Week 3 Flashcards
Two main visual streams
- Focal vision
- object identification - Ambient vision
- motion
Focal vision stream function?
- Conscious object identification
- Central visual area
What is it?
- Central visual area
Ambient vision stream function?
- Second visual system
- Involves entire visual field
- Non-conscious
- Works in dim lighting conditions
- Where is it?
Define photoreceptor cells
Special cells in the eye’s retina that are responsible for converting light into signals that are sent to the brain.
Define retina
photoreceptors and neurons arranged in a sheet at the back of the eye
Rods function
Process Motion
Cones function
Process Colour
what are the 2 ganglion cell types, where are they located, and function
P cells (parvo)
- Near fovea - High acuity and colour vision
M cells
- In periphery
Motion detection
Ganglion cells run along inner surface of the retina and gather together to form the…….?
Optic nerve
Function of retina cells
Involved in processing of visual information before it is transmitted to the brain
what are the 3 visual fields
Binocular zone
- Area where both eyes can see
Left and right monocular zone
- Where either eye can only see
optic nerve projects into what 3 structures
- Superior colliculus
- Lateral geniculate nucleus
- Reticular formation
Superior colliculus function
- Accommodation and light reflexes
- Coordinates eye-head reflexes
6 layers of the lateral geniculate nucleus
- Ipsilateral - 2,3,5
- Contralateral - 1,4,6
Function of layers 1 - 2
- Large cells
- M cells input
- Movement
Function of layers 3 - 6
- Small cells
- P cell input
Acuity
- P cell input
Lateral geniculate nucleus (LGN)
projects to occipital lobe
Describe retina map
- Topographical order of retinal map and hence of the visual. Your information is swapped around, upside down and back to front (e.g. bottom right, is now top left)
Define blob cells and their function
Cells for analysis of object colour
Define hypercolumn
grouping of ocular dominance and orientation columns
simple cells function
orientation and specific position
complex cells function
specific orientation but any place in the visual field
Hypercomplex cells function
responses to bars of specific length and width
Define apraxia
- Individual elements of a task can be carried out
- Patients understand what is required
- But cannot perform movement task
Define ideational apraxia
- Breakdown in ability to access the ‘ideas’ ‘memory representations’ for motor acts
- Cannot pantomime use of object (pretend to brush teeth)
- But can use actual object (will brush teeth with toothbrush)
Define ideomotor apraxia
- Breakdown in translation of memory representations into motor commands
- Inability to imitate what else is doing
