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Binocular cues
retinal disparity and convergence
Retinal disparity
left and right fields of vision provide slightly diff. visual images when focusing on a single object b/c eyes are 2.5 inches apart
Convergence
when looking at things far away, eyes are relaxed (when looking at thing nearby, eyes contract)
Monocular cues
relative size/height, interposition, shading/contour, motion parallax, constancy
Relative size
how large something is compared to another object
Interposition
objects overlap over each other
Relative height
distant objects are seen or portrayed as being smaller and higher in relation to items that are closer
Motion parallax
objects that are closer appear to move faster than objects that are far away
Constancy
an object doesn’t change even if it looks diff. to us
Weber’s Law
ΔI/I = k
Just noticeable difference (JND)
threshold at which you’re able to notice a change in any sensation
Absolute threshold of sensation
minimum intensity of stimulus needed to detect a particular stimulus 50% of the time
can be influenced by expectations, experience, motivation, alertness
not same as JND
Subliminal stimuli
below absolute threshold
Vestibular system
responsible for balance and spatial orientation
Semicircular canals
located in inner ear
Endolymph
fluid within the ear that shifts w/ movement, allowing detection of head movement direction and strength of rotation
also contributes to dizziness/vertigo
How does endolymph contribute to dizziness/vertigo?
doesn’t stop spinning when we do; indicates movement even when stopped → dizziness
Otolithic organs
utricle/saccule help detect linear acceleration and head positioning
contain Ca crystals attached to hair cells in viscous gel
What happens when you go from lying down to standing up?
otolith organs move and pull on hair cells → action potential
Signal Detection Theory
detection of stimulus depends on stimulus intensity and how much you’re paying attention to it
Bottom-up processing
stimulus influences perception; driven by processing sensory info
Top-down processing
background knowledge influences perception; driven by cognition
Gestalt Principles
similarity, pragnanz, proximity, continuity, closure
Similarity
similar items are grouped together
Pragnanz
reality is often organized and reduced to the simplest form possible
Proximity
objects that are close together are grouped together
Continuity
lines follow the smoothest path
Closure
objects grouped together are seen as a whole
Conjunctiva
mucous membrane that covers front of eye; 1st layer light hits
Cornea
transparent thick sheet of tissue; anterior 1/6th
Anterior chamber
space filled w/ aqueous humor
Aqueous humor
fluid that provides pressure to maintain eyeball shape
Pupil
opening in iris that determines eye color and allows light to enter the eye
Lens
bends light to reach back of eyeball
Suspensory ligaments
connect ciliary body to lens
Ciliary body
secretes aqueous humor
Posterior chamber
area behind ciliary muscle filled w/ aqueous humor
Vitreous chamber
filled w/ vitreous humor
Vitreous humor
jelly-like substance that provide pressure to eyeball
Choroid
black network of blood vessels that reflect all light and bring oxygen/nutrients to eye
Sclera
white thick fibrous tissue that protects posterior 5/6th of eyeball and is the attachment point for muscles
Retina contains…
photoreceptors (rods/cones)
Macula
responsible for central vision; rich in cones
Fovea
completely covered in cones; no rods
Light
electromagnetic wave part of a large spectrum
Color spectrum
Violet (400nm) to red (700nm)
Rod
120 million provide night vision; contains rhodopsin; 1000x more sensitive to light than cones
slow recovery time
mostly found in periphery
Cone
6-7 million red/green/blue cones provide color vision in bright light; contains photopsin
fast recovery time
mostly found in fovea
Phototransduction Cascade
light changes shape of retinal (vitamin A derivative) → activates rhodopsin: light sensor in rods → stimulates transducin → activates phosphodiesterase: breaks down cGMP to GMP → ↓cGMP → closed Na+ channels → hyperpolarized rods → ↓glutamate release → activate bipolar cells → activate retinal ganglion cell → sends signals to optic nerve and brain → LGN in thalamus → primary visual cortex (V1) of the occipital lobe
Photoreceptor
specialized nerve that can take light and convert to neural impulse; contain optic discs
Optic disc
large membrane bound structure that contains proteins that fire APs to brain
Blind spot
no cones/rods here; where optic nerve connects to retina
Visual field processing
info in left visual field goes to right side of brain and vice versa
Feature detectors
cells that only respond to specific visual stimuli
Trichromatic Theory of Color Vision
cones are sensitive to blue/green/red, which combine so we can see many colors
Opponent process theory
color vision results from cells that respond to color in opposing pairs (red-green and blue-yellow)
Parallel processing
simultaneous processing of incoming visual stimuli from magnocellular/parvocellular pathways
Magnocellular pathway
contributes to luminance channel and detects motion; high temporal resolution and poor spatial resolution
Parvocellular pathway
contributes to red-green channel and detects object form; poor temporal motion and high spatial resolution
Ventral stream (“what pathway”)
projects toward the temporal lobe and involved in the perception of form and color
Dorsal stream (“where pathway”)
projects toward the parietal lobe and involved in the perception of motion
Sound waves
air molecules are pressurized and try to escape → areas of high/low pressure
Frequency
how close peaks of sound waves are together
Outer ear
pinna → tympanic membrane
Middle ear
malleus, incus, stapes
Inner ear
cochlea and semicircular canals
Sound Pathway
sound waves enter thru outer ear (pinna) → external auditory meatus (auditory canal) → tympanic membrane (eardrum) → vibrates malleus/incus/stapes bones → oval window vibrates → hair cells in cochlea move back and forth and send info to auditory nerve → MGN in thalamus → primary auditory cortex of the temporal lobe
Hair cells in cochlea…
move back and forth to send info to auditory nerve
Stapes
moves back and forth at same freq. as stimulus to push oval window
Oval window
vibrations lead to movement of fluid in cochlea and activation of auditory receptors
Inward oval window motion leads to…
outward round window motion
Cochlea
helps differentiate between 2 diff. sounds
Organ of Corti
receptor organ in cochlea that converts sound vibrations into nerve signals
Hair bundle
made of kinocilium filaments
Tip link
connects tips of kinocilium and is attached to K+ channel gate
when pushed, stretch and allow K to flow inside cell → activates Ca2+ → AP in spiral ganglion cell → activates auditory nerve
What is the human range of hearing?
20-20,000 Hz
Frequency theory
pitch perception occurs b/c the frequency of a sound wave corresponds w/ stimulation of the auditory nerve
Place theory
pitch perception is based on the location where sounds activate receptors along the basilar membrane
Tonotopic mapping
brain can distinguish diff. frequencies thru basilar tuning
Basilar tuning
hair cells at base of cochlea activated by high freq. (1,600 Hz)
hair cells at apex of cochlea activated by low freq. (25 Hz)
Primary auditory cortex
receives all info from cochlea
Tonotopic mapping
brain can distinguish diff. freq. thru basilar tuning
Kinaesthesia
awareness of body position/movement thru proprioceptors in muscles/joints
does not include balance
Adaptation
change over time of receptor response to constant stimulus (downregulation)
overexcited cells can die
Amplification
increased receptor response (upregulation)
Somatosensory cortex
contains somatosensory homunculus (brain’s map of body)
TrpV1 receptor
sensitive to temp./pain; experiences conformational change when exposed to heat
A-beta fibers
thick; covered in myelin → fast conduction of signals due to less resistance
A-delta fibers
medium-thick; covered in some myelin
C fibers
thin; unmyelinated → lingering sense of pain
Olfactory epithelium
area in nostril separated from brain by cribriform plate
Olfactory bulb
bundle of nerves that sends projections through cribriform plate into olfactory epithelium, which branch off
at end of each connection are receptors, each sensitive to 1 type of molecule
Glomerulus
olfactory bulb targeted by all ORNs that respond to 1 type of stimulus
ORNs synapse on a mitral/tufted cell that projects to brain
Accessory olfactory epithelium
specialized part of olfactory epithelium in animals that sends projections to accessory olfactory bulb
Accessory olfactory bulb
contains the vomeronasal system
humans don’t have an accessory olfactory bulb
Vomeronasal system
contains basal/apical cells that have receptors at tips
activated basal cell sends axon thru accessory olfactory bulb to glomerulus → amygdala: involved w/ emotion/aggression
Umami
ability to taste glutamate
Taste buds are concentrated anteriorly on tongue and can be…
fungiform, foliate, circumvallate
Labeled lines model
each taste bud receptor has 5 axons (1 for each taste), which send info to diff. parts of the gustatory cortex
What types of taste cells bind to GPCR receptors?
sweet, umami, bitter