2 - Additional Notes from Videos & Book Flashcards
Visual anatomy
- As iris gets bigger, pupil gets smaller
- Lens focuses light (convex lens) - converging point at retina
- Retina- duplexity
- Retina- photons/absorb light, to electrical signal
- Light absorbing portion of photoreceptors faces back of retina
- Membrane shelves / discs lined with rhodopsin
- Mitochondria, synapse at front of retina
-Rods- single rhodopsin pigment; less detail but night vision
- Cones- shorter membrane shelf; 3 opsin pigments = color, detail- red, green, blue; bright light
- concentrated at fovea
- 1 cone cell per bipolar cell; multiple rod cells = less detail
- also reason for less cones than rods overall (20x more rods than cones)
- bipolar cells - gradients
- horizontal and amacrine cells - ancillary/support for bipolar; info from multiple retinal cells; edge detections and contrasts = refined
Visual Pathway
Info eyes to brain
- temporal fibers, nasal fibers
- optic chiasm- nasal fibers cross
Visual Processing
LGN of thalamus, visual cortex of occipital lobe, superior colliculus, midbrain
Visual processing
1) Parallel processing - identify key characteristics, commit to memory, recall name or description of object- simultaneous analysis of color, shape, motion
2) Feature detection - recognize features to identify desired object in visual field; filter out important info
Dim Room
- involuntary muscles of iris contract
- enlarge pupil
Object in front of right eye
is still processed by both hemispheres b/c right side of object processed by left visual field which goes to the left hemisphere
Outer ear
-Pinna/auricle, ear lobe, external auditory canal, meets tympanic membrane
Sound waves
longitudinal waves- a wave that vibrates in the direction of propagation
-period (time for one full wave to pass), speed, frequency
period=1/freq
Frequency = number of waves/revolutions per sec = pitch (amplitude/loudness = intensity)
sound waves hitting your ear drum and vibrating is literally moving air particles
Middle Ear
- ossicles
- connects to Eustachian tube - part of nasal cavity; equalizes pressure; ear popping in plane
- oval window
Inner Ear
- Vestibule, 3 semicircular canals, cochlea
- Cochlea = hearing apparatus; has hair cells- signal transduction of turning vibrations into nerve impulses
- Perilymph cushions and transmits vibrations from oval window to cochlear duct
- Endolymph fills cochlea and semicircular canals- bathes hair cells
- Basilar membrane separates perilymph and endolymph
- Tectorial membrane is immobile
- Hair cells (not hair, tufts of cilia/stereocilia with mechanosensory receptors)
- Hair cells depolarize when tufts of cilia bend when they come into contact with the immobile tectorial membrane
Semicircular canals & Vestibule
SEMICIRCULAR CANALS
3 —- X, Y, Z axes
-rotational acceleration
VESTIBULE
- Linear acceleration - utricle = hor, saccule = verti.
- Balance & orient in space
Both have hair cells sensitive to movement
Auditory Processing
Signal from cochlea to auditory nerve, to superior olive, to inferior colliculus, relayed to MGN, to temporal cortex
Smell
Olfactory chemoreceptors
- many
- specific
- lie in olfactory epithelium
-once chemical binds, signal to olfactory bulb (forebrain) -olfactory tract, to higher regions of brain
(Eyes: chiasm to tract to brain; Nose: bulb to tract to brain)
- Pheromones bind olfactory receptors
- –contain endocrine info; mating/food foraging
- dunno if humans can detect pheromones
- HIPPOCAMPUS not thalamus
Taste
- Tongue chemoreceptors in taste buds in papillae
- Sour = acid; Salt = alkali metals
- Umami/savory, bitter, sweet- specific molecules
- Molecule binds to taste buds- into to brainstem, to thalamus, to higher brain
Somatosensation
- info through PNS
- 4 modalities: pressure, vibration, temp, nociception
- 2 point threshold- minimum distance to detect 2 distinct stimuli
- physiological zero- temp that feels neutral to our skin/body; if it feels hotter, it’s hotter than your skin
Kinesthetic sense
=proprioception
-where our limbs are in space = orientation/body position
PROPRIORECEPTORS in MUSCLES AND JOINTS
-hand-eye coordination, balance, mobility
-a football player will use his kinesthetic sense, vestibular sense (balance, detect acceleration), somatosensation (feel ball reach hands), nociception (is he injured)
- if a woman can recover from balance while her eyes are closed, her vestibular sense is gucci (doing great lol)
- if she’s bumping into people in crowds, if she’s aiming to touch her nose and hits her cheek, if she’s bumping into things, her kinesthetic sense is wonky
Sensation vs Perception
sensation = transduction; perception = processing
Psychophysics
associated w/ sensation and perception
Ganglia
collection of neuron cell bodies - CNS
tract = CNS, nerves = PNS
projection areas
motor cortex
vs association areas- prefrontal cortex
mechanoreceptors
pressure, movement
hair
osmoreceptors
blood osmolarity; kidneys
absolute threshold
minimum INTENSITY at which SIGNAL is transduced 50% of time
SENSATION
varies w/ threshold of conscious perception - does not reach higher order/consciousness
Io
absolute threshold of normal human hearing
10^-12 W/m^2
limina
thresholds
subliminal = below threshold
difference threshold
just-noticeable difference
Weber’s
3 Hz / 440 Hz = x / 1000 Hz; x = 6.8 Hz
100 and 125 detectable, which is right? (100%, 125%) 5, 6 x 25, 35 :) 125, 150 x (same) 225, 275 x
discrimination testing
find JND conscious perception (color gradient) & difference threshold (auditory)
Signal detection theory
how our sensation/perception thresholds change based on internal and external contexts
internal - personality/shy
external- loud room, hear your name
ASSOCIATE W/ HIT/MISS EXPT
signal present = noise trial (response: Y = hit, N = miss)
signal absent = catch trial (Y = false alarm; N = correct neg)
Related: type 1/2 errors
Reject Ho (if was true, type 1 error; if false, yay) FTR Ho (if Ho was true, yay, if false, type 2 error)
problem - response bias
optic disc
- blind spot
- ganglion nerves converge to optic nerve
fovea
in macula
cones
Cones = S/short wavelength = blue; M = green; L/long = red
less cones than rods b/c one cone per bipolar cell vs many rods
vitreous humor
- gel-like and less clear than the watery aqueous humor
- eye shape/roundness
what produces aqueous humor?
what drains it?
posterior chamber (in front of lens, behind iris); specifically ciliary body, which iris is continuous w/
anterior chamber is in front of iris and lens
Canal of Schlemm drains it
-if issue w/ it- pressure = glaucoma, which is hereditary
Vessels
choroidal & retinal
Iris
- dilator pupillae, constrictor pupillae
- if iris constricts, pupil dilates
continuous w/ ciliary body, which includes ciliary muscle
far object = stretch lens = stretched zonular fibers (suspensory ligaments) = relaxed ciliary muscle
Zonular fibers
Lens shape; ACCOMMODATION!!!!
near/far
suspensory ligaments
Retina
DUPLEXITY theory of vision
rods/cones
EDGE DETECTION
-b/w bipolar and ganglion cells, associated w/ bipolar
AMACRINE and HORIZONTAL cells
Optic pathway
optic nerve -> optic chiasm (decussation of nasal fibers; not temporal/lateral) -> optic tracts to LGN then occipital
If you cleaved the optic chiasm…
you can still see in both eyes but your left eye would only see your right visual field and right eye would only see left visual field
Superior colliculus
- midbrain
- sensorimotor reflexes
- deer in headlight— head doesn’t move, eyes follow sound
-inferior + superior involved in auditory startle
auditory- flinch neck, eye in same place while moving head
Parallel processing
-simultaneous processing of color, form/shape, depth, motion
=feature detection
-feature detectors in visual cortex
we associate patterns of stimuli w/ expected behaviors, w/ help of feature detection
shape = parvo cells; motion = magno cells
(parvocellular, magnocellular) in LGN
Parvo- high spatial resolution, low temporal
opposite for magno
=blurry images
Depth perception
mostly monocular cues
-binocular neurons compare inputs in each hemisphere, detect differences
Monocular cues
- relative size: closer objects are larger
- interposition: in overlapping objects, front one is closer
- linear perspective = convergence of parallel lines
- motion parallax
Binocular
- retinal disparity- eyes 2.5 inches apart; dif images in retinas = depth perception- used in VR- give each eye a slightly dif image
- convergence- brain detects the angle between two eyes (look at nose = much convergence)
- constancy - perceiving object as same even if env changes
Bony & Membranous Labyrinths
bony has perilymph
Membranous has endolymph
What’s the ampulla?
-base of semicircular canals, w/ hair cells
Semicircular canals = rotational acc
linear = vestibule
Linear acceleration
-vestibule = linear acc (rot = semi. canals)
-part of bony labyrinth
Contains utricle and saccule, which has modified hair cells w/ otoliths
What is the superior olive?
In brainstem, localizes sound
“where’s the sound coming from”?
Auditory pathway: vestibulocochlear nerve - brainstem - MGN of thalamus - auditory cortex/temporal + superior olive + inferior colliculus
I.C. for startle reflex and fix eyes on point while moving head (vestibulo-ocular reflex)
Place theory
Perceived pitch directly results from the location of hair cells that vibrate when exposed to frequency
-higher frequencies vibrate hair cells closer to oval window
type of sound is irrelevant; same freq sounds should sound the same way
Place theory: “our PERCEPTION of sound depends on where each component frequency produces vibrations along the basilar membrane”
Cochlea is TONOTOPICALLY organized - which hair cell vibrates gives brain indication of sound pitch
Stereocilia
Hair cells
Cochlea; place theory
Sound
Frequency = pitch Loudness = intensity
The horrid corpuscles
Pacinian- deep pressure/vibration Meissner- light touch Merkle discs- deep pressure/texture Ruffinian- Stretch Free nerve endings- pain, temp
Gate theory of pain
gate on nociceptors brain can turn pain on/off pain = smaller nerve fibers explains why rubbing an injury seems to reduce pain of injury (touching sensation overpowers pain) forehead kiss on toddler
may or may not be right but first theory
Processing
Bottom-up = data driven = science/inductive Top-down = conceptually driven = influenced by experiences & memories = more prone to error = deductive
PERCEPTUAL ORGANIZATION combines both processing to make complete picture
Gestalt
whole > sum of parts
Proximity - make shapes
OOO
OO
O
Similarity —-triangle among background of dots
………[]……….
…..[]…..[]……
…[]….[]….[]…
OR alternating rows of gray and white balls
Good continuation
2 overlapping squiggles looks like just that rather than 2 jagged lines
OR a + sign is 2 overlapping lines rather than 2 L’s
Subjective contours = incomplete shapes make “psuedooutline” of shape in middle
Closure - a square is not seen as 4 L’s slightly apart
Law of Pragnanz = explains gestalt
See things simply/symettrically
