Vision

Front 1

normal eyeball

Back 1

emmetropia

Front 2

short eye ball

Back 2

farsightedness-hyperopia

Front 3

long eyeball

Back 3

nearsightedness-myopia

Front 4

photopigments

Back 4

which break down in presence of light

Rods contain rhodopsin

Cones contain iodopsin

Front 5

Rods

Back 5

contain rhodopsin
Rhodopsin is extremely sensitive to light.
Rods function well in dim light, poorly in bright light
Rods do not distinguish color
In peripheral retina

Front 6

Rhodopsin

Back 6

Rhodopsin is extremely sensitive to light.
Rods function well in dim light, poorly in bright light

Rods do not distinguish color
In peripheral retina

Front 7

Cones

Back 7

contain iodopsin
Iodopsin requires bright light to function
Cones do well in daylight, not dim light
3 types of iodopsin allow cones to respond to different wavelengths
In central retina (fovea)

Front 8

Iodopsin

Back 8

Iodopsin requires bright light to function
Cones do well in daylight, not dim light
3 types of iodopsin allow cones to respond to different wavelengths
In central retina (fovea)

Front 9

cones are in central fovea

Back 9

rods are in peripheral retina

Front 10

Receptive fields of rods are large

Back 10

Receptive fields of cones are small

Front 11

Receptive fields of rods are large

Back 11

Receptive fields of rods are large
Many rods share each ganglion cell
This enhances their already greater sensitivity to light
But it reduces their acuity

Front 12

Receptive fields of cones are small

Back 12

Receptive fields of cones are small
Few cones attach to each ganglion cell; in the fovea each cone has its own ganglion cell
Thus, visual acuity - ability to distinguish details - is high

Front 13

rods

Back 13

Rods contain rhodopsin
Rhodopsin is extremely sensitive to light.
Rods function well in dim light, poorly in bright light
Rods do not distinguish color
In peripheral retina

Receptive fields of rods are large
Many rods share each ganglion cell
This enhances their already greater sensitivity to light
But it reduces their acuity

Front 14

Cones

Back 14

Cones contain iodopsin
Iodopsin requires bright light to function
Cones do well in daylight, not dim light
3 types of iodopsin allow cones to respond to different wavelengths
In central retina (fovea)

Receptive fields of cones are small
Few cones attach to each ganglion cell; in the fovea each cone has its own ganglion cell
Thus, visual acuity - ability to distinguish details - is high

Front 15

Two types of lateral processing cells

Back 15

Horizontal cells contact photoreceptors and bipolar cells
Amacrine cells contact bipolar and ganglion cells

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Horizontal cells contact photoreceptors and bipolar cells

Back 16

Amacrine cells contact bipolar and ganglion cells

Front 17

All cell types except ganglion cells generate graded potentials

Back 17

ganglion cells fire action potentials

Front 18

When light strikes rhodopsin

Back 18

retinal is activated

RPE65

Front 19

Leber’s congenital optic degeneration

Back 19

RPE65 is defective; photoreceptors degenerate; patient goes blind
Stem cells have cured this disease

Front 20

photoreceptor mechanisms

Back 20

most active when they are not being stimulated by light. In darkness, the photoreceptor's sodium and calcium channels are open, allowing these ions to flow in freely. Thus, the membrane is partially depolarized, the receptor releases a continuous flow of glutamate, and this inhibits activity in the bipolar cells. The chemical response that occurs when light stricks the photopigments closes the sodium and calcium channels, reducing the release of glutamate inproportion to the amount of light. The bipolar cells release more neurotransmitter, which increases the firing rate in the ganglion cells

Front 21

Transduction

Back 21

Light closes Na+ channels, hyperpolarizes; turns rods off!

Rods are so sensitive that at high illumination - in sunlight - all the sodium channels are closed - the rods are saturated

Front 22

Lateral inhibition

Back 22

– connected bipolar cells – inhibiting one’s neighbors produces contrast

Front 23

Visual pathway:

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Retina
Optic chiasm
Lateral geniculate nucleus (thalamus)
Visual cortex (occipital lobe)

Front 24

mach band illusions

Back 24

ganglion cell activated more -lighter band
ganglion cell minimal stimulation-darker band
receptor give neighboring ganglion cells give stimulation or activation to the ganglion cells

Front 25

two types of ganglion cells

Back 25

on center off surround

off center on surround

on is where light produces excitation, off produces inhibition

on center cells-light in the center increases firing and light in the off surround reduces firing below the resting level

Front 26

LGN of the thalamus has three cell types

Back 26

Parvocellular – four dorsal layers – small cells, small receptive fields
Magnocellular – two ventral layers – large cells, large receptive fields
Koniocellular – layers with very small cells, between main layers

Front 27

Parvocellular

Back 27

four dorsal layers – small cells, small receptive fields

Front 28

Magnocellular

Back 28

– two ventral layers – large cells, large receptive fields

Front 29

Koniocellular

Back 29

layers with very small cells, between main layers

Front 30

Primary Visual Cortex

Back 30

Primary visual cortex (V1) in occipital cortex – where most visual information first arrives

Front 31

Brain maps of visual space are mostly devoted to the fovea

Back 31

Simple cortical cells
Complex cortical cells

Front 32

Cells are classified as simple or complex,

Back 32

depending on their receptive fields

Front 33

Simple cortical cells

Back 33

Simple cortical cells – also called bar or edge detectors – respond to an edge or bar of a particular width, orientation, and location

Front 34

Complex cortical cells

Back 34

Complex cortical cells – also respond to a bar of a particular width and orientation, but may be located anywhere in the visual field

Front 35

Simple cells

Back 35

Simple cells are line detectors. They are part of the recognition/location system. They are more responsive to flashes of light, than to static, steady illumination or diffuse illumination

Front 36

Complex cells

Back 36

Complex cells are concerned more with recognition of external objects than with their precise localization.

Front 37

Simple neurons receive input from neurons in the lateral geniculate;

Back 37

complex neurons receive input from simple cells

Front 38

Form Vision Spatial Frequency Theory

Back 38

Visual cortical cells do a frequency analysis of the luminosity variations in a scene
Different visual cortical cells have different sensitivities, not just those required to detect edges
As a result, visual cortical cells can detect not just edges but grades of luminosity change

Front 39

High vs. Low Frequencies in Vision

Back 39

Images with only high frequency transitions are not meaningful. Those with more gradual transitions (low frequencies) are more recognizable

Support for the theory: Cortical cells respond to light-dark “gratings” containing a specific combination of frequencies

Front 40

V1

Back 40

(primary visual cortex) perceives objects and is necessary in forming mental images
color

Front 41

V2, V4

Back 41

, and the inferior temporal lobe - perceive complex form

Front 42

V5

Back 42

is specialized for motion perception

Front 43

V2 is important for this -
“fills in the gaps

Back 43

Much of vision
is extrapolating (predicting) from what is actually ‘seen’

Front 44

V4 cells respond to concentric and radial stimuli

Back 44

V4 is also involved in color perception

Front 45

Motion detection

Back 45

Retinal periphery (rods) sensitive to motion
Cortically, V5 is important
Motion blindness (akinetopsia)

Front 46

Types of input from LGN to V1 – 3 channels

Back 46

1. M channel (magnocellular pathway) –
orientation selective, directional sensitive for movement, no color sensitivity - analysis of object motion
2. P-IB channel (parvocellular interblob pathway) –
high orientation sensitivity, no color sensitivity, small receptive fields - analysis of object shape
3. Blob channel (parvocellular blob and koniocellular pathway) -
no orientation sensitivity, color sensitivity - analysis of object color

Front 47

. M channel (magnocellular pathway) –

Back 47

orientation selective, directional sensitive for movement, no color sensitivity - analysis of object motion

Front 48

. P-IB channel (parvocellular interblob pathway) –

Back 48

high orientation sensitivity, no color sensitivity, small receptive fields - analysis of object shape

Front 49

Blob channel (parvocellular blob and koniocellular pathway) -

Back 49

no orientation sensitivity, color sensitivity - analysis of object color

Front 50

Area V1 Is Organized in Columns and Slabs

Back 50

An ocular dominance column is a region of cortex with greater synaptic input from one eye

Front 51

Two hypotheses of color perception

Back 51

Trichromatic hypothesis:
Three types of cones
Each responds to a part of the spectrum
Each has a separate pathway to the brain

Opponent-process hypothesis:
Three color axes (opposed pairs of colors)

Front 52

Spectral Sensitivities of Human Photopigments

Back 52

Supports the trichromatic theory

In the retina

Front 53

Afterimages

Back 53

opponent-process theory

When one member of the color pair is "fatigued" by extended inspection, inhibition of its corresponding pair member is reduced. This increases the relative activity level of the unfatigued pair member and so its color is perceived.

Front 54

Opponent Process:

Back 54

Cells in the retinal ganglion and thalamic parvocellular layers fire to some wavelengths, and are inhibited by others

Front 55

Synesthesia

Back 55

: activation of V4 and fusiform gyrus by spoken words

Front 56

Alice in Wonderland syndrome

Back 56

Micropsia, macropsia that alternates

Occurs in migraine, EBV (‘mono’) infection

Common in children

Front 57

Simultagnosia

Back 57

Inability to attend to more than a very limited area of the visual field despite normal visual fields

Patients can see individual objects but cannot perceive a visual scene as a whole

Front 58

Palinopsia

Back 58

Patients see afterimages, both as a reduced amount of time required to form an afterimage, and an increased duration of the afterimage. Even routine eye movement is accompanied by flickers of what the eye has scanned ("tracers").

Front 59

Left hemisphere reads words

Back 59

Right hemisphere reads color

Front 60

Patient G.Y.: Blindsight is due to minor pathways into extrastriate cortex that bypass V1 (maybe)

Back 60

Blindsight: patients with damage to primary visual cortex can tell where an object is although they claim they cannot see it