Chapter 2: Sensation and Perception

Question 1

sensation

Answer 1

• transduction - convert physical, electromagnetic, auditory, to electrical signals
  
  • action potentials and NT to the CNS
• performed by receptors in peripheral NS
• raw unprocessed signal

Question 2

Perception

Answer 2

• process info to make sense of it
• what makes AI hard
• AI knows sensation but not perception

Question 3

sensory receptors

Answer 3

• neurons respond to stimuli and trigger electrical signals
• distal stimuli from outside of the body
  
  • ex campfire
• proximal stimuli - direct interaction with receptors
• ex photons and heat that the campfire produce

Question 4

psychophysics

Answer 4

relationship between physical nature and sensations and perceptions they evoke

Question 5

Types of sensory receptors

Answer 5

• ganglia - collection of neuron cell bodies, outside CNS
• projection areas - parts of brain that analyze sensory input
• photoreceptor - EM waves in visible spectrum
• Hair cells - movement of fluid in inner ear
• nocireceptor - pain
• thermo - temperature
• osmo - blood osmolarity
• olfactory - volatile compounds, smell
• taste - dissolved compounds

Question 6

threshold

Answer 6

• element of perception
• minimum amount of stimulus that renders a difference in perception
• absolute threshold
• threshold of conscious perception
• difference threshold

Question 7

absolute threshold

Answer 7

• minimum stimulus energy that is needed to activate a sensory system
• threshold in sensation NOT perception
• level at which the stimulus will cause a transduction to the CNS

Question 8

Threshold of conscious perception

Answer 8

• subliminal perception - perception of stimulus below a given threshold
  
  • threshold of conscious perception
• signal reaches CNS but does not reach higher order brain where consciousness resides
• discrimination testing or psychophysical discrimination testing - increase the difference between 2 stimuli slightly until participant notices the difference

Question 9

difference threshold

Answer 9

• just noticable difference (jnd)
• minimum difference in magnitude between two stimuli before one can perceive the difference
• Weber’s law - constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus
  
  • use a percent to determine the ratio
    
    • not valid for extremely high or low end ranges

Question 10

signal detection theory

Answer 10

• changes in our perception depending on internal (psychological) and external (environmental) context
• response bias - systematically respond to stimulus in a particular way due to nonsensory factors
• signal detection experiment -
  
  • catch trials - signal present
  • noise trials - signal absent
  • hit - yes, signal present
  • miss - no, signal present
  • false alarm - yes, signal absent
  • correct negative - no, signal absent
• high rate of false alarms and misses suggest response bias

Question 11

adaptation

Answer 11

• detection of signal changes
• can effect perception and sensation
• focuses attention on most relevant stimuli
• ex - stop feeling clothes after we put them on, get used to being in cold water

Question 12

structure of eye

Answer 12

• sclera - white of the eye, not over cornea
• retinal and choroidal vessels supply nutrition
• retina - inner most layer of the eye
  
  • contains photoreceptors
• cornea - clear domelike window that focuses and gathers light
• anterior chamber - front of the eye, in front of iris
• posterior chamber - between iris and lens
• iris - colored part of eye
  
  • dilator pupillae - open pupil, symapthetic
  • constrictor pupillae - closes pupil, parasympathetic
• choroid - between retina and sclera, continuous with iris
  
  • ciliary body - produces aqueous humor
  • canal of Schlemm - drains aqueous humor
• lens - behind iris, controls refraction
• ciliary muscle - controlled by parasympathetic
  
  • pulls on suspensory ligaments to change shape of lens
    
    • accomodation - change in lens shape
• vitreous humor - behind lens, gel that supports the retina

Question 13

Retina

Answer 13

• back of eye
• convert photons to electrical signals
• duplexity or duplicity theory of vision - 2 types of photoreceptors in retina, some for light/dark and some for color
• 6 million cones and 120 million rods
• cones - color and fine details, most effective in bright light
  
  • short (blue), medium (green), and long (red) cones
• rods - sensation of light and dark, better in reduced light, low sensitivity to details
  
  • rhosopsin - pigment in rods
• macula - high conc of cones, central of retina
  
  • fovea - center of macula, only cones
  • best vision at the fovea
• optic disk - blind spot, no photoreceptors

Question 14

neurons in eye

Answer 14

• bipolar cells - connect rods and cones
• ganglion cells - synapse with bipolar cells
• optic nerve - gathering of ganglion cells
• bipolar cells and ganglion are forward from rods and cones, towards lens
• less cones per ganglion then rods per ganglion and therefore better resolution from cones
• loss of detail as info from photoreceptors is combined
• amacrine and horizontal cells - input from multiple retinal cells before passign to ganglion cells
  
  • important for detecting edges and contrasts

Question 15

visual pathway

Answer 15

• right side of vision projects to left side of retina
• left side of vision projects to right side of retina
• nasal half of vision (temporal half) crosses at optic chiasm
  
  • left vision from both eyes to right brain
  • right vision from both eyes to left brain
• optical tracts - pathway after optic chiasm
• optical tract to
  
  • lateral geniculate nucleus (LGN) of the thalamus
  • visual cortex of occiptal lobe
  • superior colliculus - response to visual stimuli and eye reflex

Question 16

parallel processing

Answer 16

• simultaneously analyze and combine info regarding color, shape, motion
  
  • compare to memories
• feature detection -
  
  • color - cones
  • shape - parvocellular cells - high color spacial resolution
    
    • fine detail of stationary or slow moving object
    • low temporal resolution
  • motion - magnocellular cells
    
    • high temporal resolution
    • low spacial resolution
    • lack detail when moving

Question 17

vestibular sense

Answer 17

• rotational acceleration
• linear acceleration

Question 18

structure of ear (I)

Answer 18

• pinna/auricle - outer ear - channel sound waves into external auditory canal
• external auditory canal directs sound waves to the tympanic membrane (eardrum)
• eardrum - vibrates with incoming sound waves
  
  • frequency determines rate of vibration
  • louder has greater intensity, greater amplitude of vibration
• membrane divides outer and middle ear
• ossicles - 3 small bones
  
  • transmit and amplify vibrations
  • malleus - affixed to membrane, acts on incus, which acts on stapes
• stapes rests on oval window of cochlea
• eustachian tube - connect middle ear to nasal cavity, equalizes pressure
• inner ear in a bony labyrinth of cochlea, vestibule, semicircular canals
  
  • membranous labyrinth filled with endolymph and suspended in perilymph all inside of the bony labyrinth

Question 19

cochlea

Answer 19

• spiral shaped
• 3 parts called scalae
• organ of Corti - actual hearing apparatus
  
  • thousands of hair cells in endolymph
  • rests on the basilar membrane
  • techorial membrane over organ of Corti
• other 2 scala filled with perilymph
  
  • continuous with round and oval windows
  • round window allows perilymph to move in the cochlea
• organ of Corti sends electrical signal through the auditory (vestibulocochlear) nerve

Question 20

Vestibule

Answer 20

• part of bony labyrinth
• contains utricle and saccule
• sensitive to linear acceleration
• balancing and orientation in 3D space
• Modified hair cells covered in otoliths
  
  • resist motion and stimulate hair cells

Question 21

Semicircular canals

Answer 21

• sensitive to rotational acceleration
• three are perpendicular to each other
• ends at an ampulla that has hair cells
• endolymph bends hair cells when head rotates

Question 22

Auditory pathway

Answer 22

• vestibulocochlear nerve to the brain stem
• medial geniculate nucleus (MGN) of the thalamus
• auditory cortex - temporal lobe - sound processing
• some sound to the superior olive - localizes sound
• inferior colliculus - startle reflex
  
  • keep eyes foxed on point where head is turned (vestibulo-ocular reflex)

Question 23

Hair Cells

Answer 23

• sterocilia - on the surface of hair cells
• they sway in the endolymph when vibrations occur
• swaying opens ion channels that cause a potential
• some hair cells also connect to the tectorial membrane and amplify sound
• place theory - location of hair cell on basilar membrane determines the perception of pitch
  
  • close to the oval window is high frequency
  • far from the window (apex) is low frequency
  • tonotopically organized

Question 24

smell

Answer 24

• chemical sense
• olfactory chemoreceptors - in epithelium of upper nasal cavity
• specific chemoreceptors for chemicals
• pheromones - secreted from an individual or animal and influence behavior when bonded to a chemoreceptor
• pathway - inhaled then contact epithelium and chemoreceptors, receptor activated and signal sent to olfactory bulb, olfactory tract to brain such as limbic system
  
  • only sense that DOES NOT travel to thalamus

Question 25

taste

Answer 25

• sweet, sour, umami, bitter, salty
• chemoreceptors - dissolved compounds
• papillae are bumps on the tongue that contain taste buds
  
  • groups of cells with receptors form taste buds
• pathway - taste bud to brainstem to taste center in the thalamus to higher order brain

Question 26

somatosensation (touch)

Answer 26

• pressure, vibration, pain, temperature
• pacinian corpuscles - deep pressure and vibration
• meissner corpuscles - light touch
• merkle cells - deep pressure and texture
• ruffini endings - stretch
• free nerve endings - pain and temperature
• pathway - transduction from receptor - CNS - somatosensory cortex (parietal lobe)

Question 27

two point threshold

Answer 27

• minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli

Question 28

temperature and pain perception

Answer 28

• physiological zero - normal temp of skin
  
  • warm if above
  • cold if below
• nociceptors - signal due to pain
• gate theory of pain - special gating mechanism that can turn pain signals on and off
  
  • spinal cord can signal pressure or temperature instead of pain

Question 29

kinesthetic sense

Answer 29

• proprioception
• orientation in space
• receptors in muscles and joints
• important for hand eye coordination, balance, mobility

Question 30

bottom up processing

Answer 30

• aka data driven processing
• combine individual stimuli to create cohesive image
  
  • parallel processing and feature detection

Question 31

top down processing

Answer 31

• aka conceptually driven processing
• recognize objects using memories and expectations then analyze the parts
• need top down AND bottom up processing
• deja vu - when using bottom up processing because it is a new experience, but top down processing brings back a memory

Question 32

perceptual organization

Answer 32

• use 2 processes and sensory clues to create complete picture
• fillin the gaps
• use Gestalt principles
• ex. Depth perception - use monocular and binocular cues
  
  • monocular - relative size, position of object, lighting, shadowing
  • binocular - bring images together and into focus

Question 33

Form and constancy

Answer 33

• form - determined using parallel processing and feature detection
  
  • motion via magnocellular cells
• constancy - characteristics of object stay the same regardless of the environment
  
  • color, brightness, size, shape

Question 34

gestalt principles

Answer 34

• infer missing parts of a picture
• law of proximity - elements close to one another tend to be perceived as a unit
• law of similarity - objects similar tend to be grouped together
• law of good continuation - elements that appear to follow in the same pathway tend to be grouped together
• subjective contours - perceiving shapes that are not present
• law of closure - when space is enclosed by a contour it tends to be perceived as a complete figure

Overall, law of pragnanz - organization will always be as regular, simple, and symmetric as possible