Name the cells from where the optic nerve originate. Where are these cells located?
Ganglion cells are found in the ganglion cell layer (closest to the vitreous humor) of the retina
List the places in the CNS where the optic nerve fibers terminate.
Most optic nerve fibers (80%) synapse on the Lateral Geniculate Nucleus of the thalamus, then go on to the primary visual cortex.
superior colliculus (10%)
pretectal area (5%)
SCN of the hypothalamus (5%)
How do we call the fiber tracts transmitting visual information from thalamus to cortex? What is the anatomical relationship between these fibers and the lateral ventricles?
These fibers are the optic radiations
The optic radiations leaving the LGN enter the white matter to sweep over and lateral to the atrium and temporal horn of the lateral ventricle and then back toward the primary visual cortex in the occipital lobe. As they do so, these axons fan out over a wide area, forming the optic radiations.
Where is the primary visual cortex located? Indicate the lobe of the brain, the Brodmann's area and the specific location.
The primary visual cortex lies alongside the calcarine fissure in the occipital lobe in Brodman's area 17.
Fibers leave the retina at the optic disk located medial to the posterior pole of the eye. This area represents a blind spot. Why?
There are no photoreceptors at the optic disc to allow the ganglion cell axons to exit the eye.
At the optic chiasm the nasal fibers traveling with each optic nerve cross over the midline and join the contralateral temporal fibers. Where in the retina do the fibers in the optic tracts come from?
Right optic tract: Left nasal retina and Right temporal retina
Left optic tract: Right nasal retina and Left temporal retina
What part of the visual field is represented in each optic tract?
Right optic tract: Left Temporal field and Right Nasal field = left visual field in the binocular representation
Left optic tract: Right Temporal field and Left Nasal field = right visual field in the binocular representation
Axons of the LGN neurons will form 2 pathways that head towards the visual cortices. What parts of the retina are represented in Meyer's loop?
The lower nasal retina of the contralateral eye and the lower temporal retina of the ipsilateral eye
What parts of the visual field are represented in the Right Meyer's loop?
The left upper quadrant of the visual field of both eyes
Which of the 2 optic radiation pathways terminates in the superior bank of the calcrine sulcus?
The upper portions of the optic radiations project to the superior bank of the calcarine sulcus. Upper bank lesions thus cause contralateral inferior quadrant defects.
What parts of the calcarine sulcus are devoted to foveal representation?
The region of the fovea is represented near the occipital pole. Despite its small retinal area, because it is the region of highest density of photoreceptors and ganglion cells correspondingly high visual acuity, the fovea has a disproportionate cortical representation, occupying about 50% of the primary visual cortex. The fovea and mostly the foveola provides one to one connection between cones and ganglion cells.
What parts of the visual field are represented in the superior bank of the calcarine sulcus of one side?
Contralateral inferior quadrants.
What visual deficit would be present in a patient with a lesion of the left optic tract?
A right homonymous hemianopia
What visual deficit would be present in a patient with a pituitary tumor compressing the fibers of the optic chiasm?
A bitemporal (heteronymous) hemianopsia
What visual deficit will be present in a patient with a lesion of the right Meyer's loop?
Left upper quadrantanopsia
What deficit will be present in a patient with a lesion of the right lateral geniculate nucleus?
Left homonymous heminanopsia
-Lesion of parieto-temporal junction
-Deficit of spatial attention
-Difficulty to scan a complex visual scene or identify moving objects
-Patients have optic ataxia, ocular apraxia, and simultanagnosia
-Each layer has a complete retinotopic map
-Each point in space is represented 6 times
-Fovea is over-represented in the LGN
-Goes to the inferior bank of Calcarine sulcus
-Upper visual field quadrants
Direct Tract/Superior pathway
-Goes to the parietal lobe to reach the occipital cortex
-Goes to superior bank of Calcarine sulcus
-Lower visual field quadrants
Ocular Dominance Column
-react to color
-able to communicate laterally with the next column and see binocular space
-cells with complex receptive fields that allow them to have orientation selectivity
-sense movement and have direction selectivity
Parahippocampal place area (PPA)
Localize and identify places
-houses, landmarks, indoor and outdoor scenes