SENSORY SYSTEMS:
THE VISUAL SYSTEM
MODULE 2: NEUROSCIENCE
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The Auditory System
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The Tactile System
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The Visual System
SECTION OVERVIEW
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WHAT WE KNOW...
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KEY QUESTIONS:
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THE VISUAL CORTEX
Location: Occipital Lobe
Subdivisions: V1-V5, other higher processing areas
Organization: Retinotopic map
Inputs: contralateral
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The Eye and the Retina
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Rods and cones are intermixed in the retina
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PHOTORECEPTORS�Cell types: photoreceptor cells (rods and cones); specialized phototransduction that transforms stimulus (photons) into neural signals which detect brightness, contrast
Rods
Cell Structure: free floating disks within membrane
Function: detect objects under dim light
Cones
Cell Structure: disks continuous with membrane
Function: detect objects under normal light
Types: Longwave, mediumwave, shortwave
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Phototransduction
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VISUAL PROCESSING
Photoreceptors
Optic nerve
Thalamus
From the photoreceptors, the signal moves through the retinal ganglion cells that make up the optic nerve. From there, the signal travels to the thalamus, where it leaves on one of three pathways. The M cells take information about movement, the P cells take information about spatial resolution, and K cells take information about color. After processing, the signal is sent to the temporal lobe or the parietal lobe through the ventral or dorsal streams, respectively.
Visual Cortex
Temporal Lobe/Parietal Lobe
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RESTORING VISION
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Summary/What’s Next
Summary:
Vision processing starts with the photoreceptors in the retina, and follow retinotopic pathways through the optic nerve to the thalamus and then the visual cortex. From the visual cortex, information is sent to the temporal and parietal lobes. Damaged photoreceptors can be replaced by an artificial retina.
What’s next:
Tactile Sensation
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THANKS FOR LISTENING!
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