Vision is more than what we see Karl

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

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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