Exam 4: Visual system pathways- Michaels Flashcards
Describe the general visual pathway
1)Retinal ganglion cells found at the back of the eye pick up information. 2)send down the optic nerve, cross at the optic chiasm. 3)Go down the optic tract to Lateral Geniculate Nucleus. 4) Follow Optic radiation to visual cortex in occipital lobe
What are the names of the two hemiretinas?
Nasal and Temporal
What makes up the optic nerve?
Axons from the retinal ganglion cells
What order nerve are ganglion cells and where do they synapse?
Third order; most will synapse in lateral geniculate nucleus
Define monocular visual field
what is seen through one eye when the other is covered
Define binocular visual field
includes the monocular field of each eye
Where does information from the left visual field project to?
Contralaterally; projects to right thalamus and cortex
What can happen when there is a lesion near the pituitary gland?
Can disrupt the optic chiasm because they are so closely related; will affect the nasal hemiretina (temporal field) of both eyes
What axon of fields crosses at the optic chiasm?
Nasal fields
Define a homonymous lesion of the optic tract and what will result
Defects in one visual field/eye because the optic tract contains all the neurons for input from both eyes (will lose entire RIGHT VISUAL FIELD if there’s a lesion at the left optic tract).
Define heteronymous damage and where it could occur
Defects in parts of both visual fields and defects are not overlapping- occurs at the chiasm
Where do lateral geniculate nuclei receive input?
only one contralateral visual field
Describe the mapping of the lateral geniculate nucleus
Split in half with lower visual field medial to the upper visual field. From lateral to medial in the lower visual field, the map is: Macula (overrepresented), binocular, monocular.
How does the lower visual field travel to the cortex from the lateral geniculate nucleus
retrolenticular tract (through parietal lobe)
How does the upper visual field travel to the cortex from the lateral geniculate nucleus?
Via sublenticular tract through meyers loops (temproal lobe)
Describe the gyri that are superior and inferior to calcarine fissure in the olfactory lobe
Lingual gyrus (upper visual fields) is inferior to the calcarine fissure. Cuneate gyrus (lower visual fields) is superior to the calcarine fissure
How are the gyri around the calcarine fissure mapped posteriorly to anteriorly?
Posterior to anterior: Macular, binocular, monocular vision
Where is the visual association cortex located
Areas 18 and 19
What does the visual assocation cortex do?
deals with complexity of vision (object recognition and significance, hand-eye coordination, eye movements)
Where does dorsal stream of the visual association cortex project to? What information does it deal with?
projects to parietal and upper temporal cortex; info about the “where” of the visual stimulus (location, movement, position in space)
Where does the ventral stream of the visual association cortex project to? What information does it handle?
Projects to inferior temporal cortex; info about “what of a stimulus (form, color, object recognition, memory)
What order neuron are cells that have their cell bodies in the lateral geniculate nucleus and project to the occipital lobe?
4th order
