L7: Vision Flashcards
What are the 4 types of neuron in the retina?
Bipolar, horizontal, amacrine & ganglion cells.
What is the Fovea?
Centre of the retina, makes reading possible.
What is the Lens?
A curved structure in the eye that bends light and focuses it for the retina to help you see images clearly.
What is accommodation in regards to the Lens?
When muscles adjust the curvature of the Lens to focus on near or far objects.
What is the Cornea?
The main lens of the eye, first point of contact for light information.
What is Hyperopia and how can it be corrected?
When the Lens is too weak or the cornea is particularly flat causing long-sighted vision, can be corrected with a converging lens.
What is Myopia and how can it be corrected?
When the lens is too strong or the cornea is particularly curved causing short-sighted vision, can be corrected with a diverging lens.
What is Presbyopia?
A refractive error that makes it hard for middle-aged and older adults to see things up close.
Behind the 4 types of Neurons, what are the 2 photoreceptors?
Cones and Rods.
What are rods and cones?
Rods: a photoreceptor that is Very sensitive to low luminescence, assists in night vision, none in the fovea and only has one colour receptor (Rhodopsin).
Cones: Very responsive to bright light, helps us to see fine detail, highly concentrated in the fovea and has 3 colour receptors (R, G, B).
What do bipolar neurons/cells do?
They connect the outer retina to the inner retina, they convey light signals from rods and cones to the retinal output.
What are the 2 categories of retinal ganglion cells/neurons?
Magnocellular (M-cells)
Parvocellular (P-cells)
What are the characteristics of an M-cell?
Sensitive to light not colour, get info mainly from rods.
What are the characteristics of an P-cell?
Smaller than M-cells, sensitive to colour, get info mainly from cones.
What is the blind spot?
A small area in the retina where blood vessels enter and exit the eye, has no photoreceptors.
What is the optic chiasm?
Where the pathways from each eye cross.
What are the two different routes to the brain called for visual information?
Geniculostriate system
Tectopulvinar system
What is the Geniculostriate system pathway?
All P-cells and some M-cells travel from the retina through the lateral geniculate nucleus (LGN) (in Thalamus) > striate cortex (in Occipital lobe) > Visual cortex areas.
What is the Tectopulvinar system pathway?
The remaining M-cells travel from the retina through the superior colliculus (in Midbrain) > Pulvinar (in Thalamus) > Parietal and Temporal lobes.
What is the Primary Visual Cortex?
The main area of the brain that receives and processes visual information from the retinas, located in the Occipital lobe.
What is the Calcarine fissue?
A deep groove located on the medial surface of the occipital lobe that divides the visual cortex.
What is Retinotopy?
Mapping of the visual field on the brain.
What is the Ventral (what) pathway through the Temporal lobe?
For form and colour info;
P-cells > Parvocellular LGN > V1 > V2 > V4 > inferior temporal cortex.
What is the Dorsal (where) pathway through the Parietal lobe?
For space and motion info;
M-cells > Magnocellular LGN > V1 > V2 > V3 > V5 > Posterior parietal cortex.
What are the specialised functions of the Ventral stream?
Processing faces and places.
What are the specialised functions of the Dorsal stream?
Controlling eye movement, visual control of grasping with hands, and reaching.
What does Centre-surround receptive field refer to?
A receptive field found in retinal ganglion and bipolar cells with a central ‘ON’ area.
What are the two types of concentric receptive fields within a bipolar cell?
On-center and off-center.
What is Cortical magnification and what part of the visual cortex does it take place?
Cortical magnification takes place in V1 and describes how many neurons in an area of the visual context are ‘responsible’ for processing a stimulus of a given size as a function of visual field location.
What are the 5 visual cortex areas?
V1: Segregates pattern from motion signals
V2: 3D vision/ recognising camouflage/complex patterns
V3: Shape perception
V4: Colour area and advances shape perception
V5: Motion area
