Vision Flashcards
What are Ganglion Cells important for?
image and non-imaging functions
What are the most common Ganglion cells
M and P cells
Where do the ganglion cells signal to
The LGn (Lateral Geniculate Nucleus) of the thalamus
Where do the M ganlgion cells signal to
The Magno region ( the 2 thicker regions due to larger cell volumes)
Where do the P ganglion cells signal to
The Parvo region (4 layers)
What is to contribution of each eye to the LGN layering system
Right (layers 2,3 and 5), Left (1, 4 and 6)
After the LGN, describe the pathway of the optic radiations
White matter tract that projects to the primary visual cortex (V1)
Describe the Primary visual cortex
Central vision is the most posterior (regions 1-4) while the peripheral vision is located more deep
Describe the 3 different lesions and where they occur, and what effects this has on visual field
Optic Canal - Vision lost in 1 eye only
Optic Chiasm - Vision lost from 2 different temporal fields (bitemporal hemianopia)
Post-Optic Chiasm - Vision lost from same visual field of different eyes (homonymous hemianopia)
Describe Macular sparing
Is homonymous hemianopia yet macular is spared. Is an indication of vascular problem to the primary cortex yet doesn’t involve the supply to the most posterior region (central vision) and therefore spares the macula
Describe the non-visual functions of Ganglion cells
Circadian Rhythm, Pupil response and Photophobia
Describe the projections of non-visual ganglion cells
Circadian Rhythm (Suprachiasmatic nuclei of hypothalamus), Pupil response (pretectal nucleus of midbrain) and Photophobia (posterior thalamic nuclei of thalamus)
Describe non-visual ganglion cells
Activated by light due to the presence of melanopsin - a rhodopsin family member aka ipGCs
Describe the pupil response
ipGCs are activated by light and project to the pretectal nucleus. This will then synapse in an ippsilateral and controlateral manner to the Edinger-Westfal nucleus of CNIII PNS devision. Will then project to the Cillary ganglion where they will synapse a final time before projecting to the sphincter pupillae for iris constriction.
What do M ganglion cells encode for?
Motion
What do P ganglion cells encode for
Visual acuity and colour
Which regions of the Visual cortex do M ganglion cells project to?
Layer IV Ca
Which regions of the Visual cortex do P ganglion cells project to?
Layer IV Cb
What is Layer IV B involved in?
Motion
What are the two visual pathways
Ventral and Dorsal
What are each of the visal pathways important for?
Ventral - What (colour, perception and visual memory)
Dorsal - Where (Motion and response to movement)
Describe the different regions of the Dorsal Pathway and their function
Area MT - processing objects that are moving, neurons have large visual fields and are directionally selective
MST - navigation, directing eye movement and motion perception
Describe the different regions of the Ventral Pathway and their function
V4 - colour perception
Area IT - Visual perception and Visual Memory
Characteristic of Colour in relation to vision
Colour is not all about detection, instead it is about comparison
What is a lesion in V4 going to result in?
achromatopsia (loss of colour)
What are the wavelengths of stimulation for the cones
Blue is 430, green is 530 and red is 560
What are ‘buddy’ colours
red/green and Blue/yellow
Describe ON ganglion cells
Will fire Action potentials in response to light
Describe OFF ganglion cells
Will fire Action potentials in response to dark
How do colour P ganglion cells differ from rod ganglion cells
Light = colour and Dark=buddy colour
What is Anomalous Trichromy
Colour Blindness where 3 cones are present yet 1 is abnormal
Names for different cones
Protan = red Deutan = green Tritan = Blue
