Topic 110 - Object viewing, visual acuity, visual field, visual pathway  Flashcards

Object viewing, visual acuity, visual field, visual pathway 

1
Q

Words to include in visual field

A
  • Monocualr visual field
    • Preys
    • Spatial vision (less accurate)
  • Binocular visual field
    • Predators
    • Primates
  • Measurement of visual field
    • Perimeter
    • Hemisphere
    • Center of the sphere
  • Spatial vision
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2
Q

Words to include in visual acuity

A
  • Sharpness of vision
  • Minimal visual angle
  • Anatomical mosaic of retina
  • Functional mosaic of retina
    • Antagonizing system of the receptive fileds
  • Chromatic aberration
  • Difraction
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3
Q

Words to include in object viewing

A
  • Eye movement
    • Gaze movement
    • Saccadic movement
      • Scanning the object
    • The third eye movement
      • Fixation of an object
      • Small translocation
  • Pupil reflex
    • Ampleness of the pupil
    • Smooth muscles
    • Sphinter muscles
      • Constricting the pupil
      • Parasympathetic nerves
    • Dilator muscles
      • Dilating the pupil
      • Sympathetic nerves
    • Reflex mechanism
      • Diameter of pupil
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4
Q

Words to include in visual pathway

A
  • Decussation in the optic chiasm
  • Axons of the retinal ganglion cells
  • Lateral geniculate body
  • Primary visual cortex
  • Temporal part of visual field
  • Nasal part of visual field
  • Dorsal part of visual field
  • Ventral part of visual field
  • Visual cortex
  • Retina
  • N. opitcus
  • Optic tract

  • ​Visual reflexes
    • Pupil reflex
    • Accommodation
    • Convergence
  • Pretectum
    • ​Pretectal area
    • Midbrain structure
    • Subcortical visual system
    • Pupillary light reflex
    • Optokinetic reflex
    • Temporary changes to the circadian rhythm
  • Superior colliculus
    • Tracts from the visual cortex (innervates superior colliculus)
    • Integrator of saccadical eye movement
    • Localization
  • Lateral geniculate nucleus (LGN)
    • Thalamus
    • Relay station
    • Mangocellular part
      • M-type ganglion cells of the retina
    • Parvocellular part
      • P-type ganglion cells of the retina
    • Afferents
      • Sensory cortex
      • Thalamus
      • Brainstem
    • Filter
      • Non-retinal afferents
    • Retinal stimuli
      • ​Higher cortical areas (ø)
  • Optic radiation
    • Occipital lobe
    • Visual cortex
  • Primary visual cortex
    • (Brodman’s 17)
    • Occipital lobe (medial and caudal)
    • Ocular dominance
      • ​Striated cortex
    • Neuronal columns
    • Cylinders
  • Circadian rhythm
    • Hypothalamus and pineal gland
      • Suprachiasmatic nucleus
  • Vestibulocerebellum
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5
Q

Visual field

Define visual field

A
  • Visual field: Fy fixed gaze the animal sees only a part of the surrounding space
  • The sized of visual field differes for each color
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6
Q

Visual field

Types

A
  • Monocular vision
    • ​Spatial vision is less accurate, but the animal senses almost all the surrounding space by the eyes without moving the head
    • Preys
  • Binocular vision
    • Controls a limited part of space but the accuracy of spatial vision is very high
    • Predators
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7
Q

Visual field

Measurement of visual field

A
  • Perimeter is used (can also measure color vision)
  1. A small light spot is projected to the inner surface of a hemisphere positioned in front of the head
  2. The eye examined is in the center of the sphere
  3. The person examined signals when he/she sees the light spot moved into the visual field
  4. Using different colors in different experiment, the edges of the visual field can be examined
  • Visal field is smallest for red, and largest for white
  • Nasal visual field is smaller than temporal visual field
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8
Q

Visual acuity

Define visual acuity

A
  • Visual acuity: Sharpness of vision (visual acuity) is the smallest angle under which two neghboring object-point will be still sensed as two distinguishable points
    • Minimal visual angle
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9
Q

Visual acuity

What is the sharpness of vision determined by?

A

By the anatomical and functional mosaic of the retina

  • Functional mosaic of retina: the vision of object is modified by the antagonizing system of the receptive fields
    • Several cones react together in the receptive field
  • Anatomical mosaic of retina: light beams coming from the two neighboring object-points do not hit cones next to each other in the fovea
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10
Q

Spatial vision

A
  • Spatial vision is provided by two fundamental processes
    1. Only binocular vision
    2. Both monocular and binocular vision
  • Nearly perfect spatial vision is assured by:
    • Light intensity
    • Color and black-and-white contrasts
    • Head movements
    • Movement of objects relative to each other
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11
Q

Eye movement

Give the types of eye movement

A
  1. Gaze movement
    • ​The animal is able to see the object sharply within the visual field
    • Slow, wide range movement
  2. Saccadic movement
    • Scanning the object​​
    • Fast movement
  3. The thrid eye movement
    • ​​Occuring with fixation of an object
    • Fast, with small translocation (drift)
  • In some species (dogs) the eyes can move in a large range
  • In other species (cat) the eyes cannot move as much, so the neck muscles play a role in looking at the object of interest
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12
Q

Pupil reflex

A
  • The amount of light entering into the eyes is determined by the ampleness of the pupil, which is regulated by smooth muscles
  • The muscle constricting the pupil (sphincter muscle) is innervated by parasympathetic nerves
    • ​Mydriasis
  • The muscle dilating the pupil (dilator muslce) is regulated by sympathetic nerves
  • The diameter of the pupil is controlled by several reflex mechanisms
    • Throwing light into one eye elicits the constriction of the pupil, and at the same time a similar reaction is seen in the other eye.
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13
Q

Visual pathway

A
  • After decussation in the optic chiasm the axon of the retinal ganglion cells project to the lateral geniculate body, from where the next fibers reach the primary visual cortex
  • The primary visual area (Brodmann’s area 17) projects to further brain regions
  • Retina:
    • The temporal visual field and nasal visual field project to the opposite sides of the retina
    • The dorsal and ventral parts of visual field are reversed in the same way
    • The same mapping occurs in the visual cortex and retina
  • Optic nerve:
    • Fibers of n. opticus originating from the same quartes of retina run together
  • Optic tract:
    • Formed by medial and lateral bundle
      • Lateral branch:
        • Towards lateral geniculate body
        • Perception of visual information
      • Medial branch:
        • Towards pretectum, superior colliculus
        • Visual reflexes (pupil reflex, accommodation, convergence)
  • Pretectum:
    • Midbrain structure
    • Involved in mediating behavioral responses to acute changes in ambient light such as:
      • Pupillary light reflex
      • Optokinetic reflex
      • Temporal changest to the circadian rhythm
  • Superiro colliculus:
    • Innervated by tracts from the visual cortex
    • Integrator of accadical eye movement
    • Main function: localization of an object
  • Lateral Geniculate Nucleus (LGN)
    • Part of thalamus
    • Important relay station
    • Function: filter which, depending on the non-retinal afferents, does not let certain parts of the retinal stimuli pass to the higher cortical areas
    • Fibers of the LGN radiate to the primary visual cortex (Brodman’s area 17)
      • Location: medial and caudal regions of the occipital lobe
  • Optic radiation:
    • In the medial part of the occipital lobe, the information is transmitted to the visual cortex via radiation
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