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19 Cards in this Set

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MAGNOCELLULAR NEURONS
VS.
PARVOCELLULAR NEURONS

-INPUT
-OUTPUT
INPUT:
-RETINAL GANGLION CELLS
-PC = P CELLS
-MC = M CELLS

OUTPUT

PC = PRIMARY VISCTX 4C-BETA
MC = PRIMARY VISCTX 4C-ALPHA

"PCBETA, MCALPHA"
T/F

CONVERGENCE INPUT FROM THE TWO EYES DOES NOT OCCUR AT THE LEVEL OF THE LGN
TRUE.

There is NO CONVERGENCE of input from the two eyes onto individual neurons in the LGN. Input from the two eyes is kept separate until the level of the visual cortex.
DEFECT:

BITEMPORAL HEMIANOPSIA
This defect is common with pituitary tumors
WHAT THREE THINGS DOES STEREOSCOPIC VISION DEPEND ON?
Depends on the convergence of inputs from the two eyes.

Requires proper alignment of the two eyes.

Depends on visual experience during a “critical period” of development.
WHAT DO EACH OF THESE MEDIATE?

RGS:
RT:
RPT:
RH:
The retino-geniculo-striate pathway mediates form vision.

The retino-tectal pathway mediates visually-guided behaviors (catching a ball).

The retino-pretectal pathway carries visual information for modulating ocular reflexes.

The retino-hypothalamic pathway entrains circadian rhythms.
AREA 17==>

AREA 18+19==>
-DAMAGE HERE WILL CAUSE PROBLEMS WITH _____________
Area 17: Striate cortex
Primary visual cortex (V1)

Visual association areas:
Area 18 & Area 19

Damage TO 18/19:
May cause problems with visual perception
Conscious perception of visual information

TAKES PLACE (NAME PATHWAY)
1) Conscious perception of visual information, what we mean by “seeing”, requires the relay of information from the eye to the brain along the retino-geniculo-striate pathway.
CORTICAL NEURONS W/IN CENTER OF STRIPES

VS.

CORTICAL NEURONS AT THE BORDER
Cortical neurons within the center of the stripes respond primarily to one eye (receive monocular input). Cortical neurons at the border respond to both eyes (receive binocular input).
DAMAGE TO TEMPORAL LOBE

VS.

DAMAGE TO PARIETAL LOBE
Damage to the temporal lobe can damage the axons of Meyer’s loop, causing contralateral homonymous superior quadrantopsia --The case of the disappearing volley ball.

Damage to the parietal lobe can damage the axons carrying information from the lower visual field, causing contralateral homonymous inferior quadrantopsia
DESCRIBE HOW THE GENICULOSTRIATE PROJECTS
Geniculo-striate projections loop around the lateral ventricle through the temporal and parietal cortex, and continue as optic radiations to terminate in the area of the cortex that surrounds the calcarine fissure.
NAME 5 PROJECTIONS FROM THE OPTIC NERVE
(LGN).

superior colliculus.

The pretectal area.

The pregeniculate nucleus.

Suprachiasmatic nucleus of the hypothalamus.
OUTER NUCLEAR LAYER

OUTER PLEXIFORM LAYER

INNER NUCLEAR LAYER

INNER PLEXIFORM LAYER
RODS AND CONES

HORIZONTAL CELLS

BIPOLAR AND AMACRINE

AMACRINE
Binocular

VS.

MONOCULAR SEGMENTS
The visual field of each eye extends from about 90o laterally to about 60o medially.

The portion of the visual field that can be seen by both eyes is the binocular segment.

The lateral most 30o that can be seen by only the ipsilateral eye is the monocular segment.
LESIONS TO 18
*REAL OR DRAWN OBJECTS
*RECOGNIZE FACES
*ASSOC. COLORS W/ OBJECTS
*NAME COLORS
*DISTINGUISH HUES
*JUDGE DEPTH (STEREOPSIS)
WHERE DOES HIGHER ORDER VISUAL PROCESSING OCCUR?
Higher order visual processing occurs in “visual association areas”, including areas 18 and 19.
TELL ME THE SYSTEM:

MOTION/SPATIAL RELATIONS

FORM (SOME COLOR)

COLOR
The magnocellular system is specialized for motion and spatial relations.

The parvocellular-interblob system is specialized for the detection of form and to some extent color.

The parvocellular blob system is specialized for color.
COMPLEX CELLS
Complex cells have orientation selectivity
HOW DO RECEPTIVE FIELDS OF RETINAL GANGLION CELLS DIFFER FROM

RECEPTIVE FIELDS OF STRIATE CTX NEURONS
Receptive fields are not center-surround; instead cortical neurons respond best to light-dark boundaries.
RECEPTIVE FIELDS:

RETINAL GANGLION

VS.

LGN
Receptive fields are basically circular

The fields have a center-surround organization.

There are both on-center and off-center receptive fields.
There are also directionally-selective cells.

ALL LGN neurons are monocular.