Lecture 44 - Vision Flashcards
Vision
A dynamic, interactive process of motor and sensory function mediated by the eyes for the purpose of simultaneous organization of posture, movement, spatial orientation, manipulation of the environment and to its highest degree perception and thought
What are the 3 optical components of the eye
- Cornea
- Lens
- Iris
The cornea and the lens
Refract light to focus image on the retina
Iris
Controls the amount of light that enters the eye
The 2 neural components of the eye are the
- Retina
- Optic Nerve
Fovea
Sharpest central vision and contains only cones
Optic disc
The blind spot of the eye where no photoreceptors are (where optic nerve is)
The 2 photoreceptors of the eye are
- Rods
- Cones
Rods
Night vision and dim light and low resolution and converge onto single ganglion cell
Cones
Bright light and provide color and high resolution detail
What are the 3 types of cones
- Red
- Green
- Blue
Color blindness
When a person lacks a certain type of cones
What are the visual pigments in rods and cones
Rods: Rhodopsin
Cones: Iodopsin
T or F: The eye has both monocular and binocular visual field
T
eye teaming
It is binocular vision -> ability to use info from both sides at once
Binocular vision is important for
depth perception (stereopsis)
What disorders can impair binocular vision
Cranial nerve palsy, eye injury, cataracts, strabismus (abnormal eye alignment)
Describe the pathway of the visual field back to the cortex
Describe retinotopy and somatotopy (vision)
Areas of left and right visual field are represented in specific areas on the retina which align with the somatotopy of the visual cortex
T or F: Visual pathway do stop at the primary visual cortex
F, they dont
T or F: The left visual hemifield is picked up by left nasal retina and right temporal retina
T
Visual Processing
Accurate input of visual info and integration of sensory and proprioceptive info that influences and guides motor output
Visual acuity
How clearly we see things
Focal/Parvocellular Vision
Detailed (What is it)
Spatial/Magnocellular Vision
Big picture (Where is it)
Focal System 5 Characteristics
- What is tested during eye exam
- Detailed
- Colour vision
- Sensitive to high contrast (detailed stimuli)
- Transmits more slowly
Spatial System 5 characteristics
- Responds rapidly
- Sensitive to large contours, lower contrast stimuli
- Not good for detail
- More distributed in periphery of retina
- Large impact on balance/posture and function
T or F: We need to be able to switch back and forth between the focal and spatial system
T
What can affect the switch back between focal and spatial system and symptoms
- Neurological events -> stroke, concussion
- Lesions
Symptoms: Headaches, blurred vision, memory and balance impairments
Bimodal processing occurs in the
Ventral and dorsal streams
Dorsal Stream
Primary visual cortex along posterior parietal lobe (Spatial system: Where is it?)
Ventral Stream
Primary visual cortex along posterior temporal lobe (Focal system: What is it?)
What are 3 common lesions that affect dorsal stream and describe them
- Visual neglect: Inattention to stimuli in visual field opposite to side of lesion
- Optic Ataxia: Poor accuracy with visual guided movement
- Motion Blindness: Can see objects at rest, but not when object is moving
What are 3 common lesions that affect ventral stream and describe them
- Prosopagnosia: Cannot recognize people’s faces
- Object agnosia: Cannot recognize object
- Cortical Colour Blindness: Cannot recognize colour
