PSYC100 Study Guide - Midterm Guide: Fluid And Crystallized Intelligence, Mental Age, Neural Coding
31 May 2018
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14 Vision: From Eye to Brain
pages 182-185
· What are receptor cells? What is an adequate stimulus?
o Receptor cells are cells that are able to respond to external stimulus and transmit a signal to
a sensory nerve. (rods and cones)
§ Rods: Respond to low levels of light and are responsible for night vision. Poor at fine detail
§ Cones: Less sensitive to low levels of light. Responsible for vision under brighter conditions
and for seeing both color and detail
o Adequate stimulus: A stimulus to which a particular receptor responds effectively and gives
rise to a sensation
· What is the pathway of information from retina to brain (all the way to what/where
regions) regarding the detection of a light stimulus? Know the points of cross-over of
information, as well as pathways that maintain information about which visual field a
stimulus was in.
o Retina (rods and cones)àGanglion cells (first neurons in the visual pathway)àSend signals
along their axons from the eye to the ThalamusàGathered into a bundle (the optic nerve)àexits
at the back of the retinaàoptic chiasm (where half of the axons cross. This information causes
left side of visual space to be projected to right hemisphere of brain and vice versa)àReaches
visual area of the thalamusàprimary visual cortex (processed)
o Ventral stream: (lower) specialized for perception and recognition of objects
o Dorsal stream: (upper) specialized for spatial perception (where an object is and relating it to
other objects)
· Know the layers of cells in the retina, and what the rods and cones do.
o 1. Choroid: Supply oxygen and nutrients to retina
o 2. Pigment epithelium: Provide nutrition and waste removal for photoreceptor cells
o 3. Photoreceptors: Rods and cones that convert light into electrical signals
o 4. Horizontal cells: Help integrate and regulate the input from multiple photoreceptors
o 5. Bipolar cells: Takes electrical information from photoreceptor cells and pass it along to
other retinal cells
o 6. Ganglion cells: Extend to form an optic nerve that conveys information to the brain and
processes information from bipolar cells
o Rods: Respond to low levels of light and are responsible for night vision. Poor at fine detail
o Cones: Less sensitive to low levels of light. Responsible for vision under brighter conditions
and for seeing both color and detail
· Understand how a neural network can give rise to a receptive field – a single cell
giving a response to a stimulus occurring in a particular region of the visual field. What
is the difference in firing patterns for a center-on surround-off versus a center-off
surround-on neuron?
○ ON center/OFF surround cell: Flashing small bright spot in the center sub region
increases the cell's response. Flashing a bright annulus in the surround sub region
inhibits the cell's response. There is little or no response to a large (full field) spot of
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light that covers both the center and the surround because excitation in the center
cancels the inhibition from the surround, called lateral inhibition.
○ OFF center/ON-surround ganglion cell: has the opposite arrangement. It gets inhibition
from a small spot of light in the center, and excitation from an annulus in the surround.
15 Vision: Perception of Color, Shape, and Form
pages 186-190
· According to the trichromatic theory of color vision, how do we detect and interpret
colors?
o Color vision results from activity in three different types of cones which are sensitive to
different wavelengths
o One is sensitive to short wavelengths (blue-violet light)
o One is most sensitive to medium wavelengths (yellow-green light)
o One is most sensitive to long wavelengths (red-orange light)
o Called the SML cones
· How does the trichromatic theory of color vision explain many forms of color
blindness?
o Two main types of blindness determined by the relative activity among the three types of
cone receptors
o Not blind just see partial colors
o May be missing the photo pigment sensitive to either medium or long wavelengths
§ Resulting in red-green colorblindness
o May be missing the short-wavelength photo pigment
§ Resulting in blue-yellow colorblindness
· What is color constancy? How does color constancy help us to achieve a stable
percept of the world around us?
o Color constancy: The tendency for a color to look the same under widely different viewing
conditions
§ Brain computes local rations of cone activity
o Opponent-process theory: Red and green are opponent colors, as are blue and yellow. When
we stare at red, we see green afterimage,. When we stare at green, we see red afterimage.
Blue-yellow, yellow-blue.
· What explains our differing percepts of the color of the dress (blue/black vs
white/gold) or the show (pink/white vs grey/teal)?
o The way the light hits the dress in the photo, and the time of day that someone is viewing it
makes us perceive it differently
· What is object constancy? How does object constancy help us to achieve a stable
percept of the world around us?
o Object constancy: Correctly perceiving objects as constant in their shape, size, color, and
lightness, despite raw sensory data that could mislead perception
o We cannot make ourselves not see illusions, even when we know they are not true
representations of objects or events. These constancies enable us to see a stable world and
perceptual illusions that we cannot control
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Document Summary
14 vision: from eye to brain pages 182-185. What is an adequate stimulus: receptor cells are cells that are able to respond to external stimulus and transmit a signal to a sensory nerve. (rods and cones) Rods: respond to low levels of light and are responsible for night vision. Cones: less sensitive to low levels of light. Responsible for vision under brighter conditions and for seeing both color and detail: adequate stimulus: a stimulus to which a particular receptor responds effectively and gives rise to a sensation. Know the layers of cells in the retina, and what the rods and cones do: 1. Choroid: supply oxygen and nutrients to retina: 2. Pigment epithelium: provide nutrition and waste removal for photoreceptor cells: 3. Photoreceptors: rods and cones that convert light into electrical signals: 4. Horizontal cells: help integrate and regulate the input from multiple photoreceptors: 5.
