Transcript Sensation and Perception

The Eye
Energy v. Chemical senses
Energy Senses
Chemical Senses
Transduction
• Transforming stimulus
energy (signals) into neural
impulses.
• Each sense has its own
process of transduction
• Information goes from the
senses to the thalamus ,
then to the various areas in
the brain.
Example:
Remember Ethan in Sky
High. He changes his body
to slime. Solid form to
liquid form. Change from
one form of energy to
another. Click the picture
to watch power placement.
Vision
• Our most dominating
sense.
• Visual Capture
Phase One: Gathering Light
The Stimulus Input: Light Energy
• Wavelength – distance
from one wave to the
next
• Determines hue (color)
Phase One: Gathering Light
HUE
• The length of the wave gives us it’s hue (color).
• ROY G BIV
• Example:
The Physical Property of
Waves
Intensity
•The amount of energy in a light wave, determined by
amplitude or height
•Height of a wave gives us it’s intensity (brightness).
•Example:
Phase Two: Getting the light in
the eye
The Eye
Cornea – protects the eye and bends light to provide focus
Pupil – small adjustable opening in the center of the eye
which light enters
 Dilation of the pupil allows more light to reach the periphery of the
retina where the rods are located
Iris – ring of muscle tissue that controls the size of the
pupil opening
Lens – transparent structure that focuses light onto the
retina
 Accomodation - process by which the lens changes shape (curvature
and thickness) to focus near or far images on the retina
Retina – light sensitive, inner membrane of the eye
containing rods and cones where the process of
transduction occurs
• Rods - receptor cells
–
–
–
–
Retina
Black, white, gray sensitive
Peripheral vision
Twilight vision
Most light sensitive
• Cones – receptor cells
– Color sensitive – distinguish different wavelengths of
light
– central vision
– Daylight, well-lit
– Fine detail
– Less sensitive to Dim light
• Fovea - central focal point in the retina
– Central vision
– Cones
– Fine detail
The Retina
• Rods and Cones
Cones
Rods
Rods versus Cones
Optic Nerve
• Optic Nerve – nerve
that carries neural
impulses from the
eye to the brain
• Blind Spot – point at
which optic nerve
leaves the eye
– Blind spot = no
receptor cells
Example:
Phase III: Transduction
Overview: cornea, iris, pupil, lens, retina,
optic nerve, thalamus, occipital lobe,
visual cortex, feature detector cells.
Transduction
1. Rods and Cones convert light energy to electro
chemical neural impulses = transduction
2. Rods and cons synapse with neurons called
bipolar cells located in the retina
–
–
Cones hotline to the brain
Direct link between single cone to bipolar preserves fine
detail of cones message
3. Bipolar Cells transmit to ganglion cells (another
type of neuron) whose axons form the Optic
Nerve)
4. 1/2 axons in optic nerve crisscross (called optic
chasm) sending impulses to opposite side of
brain
Visual Problems
• Farsighted – cornea too
flat or distance from
cornea to retina too short
• Nearsighted – cornea too
curved or distance from
cornea to retina too long
• Astigmatism – irregularly
shaped cornea (like a
football instead of a
baseball
Phase IV: In the Brain
• Thalamus to Occipital lobe to
Visual Cortex to…
Example: Feature Detector
cells – allow you to see the
lines, motion, curves and
other features of this
turkey.
• Feature Detectors –nerves
cells in the brain that respond
to specific features – line,
curve, shape color
Example:
• Supercell clusters – teams of
cells that fire in response to
complex patterns
Example:
Parallel Processing
Parallel Processing – brain simultaneously
process stimulus elements
Example:
Blindsight – localized area of blindness in
part of their field of vision caused by damage
to visual cortex
Example:
Color Vision
Two Major Theories
Trichromatic Theory
Three types of cones:
• Red
• Blue
• Green
• These three types of
cones can make millions
of combinations of
colors.
• Does not explain
afterimages or color
blindness well.
Opponent-Process theory
The sensory receptors
come in pairs.
• Red/Green
• Yellow/Blue
• Black/White
• If one color is
stimulated, the
other is inhibited.
• Example:
Afterimages