Exam 1 Flashcards
7 steps of the perceptual process
- Distal Stimulus
- Creation of proximal stimulus
- Receptor processes
- Neural Processing
- Perception
- Recognition
- Action
Principle of transformation
Stimuli are transformed between environment and perception
Principle of representation
Perception is based on representations of stimuli
Transduction
Transformation of environmental energy into electrical energy
Top-down processing
processing that starts with the analyzing of high-level information, such as the knowledge a person brings to the situation
Bottom-up processing
processing that is based on information from receptors
Oblique effect
The eye is better at detecting vertical and horizontal lines rather then oblique and diagonal lines
Psychophysics
Determining how a person’s psychological perception s related to physical stimuli in the environment
Method of limits
experimenter presents multiple sequences of stimuli in ascending and descending order to gauge perception
ex. eye test
Method of adjustment
participant adjusts the stimuli continuously until they can barely detect the stimulus
Method of constant stimuli
experimenter presents five to nine stimuli with different intensities in random order
more accurate but slower
Absolute threshold
minimum stimulus energy needed for an observer to detect the stimulus
Difference threshold
minimum detectable difference between two stimuli
Magnitude estimation
participant assigns numbers to stimuli that are proportional to the subjective magnitude of the stimulus
Resting potential
-70 mV
sodium outside, potassium inside
Threshold of excitation
-55 mV
sodium channels open
depolarization begins
Depolarization (rising phase)
Sodium rushes into the neuron
charge inside rises to +40 mV
Repolarization (falling phase)
Sodium channels close, potassium channels open
charge inside decreases
Hyperpolarization
Charge inside neuron decreases to -75 mV
sodium-potassium pump restores balance
Changing intensity of stimulus affects? (rate or size of reaction?)
rate/ frequency of firing
Absolute refractory period
impossible for the neuron to fire
Relative refractory period
harder for the neuron to fire
When action potentials reach the end of the axon, they release of…?
neurotransmitters
light passes through the ____ and is focused
cornea
light passes through the pupil and is focused again by the lens to form image on the ___
retina
The retina contains these receptors:
rods and cones
Optic nerve
signals flow through the retina to the optic nerve to be conducted in the brain
Accommodation
Lens changes shape to bend light
Cornea vs. Lens
Cornea- rigid, 80% of focus
Lens- flexible, 20% of focus
Presbyopia
“old eye”
Inability of eye to accommodate due to hardening of lens and weakening of ciliary muscles
Myopia
Nearsightedness
inability to see distant objects clearly
Hyperopia
Farsightedness
inability to see near objects clearly
Where are light-sensitive visual pigments found?
outer segments of the rods and cones
What are the two parts of visual pigments?
Ospin and retinal
Isomerization
When the visual pigment molecule absorbs light, retinal changes from bent to straight
How are rods and cones distributed in the fovea?
Only cones
How are rods and cones distributed in the peripheral retina
more rods than cones
Macular degeneration
destroys fovea and surrounding area
retinitis pigmentosa
degeneration of retina that first attacks peripheral rod receptors
Blind spot
area with no rods or cones where the optic nerve is
Dark adaptation
process in which our eyes become gradually more sensitive to light in a dark environment
Rod-cone break
Point where rods become more sensitive to cones
cones reach their maximum sensitivity before rods
visual pigment regeneration
leads to increased sensitivity
retinal eventually breaks off from ospin after changing shape, this bleaches the pigment and makes it no longer useful - retinal must reattach and return to bent shape
cones regenerate more quickly than rods
which photoreceptor is responsible for night vision?
rods
spectral sensitivity
sensitivity to different wavelengths/ different parts of the visual spectrum
rods more sensitive to short wavelengths (blues and greens)
cones more sensitive to longer wavelengths (yellows and reds)
Purkinje shift
at low illumination levels, sensitivity of the eye moves toward shorter wavelengths and blues
reds appear darker
Cones (three types, three one pigments, three spectral sensitivities)
Short, medium, and long
5 layers of neurons in the retina
- Rod and cone receptors
- Horizontal cells
- Bipolar cells
- Amacrine cells
- Ganglion cells
Convergence
when many neurons synapse onto one neuron
Which converges more (rods or cones?)
rods
many foveal cones have “private lines to ganglion cells
Which photoreceptor has better sensitivity
rods (due to convergence)
visual acuity
ability to see details
highest in the fovea
which photoreceptor has better visual acuity
cones (due to less convergence)
What is the optic nerve made up of
axons of the retinal ganglion cells
receptive field
region of the retina that must receive illumination in order to obtain a response from any given fiber
receptive fields overlap
center-surround receptive fields
have an excitatory area and an inhibitory area arrange concentrically, in circles
contributes to edge enhancement
Lateral inhibition
inhibitory signals that travel across the retina
chevreul illusion
in one patch of color, one side when compared to two different colors seems darker even though it is all the same shade
Visual pathway
- retina
- optic nerve
- optic chiasm
- Lateral geniculate nucleus in the thalamus
- primary receiving area in the occipital lobe (striate cortex/v1)
How does the LGN regulate information flow
signal from LGN - cortex is smaller than retina - LGN
LGN also receives signals from cortex so feedback could be involved
Simple cortical cells
excitatory and inhibitory areas are arranged side by side
complex cells
respond best to moving bars of a particular orientation
End-stopped (hypercomplex) cells
fire to moving lines of a specific length or o moving corners or angles
Feature detector
neuron that responds selectively to a specific feature or stimulus
Selective adaptation
when an organism is selectively exposed to one stimulus, resulting in decreased sensitivity to that stimulus
neurons that were firing eventually become fatigued- their firing rate decreases, fire less when the stimulus is immediately presented again
Selective rearing
animals are reared in a special environment containing only certain types of stimuli, resulting in more neurons that respond to those stimuli
more long term than selective adaptation
retinotopic organization
organization of v1
location on the cortex correspond to locations on the retina
cortical magnification
when a disproportionately large area in the cortex is activated by stimulation of a small area on the receptor surface
points in the fovea get more representation in the cortex than points in the periphery
extrastriate cortex
made up of areas in the occipital lobe outside of v1
receptive fields get larger
more complex processing
Ventral pathway
object discrimination
“What” pathway
Dorsal pathway
How or action pathway
inferotemporal cortex
responsible for the perception of complex objects
Double dissociation
Damage to area A in the brain causes function A to be absent while function B is present and vice versa
Fusiform face area (FFA)
part of the inferotemporal cortex with many neurons that respond to faces
Inverse projection problem
challenge of determining the objects and properties in the environment that produced a particular sensory input
The same image on the retina could be produced by a number of different stimuli viewed from different distances or vantage points
Problems in perception
- stimulus in the receptors is ambiguous
- objects can be hidden or blurred
- Objects look different from different viewpoints
occlusion
when one object is partially hidden by another object
viewpoint invariance
ability to recognize an object seen from different viewpoints
Perceptual organization
process by which elements in the environment become perceptually grouped to create our perception of objects
Gestalt approach
emphasizes that the whole is different from the sum of its parts
Apparent movement
illusion of movement that occurs when objects separated in space are presented rapidly, one after another, separated by a brief time interval
ex. stock signs
Gestalt organizing principles
rules that determine how elements in a scene become grouped together
- Good continuation
- Pragnanz
- similarity
- proximity
- Common fate
- Common region
- Uniform connectedness
Good continuation
Lines are seen as straight or smoothly curving
Pragnanz
stimuli are seen in such a way that the resulting structure is as simple as possible
Similarity
Similar elements appear to be grouped together
Proximity
Elements near each other appear to be grouped together
Common fate
elements moving in the same direction appear to be grouped together
Common region
Elements within the same region of space appear to be grouped together
Uniform connectedness
Connected regions of a visual stimulus are grouped together
Figure-ground segregation
perceptual segregation of an object from its background
Border ownership
Figure-ground border appears to belong to the figure
Areas lower in the field of view are more likely to be perceived as the?
(Figure or ground)?
Figure
Areas on the convex side of borders are more likely to be perceived as the?
(Figure or ground)?
Figure
Physical regularities
regularly occurring physical properties of the environment
semantic regularities
characteristics associated with the functions carried out in different types of scenes
