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
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
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
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
- Hypothalamus and pineal gland
- Vestibulocerebellum
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
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
7
Q
Visual field
Measurement of visual field
A
- Perimeter is used (can also measure color vision)
- A small light spot is projected to the inner surface of a hemisphere positioned in front of the head
- The eye examined is in the center of the sphere
- The person examined signals when he/she sees the light spot moved into the visual field
- 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
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
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
10
Q
Spatial vision
A
-
Spatial vision is provided by two fundamental processes
- Only binocular vision
- 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
11
Q
Eye movement
Give the types of eye movement
A
-
Gaze movement
- The animal is able to see the object sharply within the visual field
- Slow, wide range movement
-
Saccadic movement
- Scanning the object
- Fast movement
-
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
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.
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)
- Lateral branch:
-
Formed by medial and lateral bundle
-
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