Vision, including kahoot Flashcards
Retina
Layer with light sensitive receptor cells in the back of the eye
First place where visual info comes in
Rods and cones
Receptor cells, that pass info on to bipolar and ganglion cells
Photopic system
- Cones
- low sensitivity (day vision/light)
- Colour vision
- 3 types of opsin
Scotopic system
- Rods
- high sensitivity (night vision)
- Rhodopsin (photopigment)
When you see an object in your left visual field the info from LGN arrives at
Contralateral occipital cortex
When light falls onto the retina it
Hyperpolarises receptor cells
The retina fovea contains mostly
Cones
(Cones are involved in colour vision and fill up the fovea, best vision is in fovea)
(There are no rods in the fovea)
When light falls on the retina outside the fovea the first cells it reaches are
Ganglion cells
`choriod, a important layer nearby receptors
Blood vessels, for blood supply
Important for: high energy demands
Provides: 02 and glucose
- And glucose
RPE, a important layer near receptors (Retinol pigment epithelium
Constant maintenance of rods/cones (onderhouden)
- Retinol is regenerated here
Patients with blindsight have suffered damage to
Primary visual cortex
A receptive field is characteristic of
A neuron
Hubal and Wiesel (nobel prize wining men) discovered 2 kinds of columns (column of cell that have a similar function) in V1, orientation column and
Occular dominance column
The types of cells in V1 are
Simple and complex cells
The mechanism of colour vision in ganglion and LGN cells is
Spectral opponent
Jennifer Aniston / Godmother cells were found in
Hippocampus
(medial temporal)
NOT VISUAL CORTEX
Why is vision the best in the fovea
Obstruction by other cells are removed, light directly reaches receptors cells.
(Instead that it first had to go trough multiple other cells/layers)
Blind spot
Where nerves in blood vessels leave the eyeball. There are no photoreceptors, no bipolar cells and no ganglion cells in there, so no vision which is why it is called the blindspot
Why is the structure of the retina not logical?
Because of regeneration
Lateral inhibition
Principle that serves to detect edges and contours.
- Bipolar cells have lateral inhibition. - - They laterally inhibit each other. When they are excited, they have inhibitory connection with the neighbour cells.
Inhibit (vertaling)
Onderdrukken, hinder, restrain, or prevent (an action or process).
Information from the left VISUAL FIELD reaches the …
Right visual cortex (right brain)
Information from the left EYE reaches the …
Left visual cortex
Partial crossover of visual nerves in the optic chiasm
Information from the left visual field reaches the right visual cortex.
Information from the right visual field reaches the left visual cortex.
Blindsight due to cortical blindness
Damage (leasion, surgery) to primary visual cortex can lead to blindness for stimuli that are in the receptive field of those cortical regions
NO VISUAL CELLS IN PART OF CORTEX
Explanation for blindsight
Functioning of intaxt subcortical connections, from retina to superior coulculus
Superior colliculus explain which we can see unconsciously
(in case of blindsight)
helps coordinate rapid movement of eyes towards a target
This is enough for the brain to register visual info even if we are not aware of it
What needs to be intact, for conscious awareness of visual info
The visual cortex
Scotoma/field cut vertaling
uitval van een stukje gezichtsveld
Explanation blindsight
Might because of a result of the functioning of the intact subcortical connections (cortex is destroyed or severely impared, but subcortical connections are intact) particular these from the retina to the superior collicus
Superior collicus
Help coordinate rapid moveemnt of eye toward a target.
Optic chiasm
The information of both visual field come together trough nerves in optic chiasm. IN HERE THEY CROSSOVER.
Only requirement for evolution of the eyes
Is existence of light sensitive cells
What happens when light is off
The cell is depolarized, which increases glutamate release
In which lobe is vision (think ab vision in the bottom back of the head)
Occipital lobe
how can people with blindsight still sort of see?
They see unconsciously
Lateral geniculate nucleus (LGN)
Is where optic nerves end in the thalamus
In here, each neuron has a receptive field
v1, and the 2 types of cells in it
Responsitiveness of neurons of layer of visual cortex
Most cells in it are tuned for specific spatial frequencies
Cells:
1) simple cortical cells
2) complex cortical cells
Orientation columns
Are cells that respond to stimuli at specific orientations (vertical, horizontal and everything in between)
Center surround organization
- Lateral inhibition (allows to detect edges)
- V1, complex&simple cells, bar of light
- Direction of movement
Trichromatic hypothesis (for colour vision)
Green, blue and red (receptors cones) are combined to see colors
Opponent process hypothesis (for colour vision)
Different receptors are sensitive for opponent processes
Its either
- Blue vs yellow
- Red vs green
- Black vs white
Dorsal visual pathway
V1 to parietal cortex
Where (you see) is the movement of stimulus
- Allows to contact a ball
Ventral visual pathway
V1 to temporal lobe
Identification/localisation of stimulus
- Recognise a ball
Damage in ventral pathway
Trouble locating/identifying objects
BUT YOU CAN STILL SEE
V4 (visual area) in involved in processing
Colour
Prosopagnosia
Unable to recognise faces.
Particular pat in the brain is responsible to recognise faces.
