Exam 2 Flashcards
1
Q
JND / difference threshold
A
Just Noticeable Difference. The smallest detectable difference between two stimuli. Can be predicted by Weber’s Law.
2
Q
receptive field
A
The area of the body that, when stimulated, will cause the associated neuron to change its activity
3
Q
themoreceptors
A
Receptors in the skin that detect either warm or cold temperatures. They are specific to either warm, OR cold. Temp-sensitive ion channels open at the proper temp. Firing rate of thermoreceptors slows when the temp remains constant for a while.
4
Q
nociception
A
Sense of pain. Caused by activation of very small diameter nerve endings. When tissue is damaged, chemical substances are released that stimulate these fibers. Extreme hot or cold, or intense mechanical stimuli, can also stimulate them.
5
Q
lateral inhibition
A
One neuron’s inhibition of surrounding neurons. In the somatosensory system, neurons in the center of the receptive field send input to inhibitory neurons that, in turn, project to other neurons. Helps improve accuracy by reducing random stimulation of surrounding areas.
6
Q
absolute threshold
A
The smallest amount of stimulus energy that can be detected by an observer at above chance (>50%)
7
Q
relative threshold
A
The amount that a stimulus of standard intensity must be changed in order for a difference to be noticed
8
Q
Weber’s Law
A
A mathematical formula for JND, which says the JND is a fixed percentage of the reference (starting) stimulus.
K= ΔI / I
K= Weber constant
ΔI = the difference between the reference stimulus and the comparison stimulus
I = the reference stimulus
9
Q
psychophysics
A
The systematic study of the relationship between the physical properties of a stimulus in the environment and the perception of that stimulus.
10
Q
method of limits / “staircase method”
A
A method for measuring absolute threshold. Stimuli are presented in sequential (ascending/descending) order, and the subject reports when they detect the stimulus. The threshold are the point at which the frequency of “yes” answers are equal to the frequency of “no” answers.
11
Q
method of adjustment
A
A method for measuring absolute threshold. The subject himself adjusts the stimulus until it becomes detectable or until it disappears.
12
Q
method of constant stimuli
A
A method for measuring absolute threshold. Stimuli are presented in random order, determined by the experimenter. Subject reports whether they detect the stimulus. Helps reduce expectation/adaptation effects.
13
Q
catch trials
A
Trials on which no stimulus is present. If the subject is guessing, he will say “yes” on about 50% of these trials
14
Q
2-alternative forced choice method
A
A stimulus is presented at one of two locations (the other location has no stimulus). The level of the stimulus is randomly varied to determine the level at which it is detectable 50% of the time. The subject must choose the location at which the stimulus is present. An objective method that can be used with animals, infants, or hard-to-test subjects.
15
Q
psychometric function
A
A plot of threshold as a function of some other parameter value. i.e., threshold for sound loudness as a function of sound pitch
16
Q
reaction time
A
The time between a stimulus and a behavioral or neural response. Can be used to measure processing time.
17
Q
magnitude estimation
A
The relationship between the physical intensity (or some other parameter) of a stimulus and the perceived intensity (or other attribute). Response is usually proportional to stimulus magnitude, but seldom a 1:1 relationship.
18
Q
direct scaling
A
A method for measuring magnitude estimation. The subject assigns a value to the perceived magnitude of the stimulus.
19
Q
matching
A
A method for measuring magnitude estimation. A reference stimulus (in another modality) is adjusted to be “equal” to the perceived magnitude of the test stimulus
20
Q
Steven’s Power Law
A
The mathematical relationship between the physical magnitude of a stimulus and its perceived magnitude includes a number raised to a power.
P = (KS)^n
P = perceived stimulus magnitude
K = constant
S = the actual physical magnitude of the stimulus
n = exponent
21
Q
response expansion
A
When the magnitude of a stimulus is perceived as being stronger than it actually is. Indicated by a n > 1 in Steven’s Power Law.
22
Q
response compression
A
When the magnitude of a stimulus is perceived as being weaker than it actually is. Indicated by a n < 1 in Steven’s Power Law.
23
Q
paradoxical cold
A
Cold receptors are also activated by high temperatures, so we get the sensation of something really hot being cold
24
Q
sense of itch
A
In response to a stimulus or immune response, cells release chemicals such as histamine, serotonin, proteases, and other substances. These chemical signals stimulate “itch-sensitive” fibers
25
sense of tickle
It is thought that tickling involves free nerve endings, possibly a combination of those sensitive to pain and light touch, or possibly specialized ones. Tickle stimuli always involves some type of temporal pattern.
26
cutaneous senses
The somatosensory systems of touch, pressure, stretch, vibration, temperature
27
proprioception
The somatosensory system of body position recognition
28
kinesthesis
The somatosensory system of body movement
29
mechanoreceptors
Somatosensory receptors that respond to pressure, stretch, vibration, touch, etc.
30
chemoreceptors
Somatosensory receptors that respond to chemicals (irritants, substances released by injured tissue)
31
How does transduction in mechanoreceptors work?
Mechanoreceptors generally have a covering on their nerve ending. Mechanical changes (stretching, pressure, etc.) to the covering of the nerve ending activate mechanically-gated ion channels. When these channels open, they admit positively charged ions and depolarize the nerve ending. If the depolarization (receptor potential) is large enough, action potentials are generated and transmitted along the axon.
32
Pacinian corpuscles
A type of mechanoreceptor in deep skin. Responds best to high frequency vibration. Adapt quickly. Large receptive fields.
33
Meissner's corpuscles
A type of mechanoreceptor in shallow skin. Responds best to low-frequency "flutter". Adapt quickly. Small receptive fields.
34
Merkel's disks
A type of mechanoreceptor in shallow skin. Responds best to low frequency pressure changes. Adapt slowly. Small receptive fields.
35
Ruffini cylinders
A type of mechanoreceptor in deep skin. Responds best to high-frequency "buzz" or stretch. Adapt slowly. Large receptive fields.
36
2-point discrimination
The smallest distance between 2 points of touch on the skin that are recognizable as being 2 separate points. Varies across different parts of the body.
37
stretch receptors
Receptors embedded in muscles and tendons that respond to stretch
38
hair follicle receptors
Receptors in hair follicles that respond to movement of the hairs. Whiskers on animals is an example.
39
What's the difference between large- and small-diameter nerve fibers?
Large nerve fibers transmit information more quickly.
40
dorsal root ganglion
A group of sensory neuron cell bodies located near the spinal cord, whose axons innervate the skin somatosensory receptors.
41
ventral horn ganglion
A group of motor neuron cell bodies, whose axons exit at the ventral root and send info to muscles
42
interneurons
Neurons in the dorsal root ganglion that connect between sensory and motor neurons. Can be used as a gating mechanism or to change signals.
43
dorsal columns
Fiber tracts in the spinal cord that transmit info about touch, vibration, 2-point discrimination, and proprioception to the thalamus, via nuclei in the brainstem and the medial lemniscus (a CNS fiber tract)
44
spinothalamic tracts
Fiber tracts in the spinal cord that transmit info about temperature and pain to the thalamus and from there to the context, via the anterolateral pathway
45
parallel pathways
Different sensory stimuli might be processed in different neural pathways; Same sensory stimulus might be processed in different neural pathways for different purposes
46
somatosensory path of information flow
skin receptors --> spinal nerves --> dorsal root ganglion --> dorsal column/spinothalamic tracts --> dorsal column nuclei in medulla --> ventral posterior nucleus in thalamus --> primary somatosensory cortex/motor cortex
47
homunculus
A distorted representation of a human showing the relative expansion/contraction of cortical representation for each body part in the cortex. There's one for sensory, one for motor
48
magnification factor
The amount of expansion or contraction a certain sensory area receives in the cortex relative to its size.
49
topographic map
A spatially organized neural representation of a stimulus parameter (in the somatosensory system, points on the body). There is an orderly representation of that parameter across a neural array in the cortex.
50
cortical column / cortical module
The cortex has many input and output layers. A column is a vertical group of cells down these 6 layers. Cells in each column respond to a particular type of input (e.g., vibration, pressure, temperature...)
51
neural plasticity
Changes in the brain based on experience. Can happen through:
Growth, branching, or retraction of axons and dendrites
Up-or down-regulation of neurotransmitters, ion channels, receptors, etc.
Increased or decreased excitability of specific synapses
Production of new neurons (limited in humans)
52
phantom limb phenomenon
If a digit or limb is lost, there frequently remains a sensation that the body part is still present. This is because the cortical representation of the body part still exists, so any stimulus that activates that representation will be perceived as coming from the body part
53
reaction time
The time between a stimulus and a neural or behavioral response. Processing takes time, harder processing takes more time. Example: Stroop Effect
54
Wundt curve
A model that was originally developed to show that performance on a task is an “inverted-U”shaped function. This means that performance its best when motivation is at an intermediate level. This curve has tons of applications in psychology.
55
rapid adaptation (of a somatosensory receptor)
There is no response to sustained pressure, only to changes in pressure. Pacinian and Meissner's corpuscles adapt quickly.
56
slow adaptation (of a somatosensory receptor)
When pressure is applied, there is a long-lasting response that persists for the duration of the pressure, and only very slowly decays. Ruffini cylinders and Merkel's disks adapt slowly.
57
center-surround organization
Organization of receptive field in somatosensory and visual receptors. Stimulus in the center excites activity of the cell at the center, while stimulation in the surrounding area inhibits the activity of the cell at the center.
58
spinal nerve
Nerves from/to different parts of the body that enter the spinal cord at different places. Each spinal nerve innervates a specific area of the body.
59
referred pain
A given spinal segment may be innervated by the skin, muscles, and internal organs. The spatial connection is not always straightforward. Pain in an organ may be attributed to the related area of the skin, muscles, etc.
60
primary somatosensory cortex
The part of the cortex to which somatosensory information is first sent by the thalamus.
61
light
a form of electromagnetic radiation emitted by the oscillation of electrically charged material
62
visual field
The region of space in the environment from which light is transmitted to the retina. What's inside the visual field changes as the head, eyes, and body moves, but each point on the retina always corresponds to some point in real space, so the visual field can be represented in retinal coordinates that do NOT vary.
63
cornea
Clear covering over the front of the eye
64
iris
Muscles around the pupil that regulate the amount of light entering the pupil
65
pupil
The opening through which light enters the eye
66
lens
Focuses light on the back part of the eyeball in a process called accommodation. The lens changes shape to adjust focus
67
retina
The screen at the back of the eye onto which light projects. Made up of 3 layers: ganglion cells, bipolar cells, and rods/cones.
68
rods
Visual receptors that are located all over the periphery (around the fovea) of the retina. More abundant than cones. They adapt slowly to dark after being "bleached" by light, but become very sensitive in very low light. Do not help with color vision.
69
cones
Visual receptors that are concentrated in the fovea of the retina. Less abundant than rods. They adapt quickly to dark after being "bleached" by light, but do not get very sensitive in low light. We have 3 types: short (blue), medium (green), and long (red) that each contain a different photopigment that has its best absorbency at a certain wavelength.
70
fovea
a small depression in the retina where visual acuity is highest. The center of the field of vision is focused in this region, where retinal cones are particularly concentrated
71
optic nerve
connects the eye to the brain. The optic nerve carries the impulses formed by the retina. Exits at the blind spot
72
blind spot
The part of the retina where there are no receptors, because this is where the optic nerve exits the back of the eye. We don't usually see it, because our brains fill in the missing info.
73
photopigments
Light-sensitive molecules in the rods and cones. Consist of opsin and retinal, which separate when they contact light. This is the only part of vision which depends on light.
74
visual transduction
When light strikes the retina, it interacts with photopigments in the rods and cones. When the light hits the retinal component of the photopigment, it changes shape and releases from the opsin component. Through a series of steps, this causes a sodium ion channel that is usually open, to close. This results in the photoreceptor becoming hyperpolarized (more negative), and the normal release of glutamate that happens in the dark stops. This lack of glutamate will depolarize the on-center bipolar cells, which are inhibited by glutamate, and cause them to create graded potentials. If these potentials are large enough to meet the threshold of connected ganglion cells, the ganglion cells create an action potential which is sent to the brain.
75
bipolar cells
The middle layer of the retina, contacts both the rods/cones and the ganglion cells. Produce graded potentials as received from the photoreceptors.
76
ganglion cells
The outer layer of the retina, contacts the bipolar cells. The first true neurons in the visual system, produce action potentials which are sent to the brain via their axons in the optic nerve
77
off-center bipolar cells
bipolar cells that are excited by glutamate and are depolarized by dark, and hyperpolarized by light (respond when light is OFF)
78
on-center bipolar cells
bipolar cells that are inhibited by glutamate and are depolarized by light and hyperpolarized by dark (respond when light is ON)
79
rod pathway
Amplifies the signal of light under low light conditions, due to many rods providing convergent input to a single large ganglion cell. This leads to more light perceived, but less spatial acuity.
80
cone pathway
Provides info about color and fine detail. Do not have convergence, so it is less sensitive under low-light conditions but has a higher spatial acuity when there is enough light.
81
horizontal and amacrine cells
Cells that connect horizontally along layers of the retina. These lateral connections allow cells in one part of the retina to influence the activity of cells in another part (i.e. lateral inhibition)
82
on-center, off-surround ganglion cell
Due to a mix of bipolar cell response and lateral interaction, on-center ganglion cells are excited by light in the center, inhibited by light in the surround
83
off-center, on-surround ganglion cell
Due to a mix of bipolar cell response and lateral interaction, off-center ganglion cells are excited by dark in the center, inhibited by dark in the surround
84
color-opponent retinal cells
Cells that receive information from cones may have receptive fields with a center excited by one color and inhibited by the “opposite” color.
85
trichromatic model of color vision
For each wavelength, the ratio of activity in the 3 classes of cones will be different. The three different types of receptors participate in a population code thanks to different amounts of activity in each class of cones.
86
categorical perception of color
Wavelengths throughout some range are all perceived as belonging to a certain category, e.g., “blue”.
87
perceptual constancy
The tendency to perceive and object you are familiar with as having a constant shape, size, and brightness, despite stimulus changes that may occur. Colors look the same regardless of illumination, objects can be identified from different angles
88
Where does sensory input from the body enter the spinal cord?
Dorsal root ganglion
89
Where does motor output exit the spinal cord?
Ventral root
90
Why do we not really feel a piece of clothing or a wristwatch after we have worn it for a while?
Adaptation. The pressure isn't changing, so the response of rapidly-adapting mechanoreceptors stops. After a period of time, the response of slow-adapting mechanoreceptors have also decayed.
91
Why does a tub of lukewarm water feel cold if your hand has been in hot water but warm if your hand has been in cold water?
Only hot thermoreceptors are responding when your hand is in hot water. When you put your hand into lukewarm water, thermoreceptors with lower temperature ranges begin to respond, and your brain gets the message that it has gotten cold. Likewise, only cold thermoreceptors are responding in ice water, but when you move to lukewarm water, thermoreceptors with some higher temp ranges begin to respond.
92
barrel cortex
The regions of the primary somatosensory cortex that receive input from the whiskers in animals like rats/other rodents.
93
What is the difference between white light and colored light?
White light contains all wavelengths of the visual spectrum, colored light contains only a certain wavelength.
94
What is the difference between mixing wavelengths of light and pigments in terms of what colors we perceive?
Mixing different wavelengths of light is an additive process as we absorb them. Mixing pigment is a subtractive process (the pigment absorbs light; the wavelength(s) it reflects give it its color)
95
What types of processing occur in the retina?
Rod pathway amplifies light, cone pathway responds to color and sharpens contours. Lateral inhibition
96
Why does the release of glutamate from photoreceptors cause some bipolar cells to become depolarized and others hyperpolarized?
Depending on the receptors the bipolar cells have in their surface, glutamate from photoreceptors can either excite (depolarize) off-center bipolar cells, or inhibit (hyperpolarize) on-center bipolar cells.
97
after-image
Visual illusion in which retinal impressions persist after the removal of a stimulus, believed to be caused by the continued activation of the visual system. The afterimage may be positive, corresponding in color or brightness to the original image, or negative, being less bright or of colors complementary to the original.
98
Describe two ways in which processing in the retina might affect our visual perception.
See things more brightly than they are when we use our rods thanks to convergence on large ganglion cells. See things as darker than they are due to lateral inhibition from nearby lighter things.
99
accommodation
The ability of the eye to change its focus from distant to near objects (and vice versa). This process is achieved by the lens changing its shape, thanks to muscles around it. Helps give us cues about 3D surroundings.
100
What are some monocular, static cues that help with 3D perception?
Shadow placement, texture gradients, overlap of objects, size and height, texture discontinuity, linear perspective, atmospheric haze
101
motion parallax
Motion-related monocular cues that give us info about 3D surroundings. When you move, things closer to you pass through your visual field faster than things farther away.
102
binocular disparity / stereopsis
A binocular cue that gives information about 3D surroundings. For objects at different distances, each eye sees a slightly different view
103
contours
Basic elements of visual perception that help us distinguish forms
104
saccades and microsaccades
Saccades are large scanning movements of the eyes, while microsaccades are tiny jiggling motions of the eyes. Both provide changes in illumination that help us see
105
figure
an integrated group of contours
106
ground
the background against which a figure appears
107
Gestalt theory
An attempt to formalize a set of cognitive principles according to which, visual grouping of elements and object perception occur, based on the premise that “the whole is greater than the sum of its parts”
108
Gestalt laws
principles of how elements are grouped together to form figures
109
Law of Simplicity / Good Figure
The form that is perceived is the simplest one possible.
110
Law of Good Continuation
Elements that appear to follow in the same direction tend to be grouped together
111
Law of Similarity
Similar elements are grouped together
112
Law of Proximity
Elements close to one another tend to be grouped together
113
Law of Familiarity
Elements that form a familiar shape tend to be grouped together. Based on prior experience and context.
114
Law of Common Fate
Elements that move together tend to be grouped together
115
feature integration theories
Theories that assume that there are multiple sequential stages of processing in which visual form percepts are built up from fundamental “features”, elements, or components. Theories vary on what the fundamental features are.
116
spatial frequency theory
A theory of form perception that says any visual stimulus can be broken down into a series of spatial frequencies. Different channels of the visual system break down visual field into frequencies for analysis.
117
binding problem
A problem shared by all form perception theories. What are the mechanisms that link related features together to form an object? Some assume there is some sort of “homunculus” or observer that puts everything together
118
Information flow of visual system from retina to cortex
Rods/cones in retina--> M and P ganglion cells--> lateral geniculate nucleus in thalamus --> V1 of visual cortex --> other cortex areas
119
suprachiasmatic nucleus (SCN)
A region involved in regulating circadian (daily) rhythms. Uses input from light-sensitive ganglion cells in the retina, regulates melatonin production. Some visual info goes straight here from optic tract, instead of thalamus first.
120
superior colliculus
A region for reflex movements of the eyes, head, neck, and “gaze”. Some visual info goes straight here from optic tract, instead of thalamus first.
121
lateral geniculate nucleus (LGN)
A 6-layered structure in the thalamus. Each eye has 3 layers--an M (magnocellular) layer and two P (parvocellular) layers. Sends information to the visual cortex.
122
Magnocellular (M) pathways
"Where" pathways in the visual system, sensitive to general form and motion
123
Parvocellular (P) pathways
"What" pathways in the visual system, sensitive to color and fine detail
124
simple cells
Neurons that respond best to a bar or stripe of light in a specific orientation
125
complex cells
Neurons in primary visual cortex (area 17) and higher levels (area 18) respond best to a bar in a specific orientation that moves in a specific direction, at a specific speed.
126
hypercomplex cells
Neurons mainly in visual areas 18 and 19 that respond best to a bar of a specific length, in a specific orientation that moves in a specific direction and at a specific speed
127
hypercolumns in visual system
Functional modules in the visual cortex composed of 6 layers (correspond to the 6 projecting layers of LGN), divided into ocular dominance columns, orientation columns within those, and blobs.
128
ocular dominance columns
Two columns within each hypercolumn that receive input from one eye each. Further divided into orientation columns
129
orientation columns
Subdivisions of the ocular dominance columns which contain cells specialized to specific orientations
130
blobs
Areas of hypercolumns which contain neurons sensitive to color.
131
critical period
A time early in life during which visual experience is necessary to establish cortical organization.
132
visual event
Something that happens in both space and time. Multiple visual events in a sequence provide info about how the visual world changes over time. When these events occur on the right time scale, we perceive motion
133
When our eyes move, we don’t perceive the world or objects as moving. Why?
Information from the occulomotor system (corollary discharge) is compared with our sense of proprioception (body movements)
134
How might movement direction and speed be computed in the nervous system?
Through convergence of delay lines on coincidence detector neurons
135
illusory/ stroboscopic movement
When two stimuli are presented in rapid succession, this results in the perception of “apparent movement”. Works best when the delay between stimuli is ~60ms
136
induced movement (train illusion)
Seeing the movement of a neighboring train creates the illusion that one's own stationary train is moving.
137
movement aftereffect (waterfall illusion)
When you watch a moving stimulus for a while, and then look away, things in your visual field seem to be moving the opposite way. Caused by adaptation of motion-sensitive cells for the direction you watched
138
How is increased sensitivity due to convergence of photoreceptor inputs related to acuity?
Convergence of photoreceptor inputs strengthens the signal of the stimulus, making it easier to detect, but giving less precision in location
139
What feature of the visual stimulus is most important for activating cells in V4?
color
140
What feature of the visual stimulus is most important for activating cells in the inferotemporal cortex?
form
141
What feature of the visual stimulus is most important for activating cells in the medial temporal area (area MT)?
movement
142
What is the most common cause of color blindness? Why is color blindness more common in males than in females?
The most common cause of color blindness is the lack (or anomaly) or one or more cone photopigments. It's a sex-linked trait on the X chromosome
143
According to feature integration theory, what stages of processing are hypothesized to occur? What happens during each stage?
1) Preattentive process: primitive features are extracted
2) Primitives grouped into preliminary figures
3) Focal attention: combines preliminary figures into "object files"
4) Object files compared with memory templates to identify
