Perceiving Objects Flashcards
Large lesions of temporal love including amygdala produce this
Psychic Blindness
Gradient flow
closer objects seem to move faster than distant objects
Psychic blindness a syndrome that includes__, responding to visual objects inappropriately
Visual agnosia
The inability to recognize faces is called__
And results from damage to the __ area in the human cortex
Prospagnosia, fusiform facial
Studies using __ show that activity in this area is highest when __ are presented
FMRI, familir
Studies using __ show that cells in a nearby area respond best to __ faces.
(Kobe Bryant)
Electrophysiology, particular
Studies have shown that some cells in the __ area of the monkey cortex respond most strongly to __ stimuli, a feature that helps discriminate a figure from ground-Gestalt theory
V4, Concave
Fusiform face area
Small circle spots within Inferotemporal cortex.
Location
Cells in the V4 of the monkey cortex
-on the border between occipital and temporal lobes
Response
Either to convexity or concavity,
Features which help discriminate figure from ground according to Gestalt Psychology
Ventral pathway
Flows through V2 and eventually into the temporal lobe and is concerned with object identification and color pereception
Kluver bucy Syndrome
-removal of temporal lobe including the amygdala
-psychic blindness, responding to visual stimuli inappropriately, suggesting lack of recognition
Object Agnosia
-removal limited to the lower temporal lobe, sparing the amygdala
-failure on the object discrimination task
Results of the Harrison Ford experiment
High response for FFA= correct recognition
Second highest= seen a face but incorrectly identified it
Lowest response= not seeing a face
FFA shows a selective response to familiar faces rather than all faces, but may not discriminate among equally familiar faces
Results. Of the kobe bryant experiment
-gma cella exist in medial temporal lobe
-single cell recordings in the medial temporal lobe of epileptic patients being preped for electrolytic lesions yo prevent the spread of seizuress
-one cell responded to images of kobe bryant but not other people
-another cell responded to the image of the Golden Gate bridge but not the leaning tower of pisa
-consistent with monkey single cell evidence
Bottom up form perception
-features extracted from the environment by receptors
-combined into more complex representations by the brain and then
-recognized through memory
-reductionist approach to perception
-physiological methods
Primary-dorsal pathway-frontal cortex
Challenges to Bottom up Theory
Illusory contours:non existent edges perceived
Feature detectors can’t detect them
Other processes contribute to perception
Gestalt Theory/ Top-Down perception
Evidence for active form perception
1. Separate stimulus into figure and ground
2. Determine figure using group rules
(Continuation, proximity,similarity,common fate, symmetry, closure)
Different types of cones are stimulated by different__ in the ___ spectrum
Wavelengths, electromagnetic
According to __ theory, there are __ kinds of comes maximally sensitive to __ respectively.
Trichromatic, 3 , blue-green-red
The phenomenon of __ suggests that there are ___ types of color sensitive cells, each of which is influenced by __ pairs of colors, according to the ___ theory
Afterimages, 6, complimentary pairs, opponent processing theory
When light that stimulates cells of one type is turned off, cells of a different type are ___ resulting in the perception of a color that isn’t physically present
Excited
Properties of Light
-Visible light is part of electromagnetic spectrum
-some animals can see energy in other parts of the spectrum(dog/cat/bird)
-it travels in waves
-Blue light= short wave, Red light= long wave, white light= combination of all wave
Additive color mixing
Occurs when new colors are made by the combination of different colored lights
-examples are stage lighting, tv screen, computer
-absorbs light dont emit them
-mixing red blue green( because any color can be matched by mixing them)
-perceived light=mixed wavelength
Subtractive Color Mixing
-what happens when mixing paint (blue and yellow)
-mixing paints w/ different pigments
-additional pigments=fewer wavelengths
-Mixing blue and yellow leads to green
Color matching experiment
Observer adjusts the amount of three wavelengths in one field so it matches the test patch color of the single wavelength in the other field
Trichromatic theory of color vision
-3 types of color receptors with different spectral sensitivities
-short wave=Blue(400nms)
-medium wave=Green(500nms)
-long wave=Red(675nms)
Psychophysical basis of the trichromatic theory
-Issue:Determining # of color receptors without physiological tools
-since people with normal vision need only 3 wavelengths to match all wavelengths in the spectrum
-color vision depends on 3 different receptor mechanism
Physiological Trichromatic Evidence
-color perception is based on the response of the 3 different types of cones
-3 different absorption spectra
-combinations of the responses across all 3 cone types lead to perception of all colors
Psychophysical basis of the opponent processing theory
-people who are color blind to red are aslo color blind to green
-people who are color blind to yellow are also color blind to blue
Opponent processing theory
-after image: a visual image in the complementary colors of the original image
-complementary colors produced gray when mixed together
-Opponent theory: cells make antagonistic responses to pairs of complementary colors (yellow-blue, red-green, black-white)
Cones follow trichromatic theory, cells higher up in the system follow the opponent processing theory
Theories that explain mechanism of retina
Trichromatic theory explains the responses of the cones in the retina
Theory that explains mechanism of cells connected to cones
Opponent process theory explains neural response for cells connected to the comes further in the brain
Theory that explain after images
Opponent disinihibition
Some info about depth or distance can be detected by using only one eye. These include ___ cues which allow us yo perceive three dimensions on surfaces with __ dimensons
Pictorial cues, two
Among such cues are __ which causes us yo see objects which cover other objects as __ to us.
Occlusion, closer
In addition, objects appear to be relatively far away if they are __ in our field of view.
Higher
Other types of monocular depth cues include __ which causes objects that are closer to us to move ___ than those that are father away
Motion parallax, faster
Finally ___ cues which depend in eye muscle feelings include ___ when the eyes turn in, the closer an object is and __ during which our lens muscles tighten to fixate objects that are close to us
Oculomotor cues, convergence, accomodation
Cue Approach to Depth Perception
Our visual systems create the 3D world using our 2D retina
Image shows the equivalence of size of objects @ different distances from the retina.
Everything along this cone projects the same size image onto a flat retina
Visual system must then determine relative size and distance
Convergence
Eye muscles turn eyes in the closer the object is to eyes the greater convergence
Accommodation
Lens muscles tighten to curve lens for close fixation
Oculomotor Cue Summary
-Convergence
-Accommodation
-Muscle sensations provide distance cues
-Convergence Sensations> Accommodation( C contributes more than A but A is important in an environment that depends upon reading for communication)
Why is depth perception important
Stops us from falling or bumping into things.
Monocular Distance Cues
-Familiar Size
-Persoective convergence
-texture gradient
-atmospheric persepctive
-occlusion
-relative height
-light and shadow
Familiar Size
-similar objects that are larger seem closer together than those that are smaller (
Texture gradient
Increasing fineness of texture as distance increases enhances the perception of depth
Atmospheric Perspective
Pictures of fog and a mountain (mountains become less sharp with increasing distance, because they are more particles in the atmosphere between the observer and them)
Retinal Explanation of Motion Parallax
As you move, objects closer to you appear to move faster, whereas objects father away appear to move slower. This is because the closer objects move a greater amount on your retinae from time 1 to Time 2 than do the more distant onjects
Motion Parallax
Objects that are closer to us move across the retinal more rapidly and in the opposite direction from us. Objects that are father away move more slowly across the retina and in the same same direction as we do
Deletion and Accretion
Objects are covered or uncovered as we move relative to them
-covering an object is deletion
-uncovering an object is accretion
(Moving across the room diff students are accreted and deleted from sight)
Movement produced distant cues
Motion parallax
Deletion and accretion
Visual illusions based on failed distance curs
Ponzo illuson
Muller-lyee illusion
-when distance cues are unexpected, we see illusions
Distance illusion summary
Ponzo illusion violates linear persoective
Muller violates 3 dimensional distance rule
Focus of expansion
the point in an optic flow display from which perceived motion arises (global optic flow)
Global Optic Flow
-if the entire array moves, then the observer is moving
-objects get bigger as they approach us
(global optic flow)
explanation of global optic flow
if you are moving, the background moves around you. As we move in one direction, objects appear to get bigger as they approach us.
-this being a cue for depth it also indicates motion
-close objects move more quickly than objects in the distance(length of arrows)
-the horizon is the point at the gradient of flow comes to zero
Neural Explanations of Motion Perception
-retinal information
-the corollary discharge model
-brain mechanisms
Retinal information for Motion Perception
Reichardt circuits
-results in neurons that fire to motion in one direction
-movement in one direction:excitation
-movement in other direction:inhibition
-detect motion when the eye is stationary
Smooth pursuit eye movements
used of tract objects that are moving in the environment
-following a tennis ball
Saccades
jumpy eye movements used to read books and prevent adaption , bleaching of stimulated spots on the retina
3 saccades per second- when not engaged in smooth pursuit
plan these and do not perceive while we are making them
-reading a book
The Corollary Discharge Model
-movement is not perceived when a comparator in the brain receives
-a movement signal from the retina and a movement signal from the eye muscles (motor signal)
The Lateral Interparietal Area and Saccade Planning
-Monkey is trained to move eyes to an area
-after a target has disappeared
-cells in the LIP fire just before the move is made
-May be involved in corollary discharge
–site of comparator is somewhere in the brain, but we don’t know where
Motion Perception and the Brain
-non human primate evidence:medial temporal cortex and motion coherence
-Human evidence: the superior temporal sulcus and biological motion perception
Medial temporal area
MT aka V5 is anterior in the occipital lobe, located just above the temporal lobe. The map also shows motion-sensitive areas in the parietal lobe.
Motion Coherence experiment
-coherence of movement of dot patterns was varied
-monkeys were taught to judge direction of dot movement during MT neuron recording
-As coherence of dot movement increased
-so did the MT neuron firing and
-the judgement of movement accuracy
Biological motion study
Participants viewed point light stimuli for activities
-Task was to determine whether motion was biological or scrambled
noise was added to dots so they could only achieve 71% accuracy
transcranial magnetic stimulation applied to STS caused a decrease in ability to detect biological motion
Functions of Motion Perception
-interacting with the environment(crossing street)
-Attracting attention(attracting mates/ waving)
-perceiving objects(distinguish figure from background)
Interacting w/ the environment
Akinetopsia: blindness to motion
(found in a women with a stroke in the superior temporal lobe)
-couldn’t fill a glass with water or gauge how quickly a car was coming towards
Attracting Attention
-predators use movement of prey as primary means of location in hunting
-Attentions Capture:motion attracts attention to the moving object
-freezing:lack of motion seen in many secies to avoid predation
-mating displays:movement designed to attract a mate
Perceiving Objects
-movement of objects or the observers movement through objects
(biological motion and point walker display)
Types of Motion Perception
-real motion: an object is phsycially moving
-illusory motion:
-apparent movement:stationary stimuli are presented in slightly different locations
(basis of movement in movies and tv)
Psychological explantions of real movement perception
-J.J Gibsons ecological approach
-affordance
-global optic flow
JJ Gibsons ecological approach
-how motion is perceived in everyday life
-perception is determined by function, not just visual characteristics
-goal of motion perception is ot help guide our own action
Affordance
-info in the visual world that specifies how objects can be used
-functions rives perception
-applies to both moving and stationary objects that affect our actions
example: a laser pointer affords play for a kitten
what are the ways in which movement perception is crucial for survival in most species?
Motion aids object identification, aids interaction with the environment
what is motion coherence? what non human primate study provides a possible physiological basis for perception of it?
Displays of dots moving in same directions=motion coherence,
monkey were taught to judge direction of dot movement by pushing on lever to get food. WHen motion coherence detected, neurons from parietal lobe fired.
According to the corollary discharge theory what mechanism prevents us from perceiving that the world moves when we move our eyes?
Comparator neuron compares a motor command from the eye with a change in the visual field
What is the optic array?How does it allow us to distinguish our own movements from environmental movement?
Optic array is a change in the visual world resulting from you moving environment. Allows us distinguish because everything moving means we are moving creating this perception
What is biological motion? what is a possible physiological basis for it?
- a light point experiment, perceived bodily movement from looking at lights.
- disrupted by adding noise and magnetic stimulation caused disruption of the superior temporal interferes w the perception of biological motion
When. sound waves reach the __membrane at the end of the auditory canal, it __ as a resultt.
tympanic, vibrates
The frequency of this activity ultimately determines which __ cells on the __ membrane of the __ in the inner ear are maximally stimulated.
hair, basilar, cochlea.
Maximum stimulation for low tones occur at the __ and those for higher tones @ the __ of the membrane respectively.
Apex, base
When damage to the __ cells causes sensorineural deafness,electrodes in cochlear implants can bypass these cells and stimulate the __ directly
hair, auditory nerve
Speech production is best in deaf children given these implants __ the age of years
before
What is the physical difference between pure tones and most of the sounds we hear?
Human beings don’t produce true tones pure tones are sounds that have single frequency and in the shape of sound-wave.
Most sounds we make do not have single frequencies waves and not in the shape of sound=complex sounds
Why are sound amplitudes specified in decibels rather than sound wave heights?
Used to compact a wide range of amplitudes into a mathematically useful scale, easier to manipulate and measure.
How does the audibility curve explain why you lose bass notes first when you turn down the volume on your stereo?
Lower bass notes frequency has higher absolute threshold than higher note frequencies curve plot frequencies vs decibels necessary to detect them
What is health reason for avoiding parties with loud music?
Can permanently damage which kills hair cells
