Visual System:From Your Eyes To Your Cortex

Question 1

Light enters the eye

Answer 1

Detect different wave lengths & intensities of light
Human Visual spectrum is between 380-760 nanometers
Travels at 186,000
Length colour
Amplitude - brightness

Question 2

Structure of the Eye

Answer 2

Eye detects change in wavelength & intensity of
Light
Cornea gathers light 
Light passes through the cornea
On pupil the hole in the iris
Iris regulates the amount of light
Then go onto the lens which focuses light onto retina
Iris controlled by ANS
Light entering the eye
Dilate dark arousal
Constricted high illumination increased acuity
Lens
Bring image into focus on retina
Accommodation 
Controlled by muscles

Question 3

Structure of the retina

Answer 3

2 types light sensitive receptors on retina
Rods 120mil
Comes 6mil
Ganglion cells axons (800,000) bunch together to form optic nerve

Question 4

3 types of Cones

Answer 4

Cones that absorb long wavelength light (red)
Absorb middle wave length (green)
Absorb short (blue)

Question 5

Colour vision

Answer 5

Trichromatic (3 cells) theory of colour
Colour blindness - red and green - yellow and blue

Herring laws, opponent theory of colour
- Ganglion cells LGN

Question 6

From retina to V1

Answer 6

Optic chiasm - cross over point - nasal side of retina to cross the opposite side of the brain
About 80% lateral geniculate nucleus of the thalamus
Then here to primary visual cortex in occipital lobe

Question 7

Cortical Visual Areas

Answer 7

Organised into two major streams
A ventral what stream that serves in the recognition of faces and objects and a dorsal where/ how stream that serves in location and visuomotor skills
Part of dorsal visual stream inc mirror neurons that respond sight of another individuals actions

Question 8

M system

Answer 8

Parallel visual pathways
Begin at the retina
Small P and large M ganglion cells
Main evidence monkeys (single cell recordings)

Question 9

Ventral stream

Answer 9

Conscious pathway

Question 10

Dorsal stream

Answer 10

Unconscious stream

Question 11

Parvocelluar

Answer 11

High spiral
Low temporal frequencies
Colour sensitive

Question 12

Mangocellular

Answer 12

Low spiral
High temporal frequencies
Insensitive to changes in colour

Question 13

Impaired m cell

Answer 13

Has been found prematurity , foetal alcohol syndrome, development dsylexia ,dyspraxia,ADHD , schizo , depression and violent personalities

Question 14

From primary visual cortex

Answer 14

Visual info passes through V2 3 4 5
Colour motion and orientation largely independent
Channelled through where or what pathways

Question 15

Visual Agnosia

Answer 15

Neurological disorder
Inability to recognise familiar objects
May be able to point and describe
Not recognise

Question 16

Apperceptive Agnosia

Answer 16

Individual is completely in cable of recognising objects
Difficultly between shapes
Difficult matching or copying
Early stage of visual processing

Question 17

Associative Agnosia

Answer 17

Unable to assign meaning to objects
Damage to temporal and occipital 
Draw & copy unable to identify
Co occurs with language or memory impairment
Underlying problem ?
Higher order visual perception
Disconnection syndrome 
Prob W/ semantic processing (Brian)

Question 18

Blindsight

Answer 18

Ability to respond to visual stimulus even with no conscious awareness
Some connections may exist in V1
Messages may get to brain by connections that do not pass the scotoma

Question 19

Hemispatial Neglect

Answer 19

Known as unilateral neglect
One hemisphere is damaged
Causes deficit in attention to opposite side of space
Sometimes the patients with hemispatial neglect disclaim ownership of their limbs and even disregard their body