sphere=brings focal point close to lens
   2c. vitrous chamber: has vitrous humor that focuses light to be projected on retina
   2d. Choroid: blood vessels
   2e. Sclera: white of eye

Question 23

Rods and cones

Answer 23

1. Rods: rhodopsin is the pigment in rods which is a form of vitamin A (light/dark)
2. Cones in fovea of retina:
   2a. 3 types for Color: trichromatic theory of vision

Question 24

Iris and autonomic control

Answer 24

1. Creates opening called pupil
   1a. Sympathetic /dark: contracts radical muscles of iris, dilates pupil
   1b. Parasympathetic/light: contracts circular muscles of iris, constricts pupils

Question 25

Types of sight

Answer 25

1. Nearsighted: myopia 1a. Can’t see far 1b. Image is in front of retina 2. Farsighted: hyperopia 2a. Can’t see close 2b. Image is behind retina 3. Just right: image is on retina

Question 26

Phototransduction cascade

Answer 26

1. Light->ganglion cells->bipolar cells-> rods/cones (photoreceptors) 1a. Ganglion cells become optic nerve 2. Photoreceptors at rest (polarized): releases glutamate (excitatory) 2a. Photons activate retinal from cis to trans retinal in rhodopsin->GPCR activated ->activates phosophodiesterase->hyperpolarizes->no glutamate->active

Question 27

Visual processing

Answer 27

1. When signal crosses optic chiasm ->LGN in thalamus ->primary visual cortex in occipital lobe

Question 28

Parallel processing /feature detection

Answer 28

1. Parallel processing is efficient, allows specialization, integration, and redundancy 2. Cell types 2a. Parvocellylar pathway: responds to fine detail, Color, size, shape 2b. Magnocellular: location, speed, direction of movement

Question 29

Feature detection

Answer 29

1. Describes how brain perceives external world by dividing it into specific features

Question 30

Structure and function of the ear

Answer 30

1. Outer ear 1a. Auricle/pinna directs sound into external auditory canal which carries wave to tympanic membrane/eardrum 2. Middle ear has 3 bones (ossicles) 2a. Malleus, incus, stapes which translate wave into physical vibration which is conveyed into oval window 3. Inner ear: 3a. Oval window -> scala vestibuli -> cochlea -> scala tympanic -> round window ->movement of wave causes organ of corti to vibrate (organ of corti sits on basilar membrane) 3b. Hair cells in organ of corti have stereocilia which cause action potentials to be fired ->auditory nerve ->brain

Question 31

Inner ear: vestibular system

Answer 31

1. semicircular canals: detect angular acceleration (twist of head) 2. otoliths: linear acceleration: up down or tilt

Question 32

Auditory processing

Answer 32

1. Hairs in organ of corti are mechanoreceptors…when they depolarize after binding they release a neurotransmitter that causes electrical signal to go to brain 1a. Sound information: auditory nerve->cochlear nuclei in medulla ->inferior colliculus -> Medial geniculate nucleus of thalamus ->auditory cortex in temporal lobe

Question 33

Basilar tuning

Answer 33

1. Humans hear from 20 Hz to 20 000 Hz 2. We distinguish high and low frequencies from high frequency waves stimulating the narrow cochlear base and low frequency waves stimulating the wider cochlear apex

Question 34

Gustation

Answer 34

1. Relies on chemoreceptors calledgustatory cells in taste buds 2. There are 5 tastes: bitter, sour, salty, sweet, umami (savoury) and each gustatory cell detects all 5 tastes

Question 35

Olfaction

Answer 35

1. Relies on chemoreceptors that bind to odorants 2. Axons of olfactory chemoreceptors form olfactory nerve and when it’s GPCR binds to chemicals it triggers AP to be sent from olfactory nerve to olfactory bulb ->piriform (olfactory) cortex in temporal lobe ->orbitofrontal cortex 3. Only sense that doesn’t relay into thalamus

Question 36

Pain

Answer 36

1. Detected by nociceptors 1a. Bottom up processing detects pain 1b. Top down processing: impacts how people experience pain

Question 37

Kinesthetic sense

Answer 37

1. Knowing bodies position and motion 2. Ex: muscle memory

Question 38

Vestibular sense

Answer 38

1. Feeling of balance and spatial orientation 2. Located in inner ear