Exam 2 Flashcards
JND / difference threshold
Just Noticeable Difference. The smallest detectable difference between two stimuli. Can be predicted by Weber’s Law.
receptive field
The area of the body that, when stimulated, will cause the associated neuron to change its activity
themoreceptors
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.
nociception
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.
lateral inhibition
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.
absolute threshold
The smallest amount of stimulus energy that can be detected by an observer at above chance (>50%)
relative threshold
The amount that a stimulus of standard intensity must be changed in order for a difference to be noticed
Weber’s Law
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
psychophysics
The systematic study of the relationship between the physical properties of a stimulus in the environment and the perception of that stimulus.
method of limits / “staircase method”
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.
method of adjustment
A method for measuring absolute threshold. The subject himself adjusts the stimulus until it becomes detectable or until it disappears.
method of constant stimuli
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.
catch trials
Trials on which no stimulus is present. If the subject is guessing, he will say “yes” on about 50% of these trials
2-alternative forced choice method
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.
psychometric function
A plot of threshold as a function of some other parameter value. i.e., threshold for sound loudness as a function of sound pitch
reaction time
The time between a stimulus and a behavioral or neural response. Can be used to measure processing time.
magnitude estimation
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.
direct scaling
A method for measuring magnitude estimation. The subject assigns a value to the perceived magnitude of the stimulus.
matching
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
Steven’s Power Law
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
response expansion
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.
response compression
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.
paradoxical cold
Cold receptors are also activated by high temperatures, so we get the sensation of something really hot being cold
sense of itch
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
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.
cutaneous senses
The somatosensory systems of touch, pressure, stretch, vibration, temperature
proprioception
The somatosensory system of body position recognition
kinesthesis
The somatosensory system of body movement
mechanoreceptors
Somatosensory receptors that respond to pressure, stretch, vibration, touch, etc.
chemoreceptors
Somatosensory receptors that respond to chemicals (irritants, substances released by injured tissue)
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.
Pacinian corpuscles
A type of mechanoreceptor in deep skin. Responds best to high frequency vibration. Adapt quickly. Large receptive fields.
Meissner’s corpuscles
A type of mechanoreceptor in shallow skin. Responds best to low-frequency “flutter”. Adapt quickly. Small receptive fields.
Merkel’s disks
A type of mechanoreceptor in shallow skin. Responds best to low frequency pressure changes. Adapt slowly. Small receptive fields.
Ruffini cylinders
A type of mechanoreceptor in deep skin. Responds best to high-frequency “buzz” or stretch. Adapt slowly. Large receptive fields.
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.
stretch receptors
Receptors embedded in muscles and tendons that respond to stretch
hair follicle receptors
Receptors in hair follicles that respond to movement of the hairs. Whiskers on animals is an example.
What’s the difference between large- and small-diameter nerve fibers?
Large nerve fibers transmit information more quickly.
dorsal root ganglion
A group of sensory neuron cell bodies located near the spinal cord, whose axons innervate the skin somatosensory receptors.
ventral horn ganglion
A group of motor neuron cell bodies, whose axons exit at the ventral root and send info to muscles
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.
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)
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
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
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
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
magnification factor
The amount of expansion or contraction a certain sensory area receives in the cortex relative to its size.
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.
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…)
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)
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
reaction time
The time between a stimulus and a neural or behavioral response. Processing takes time, harder processing takes more time. Example: Stroop Effect
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.
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.
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.
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.
