Download Eye to cortex

Vision is more than what we see.
Karl
Lashley
American Psychologist
1890-1958
Memory storage
Migraine Headaches
Migraine alters Vision
KW p.278
Lashley’s Migraine
Sensation and Perception
• Sensation
– a process by which our sensory receptors
and nervous system receive and represent
stimulus energy
• Perception
– a process of organizing and interpreting
sensory information, enabling us to
recognize meaningful objects and events
Perception at Work
Bill or Monica?
Eye as Camera
KW 8-3
Eye Structures
Figure 6.2 Cross section of the vertebrate eye
Note how an object in the visual field produces an inverted image on the retina.
Visual Coding and Retinal Receptors
The Eye and Its Connections to the Brain
Pupil-opening in the center of the eye that allows light to
pass through
Lens-focuses the light on the retina
Retina-back surface of the eye that contains the
photoreceptors
The Fovea-point of central focus on the retina
blind spot-the point where the optic nerve leaves the eye
Visual Coding and Retinal Receptors
Transduction-the conversion of physical energy to an
electrochemical pattern in the neurons
Coding- one-to-one correspondence between some aspect of
the physical stimulus and some aspect of the nervous
system activity
Visual Spectrum
KW 8-2
Retina
KW 8-5
Optic Nerve Exits
Figure 6.4 Visual path within the eyeball
The receptors send their messages to bipolar and horizontal cells,
which in turn send messages to the amacrine and ganglion cells. The
axons of the ganglion cells loop together to exit the eye at the blind
spot. They form the optic nerve, which continues to the brain.
Locating Blindspot
KW 8-4
Rods and Cones
KW 8-6
Visual Receptors: Rods and Cones
Rods
abundant in the periphery of
the retina
best for low light conditions
see black/white and shades of
gray
Night time
Cones
abundant around fovea
best for bright light conditions
see color
Day time
Three Cones = Color Vision
KW 8-7
Afterimages
KW 8-36
Stare a box for 30 seconds
a
Lateral
Inhibition
Rods at work
Figure 6.18 An illustration of lateral inhibition
Do you see dark diamonds at the “crossroads”?
Lateral
Inhibition
Figure 6.18 An illustration of lateral inhibition
Do you see dark diamonds at the “crossroads”?
Convergence
Retinal Circuits
Retinal Layers
Amacrine Bipolar
(Blue)
KW 8-9
(Purple)
Visual
Pathway
KW 8-11
Retina to Thalamus
An Overview of Visual System
Rods and Cones synapse to bipolar cells
Bipolar cells synapse to ganglion cells
Axons of the ganglion cells leave the back of the eye
The inside half of the axons of each eye cross over in the optic
chiasm
Pass through the lateral geniculate nucleus
Optic
Nerve
to
LGN
Nasal Fibers
KW 8-15
Temporal Fibers
LGN
KW 8-10
LGN and Superior Colliculus
KW 8-12
Striate (Primary) Cortex
KW 8-13
Cell Bodies in Striate
KW 8-13
Visual
Fields
KW 8-20
Fovea
on
Cortex
KW 8-22