Sensory processes exam 3

Cue approach to depth perception

focuses on information in the retinal image that is correlated with depth in the scene, such as occlusion

convergence

foveate on nearby objects, involves an inward movement of the eyes through ciliary muscles tightening lens

accommodation

foveate on faraway objects, involves an outward movement of the eyes through ciliary muscles relaxing the lens

monocular cues

come from one eye

pictorial cues

receive sources of depth information that come from 2D images, such as pictures

occlusion

one object partially covers another

relative height

objects below the horizon that are higher in the field of vision are more distant

relative size

when objects are equal size, the closer one will take up more of your visual field

perspective convergence

parallel lines appear to come together in the distance

familiar size

distance information is based on our knowledge of object size

atmospheric perspective

distance objects are fuzzy and have a blue tint

texture gradient

The visual pattern formed by a regularly textured surface that extends away from the observer. this pattern provides info for dist bc elements appear smaller as dist increases

shadows

indicate where objects are located and enhance their three-dimensionality

motion parallax

close objects in direction of movement glide past rapidly, but objects in the distance appear to move slowly

stereoscopic depth perception

depth perception created by input from both eyes

deletion

the covering of an object as you move relative to it

accretion

the uncovering of an object as we move relative to it

binocular disparity

the difference in images perceived from two eyes that can be described by examining corresponding points on the two retinas

how are 3D movies made

side by side cameras that record slightly different views and projected onto the same 2D surface. 3D glasses separate images so each eye sees its own image

the horopter

imaginary curve passing through the point of focus; objects on this fall on corresponding points on the two retinas

objects not on the horopter

fall on noncorresponding points, creating disparate images

absolute disparity

the angle between two noncorresponding points. also indicated how far an object is from the horopter

stereopsis

depth information provided by binocular disparity

random dot stereogram

two identical patterns with one shifted in position

binocular depth cells

disparity selective cells are neurons that respond best to binocular disparity

disparity tuning curve

representation of binocular depth neuron cell response rate that shows the preferred degree of disparity for a particular cell

Blake & Hirsch study

cats reared w/alternating vision: few binocular neurons and unable to use binocular disparity to perceive depth

visual angle

angle of object relative to the observers eye (depends on both size and distance of object from observer)

holway study

2 pt. 1:depth cues → judgement ofsize based on physical size. 2. → no depth info and judgement of size based on retinal image size.

size perception changes when depth info is available

size-distance scaling equation

S = K(R*D) (size = retinal size * Object Distance)

perception of object size

remains relatively constant

Emmert’s Law

retinal size of afterimage remains constant. Perceived size will change depending on distance of projection (following size-distance scaling equation)

muller-lyer illusion

lines w/inward fins appear shorter than lines w/outward fins despite being the same length. works through misapplied size-constancy scaling or conflicting cues theory

relative size

perception of size depends on size relative to other objects

locust depth perception

motion parallax

motion parallax

uses the changes in perspectives as observer moves

echolocation

sound emitted and interval noted between sent and received

physical sound

pressure changes in the air or other medium

perceptual sound

the experience when hearing

speaker sound creation

condensation and rarefaction create high and low pressure regions traveling through the air

condensation

diaphragm of the speaker moves out, pushing air molecules together

rarefaction

diaphragm of speaker moves in, pulling air molecules apart

pure tone

created by a sine wave of high and low pressure

loudness

perception of amplitude

amplitude

pressure difference between high and low peaks of wave

decibel

measure of loudness = 20log(p/p0), relates amplitude of the stimulus with psychological experience of loudness

pitch

perception of frequency, the perceptual quality we describe as high and low

frequency

number of cycles within a given time period

hertz

measure of pitch (= 1 cycle/second)

periodic tones

sounds that repeat at regular intervals over time and can include both pure sine waves and complex tones. created by fundamental frequencies and other harmonics

complex waveform

create complex sounds

fundamental frequency

repetition rate in periodic tones

harmonics

additional pure tones in periodic tones

additive synthesis

process of adding harmonics to create complex sounds

frequency spectrum

display of harmonics of a complex sound

timbre

quality of sound (perceptual aspects of sound besides loudness, pitch, and duration) (harmonics, attack, and decay of tone)

perceived loudness

as sound intensity increases so does perceived loudness of sound

human hearing range

20-20,000 Hz

threshold of feeling

tones loud enough to feel and cause pain

audibility curve

shows the threshold of hearing in relation to frequency

auditory response area

falls between the audibility curve and threshold for feeling

most sensitive hearing Hz

2-4k Hz

equal loudness curve

perceived loudness of a sound varies with frequency

outer ear

pinna and auditory canal

pinna

helps with sound location

auditory canal

tube-like 3 cm long structure, protects the tympanic membrane at the end of the canal. amplifies frequencies between 1-5k Hz

middle ear

2 cm³ cavity separating inner from outer ear, contains malleus; incus; stapes. acts as amplification system to transmit weak air pressure changes to liquid in the inner ear

malleus

moves due to the vibration of the tympanic membrane

Incus

transmits vibrations of malleus

stapes

transmits vibrations of incus to the inner ear via the oval window of the cochlea

middle ear muscles

help dampen sounds to protect IE by reducing ossicle vibrations in response to extremely loud noises.

inner ear fluid

denser than air so air pressure changes from outer ear transmit poorly into the denser medium of the inner ear cochlea

amplification radio between tympanic membrane and oval window

20 to 1

cochlea

fluid filled snail like structure set into vibration by the stapes

cochlear partition

divides scala vestibuli and scala tympani, extends from base (stapes end) to apex (round window), organ of corti contained within

frequency of sound -corti

place with the highest firing rate

tonotopic map

orderly map of cochlear frequencies

characteristic frequency

frequency at which a neuron is most sensitive/has the lowest threshold

outer hair cells

respond to sound by slight tilting and changing length. in three rows

place theory

different frequencies cause peak vibrations at specific places on the membrane

pitch perception

depends on neuron firing

phase locking

nerve fibers fire in bursts which occur near peaks of sine waves. even if some fibers skip beats others will catch missing peaks. several fibers create a population that will be phase locked to all peaks of the sine wave

temporal coding

the representation of sound information in the timing of neural spikes; major mechanism of pitch perception

harmonics

determining the timbre or color of a sound, hinges on basilar membranes ability to create separate peaks for those frequencies

resolved harmonics

distinguishable as separate peaks by the basilar membrane; usually lower frequency

unresolved harmonics

undistinguishable as separate peaks by the basilar membrane; usually higher frequency

cochlear nucleus

first step on auditory pathway to brain

auditory pathway to brain

superior olivary nucleus → inferior colliculus → medial geniculate nucleus

superior olivary nucleus

localizes sound by analyzing time and intensity differences between the ears

inferior colliculus

integrates auditory signals with motor responses; enhances sound localization

medial geniculate nucleus

relay station; processes complex aspects of auditory information

which coding type is more effective for hearing

place coding effective for whole range, temporal coding only up to 5k Hz

presbycusis

hearing loss; mostly at higher frequencies; affects males more severely than females

cochlear implants

electrode arrays inserted into cochlea to electrically stimulate auditory nerve fibers, stimulation sides sequentially arranged along array: highest frequency at base, lowest at apex

auditory space

surrounds an observer and exists wherever there is sound

azimuth

left-right

elevation

up-down

distance

position from observer

binaural cues

location cues based on the comparison of signals received by left and right ears

interaural time difference

difference between the times that sounds reach the two ears