Lecture 7 - vision Flashcards
What are the steps on the visual pathway that axons travel on?
retinofugal –> optic nerve —> optic chiasm (Crossover occurs) –> to lateral geniculate nucleus of the thalamus — > geniculocalcarine (thalamus to the occipital lobe) — > post-calcarine —- > parietal/, frontal, or temporal lobe
What problem can result from a lesion to the optic nerve?
monocular loss (loss of vision in one eye)
Damage to what area of the brain causes prosopagnosia?
bilateral damage to the inferior region to the calcarine sulcus at the occipital-temporal junction
What Brodmann area is the primary visual cortex?
Brodmann area 17
The ventral pathway, which extends from the occipital lobe into the inferior temporal lobe, is responsible for ______
processing shape, color, and size; it assigns meaning to objects; it is the “what” pathway
The dorsal pathway, which extends from the occipital lobe, is responsible for _____
determining where things are in your environment and detecting and processing motion. It also uses visual input to direct action. It is the “where” pathway
The anterior parts of the eye are ______
pupli, iris, lens, and cornea
Light waves enter the eye through the ______.
pupil
Light waves are refracted or bended by the _____ of the eye
lens
Why does the lens refract light that enters through the pupil?
it refracts it onto the center of the retina
The posterior or back side of the eye is the ____
retina
The retina has these type of cells:
photoreceptors
______ are responsible for detecting shape, size, and brightness.
Rods
______ are responsible for detecting color and fine details.
Cones
Which photoreceptor is not found by the fovea but distributed throughout the retina?
rods
Which photoreceptor is found in the fovea?
cones
What side is the nasal retinal field in the left eye?
the right side
What side is the nasal retinal field in the right eye?
the left side
What side is the temporal retinal field in the left eye?
the left side
What side is the temporal retinal field in the right eye?
the right side
The left visual field will hit which side of the retina?
the right side
The right visual field will hit which side of the retina?
the left side
What is the starting point of the visual pathway?
optic nerves from the retina extending into the optic chiasm.
Most of the optic nerves in the optic tract extend to the ______ and synapse onto ______
lateral geniculate nucleus of the thalalmus; thalamic neurons
What areas of the brain do the optic tract synapse onto?
Thalamic neurons of the lateral geniculate nucleus; midbrain; hypothalamus; superior colliculi
What is a hemianopsia?
loss of half of a visual field in either the right or left eye
What is a quadranopsia?
loss of a quarter of a visual field in either the right or left eye
What does homonymous mean?
when the same visual field is affect in the left and right eye
What does heteronymous mean?
When opposite visual fields are affected in the left and right eye;
Damage to the center of the optic chiasm result in _____
bitemporal or heteronymous hemianopsia
What happens as a result of a bilateral /heteronymous hemianopsia?
the left visual field of the left eye is gone and the right visual field of the right eye is gone.
Damage to the left side of the optic chiasm results in ______
loss of the nasal visual field in the left eye or an ipsilateral left side hemianopsia
Damage to the right side of the optic chiasm results in ______
loss of the nasal visual in the right eye or ipsilateral right side hemianopsia
Damage to the optic tract results in _____
contralateral homonymous hemianopsia
What happens when there’s damage to the right optic tract?
the left eye will lose its temporal visual field and the right eye will lose its nasal visual field. This is called left homonymous hemianopsia
What happens when there’s damage to the left optic tract?
the right eye will lose its temporal visual field.
Damage to the optic radiations will result in _______
contralateral homonymous quandrantanopsia
Unilateral damage to the occipital lobe results in ______
contralateral homonymous hemianopsia with central sparing
Damage to the ventral pathway a.k.a. “where is it?” system results in ______
agnosia
What is associative agnosia?
inability to recognize an item despite seeing it
What is agnosia?
deficit of recognition
What is prosopagnosia?
difficulty recognizing faces
What are the similarities between the visual system and auditory system?
Colliculi and thalamus are involved in each; both are sensory systems; cross over occurs in each system; starting points of both of their pathway is at a sensory organ (i.e., cochlea for the auditory pathway and retina for the visual pathway); both have primary and association areas
What are the differences between the visual system and auditory system?
Superior colliculi and lateral geniculate nucleus are involved in the visual system; inferior colliculi and medial geniculate nucles are involved in the auditory system; two auditory fields are represented in each hemisphere, whereas only one visual field is represented in each hemisphere; cochlea processes frequency and intensity (i.e tonotopy), whereas retina processes colors, shapes, sizes, and movement (i.e. retinotopy)
What is Baum’s loop?
the dorsal bundle or top part of the optic radiations or geniculocalcarine tract) that carries information about the lower visual field; it travels from the LGN to the primary visual cortex.
What is Meyer’s loop?
fibers (i.e., the ventral bundle of the optic radiations (i.e, geniculocalcarine tract)) that carry information from the upper visual field; it travels from the lateral ventricle to the primary visual cortex
For the optic radiations, ______ , or the top, carries lower VF information, allowing us to see items on the bottom.
dorsal
For the optic radiations, _____ or the back, carries upper VF information, allows us to see items on the top.
ventral
A lesion at the optic chiasm results in a _____ problem
heteronymous
A lesion at the optic nerve results in ______
monocular loss
A lesion at the optic tract results in a _____ problem.
homonymous
What causes a homonymous superior quadrantanopsia?
Damage to the optic radiation inferiorly in the temporal lobe a.k.a the temporal Meyer’s loops or the inferior portion of the occipital visual cortex below the calcarine fissue.
What part of the visual pathway is damaged when a person has a superior quadrantanopsia?
Meyer’s Loop (ventral stream)
What part of the visual pathway is damaged when a person has an inferior quandrantanopsia?
Baum’s loop (dorsal stream)
In the geniculocalcarine tract, the ______ sends visual information to the ______
thalamus; occipital lobe
In the retinofugal pathway, light is sent to the ____ when then sends that information to _____ then _____ and then to _____
retina, optic nerve, chiasm, thalamus
What is the geniculocalcarine tract also known as?
optic radiations
The ventral stream is associated with _______
Brodmann area 20 and the primary visual cortex (V1) to the inferior temporal lobe.
V3 in vision is the _____
visual association area
V4 in vision is the area associated with _____
color
V5 in vision is the area associated with _____
movement
What are the two pathways for optic radiations?
Baum’s loop and Meyer’s loop
What are the steps of the geniculocalcarine pathway?
optic tract —- > lateral geniculate nucleus of the thalamus — > through optic radiations via 2 pathways —> to calcarine fissure (a.k.a V1 or primary visual cortex or Brodman area 17)
What is the function of the lateral geniculate nucleus of the thalamus?
sends visual information from both eyes to the occipital lobe via optic radiations
What happens when there is bilateral damage to the posterior occipital lobe (a.k.a BA 17)?
cortical blindness; someone can sense light but cannot process visual information
A person who is not able to recognize line drawings, recognizes objects, draws from memory, and cannot copy has issues with ____
Ventral stream or the what is it system
Damage to what area of the brain causes apperceptive agnosia?
the ventral pathway or what is it system?
What is apperceptive agnosia?
trouble perceiving an item so they cannot recognize it; thus a person cannot copy shapes and line drawings, cannot read letters, and objects appear blurry
What is associative agnosia?
You can recognize objects, but cannot identify them; e.g., you can draw a picture but cannot identify what the picture is
Damage to what part of the brain causes associative agnosia?
inferior occipitotemporal lobe or farther down the ventral stream or the anterior temporal lobe; semantic memory is damaged
The dorsal stream carries information about the ______
Lower part of the visual field
The ventral stream carries information about the ______
Top parts of the visual field
