unit 3 sensations & perception Flashcards
transduction
process that stimuli received by our sensory organs go through
- signals are transformed into neural impulses
- neural impulses travel first to thalamus then to different cortices of brain (exception: smell)
sensory adaptation
decreasing responsiveness to stimuli due to constant stimulation
sensory habituation
perception of sensations due to how focused we are on them
- what we perceive depends on what sensations activate our senses & by what we focus on perceiving voluntarily/involuntarily
sensation
activation of senses (e.g. ears, eyes…)
perception
process of understanding sensations
vision (energy sense) - 1. light is reflected off objects & gathered by eye
color perceived depends on
- light intensity: determines how bright object appears
- light wavelength: determines particular hue we see (red-longest, violet-shortest)
vision (energy sense) - 2. within eye
1) reflected light enters eye thru cornea
2) light goes thru pupil: iris (=muscle that controls pupil) open it (=dilate) to let more light in & close to let less light in
3) accommodation: light that enters pupil is focused my lens, image gets upside down & inverted
4) focused inverted image projects on retina where there are specialized neurons activated by different wavelengths of light
vision (energy sense) - 3. transduction
translation of incoming stimuli to neural signals occurs when light activates neurons in retina (has several layers of cells)
- 1st layer: directly activated by light
- cones: cells activated by color, concentrated in center
- rods: cells respond to black/white, distributed throughout retina
-> more rods than cones
- fovea (indentation) @ v center of retina: contains highest conc of cones
- 2nd layer: bipolar cells
- next layer: ganglion cells activated when enough bipolar cells fire
- optic nerve: made up by axons of ganglion cells, sends impulses to lateral geniculate nucleus (LGN) in thalamus
-> messages sent to visual cortices @ occipital lobe
- blind spot: where optic nerve leaves retina so no rods&cones
- optic nerve is divided into 2 parts: impulses from left side of each retina go to left hemisphere…, optic chiasm=spot where nerves cross each other
vision (energy sense) - 4. in the brain
visual cortex @ occipital lobe receives impulses from retina cells that activate feature detectors
- David Habel & Torsten Wiesel) discovered that groups of neurons in visual cortex respond to diff types of visual message, what we perceive visually is combination
trichromatic theory - theory of color vision
3 types of cones in retina that detect red/green/blue
- cones are activated in diff combinations to produce all colors
- can’t explain some visual phenomena:
- afterimage: staring @ one color for a while then looking @ white/blank space -> color afteriamge
- colorblindness: dichromatic - can’t see red/green or blue/yellow shades // monochromatic - only see shades of grey
opponent-process theory - theory of color vision
sensory receptors arranged in retina come in pairs: red/green, yellow/blue and black/white pairs
- when one sensor is stimulated, its pair is inhibited from firing
- explains color afterimage: if u stare @ red for while, you fatigue sensors for red & opponent part of pair for red fires when looking @ blank wall -> sees green afterimage
- explains color blindness: individuals missing one pair has difficulty seeing those hues
hearing (energy sense)
sound waves: vibration in air NOT electromagnetic waves
- created by vibrations that travel through air -> are connected by ears -> go through transduction into neural messages & sent to brain
- has amplitude & frequency
- amplitude: determines loudness
- frequency: determines pitch (high pitched=high frequency)
process of hearing (energy sense)
1) sound waves collected in outer ear (pinna)
2) waves travel down auditory canal until they reach eardrum (tympanic membrane) - vibrates
- eardrum is attached to ossicles (3 small bones): eardrum connects to hammer(malleus) which connects to anvil(incus) which connects to stirrup(stapes)
3) vibration of eardrum transmitted by these 3 bones to oval window which is attached to cochlea (snail’s shell shape w/ fluid)
- as oval window vibrates, fluid moves
- floor of cochlea = basilar membrane (covered w/ hair cells connected to organ of corti - neurons activated by hair cell movements)
-> fluid moves -> hair cells move & transduction occurs -> organ of corti fires & impulses transmitted to brain via auditory nerve
place theory - pitch theory
hair cells in cochlea respond to diff frequencies of sound based on their location in cochlea -> move in diff places
frequency theory - pitch theory
hair cells fire @ diff rates (frequencies) in cochlea
- lower tones: sensed by rate that cells fire
- accurately describes how hair cells sense upper range of pitches but not lower tones
deafness
- conductive deafness: smth wrong w/ system of conducting sound to cochlea
- nerve (sensorineural) deafness: hair cells in cochlea are damaged (usually by loud noise), they don’t regenerate
touch
brain interprets amount of indentation/temp change as intensity of touch (some nerve endings in skin respond to pressure, some to temp)
- when stimulated sharply) pain receptors fire
- grate-control theory: some pain messages have higher priority than others
- high priority -> gate swings open for it
- low priority -> gate swings shut -> doesn’t feel it
- endorphins (pain-killing): swings body shut, natural endorphins in brain control pain
taste (gustation) - chemical sense
taste buds: absorb chemicals from food
- located on papillae (bumps on tongue)
- located all over tongue
- more densely packed = more chemical absorbed, more intensively food tastes
humans sense 5 types of tastes: sweet, salty, sour, bitter, umami (savory)
- some taste buds respond more intensively to specific taste
- flavor of food = combination of taste & smell
smell (olfaction) - chemical sense
molecules rise to air, some drawn to nose -> molecules settle in mucous membrane @ top of nostril & absorbed by receptor cells there
- receptor cells are linked to olfactory bulb which gathers messages from olfactory receptor cells & sends info to brain
- impulses from other senses go through thalamus first before cortex BUT smell impulses go directly to amygdala (emotional) than to hippocampus (memory)
-> this direct connection to limbic system may explain why smell is powerful trigger for memory
vestibular senses - body position sense
how body is oriented in space
3 semicircular canals in inner ear give brain feedback about body orientation:
- canals: tubes partially filled w/ fluid
- position of head changes -> fluid moves -> sensors in canals move
- movement of hair cells activate neurons -> impulse goes to brain
kinesthetic sense - body position sense
feedback about position & orientation of specific body part
- receptors in muscle & joints send info to brain about limbs -> info + visual feedback lets us keep track of body
perception
process of understanding & interpreting sensations
- psychophysics: study of interaction btwn sensations we receive & our experiences of them
threshold
absolute threshold: smallest amount of stimulus we can detect
- of vision: smallest amount of light we can detect
- minimal amount of stimulus we can detect 50% of time
- subliminal: stimulus below absolute threshold
different threshold: smallest amount of change needed in stimulus before we detect change
- Weber’s law: change needed is proportional to original intensity of stimulus
- more intense stimulus, more it needs to change before we notice difference
signal detection theory - perceptual theory
- investigates effects of interference we experience while perceiving
- tries to predict what we’ll perceive among competing stimuli
- response criteria (receiver operating characteristics): how motivated we are to detect certain certain stimuli & what we expect to perceive
- false positive: we think we received a stimulus that’s not there
- false negative: not perceiving a stimulus that’s present
