Occipital Lobe

Cornea

80% of the eye’s focusing power. Differences in shape cause astigmatisms

Pupil

Expands and contracts like a camera lens

Lens

20% of the eye’s focusing power. The Ciliary muscles change its shape to be flatter or curved depending on the focused object

Retina

Contains photoreceptive cells, the fovea and a blind spot

Fovea

Part of the retina with the highest visual acuity

Optic Nerve

Part of the peripheral nervous system, signals from the eye leave to the CNS

Upper Retina Processes Which half of an image?

The lower half of the image

The lower retina processes which part of an image?

The upper half of an image

Photoreceptors

Type of neuron receptive to light

Two kinds of photoreceptors:

Rods and Cones

What kind of photo receptors are primarily found in the peripheral visual field

Rods

Rods are most active in what level of light?

Lower levels of light

Rods can process what type(s) of wavelengths of light?

Monochromatic

Do rods have high or low visual acuity?

Low visual acuity

Acuity

Precision of perceiving detail

How sensitive are rods?

Highly sensitive

There are approximately how many rods in the eye?

~120 million

Cones are primarily found where?

In the fovea/central vision

Cones are primarily active in what level of light?

Higher levels of light

What wavelengths of light do Cones process?

Color vision: Blue, Green, Red

S-Cones Process What kind of light?

Blue light (short-wavelength light)

M-Cones process what wavelength of light?

Green light (medium wavelength)

L-Cones process what wavelength of light?

Red light (long wavelength)

The visual acuity of cones is?

High

How sensitive are cones?

Low sensitivity — Accurate but need illumination to detect changes

How many cones are in the eye?

~6 million

The blind spot in the eye contains

No receptors

The fovea contains

A majority of the cones in the eye

The eye’s blind spot is approximately where?

~15 degrees laterally of the fovea on the nasal retinal side

The axons from the retinal ganglion cells form?

The optic nerve

The optic nerve is formed by

The axons from rentinal ganglion cells

Horizontal cells

Allow communication between rods and cones and bipolar cells

When light hits the retina its processed last by:

Retinal ganglion cells

Bipolar Cells

Receive signals from rods and cones and transmits the signals to retinal ganglion cells

Horizontal Cells

Connects photoreceptors and bipolar cells laterally

Amacrine cells

Connect bipolar cells and retinal ganglion cells laterally

How many fibers make up the optic nerve

1 million

Retinal circuitry

Converges a large among of visual inputs into more condensed outputs

The input to output ratio of Cones

1:1

The input to output ratio of Rods

8:1

Cone-fed circuits are

Low convergence circuits

Rod-fed circuits are

High convergence

Channels of info broadcasting to the optic nerve

M- and P-Channels

The left half of each retina goes

To the left hemisphere

The right half of each retina goes

To the right hemisphere

Temporal retina sees

The nasal visual field

The nasal retina sees

The temporal visual field

Magnocellular layers of the LGN

Get inputs from rods, process luminance, motion, depth. Is faster

Parvocellular Layers of the LGN

Input from cones, processes colour, high acuity vision. Is slower

Koniocellular interlaminar layers

Gets input from rods and codes, processes blue light, motion, and has a role in the circadian rhythm

Layers 1-2 in the LGN

Magnocellular

Layers 1-6 in the LGN

Parvocellular

Interlaminar layers

Koniocellular

How many Koniocellular layers are in the LGN

6

Meyers Loop

Optic radiations carrying information about the upper visual field to the primary visual cortex

Dorsal Optic Radiations

Carry information about the lower visual field from the LGN to the primary visual cortex

Superior Retinal Quadrants see

the inferior visual field

Inferior reitinal quadrants see

the superior visual field

Superior calcarine sulcus

Processes the inferior (lower) visual field

Inferior calcarine sulcus

Processes the superior (upper) visual field

Parietal-occipital sulcus

Is the boundary between the occipital and parietal lobes

The first cortical region that receives input from the retina

V1; the primary visual cortex

Layer 4C Alpha in the V1

Magnocellular (V1)

Layer 4C Beta in the V1

Parvocellular (V1)

Layer 3 in the V1

Konicellular (V1)

V3 Dorsal

Uses visual information to control actions

V3 Ventral

Uses visual information for perception

Lateral Occipital (LO)

Processes outline and contours of objects

V4 and V8

Uses visual information for color

Damage to V4 and V8

Results in cortical colour blindness

LIP

Has a role in eye movements and attention

V7

Important for visuomotor transformations

Extrastriatal Body Area (EBA)

Processes bodies, body language, fine tuning movements

Middle Temporal Cortex (MT)

Responsible for motion perception

Damage to MT

Results in problems perceiving movement

FFA (generally)

Responsible for faces

Parahippocampal Place Area (PPA)

Specialized for places, spatial memories and cognitive maps

V1 is topographically organized

Meaning, damage to a specific part of V1 results in blindness in a specific portion of the visual field

Hemianopia

Homogenous loss of vision

Monocular blindness

Loss of vision in one eye

Bilateral Hemianopia

Loss of vision in the temporal fields

Nasal hemianopia

Loss of vision in the nasal field of one eye

Homonymous Hemianopia

Loss of the temporal visual field in one eye and the loss of the nasal field in the other

Quadrantanopia (lower)

Loss of vision in the left or right inferior quadrant of both eyes

Quadrantanopia (upper)

Loss of the superior quadrant of the left or right visual field

Damage to the optic nerve in one eye

Results in monocular blindness

Damage to the optic chiasm

Results in bitemporal hemianopia

Damage to an uncrossed fiber coming from one eye

Results in nasal hemianopia

Damage to the optic tract

Results in homonymous hemianopia

Damage to the upper (superior) V1 radiations

Results in Quadrantanopia (lower)

Damage to the lower (inferior) V1 optic radiations

Results in quadrantanopia (upper)

Damage to upper and lower V1 radiations

Results in homonymous hemianopia

Damage to the V1 in the right hemisphere

Results in hemianopia with macular sparing

Dorsal Processing stream

Guides action

Ventral processing stream

Perception and recognition

Visual Form Agnosia

Without knowledge of visual form, cant recognize objects visually

Visual Form Agnosia = ____ Stream damage

Ventral

Optic Ataxia

Impaired at visually guided actions

Optic ataxia = ____ Stream Damage

Dorsal