Visual System - Essential Concepts Flashcards
What are the key tasks for the visual system (2)?
To gather information about the spatial & temporal distribution of light reflected from objects & the surrounding scene AND Reconstruct this information to form meaningful representations (perceptions) of the visual world.
What are the different methods of studying the visual system?
To study the anatomy via a microscope.
To study the anatomy via pathway tracing
To study via Functional imaging
To study Clinical neurology
Single Cell electrophysiology
What is functional imaging?
To examine brain activity in neurologically-intact (i.e., healthy) people while they perform specific visual tasks (e.g., functional Magnetic Resonance Imaging; fMRI)
What does clinical neurology involve?
Identifying the specific visual deficit(s) that the brain-damaged subjects experience & relating these to the location of the lesion (damage) site.
What concept is clinical neurology based on?
‘Loss-of-function’ is due to loss of the brain region specialized to carry out that function. (Idea different functions of the brain carry out different tasks)
What is the theory behind focusing on microscopic anatomy to study the visual system?
Neurons with different structures & function occupy different layers of the given tissue. Thus by learning and identifying these we can learn more about different parts of the visual system.
What is this?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/436/587/758/q_image_thumb.jpg?1602811422)
A cross section of the retina.
[you should be able to label the cross section]
![](https://s3.amazonaws.com/brainscape-prod/system/cm/436/587/758/a_image_thumb.png?1602811475)
What happens in pathway tracing?
You inject a substance into a local region of the visual pathway & examine where the neurons there transport it to down their axons, thus revealing their connections with other parts of the system.
[Not usually done in humans]
What is the theory behind pathway tracing of the visual system?
Visual Pathways/Processing occurs in sequence: PhR (Photoreceptors)-to-Ganglion Cells-to-LGN (lateral geniculate nucleus) -to-Cortex
Do neurones with different structures have the same function?
No they have different functions
Do neurones of similar functions cluster together?
Yes they will do this for example in the same cell layer, vertical column or area.
What is over-represented in MAPS of the visual field?
The high acuity central (~15 degrees of vision) as it has the most photoreceptors (from which most stimuli is recieved).
[E.g. 66-75% of V1 processes information from the fovea and macula]
What does every neurone in your central nervous system have?
What does every visual neurone possess?
[same answer for both]
A Receptive Field
What do serial (step by step) processing/pathways in the visual system do?
Reconstruct the image.
“•Serial (step-by-step, sequential) pathways (e.g., cones-bipolar cells-ganglion cells-LGN-visual cortex) = Reconstructing the Image”
What do parallel (side by side) processing/pathways in the visual system do?
Allow for functional specialisation/division of labour
(In the visual system this would happen for things like colour or motion)
What is the primary visual pathway?
By definition the primary visual pathway involves the ganglion cells of your retina, that give rise to the axons that travel down the optic nerve, pass through the optic chiasm into the optic tract and by defintion make connections with neurons in the Lateral geniculate nucleus of the thalamus. Neurones in the lateral geniculate nuclei then give rise to axons of their own which travel in the optic radiations (this is white matter under the occipital lobes of the cerebral cortex) and end up making connections with neurones in the primary visual cortex (otherwise known as V1).