Occipital Cortex Flashcards by Blaire Cardemway

Vision

Series of action potential (processing via electrical signals)
Retina–>Optic Nerve-> Optic chiasm–>Optic Tract–> Lateral geniculate body (LGB in thalamus)–> Optic radiation –> Primary Visual cortex (first point where visual info is processed)

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Primary Visual Cortex

V1->V5 increases acuity of visual info ei light vs dark to finer details

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Calcarine Sulcus

Divides the crude visual info from V1 into upper and lower halves in the Occipital Cortex
(Sulcus are cracks in the brain)

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Lingual Gyrus

Visual cortical region of V2 and Ventral Posterior area

Gyrus are bumps in the brain folds

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Fusiform Gyrus

V4 Complex processing near the temporal lobe (hearing and vision) aiding with processing

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Human Cortex

6 layers of cells

V1 could have more than 6

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First cortical area involved in visual processing
Relays visual input from LGN to the extrastriate cortex for higher-order processing (ei shape motion and colour)
Laminar (dark then light repeat) organization (striated)
Heterogeneous with more than 1 distinct function with the function preserved in V2

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Striated Cortex (V1 and V2)

Thin Stripe = color perception
Thick Stripes = form and motion
Blobs = metabolically active and sensitive to colour
Interblobs = sensitive to orientation

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Colour vision and facial recognition movement depth and position

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Connections of the visual cortex

V1 inputs from LGN to upper levels
V2 further outputs to other levels
Other outer outputs include:
Parietal lobe -> Dorsal Stream

Superior Temporal Sulcus -> STS stream

Inferior Temporal Lobe -> Ventral Stream

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Dorsal Stream

Parietal Lobe
Visual Guidance of Movement
“the where”

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Ventral Stream

Temporal inferior
Object Perception
the What

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Superior Temporal Sulcus

Combination of visuospatial function

Social Perception and Cognition
Language, voices, faces, biological motion, theory of mind

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Occipital Lobe Function Movement

Blobs(V1) –> V4 (Colour)
Interblobs(V1) –> V5 (Motion)
V1+V2 –> V3 (Shape of objects in motion)

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Damage to Occipital Lobe

Legions in specific areas of the Occipital lobe up the different hierarchy produce different visual deficits

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Visual Function beyond Occipital Lobe

55% of the total cortex of the brain is visually related

present in temporal, parietal and frontal lobes

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5 Categories for Vision

Vision for Action
Action for Vision
Recognition
Space
How not to get overwhelmed

Vision for Action

Parietal Visual Areas in the Dorsal Stream
Reactionary Vision
Ducking
Catching
BOTTOM UP or Reaction

Action for Vision

Attentive vision
Visual scanning
Eye Movement and Selective Attention
TOP-DOWN or cognitive Processing
Agnosic Subject have random scanning of eye movement

Visual Recognition

Temporal Lobes
Inferior temporal cortext
“what pathways” Object Recognition

Visual Space

Parietal Lobes
Spatial location ('where" pathways)
Egocentric space (location of object to self)
Allocentric space (location of objects to each other)

Visual Attention

Paying attention to certain info and filtering nonessential info
Prevents getting overwhelming of cognitive capacity

Milner-Goodale Model

2 Visual Streams (dorsal and ventral) allow for consistency even when visual stimuli is changing

Monocular Blindness

Loss of Sight in 1 eye

Due to optic chiasm legion

Bitemporal hemianopia

Partial loss of vision in both temporal (peripheral vision) fields. Usually damages to a tumor in the pituitary gland that puts pressure on the optic chiasm.

Right/Left Nasal Hemianopia

Caused by a lesion in the lateral chiasm leading to the partial loss of vision in one nasal field.

Homonymous hemianopia

The blindness of one the visual field due to damage in the optic tract, LGN or V1

Quadrantanopia

Loss of vision in 1/4 of the visual field, due to cortex lesions near the calcarine sulcus

Macular sparing

part of visual field spared from damage | legion spares the central part as there might be an increased vascular supply to prevent entire lost

Patient BK

Right infarct in occipital lobe -> Quandrantanopia Experienced Blindsight could perceive prior location once the light moved into a functioning quandrant

Patient DB

MRI showing inflamed blood vessels (angioma) in Right Calcarine Fissure Symptoms of Hemianopia and cortical blindness

Patient LM

Vascular abnormality caused by damage in V5 | Symptoms include the inability to intercept moving objects --> loss of movement vision

Patient VK

Bilateral hemorrhage in occipitoparietal region Symptom include optic ataxia the deficit in visually guided hand movements

Patient D

Right occipitotemporal lesion | Prosopagnosia: Deficit in facial recognition

Patient T

Left occipitotemporal lesion | symptoms include alexia( inability to read words )

Apperceptive Object Agnosia

Unable to recognize/copy/match shapes | Gross Bilateral damage to occipital cortex

Associative Object Agnosia

Can perceive objects but cannot identify them | caused by legions to anterior temporal lobes

Prosopagnosia

Facial agnosia | Bilateral damage to temporal cortex

Alexia

Dyslexia | Damage to left ( Left for language) fusiform and lingual areas

Visuospatial Agnosia

Topographic Disorientation | Damage to occipitotemporal regions and medial fusiform and lingual areas