- Vision gives us information about where our bodies are in space, about the relation of one body part to another, and
about the motion of our bodies.
- Visual Proprioception: gives us information about the environment but also about our own body.
Peripheral Visual System
LIGHT CORNEA LENS RETINA
- Two types of photoreceptor cells
o Rods: vision at night, when amount of light is very low and too weak to activate the cones
o Cones: Normal day light and responsible for color vision
- Fovea: where light is at its clearest form
- The blind spot where there are no photo receptors cells is where the optic nerve leaves the retina.
- Sensory differentiation is key part of motor control, meaning the visual system has to identify and determine if they
- Object Identification and Motion sense are processed through two separate pathways.
Central Visual Pathways
- Left half of the visual field projects on the medial half of the retina of the left eye and the lateral half of the retina of
the right eye.
- Right visual field projects on the medial half of the retina of the right eye and the lateral half of the retina of the left
- Optic Disk: is the point where the optic nerves from left and right eyes leave the retina
- Optic Chiasm: where the nerves from eye come together and the medial side of the eye cross while the lateral side do
- Optic tract: is the point where the optic nerves become the tract after the chiasm.
LATERAL GENICULATE NUCLEUS
- Only 10-20% of inputs from retina come into the LGN, rest goes into the cortex and
- Target of cells in the optic tract of the thalamus.
- Six layers which map contralateral visual field, these projection cells of each layer send axons to the visual cortex
o Magnocellular, most ventral, first two
o Parvocellular, last four
- Magnocellular layers, involved in the analysis of movement of visual image and coarse detail of an object, no
response to color
o more important in motor function such as balance
- Parvocellular layers, function in color vision and more detailed structural analysis.
o more important in the final phase of reaching for an object, where we need to grasp it accurately SUPERIOR COLLICULUS
- Located posterior to the thalamus in the roof of the midbrain.
o Maps the visual space around us in terms of visual, auditory, somatosensory cues.
o Mapped in terms of relationship to the retina.
- When a friend greets you as they bicyc