NEUROSCIENCE FINAL

points on the retina which project to the same direction in space are called

points on the retina which project to the same direction in space are called

corresponding points

the fovea in OS and OD are ____ ____ because each fovea projects to what we are looking at directly

corresponding points

assume that there are 50 males in the audience. how many are likely to have R/G deficiency?

4

how many of the 4 individuals have a green deficiency? how many have a red deficiency?

green 3 ; red 1

there are 200 females. how many have a red or green color deficiency?

1

your pt is a 22 years old pregnant woman (ultrasound indicates a male) with normal color vision on PIP screening (12 of 14 correct). she notes that her father is color deficient. the probability that her baby will be color deficient is

50%

electron falls from higher to lower orbit -->

energy is released

E moves forward as a ___ with a specific wavelength (meters/wave)

wave

energy vibrates as a particle named ____ with a specific frequency (waves/sec)

photon

the higher the frequency, the ____ the wavelength, the ____ the energy

shorter ; greater

visible light:

400-700 nm

why do we see 400-700nm?

visible light allows this much to pass. eyes developed to meet the nuanced colors. most radiation absorbed. constrained the evolution of cones...

precision -

1 millionth of 1 mm!

red cones outnumber....

green cones 2:1

red + green outnumber

blue cones 10:1

what is the shortest? R/G/B?

B

___ cones absent in the central fovea

what is not in the fovea?

blue

rods

which wavelength are we most sensitive to (special peak) of the:

R cones G cones B cones

566nm 541 nm 441 nm

color discrimination depends on __ ___ in cone stimulation

the difference

lack of R cones is termed

dicromacy:

protan dichromat aka protanomoly

protanomoly occurs in ___% of men

1

lack of G cones is termed

deutan dichromat

deutan dichromat occurs in ___% of males

1

plot of points equidistant with an image on the fovea of each eye is called

horopter

horopter -

spatial plot of corresponding points. all points on the horopter perceived at same distance.

points on the horopter appear...

in the same plane

deuteranomalous

M cones affected; insensitive to red-green

green shifted toward red

protanomalous

L cones affected; insensitive to red-green

red shifted toward green

protanomalous occurs in ___% of males

1

deuteranomalous occurs in __% of males

5

points off the horopter appear ____ than fixation point

closer or more distant

retinal disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

disparate retinal points

points off the horopter stimulate these

points on the retina which project to (point to) the same direction in space are called

corresponding points

___ ___ is the basis for stereoscopic depth perception

retinal disparity

brain may ___ double image

suppress

physiological diplopia

double vision caused by focusing eyes so that light from an object falls onto two separate spots on the retina and is detected in both sides of the brain

area around horopter in which all points are seen as single is called...

Panama's Fusional Area

points on retina wit common direction

corresponding points

beyond panum's area

physiological diplopia or suppression occurs

T/F a midline object closer than fixation produces a crossed disparity

T

T/F physiological diplopia occurs for disparities within Panum's area

F

T/F a midline object farther than fixation produces an uncrossed disparity

T

T/F cortical disparity detectors underline stereoscopic vision

T

T/F steroacuity is primarily limited by the diameter of foveal cones

F

T/F perception of hue depends on the difference in stimulation between at least 2 cone types

T

T/F photopic brightness depends on the number of rods stimulated

F

T/F hereditary color deficiency is 16x more common in males vs females

T

T/F the shorter the wavelength, the higher the E

T

T/F hereditary color deficiency genes are located on the Y chromosome

F

color deficients rely on: (3)

brightness, context and learning

perception of relative depth between two objects

distance between objects in real space

stereopsis

the slight difference in length of the ___ ___ ______ is used by the brain to perceive depth

lines of stimulation

what is imaged on retina of each eye as a horizontal distance (line of stimulation)

stereopsis

what is the first step in joining the perception from each eye

bring nerve fibers closer together

cross point of optic nerve

optic chiasm

LGN sent what to the visual cortex

optic radiations

in the pic chasm, nasal fibers cross such that: (2)

temporal retinal fibers OS join with nasal fibers OD

temporal retinal fibers OD join with nasal fibers OS

only nasal fibers cross (what percentage of fibers)

53-57%

function of optic chiasm

splits each half of sight from right eye and sends a half to both hemispheres

retinal ganglion cell fibers form

optic nerves

ipsilateral temporal retinal fibers join with

nasal contralateral fibers

cross point -

optic chiasm

after chiasm -

optic tract

next stop -

LGN (lateral geniculate nucleus)

why do certain occupations need normal color vision?

they cannot perform critical tasks as well

this performance decrement may be worsened by?

stress, altitude/hypoxia, low light, fatigue

VA of a 1-month old is...

1 cycle/deg AKA 20/600

acuity reaches 20/100 by what age?

1 year old

improves to 20/20 by what age?

3-5

visual evoked potentials (visual brainwaves) indicate?

more rapid development of VA

limitation of VA during 1st year of life due to?

immaturity of retina

foveal cones

what are some techniques used to check VA of infants or nonverbal patients? (3)

optokinetic nystagmus preferential looking VEP's

optokinetic nystagmus

a reflexive eye movement in which the eyes will involuntarily track a continually moving object

infants prefer to look at?

what is its success percentage?

patterned stimuli to uniform fields of the same mean luminance (average brightness)

75%

VEP

visual evoked potential

by change in pattern

where is VEP

back of the head which receives information from fovea (center) of retina

can be used to estimate visual acuity

peak of contrast sensitivity reaches adult value at

4 years old

fully developed contrast sensitivity by

9 yrs old

limitation on ___ & __ during 1st year of life due to immaturity of retina; particularly foveal cones

VA & CS

vernier acuity

the smallest displacement of a line that can be detected

ability to align targets

stereopsis is present at how old?

3-6 months old

stereopsis matures rapidly at what age?

1 year old

at what age does adult levels of stereopsis reach?

after age 5

temporal vision

ability to detect high rates of flicker present at 1 month of age and reaches adult levels by 4 - 6 months

night vision

rod sensitivity developed by 1st month; adult levels by 6 months of age

color vision

basic red-green discrimination is present by 2nd month; adult levels by age 1

T/F visual acuity development is limited by cone maturation during year 1

T

T/F temporal & night vision do not fully develop until age 6

F

T/F OKN, preferential looking and VEP's are all objective measures of VA

T

T/F VEPs show better VA at an earlier age than other techniques

T

T/F normal OKN ensures normal VA

F

amblyopia

decreased vision, usually in one eye, due to visual deprivation during a critical period early in life

blur AKA

anisometrpia

misalignment AKA

strabismus

occlusion AKA

cataract

amblyopia can be mild (20/__) to severe (???)

20/25

perceives only light, not form

animal and human studies indicate that amblyopia is due to...

an anomaly in the visual part of the brain (the visual cortex)

amblyopia is not in the ____ nor in the ____ (___)

retina

mid-brain (LGN)

early in life neurons from each eye compete for?

dominance of visual cortex