Midterm 1 Flashcards
Cell body
contains nucleus
Nucleus
all computation for cell
Dendrites
important for communication
Axon
transmits electron activity
Axon terminal
transmits information to another neuron
Myelin sheath
insulation so electron signal is faster
Synapses
junction between neurons that permits information transfer
Neurotransmitter
a chemical substance used in neuronal communication at synapses
Cerebellum
used to believe it was exceptionally important to movement but now know that it is also important for sensation and perception
Occipital lobe
visual cortex
Primary visual cortex
first place where visual info goes
Secondary visual processing
where the processed info goes
Temporal Lobe
auditory cortex
What else is temporal lobe important for?
motion and visual information (sensory processing)
Parietal lobe
Primary somatosensory cortex-adjacent pars of the body are represented by adjacent parts of the brain
What kind of processing does the parietal lobe take part in?
spatial information and sophisticated motion processing
Frontal lobe
sensory processing and interpreting senses. also impulse control, judgement and motor control
Broca’s area is important for?
speech production
Primary motor cortex is..
first area involved in motor behavior (like issuing motor commands)
Basal ganglia
involved in selecting movement
Thalamus
importnat for sensory processing
Hippocampus
important for memory storage and associating sensory input together (under thalamus)
Amygdala
old structure, emotions (next to thalamus)
Pons/medulla
controls organs and their function
How do neurons send and receive information?
Synaptic transmission
What is synaptic transmission?
connection needed to be strong enough to excite the next neuron so sometimes it needs more than one neuron to signal it
Axon terminal in presynaptic cell communicates with…
dendrites of postsynaptic cell
Neurotransmitters are released by ____ vesicles in the ___
synaptic / axon
The synaptic vesicles then fit into the ___ on the dendrite on the other side of the ____
receptors / synapse
Bottom up vs Top Down
sensation -> perception -.> cognition [bottom up] reversed is top down
The interpretation of what is going on around you is…
an active process
The sensations you have experienced in the past allow…
you to have perceptions of experiences in the future
Define psychophysics
the science of defining quantitative relationships between physical and psychological (subjective) events
Define sensation
lowest level of processing; physical energy translated into informational signal (ie transduction)
Define perception
usually “interpretation” of the information, but the distinction is irrelevant
3 parts of perception
- what is needed for survival
- organization and selection
- bidirectional (perception effects sensation actively)
Absolute threshold
minimum intensity of a stimulus that can be detected
Is absolute threshold step or sigmoid?
sigmoid
Explain Sigmoid function
probability of detection increases with the signal intensity
Difference threshold
(aka JND) the smallest detectable difference between 2 stimuli OR min change in a stimulus that enables it to be correctly judged as diff from reference stimulus
JND
just noticeable difference or how 2 different stimuli must be for the subject to notice that they are not the same
Method of constant stimuli
in which many stimuli, ranging from rarely to always perceivable, are presented at a time
How is constant stimuli captured?
various levels of stimulus intensity is used to try to find the lowest level of intensity
Limitations of constant stimuli?
It takes a long time and you have to pick the intensity and order. So you pick three intensities at 20x. You have to do each of them 20x.
Is there ceiling/floor effects in constant stimuli?
Yes. Since it is values that are predetermined you may not capture what you want to measure
Method of limits
when particular dimension of stimulus, or difference between 2 stimuli, is varied incrementally until the participants responds differently
What are you measuring with method of limits?
thresholds going from low to high, then high to low and asking participant when they cant see the stimulus anymore
Are the values predetermined in method of limits?
No.
Cons of method of limits?
people might life, sensitivity may change, require convergence, fatigue/practice effect
What is fatigue/practice effect?
are you trying to find out when someone is getting “good” at a task? Sometimes that task can go on for a long time, are you measuring when they get “tired”?
Method of adjustment
a method in which the participant controls the change in the stimulus
Con of adjustment?
participants can be unreliable BUT avoids fatigue/practice effects
Weber’s Law
the principle describing the relationship between stimulus and resulting sensation that says that JND is constant fraction of comparison stimulus
Equation for weber’s law
difference threshold/standard = constant K OR diff intensity/intensity = constant K
Fechner’s law
a prinicple describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation increases proportionally to the log of the stimulus intensity
Equation for fechner’s law
P = K log S
What is P, S, K in fechner’s law?
P = perceptual/sensory magnitude (your experience) S= physical intensity (physical change in stimulus) K = constant
Steven’s law
principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent
Equation for steven’s law
P= k S^n
If exponent is less than 1 then…
sensation grows less rapidly
Log-Log types for Stevens law (3)
compression, veridical, exaggerated
What is compression?
when slope of line is less than 1, so perceived intensity grows less rapidly
Ex of compression
light doubling
What is veridical?
the slope of line = 1 and so the intensity grows equally to physical change
Ex of veridical
pencil length
What is exaggerated?
the slope of the line is greater than the ratio, therefore the perceived stimulus grows more rapidly than physical change
Ex of exaggerated
Electric shock
Magnitude estimation
method in which the participant assigns values according to perceived magnitudes of stimuli
Signal detection theory
theory that quantifies the response of an observer to the presentation of a signal in the presence of noise
Measures obtained from SDT are ____ and ____ from the observer
sensitivity (d’) / criterion
Criterion
an internal threshold that is set by the observer, if the internal response is above criterion then the observer gives no response and if below it gives a response
Sensitivity
value that defines the ease with which an observer can tell the diff between the presence and absence of stimulus or diff between stimulus 1 and 2
d’ = ~0
no sensitivity
d’ = ~ -1
moderate sensitivity
d’ = ~-4
high sensitivity
Cornea
first tissue that light will encounter, transparent and made of ordered fibers and has no blood vessels or blood which can absorb light
Ciliary muscles
responsible for stretching and compressing the zonules of zinn
Zonules of zinn
responsible for changing the lens to intake light
Iris
colored part of eye, has muscular diaphragm around the pupil and regulates the light entering the eye by expanding and contracting the pupil
Foveaa
small pit in the center of the macula which has the highest concentration of only cones, part of the retina with the highest visual acuity
How are images projected onto the retina?
reversed right to left and upside down
Photoreceptors
light sensitive receptors in retina
Rods
photoreceptors specialized for night vision
Cones
photoreceptors specialized for daylight and fine visual acuity and color
Bipolar cells
poken about in class when discussing convergence and are primarily thought of as the connection between rods/cones and ganglion cells- furthermore they are distinct as midget/ non midget cells where the former receive information from a single cone rather than multiple receptors.
Horizontal cells
squeezed between rods/cones and bipolar cells these are important for creation of center surround receptive fields
Visual angle
the angle that would be formed by lines going from top and bottom of a cycle on the page, passing through the center of the lens and ending in the retina
Fovea
~2 degree diameter of central vision; only cones; 1% retina and ~50% of visual cortex!!
Para-fovea
area immediately surrounding fovea (~4-5 degrees around center)
Periphery
area beyond fovea
Blind spot
location of optic nerve that leave the retina about 3 degrees diameter
Eccentricity
the distnace between the retinal image and the foeva many functions depend on eccentricity of fovea like acuity, color, and motion
Why does eccentricity influence acuity, color and motion?
because of the distribution of rods and cones
What is the distribution of rods and cones like in terms of retinal location?
Rods are in periphery and cones are in fovea
Pupil size
the diameter of pupil can vary by factor of 4; pupil size only accounts for small part of visual system ability to adapt to light/dark condition
Photopigment regeneration
second mechanism for achieving large sensitivity range is providing by the way photopigments are used up and replaced in receptor cells
Dim lighting
plenty of photopigment is available is available and rods and cones absorb/respond to as many as they can
After a photopigment molecule is bleached what must happen to the molecule?
must be regenerated before it can be used to absorb another photon
When number of photons start to overwhelm the system what happens?
photopigment molecules cannot be regenerated fast enough to detect all the photons hitting photoreceptors
Difference between rods and cones
properties of rods and cones. their distribution across retina explains the difference in various function @ diff eccentricities
Rods and cones differ in their response to wavelengths..
cones can detect diff colors, rods only have one kind of photopigment called rhodopsin
Retinal ganglion cells
These cells are responsible for telling the brain what the eye sees
How do retinal ganglion cells tell brain what is being seen?
this is accomplished through two pathways: the M absorb information from multiple converging bipolar cells whereas those in the P pathway synapse with single bipolar cells which lead to individuals cones and less information.
Visual acutiy
he smallest spatial detail that can be resolved at 100% contrast
Difference in acuity between foveal and peripheral vision
rods and cones in periphery are packed together less tightly than in the fovea and there are many receptors converge on each ganglion cell making acuity much poorer in the periphery than the fovea!
The acuity-sensitivity trade-off
Cones have higher acuity because of their ability to see detail and color whereas rods are more sensitive as they can see in the dark, recover faster in the dark and allow you to see movement in dim lighting (this may have evo psych implications)
Sine-wave gratings
a grating with sinusoidal luminance profile as shown in figure
Sensitivity of retinal ganglion cells
responds (ON to light on-center and OFF to dark on-center) greatly to 0 degrees (upward sine wave) and 180 degrees (downward sine wave). Flat line response at 90 degrees and 270 degrees (responding to half light/dark in center).
phase
relative position of grating
spatial frequencies
the number of grating cycles (dark + bright bars) in given unit of a space
Lateral Geniculate Nuclei
a structure in the thalamus, art of the midbrain, that receives input from the retinal ganglion cells and has input and output connections to the visual cortex.
Topographical mapping
the orderly mapping of the world in the lateral geniculate nucleus and the visual cortex; Adjacent things are adjacent.
Magnocellular layers
- bottom two layers
- larger cells
- receive input from M ganglion cells
Parvocellular layers
- top four layers
- smaller cells
- receive input from P ganglion cells
Primary visual cortex (V1) aka striate cortex
the area of the cerebral cortex of the brain that receives direct inputs from the lateral geniculate nucleus, as well as feedback from other brain areas, named because it has white stripes.
Cortical magnification factor
Foveal representations are ‘expanded’ relative to peripheral representations. The amount of cortical area (usually specified in millimeters) devoted to a specific region (e.g., 1 degree) in the visual field).
Receptive field
the region in space in which stimuli will activate a neuron.
Cells in V1
a cortical neuron whose receptive field has clearly defined excitatory and inhibitory regions
Simple cells
Respond to edges/bars of specific orientations
- orientation
- spatial frequency
- phase sensitive
Complex cells
Orientation specific (like simple cells). But, they are most active when the oriented stimuli is moving
- orientation
- spatial frequency
- phase insensitive
- motion detection
End-stopped cells
Like complex cells but respond to lines of only a certain length.
- Orientation specific
- Motion specific
- Length specific
- corners
- motion direction
V1 Organization
The cortex is organized into ‘columns’ that represent specific values of a feature. A column is a vertical arrangement of neurons. Neurons within a single column tend to have similar receptive fields and similar orientation preference.
location columns
- Columns of neurons that all have their receptive field on roughly the same location on the retina.
- Run perpendicular to the cortex:
orientation columns
- Column of cells that all prefer the same orientation
* Aligned perpendicular to cortex (like location columns
ocular dominance columns
property of receptive fields of striate cortex neurons by which they demonstrate a preference, responding somewhat more rapidly when a stimulus is presented in one eye than when it is presented in the other.
Hypercolumns
Complete set of orientation and ocular-dominance columns for a given retinal location.
- Like a ‘super-column’ that contains all the column types
Spatial frequency
essentially, the amount of ‘stuff’ present per unit length
• V1 cells are also tuned to spatial frequency
• Similar to orientation tuning
Contrast sensitivity function(CSF)
The psychophysical contrast threshold is a function of spatial frequency
Ventral stream (the “What” pathway)
Processes shape/form
Dorsal stream (the “Where” pathway)
Parietal lobe.Processes location, and HOW to interact with it based on location (used to plan action).
• Location (e.g. left vs. right) • More recently described as the How path
• We know “how” to interact with something, and thus where it is
• How path is used to plan action
V2
Illusory contours
V3
Maybe combining info for 3D perception? Unknown
V4
Color
MT (Medial Temporal)
Motion
IT (Infero Temporal)
Shapes, form, faces
Hue
the color: hue is related to wavelength (not simple relation)
Saturation
distribution of light
How “pure” is it?
1 wavelength is pure, lots of wavelengths is not
Many different wavelengths is called
broadband
Brightness
the intensitiy of light
People see color from
light to dark
Functions of color vision
having color vision makes it easier to discriminate good food from bad food.
Object detection
Perceptual organization and object segmentation – the fruit theory of origin of color vision → (which is a tree branch with color and then monotone)
Object recognition and identification
Fruits that are their actual color vs not
Additive Color Mixing
Adding lights. A mixture of lights. If light A and light B are both reflected from a surface to the eye, in the perception of color the effects of those two lights add together.
Subtractive Color Mixing
Adding pigments. A mixture of pigments. If pigments A and B mix, some of the light shining on the surface will be subtracted by A. and some by B. Only the remainder will contribute to the perception of color.
Each pigment reflects a certain band of wavelengths
Simultaneous Color Contrast
Your perception of an object may be different due to different backgrounds OR a color in one part in the visual field affects your perception of another color
Successive Color Contrast
Referred to as Afterimages, think of when you stare at an image for a long time and it gives an “after effect” when you see another image.
Color Deficiency Observations
- People who are color-blind to red are also color-blind to green.
- People who are color-blind to blue are also color-blind to yellow.
Hering’s Observations
Types of Color deficiencies – Red-green color blindness – Blue-yellow color blindness
Color-normal people can’t see red-green together, nor blue-yellow together
Response patterns of the three types across different wavelengths
Cones and 3 types of photoreceptors with preferential sensitivity
S-cones
SHORT wavelengths (blue cones)
M-cones
MIDDLE wavelength (green cones)
L-cones
LONG wavelengths (red cones)
The problem of univariance:
different wavelength-intensity combinations can elicit exactly the same response from a single type of photoreceptor. Need multiple types to discriminate. (Univariance = there’s only 1 quantity (one dimension of input and one of output) that can vary).
Trichromatic theory
With three cone types we can tell the difference between lights of different wavelengths.
Evidence for the theory
3 Receptors →3 primary color sensations: Blue, Green, Red. (Yellow is claimed to be combination of green & red)
color matching experiment
By adjusting proportions of 3 wavelengths it’s possible to match the color of comparison to a single wavelength testfield, but need at least three wavelengths to match all wavelengths in spectrum
Opponent color theory
The theory that perception of color is based on the output of three mechanisms, each of them on an opponency between two colors:
red–green
blue–yellow
black–white
Evidence for the opponent color theory
better at explaining simple and complex colors, contrast, exclusivity (no bluish yellow), and the color yellow itself
Physiological evidence, Opponent neurons: B+Y-, Y+B-, G+R-, R+G-
What are the 5 color phenomena and our intuition?
- Color Mixing
- Contrast
- Intuitions
- Color Blindness
- Color Cancellation
hue cancellation experiment
Famous experiments: Hurvich & Jameson (1957) Cancellation experiments estimated the strength of each mechanism along the wavelength dimension.
Unique hues
any of four colors that can be described w/only a single color term: red, yellow, green, blue. (other colors (e.g., purple or orange) can also be described as compounds (reddish blue, reddish yellow).
Is young Helmholtz theory correct?
No.
Color vision is ____ but it is based on the _____
trichromatic / 3 mechanisms at the retina
First stage of color processing is
captured well by the trichromatic theory (color matching),
Second stage of color processing
captured well with the opponent-process theory (afterimages, simultaneous contrast).
What helps achieve color constancy
physical constaints
assumptions about the surfaces
What are mechanisms involved in color constancy
– Chromatic adaptation
– Memory color
Color adaptation is
The eye adjusts its sensitivity to different wavelengths and this helps achieve partial color constancy
Color memory is
characteristic color of familiar objects affects their color perception. • People judge the familiar objects to have a richer more saturated color than unfamiliar objects with the same wavelengths
