Term
| What are the 8 stages of the perceptual process? |
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Definition
1. The environmental stimulus
2. The attended stimulus
3. Stimulus on the receptors
4. Transduction
5. Neural processing
6. Perception
7. Recognition
8. Action
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Term
| What is the difference between the psychophysical and physiological levels of perception? |
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Definition
The psychophysical level is:
The relationship between stimulus & perception
The physiological level is:
The relationship between stimulus & physiology, and the relationship between perception & physiology. |
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Term
[more on the 'psychophysical level']
What are the 5 ways the perceptual level can be measured? |
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Definition
1. The phenomenological method, or description method, the experimenter simply asks the subject to report his perception.
2. Recognition: involves correct identification or categorization
E.g. It’s a beetle!
3. Search: The process of finding a particular stimulus (target) among other stimuli (noise).
(Psychophysicists love to measure the time it takes to do that (note: reaction time increases with noise).)
4. Detection: Identifying the smallest possible amount of stimulus energy necessary for detection to occur (absolute threshold).
method of adjustment, method of limits, method of constant stimuli, method of limits, method of constant stimuli.
5. Magnitude Estimation: If we double the intensity of a stimulus, do we perceive it twice as strong? |
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Term
| Our brain has a modular organization -- what are the modules (or parts) involved in perception? |
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Definition
Occipital (vision)
Temporal (hearing)
Parietal (touch) |
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Term
| What are two ways in which light behaves? |
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Definition
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Term
| What is the spectrum of light called? |
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Definition
The electromagnetic spectrum.
Visible light ranges from 400 - 700nm. |
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Term
| What are the three main parts of the brain associated with vision? |
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Definition
The lateral geniculate nucleus (dLGN).
The primary visual cortex (V1; striate).
The extrastriate cortex (higher visual areas). |
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Term
What are the 4 types of retinal cells?
(and which are considered "horizontal"?) |
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Definition
Amacrine, bipolar, horizontal and ganglion cells.
(Amacrine and horizontal cells are "horizontal"). |
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Term
| How does Transduction work? |
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Definition
Transduction occurs as light hits the outer segments of our photoreceptors.
These outer segments are made of stacked disks containing visual pigment molecules.
These molecules have two components:
A large protein called opsin
A small light-sensitive molecule called retinal
When a photon of light hits the retinal molecule, the visual pigment molecule changes its shape:
Opsin and retinal become separated, isomerizing a single visual pigment molecule which triggers an enzyme cascade.
Thousands of chemical reactions which in turn trigger thousands more.
The final results is an action potential in the ganglion cell leaving the eye via the optic nerve. |
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Term
| What is pigment bleaching? |
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Definition
After isomeration and transduction, retinal detaches itself from opsin.
This causes pigment bleaching: the retina takes on a lighter color.
Before the visual pigment can repeat the process, opsin and retinal must be reunited.
Cone pigments regenerate in 6 mins.
Rod pigments regenerates in 30 mins.
In both cases, the rate of pigment regeneration matches the rate of dark adaptation! |
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Term
| How can we test for spectral sensitivity of cones and rods separately? |
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Definition
To look at the spectral sensitivity of cones, we place the test light in the line of sight (fovea). This is because the fovea only contains cones.
To look at the spectral sensitivity of rods, we can either test a rod monochromat subject or simply test subjects under dark-adapted conditions (when visions switches from cones to rods). |
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Term
| At what wavelength do rods absorb light best? |
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Definition
| The rod pigment best absorbs light that has a wavelength at 500 nm (blue-green). |
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Term
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Definition
Convergence occurs when more than one neuron synapses on another neuron.
Rods have more convergence than cones (which is why we have better night vision with rods!).
(cone-vision is said to have greater visual acuity.) |
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Term
| Describe the process of inhibition in words. |
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Definition
| As the excitatory signal travels down from receptors to bipolar cells to ganglion cells, it triggers lateral inhibition from the horizontal and amacrine cells. |
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Term
| What is meant by inhibition and excitation? |
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Definition
Some neurons produce excitation: Their input to another neuron increase the chance that this second neuron will fire.
Some neurons produce inhibition: Their input to another neuron decreases the chance that this second neuron will fire. |
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Term
| The dLGN is responsible for organizing and regulating incoming visual information, in what ways does it do this? |
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Definition
1. The eye of origin. (C I I C I C)
contralateral: on opposite side of body
ipsilateral: on same side of body
2. The spatial (retinotopic) organization of the receptors that created them.
3. The type of information about the visual scene that they contain. |
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Term
| What does the V1 do? (and what kinds of cells are contained in the V1)? |
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Definition
Neurons in V1 are considered to be feature detectors: They become specialized to respond best to specific features of the visual scene (think: neurons responding to specific orientations).
The V1 is made up of simple cells, complex cells, and end-stopped cells:
Simple cells respond to stimulus of particular orientation.
Complex cells respond to stimulus of particular orientation that is moving in a particular direction.
End-stopped cells respond to stimulus of a particular orientation, moving in a particular direction, and of a particular length.
(think about the guys who measured neuron firing with the projector and the moving lines.) |
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Term
| What does cortical magnification refer to? |
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Definition
| The fovea is a very small part of the retina (0.01%), but the fovea makes up 8-10% of the visual cortex! (It's just that important). |
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Term
| What is occular dominance? |
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Definition
V1 is the first place along the visual system where neurons receive input from both eyes. Most of these binocular cells respond better to stimulation of one eye. This preferential response is referred to as occular dominance.
(our V1 likes one eye more than the other, some speculate this is in part due to dominant side "laterality" i.e. right or left-handedness) |
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Term
| We have two pathways for vision -- the "what" and the "where" pathways, where are they located? |
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Definition
The “Where” pathway is located in the parietal lobe (and is called the dorsal pathway).
The “What” pathway is located in the temporal lobe (and is called the ventral pathway).
NOTE: These pathways are not fully independent. There is a lot of cross-talk. |
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Term
| What is visual form agnosia? |
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Definition
| A disease which causes an inability to recognize familiar objects. |
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Term
| We have 4 other areas of our visual cortex, what are they and what do they do? |
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Definition
MT is specialized for movement.
V4 is a module for color processing.
IT (inferior temporal lobe) is a module for form processing.
Within the IT is the FFA which is a specialized area for processing faces.
Damage to the FFA causes prospoagnosia. |
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Term
| Sensory code (in the neural coding of objects) works in two ways, name them and what they are for? |
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Definition
Sensory code is the information contained in the firing of neurons that represents what we perceive.
How does that code work?
Specificity coding: Specific perceptions are signaled by activity in specific neurons.
Distributed coding: Specific perceptions are signaled by patterns of activations across many neurons. This allows a small number of neurons to encode a large number of objects. |
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Term
| How do neurons become specialized? |
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Definition
Natural selection: the characteristics that augments an organism’s chance to survive and reproduce will be more likely to be passed on to future generations.
Nurture (experience): If monkeys or humans are trained to recognize artificial objects (e.g. greebles), neurons in IT (e.g. FFA) quickly adapt and become selective to them. |
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Term
| What are the Gestalt laws of visual perception? |
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Definition
Pragnanz or Simplicity
Similarity
Proximity
Good Continuation
Common Fate
Meaningfulness
Closure
Common region
Connectedness
Synchrony |
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Term
| Gestalt laws are Heuristics... what is a heuristic? |
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Definition
| A heuristics is a rule-of-thumb that allows for best-guest solutions to problems. |
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Term
| What was David Marr's "computational model" of the brain? |
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Definition
He described vision in 3 stages:
First, areas of dark and light from the retinal images are analyzed to detect objects’ edges and construct a Raw Primal Sketch.
Then, features similar in size and orientation are grouped and a surface representation of the scene, the 2.5-D Sketch.
Finally, the info in the surface representation is used to elaborate the 3-D representation that we actually see. |
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Term
Irv Biederman suggested that all “features” of objects are volumetric primitives (geons), and that any scene can be represented by these 36 fundamental geons.
Geons have three properties, what are they? |
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Definition
View invariance: They can be identified from any angle.
Discriminability: Any one geon cannot be confused with other geons.
Resistant to visual noise: Can be partially hidden and still be identifiable. |
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Term
| What is the inverse projection problem? |
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Definition
| The inverse projection problem states that any given retinal image could have been created by more than one visual scene. |
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Term
| What are the two color theories and who proposed them? |
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Definition
Trichromatic theory (Helmholtz)
Opponent-process theory (Hering) |
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Term
| What is the principle of univariance? |
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Definition
| Absorption of a single photon of light will cause the same effect regardless of the wavelength. |
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Term
| What are three types of color deficiencies? |
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Definition
Monochromats who see only shades of gray need only 1 wavelength to match all their perceptions of color.
Dichromats need only two. This indicates that some colors are not perceived.
Anomalous trichromats need three wavelengths (like “normals”). However they mix them differently. |
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Term
| Additionally, what is meant by Protanopia, Deuteranopia & Tritanopia? |
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Definition
Protanopia is the absence of the long cone pigment.
Deuteranopia is the absence of the medium cone pigment.
Tritanopia is the absence of the short cone pigment. |
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Term
| What are selective transmission and selective reflectance? |
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Definition
Selective reflection: The property of reflecting some wavelengths more than others.
Selective transmission: Transparent mediums appear colored if they transmit some wavelengths more than others. (think tic-tac orange). |
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Term
| What does color constancy refer to? |
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Definition
Think: sunlight vs lightbulbs. We still see colors the same in both lighting conditions because our eyes adapt.
A shirt that appears white outside should appear yellow under a light bulb!
BUT: This does not happen because our eyes quickly adapt.
For example, under the light bulb, our eyes quickly adapt to long wavelengths and this balances our perception. |
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Term
| What is Lightness Constancy and the ratio principle? |
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Definition
White is white, black is black. For example, our perception of black refers to the ratio of light reflected NOT the total amount of photons.
Black < 5-10%
White > 80-90% |
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Term
| Name the occulomotor depth cues: |
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Definition
Oculomotor Cues are based on our ability to sense the position of our eyes and the tension in our eye muscles.
Convergence - the inward movement of our eyes.
Accomodation - The change in focus of the lens in our eyes. |
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Term
| Name the monocular depth cues: |
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Definition
Monocular Cues can give us depth information from one retinal image.
Occlusion
Relative Height
Relative Size
Familiar Size
Atmospheric Perspective
Linear Perspective
Texture Gradient
Shadows
Motion Parallax
Accretion and Deletion |
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Term
| Name the binocular depth cues: |
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Definition
Binocular Cues give us depth information by comparing the two retinal images.
Binocular disparity, also called steopsis.
Convergence
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Term
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Definition
| An imaginary circle passing through he fixation point. Images in the horopter also fall on "corresponding retinal points". |
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Term
| What are disparity detectors? |
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Definition
| Cells in V1 and elsewhere which prefer stimuli with a specific binocular disparity. |
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Term
| What is up with the Boring Hallway experiment? |
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Definition
Boring and Halway discovered:
When distance cues are available, subjects adjust the comparison circle to match the actual size of the test circles.
When distance cues are not available, subjects adjust the comparison circle to match the retinal image of the test circles. |
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Term
| What is the apparent distance theory? |
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Definition
The moon appears bigger because it appears farther away. The heavens appear “flattened".
The size-distance scaling mechanism therefore makes it appear larger. |
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Term
| There are 4 types of movement, can you name them? |
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Definition
Real Movement: Moving an object across an observer’s field of view.
Apparent (stroboscopic) movement: Consecutive static images give the impression of motion. Inter-stimulus interval is 30-300ms.
Induced Movement: An illusion that occurs when movement in one object creates the perception of motion in another. (i.e. sitting in a car next to a moving bus).
Movement Aftereffect: Watching a continuous movement for a while will induce an aftereffect in the opposite direction. (i.e. the waterfall illusion). |
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Term
| Humans perceive motion according to the shortest path constraint, but what if that path doesn't make sense? |
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Definition
Think about the lady with the fist:
The length of time between the two images, or stimulus onset asynchrony (SOA) determines perception:
Below 200 ms, the hand goes through the head.
Over 200 ms, the hand goes around the head. |
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Term
| What was the deal with JJ Gibson? |
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Definition
JJ Gibson created the "ecological approach" to visual perception.
He coined the term "optic array" to describe the structure created by contours, surfaces, and textures of the environment.
More key terms:
Local disturbances, global optic flow, and gradient of flow. |
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Term
| Sound has two properties, what are they? |
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Definition
Frequency (pitch) and Amplitude (loudness).
Frequency describes the speed at which air pressure changes. It is described in cycles/second (Hertz).
Amplitude describes the difference in air pressure between the high and the low peaks of the soundwave. It is often described in decibels. |
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Term
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Definition
Timbre refer to the fact that sounds can have the same loudness & pitch (& duration) and still sound different.
This is caused by:
The differences in the energy of the harmonics of different instruments
The different attacks and decays of different instruments. |
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Term
What is the structure of the Ear?
(outer, middle, inner) |
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Definition
The Outer Ear
The pinnae, which stick out of our heads. Two functions: protection and resonance (amplifies 2000-5000 Hz). The tympanic membrane (eardrum) which vibrates in response to sound.
The Middle Ear
A small cavity connecting the outer and the inner ears. It contains the ossicles, the smallest bones in our bodies: malleus (hammer), incus (anvil), stapes (stirrup). The ossicles allow for efficient sound transmission from air to liquid.
The Inner Ear
The key structure is the cochlea, which looks like a little snail. The liquid in the cochlea is set to vibration by the action of the stapes on the oval window.
The Organ of Corti contains the receptors, called hair cells (inner and outer). It sits on the basilar membrane. It is covered by the tectorial membrane. The movement of the stapes on the oval window cause the membranes to move and the hair cells to bend (transduction!). |
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Term
| How the the cochlea encode frequency? |
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Definition
1. Different hair cells encode different frequencies.
2. Hair cells synchronise their rate of firing to VERY LOW frequencies (phase locking). |
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Term
| What is Plasticity of the Auditory Cortex? |
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Definition
| Our brains adapt to devote larger areas to sounds we often hear. Monkeys trained to discriminate tones near 2500 Hz develop larger brain areas dedicated to these tones. Musicians have larger auditory areas (25%) that respond to piano tones than non-musicians. |
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Term
| How do we localize sound? |
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Definition
| We use a number of cues to estimate azimuth (horizontal), elevation (vertical) and distance. |
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Term
| How does azimuth localization work? |
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Definition
To locate sound on the horizontal plane: We use the fact that we have two ears, which produces binaural cues.
These cues produce:
Interaural Time Differences
Sounds coming from the front (or back) reach the ears simultaneously. Sounds coming from the left or right reach one ear before the other.
Interaural Level Differences
Sounds coming from the side apply less sound pressure in the far ear because the head casts an accoustic shadow (high frequencies are maximally affected). |
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Term
| How does elevation localization work? |
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Definition
On the vertical axis, interaural time and level differences are null. So instead, elevation judgments are based largely on spectral cues that depend on the way sound interacts with the head and pinnae.
Reflections in the folds of the pinnae enhance or reduce certain frequencies, depending on elevation. |
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Term
| How does distance localization work? |
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Definition
Close vs Far sounds:
Distance of sounds close to the head (< 1m) are located accurately because of differences in intensity.
Distance of far sounds are more difficult to judge, and tend to be underestimated. Four cues have been proposed
Sound level: In an open field, doubling the distance reduces intensity by 6 dBs
Frequency: More loss of high frequencies at greater distances.
Movement parallax: Closer sounds move faster than further sounds
Reflection: Sounds coming from further are more likely to be indirect (reflected). |
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Term
| How do we group and segregate sounds? |
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Definition
Our brain uses heuristics often similar to the Gestalt Laws of grouping. These heuristics are:
Location: Sounds created by a particular source come from a stable or slowly changing position in space.
Temporal proximity: Sounds that occur in rapid progression tend to be produced by the same source.
Similarity of timbre and pitch: We group sounds that sound similar together.
Good continuation: Sounds that stay constant or change smoothly are produced by the same source.
Experience (knowledge). |
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Term
| Do vision and audition interact? |
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Definition
YES. As shown by:
The ventriloquism effect: When watching a film we perceive speech as coming from the actors’ mouths… not side speakers!
The ventriloquism aftereffect (experiment):
Subjects localize sounds in a series of speakers.
Subjects are trained to localize sounds with a flashing light that bias perception to the right.
Even without the light, localization remains biased afterwards (visual stimuli “recalibrates” audition).
Intersensory redundency: we often receive similar (complementary) information from vision and audition. The two types of information are integrated to provide us with a rich perceptual experience. The McGurk effect takes advantage of the assumption the brain makes that vision and audition “say the same thing”. |
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Term
| What is a two-point threshold of Touch? |
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Definition
| The two-point threshold is a test of sensory acuity. We have highest acuity on the fingers (2-3 mm), face and feet, and worst on the legs, arms and back (5 cm!). This is linked to receptor density and the size of receptive fields. |
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Term
| What is the neural pathway for touch? |
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Definition
| Information travels in the spinal nerves and enters the spinal cord, then synapses in the ventrolateral nucleus of the thalamus, towards S1 and S2. Touch is organized in a somatotopic fashion. |
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Term
| What is haptic perception? |
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Definition
We often explore objects by hand; a process called haptic perception, this involves:
The sensory system
The motor system
A cognitive system; what info do I need? |
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Term
| What are some parallels between touch and vision. |
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Definition
Receptor specificity:
Different receptors for different types of stimulation
Sizes and organization
Pathways: Thalamic and cortical
Plasticity
Touch and vision (and the other senses) often work together |
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Term
| Pain is multimodal, what does this mean? |
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Definition
This means that pain is not always purely sensational, it can be either:
Sensory; throbbing, dull, sharp.
Emotional; annoying, sickening. |
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Term
| Notes on the physiology of pain: |
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Definition
Free nerve endings called nociceptors encode pain.
Pain travels up the spinothalamic pathway, it activates the thalamus, hypothalamus and limbic system, and ends up in S1 and S2 as well as in the anterior cingulate gyrus. |
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Term
| What is Melzack's Gate Control Theory? |
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Definition
T-cells in the spinal cord determine the output and the amount of pain perceived, and two opponent systems fight for control over the T-cells:
SG+ opens the pain gates; it is activated by nociceptors and carried down S-fibers.
SG- closes the pain gates; it can be activated by either L-fibers (non -pain tactile stimuli) or top-down controls. |
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Term
| Notes on pain and endorphins: |
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Definition
The “cognitive” modulation of pain is modulated by endorphins.
E.g. pleasant thoughts, exercise
E.g. taking a “fake” aspirin
Drugs that block endorphins (e.g. naloxone) also block the effect of stimulation-produced analgesia (in rats) and placebos. |
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Term
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Definition
Humans are microsmatic, but far from anosmic.
We can detect small differences in intensity (5%), and can discriminate more than 10000 odors.
Smell tells us a lot about people !
Mommy? Male vs. Female? Can you smell a good potential mate?
The phenomenon of menstrual synchrony
Olfactory receptors:
Cilia
Lock and key !
How do we Smell?
In smell, molecules are “taken in” the body.
Smell receptors are replaced every 5-7 weeks.
There are 350 types of receptors.
Each glomeruli receives information from only one type of receptor.
etc... |
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Term
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Definition
The tongue, the papillae, the taste buds, the receptors.
There are 4 types of tastes.
The importance of the retronasal route.
Alliesthesia: Pleasantness of the odor/taste of food decreases as it is consumed.
Sensory-specific satiety: A mechanism to encourage variety in the diet?
How do we Perceive Flavor?
etc... |
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