Test 2: lecture 19: visual

Question 1

___converts “optical image” in to a ”neural image” for transmission
down the optic nerve to the brain for further analysis.

Answer 1

Retina

Question 2

how does light get to optic nerve

Answer 2

vertical pathway

comes in hits retina

cone → bipolar cell → ganglion cell → optic nerve

Question 3

transduction of the image by photoreceptors take physical energy photons and convert them to ____

Answer 3

electrochemical energy

light → cones/rods → bipolar cells → ganglion cells

Question 4

lateral information flow in the retina

Answer 4

amacrine cells and horizontal cells inhibit the transmission of info to the optic nerve

Question 5

cells that can see light

Answer 5

rod (night vision)

cones (day vision (color))

Question 6

Retina uses different cell types to create ___ for simultaneous transmission of multiple neural images to the brain (for motion,form,color,…)

Answer 6

parallel circuits

(needs a bunch of cells working together to reform an optic image into a neural image → each cell type has a different job)

Question 7

receptive field of a retinal ganglion cell

Answer 7

the area of cells that stimulate the ganglion cell → vertical pathway

the area of cell outside a specific area that will inhibit the vertical pathway by interacting with the horizontal cells → lateral pathway

Question 8

vertical pathway in the eye

Answer 8

photoreceptor → bipolar cell → ganglion cell

forms the center of the receptive field

Question 9

lateral pathway of the eye

Answer 9

photoreceptor → horizontal cell (amacrine) → bipolar cell → inhibits ganglion cell

forms the inhibitory surround of the receptive field

Question 10

___ : The part of the visual field in which various visual stimuli can affect the discharge rate of the cell

Answer 10

receptive field

Question 11

on center ganglion cells vs off center ganglion cells

Answer 11

on → stimulated by center

off → stimulated by surround

Question 12

The RF of a ganglion cell has two parts called a ____ and they are mutually antagonistic

Answer 12

center and surround

Question 13

Because of this center-surround RF organization, the signal leaving the retina is a ___signal (the difference between center and surround)

Answer 13

contrast

Question 14

P ganglion cells

Answer 14

can be on or off ganglion

• small receptive fields
• selective to particular wavelengths of light (color)
• concerned with analysis of fine detail and color
• terminate in P (parvocellular) layers of LGN

Question 15

M ganglion cells

Answer 15

• large receptive fields
• not wavelength selective
• respond well to large objects and movement
• terminate in M (magnocellular) layers of LGN

Question 16

___ type of ganglion cells respond to a specific cone or color

Answer 16

P cell

selective to a particular wavelength of light → fine detail and color

Question 17

P ganglion cells project to the ___

Answer 17

parvocellular layer of the LGN

Question 18

M ganglion cells project to the ___

Answer 18

magnocellular layers of the LGN

Question 19

information leaving the retina is packaged into parallel pathways ___

Answer 19

on and off center

M (motion)/P (color)

left and right eye

Question 20

For every point in the visual field we have at least 4 ganglion cell types processing information concerning the image:

Answer 20

ON-M, OFF-M, ON-P and OFF-P

Question 21

retinal ganglion cells will project to

Answer 21

Thalamus: lateral geniculate nucleus (LGN)

Hypothalamus: suprachiasmatic nucleus [SCN] (circadian rhythms)

Midbrain: superior colliculus [SC] (orienting the movement of head and eyes), pretectum (pupillary light reflex)

Question 22

fovea separates the retina into __

Answer 22

temporal and nasal retina

temporal retina → stays on the same side

nasal retina → changes sides

Question 23

Axons of retinal ganglion cells in the ___cross to the opposite side of the brain at the optic chiasm

Answer 23

nasal hemiretina

Question 24

Axons in the ___do not cross.

Answer 24

temporal hemiretina

Question 25

anything in the left visual field will end up where \_\_\_

Answer 25

on the **nasal hemiretina** of the L eye on the **temporal hemiretina** of the R eye → both will lead to the **R optic tract**

Question 26

anopsias

Answer 26

large visual field deficits

Question 27

scotomas

Answer 27

small visual field deficits

Question 28

what can each eye see at A?

Answer 28

left normal right → nothing (anopsias)

Question 29

what can each eye see at B?

Answer 29

only see the center of each field (the nasal hemiretina are cut → can't cross over) heteronomous, hemianopsia

Question 30

what can each eye see at C?

Answer 30

left homonomous hemianopsia left eye → far left is cut off cause the nasal hemiretina is cut right eye → the temporal hemiretina is cut can't see the center

Question 31

what would cause this

Answer 31

Lesion of optic tract, LGN or 1o Visual cortex e.g., tumor, stroke Left homonomous hemianopsia (varying degrees) cut at C

Question 32

what would cause this?

Answer 32

Lesion of optic chiasm e.g., pituitary tumor Heteronomous hemianopsia (both sides loss of half of the visual field) tunnel vision

Question 33

what would cause this?

Answer 33

Lesion of optic nerve e.g., optic neuritis Right eye blindness cut at A

Question 34

layers of the LGN

Answer 34

2 magnocellular layers 4 parvocellular layers in the thalamus → visual comes from optic nerve parallel pathways for M/P, left/right, On/off center

Question 35

LGN → ___ → striate cortex

Answer 35

optic radiations striate cortex also called the primary visual cortex

Question 36

the left visual field projects to the \_\_\_

Answer 36

**right primary visual cortex** | (contralateral visual hemifield)

Question 37

LGN leads to what layer of the primary visual cortex?

Answer 37

layer 4C everything remains separate (segregated) there are specific spots for M/P, On/Off, Center/surround, left/right

Question 38

where are binocular cells?

Answer 38

layer 1-3 of the neocortex of the primary visual cortex receive info from both eyes from the 4C layer

Question 39

\_\_\_ are functional columns of cells extending from pia to white matter that all share the same eye

Answer 39

ocular dominance columns

Question 40

where does convergence of the visual field take place

Answer 40

in the primary visual cortex input goes to layer 4c then mixes in layer 1,2,3

Question 41

binocular cells are important for \_\_\_

Answer 41

depth perception

Question 42

Many binocular cells code for \_\_\_- differences in images from the left and right eye that the brain uses as a binocular cue (\_\_\_) to determine depth or distance of an object.

Answer 42

retinal disparity stereopsis (depth perception)

Question 43

what happens to the on/off subregions from layer 4c to upper layers

Answer 43

they elongate → change what will trigger them (orientating tuning) convergence of inputs from rows of On/off center cells

Question 44

Answer 44

lines up at a particular orientation → **good stimulus** ## Footnote **(orientation selective)**

Question 45

Answer 45

Bad stimulus → going over + and - areas would not lead to good stimulus (orientation selective)

Question 46

orientation selectivity

Answer 46

layers 1-3 of the visual cortex are elongated in a way that specific directions of light give a good or bad stimulus

Question 47

\_\_\_ are functional columns of cells extending from pia to white matter that all share the same orientation preference.

Answer 47

orientation columns prefer bar of light in specific direction

Question 48

Orientation selectivity is the first step in visual processing to make out the ___ of objects.

Answer 48

contours ## Footnote Visual system uses information about local orientation and contrast to construct the contours and surfaces of objects

Question 49

Visual system uses information about \_\_\_and contrast to construct the contours and surfaces of objects

Answer 49

local orientation

Question 50

direction selectivity

Answer 50

parts of the primary visual cortex are selective for a specific direction of light → it will send a signal if going the correct direction (preferred or null direction)

Question 51

receptive field properties emerging in V1

Answer 51

Disparity tuning – for depth perception Orientation selectivity – for form perception Direction selectivity – for motion perception M/P pathways are still segregated

Question 52

dorsal vision pathway

Answer 52

where" spatial relationships, depth, **motion** locating and grasping **M pathway**

Question 53

ventral object recognition pathway

Answer 53

what? who color form recognizing an object P Pathway

Question 54

akinetopsia

Answer 54

inability to see motion lesion in MT → where pathway

Question 55

lesion in MT causes

Answer 55

akinetopsia (inability to see movement) issue with the dorsal pathway (where pathway)

Question 56

lesion at V4

Answer 56

involved in color perception ventral pathway (P pathway → what, who pathway) achromatopsia

Question 57

achromatopsia

Answer 57

lesion at V4 involved in color perception ventral pathway (P pathway → what, who pathway)

Question 58

lesion at IT

Answer 58

in the temporal lobe part of the ventral pathway → what pathway (P pathway) **prosopagnosia** → can't see faces **object agnosia** → can't recognize objects

Question 59

patients have no trouble recognizing faces, but cannot recognize common objects

Answer 59

Object agnosia ## Footnote Bilateral lesions of inferotemporal cortex issue with ventral pathway (P pathway → what/who pathway)

Question 60

patients cannot recognize peoples faces but basic object recognition is spared

Answer 60

Prosopagnosia ## Footnote Bilateral lesions of inferotemporal cortex (IT) issue with the ventral pathway → P pathway (what/who pathway)