midterm 1 Flashcards
Why is it so difficult for us to design a computer program that can identify objects as fast and accurately as we can (2)
Our brains allow us to classify objects very quickly;
This is very difficult to code for in computer programs, making it difficult for computers to categorize and identify objects
Why do people sometimes see/hear/feel different things when attending to the same stimuli
constructed and often somewhat subjective nature of perception
Sometimes the things we see/hear can be affected based on
{{c1::priming}}
Perceptual processing generally involves:
A __ stimulus
Processing at the ___ level (ie transduction)
Processing at the ____ level
__ processing that gives rise to particular interpretation/meaning
Some accompanying___ response (eg. action)
{{c1::distal}}
{{c1::receptor}}
{{c1::neuronal}}
{{c1::Top down}}
{{c1::behavioral}}
Objects _ the horizon (an imaginary horizontal line that is at the same level as the observer or ‘eye level’) that are higher in the field of vision are more distant
below
Objects above the horizon that are __ in the visual field are more distant
lower
object ID problem demonstrates the complexity of __ and associated__ and speaks to its constructed nature
{{c1::perception}}
{{c1::ambiguities}}
_ _ _ demonstrates the complexity of perception and associated ambiguities and speaks to its constructed nature
object ID problem
Any information the perceiver brings to a situation can be referred to as
{{c1::knowledge}}
__ is based on incoming stimuli from the environment
Sometimes referred to as ___ processing
{{c1::Bottom up processing}}
{{c2::data-based}}
___ Processing based on the perceivers previous knowledge (ie cognitive factors)
Sometimes referred to as ___
{{c1::Top down processing }}
{{c2::knowledge based processing}}
__receptors are cells specialized to respond to environmental energy(e.g. with vision, a critical element involves visual pigments reacting to light)
___ is then said to occur, which converts environmental energy into__ impulses during__ processing
Sensory
Transduction
nerve
receptor
___processing involves changes that occur as signals are transmitted through the mess of neurons in our brains
e.g. different primary receiving areas for different modalities
Neural
perceptual process order (DLR NPRA)
- distal stimulus
2 light reflected and focused
3, receptor processes - neural processing
- perception
- recognition
- action
three general kinds of perceptual relationships:
Stimulus -> Behaviour
Stimulus -> Physiology
Physiology -> Behaviour
Orientation of more _ spaced lines easier to accurately identify than _ spaced
Accurate identification of the orientation of the lines eventually becomes impossible as spacing gets sufficiently _
what type of perceptual b is this?
Orientation of more widely spaced lines easier to accurately identify than narrowly spaced
Accurate identification of the orientation of the lines eventually becomes impossible as spacing gets sufficiently close
Stimulus -> Behaviour
what relationship is this: Neural response changes in predictable ways when perceiving lines of different orientations
Stimulus -> Physiology
For horizontal and vertical orientations:
Identification is better (the oblique effect)
These stimuli result in greater neural activation
what type of perceptual b is this
Physiology -> Behaviour
oblique effect
can ID horizontal and vertical lines better
Why is the difference between physical and perceptual properties important?
One reason is because they are not always equivalent!
Response Compression
as intensity increases, the perceived magnitude increases more slowly than the actual increase in intensity
example of Response Compression
(e.g. can occur with brightness perception)
Response Expansion:
as intensity increases, the perceived magnitude increases more quickly than the actual increase in intensity
example of response expansion
(e.g. can occur with pain perception)
distal stimuli
Environmental stimuli are all objects in the environment that are available to an observer
proximal stimuli
the images formed on the retina
When an observer selectively attends to an object, receptors respond to the distal stimulus, resulting in the generation of internal representations
Principle of Representation
Everything a person perceives is based not on direct contact with stimuli but rather on representations of stimuli that are formed on the receptors and the resulting activity in the person’s nervous system
Principle of Transformation
The representations of stimuli in our environment which we construct are transformed, or changed, between the original distal stimulus and the eventual perception they give rise to
Energy can be described using__ (measured in nm: nanometers)
The electromagnetic spectrum spans a huge range, from short wavelength__ rays to long wavelength___ waves
The visible spectrum for humans ranges from ___, which we perceive as ‘colour’
wavelength
gamma, radio
400 to 700 nm
Most perceived light is__ light
reflected
Light enters the eye through the__ and is focused by the__ and lens to a sharp image on the__
pupil, cornea, retina
__ and __ are visual receptors in the retina that contain visual pigment
Rods and cones
The optic nerve carries information from the__ toward the brain
retina
___work similarly to the eye and can be a useful point of comparison
Cameras
The eye has ~__ million rods and ~__ million cones,
120M, 6M
rods and cones differ in:
Shape
Rods: Cones:
Distribution across the retina
Fovea consists solely of _
Peripheral retina is mostly _ (but also contains some _)
Shape
Rods: large and cylindrical
Cones: small and tapered
Distribution across the retina
Fovea consists solely of cones
Peripheral retina is mostly rods (but also contains some cones)
Macular degeneration: _ and small surrounding _ are destroyed (has particular implications for _ acuity vision)
Creates a ‘dead zone’ on the _
Most common in _ individuals
Fovea and small surrounding area are destroyed (has particular implications for high acuity vision)
Creates a ‘dead zone’ on the retina
Most common in older individuals
Retinitis pigmentosa: _ are destroyed first (has particular implications for _ vision)
Foveal cones can also be attacked
Linked to genetic/environmental causes
Severe cases can result in complete _
Retinitis pigmentosa: Rods are destroyed first (has particular implications for night vision)
Foveal cones can also be attacked
Linked to genetic causes
Severe cases can result in complete blindness
Problems with Receptors
Macular degeneration
retinitis pigmentosa
The location where the optic nerve exits the eye contains no receptors
blind spot
blind spot
The location where the optic nerve exits the eye contains no receptors
do/don’t notice blind spot
why? (3)
do
One eye covers the blind spot of the other
It is located towards the edge of our visual field
The brain ‘fills in’ missing information by extrapolating what’s around it (via top-down processing)
The cornea, which is fixed, accounts for about__% of the focusing power of our eye
The lens, which adjusts shape for object distance, accounts for the other__%
We can typically see far away objects relatively clearly when our lenses are___, though not near objects
80
20
relaxed
Accommodation
occurs when ciliary muscles are tightened
Accommodation causes the lens to__
Light rays then pass through the lens more___, allowing for near objects to be focussed on the retina and thus forming a clearer image
thicken
sharply
Myopia (AKA ‘nearsightedness’) refers to the inability to see__ objects clearly
Occurs when the image gets focused ____ of the retina
distant
in front
myopia can be caused by
Refractive myopia
Axial myopia
Refractive myopia:
Axial myopia:
Refractive myopia: cornea or lens bends too much light
Axial myopia: eyeball is too long
Hyperopia (AKA ‘farsightedness’) refers to the inability to see__ objects clearly
Occurs when the image gets focussed__ the retina
Usually caused by an eyeball that is too__
nearby
behind
short
Constant accommodation for hyperopia for nearby objects can lead to___ and___
eyestrain
headaches
Presbyopia (AKA ‘old eye’) occurs when __
Caused by hardening of__ and weakening of ___
Corrective___ are needed for close activities, such as reading
the lens can no longer adjust for close objects
lens, ciliary muscles
lenses
The outer segments of receptors contain visual pigment molecules, which consist of two components:
retinal, opsin
Retinal:
opsin
Retinal: a light sensitive molecule
Opsin: a large protein
Visual transduction
occurs when the retinal absorbs one photon, causing it to change shape (a process referred to as isomerization)
In total, the isomerization of a single visual pigment molecule activates about __ million other molecules, a cascade of effects which eventually results in the activation of the___
1
receptor
Dark adaption refers to the
process of increasing visual sensitivity after switching from high to low-level lighting conditions
dark adaptation curve can be determined using the following general approach:
steps 1-3
- An observer starts in a lit room and becomes ‘light adapted’
- The lights are then turned off, at which point the observer adjusts the intensity of a test light until it is just barely visible. This determines their sensitivity at the beginning of the dark adaptation curve
- As time passes, they continue to readjust the intensity of the test light (again, until it is just barely visible) to plot the change in sensitivity across time
how was dark adaptation curve measured for both rods and cones
looking directly at a fixation point while (covertly, without moving the eye) attending to a test light off to the side
results for dark adaptation curve that measures both rods and cones
- sensitivity increases in _ stages
Stage one takes place for _ to _ minutes
Sensitivity then levels off for seven to ten minutes (the - break)
Stage two shows increased sensitivity for another _ to _ minutes
2
Stage one takes place for three to four minutes
Sensitivity then levels off for seven to ten minutes (the rod-cone break)
Stage two shows increased sensitivity for another 20 to 30 minutes
are rods or cones more sensitive to peripheral light
rods
how was cone dark adaptivity tested
what were the results
which stage of dark adaptivity results indicates this
Participant fixates directly on test light
Results show that sensitivity increases for three to four minutes and then levels off
first stage
why did participants look directly on test light for cone dark adaptivity testing
This stimulates (and thus isolates the effect of) only cones, because that is the only kind of receptor in the fovea
how was rod dark adaptivity tested
what were the results
which stage of dark adaptivity results indicates this
Accomplished by using a rod monochromat participant
Results show that sensitivity increases for about 25 minutes and then levels off
The second stage of the dark adaptation curve can be attributed to this
why was a rod monochromat used for rod dark adaptivity
to isolate effect on rods
process for transduction
_ molecule changes shape
Opsin molecule _
The retina shows visual pigment _
Retinal and opsin must then recombine in a process called _, in order to be capable of responding to light again
retinal molecule changes shape
Opsin molecule separates
The retina shows visual pigment bleaching
Retinal and opsin must then recombine in a process called regeneration, in order to be capable of responding to light again
Pigment bleaching accounts for being ….
because your entire supply of pigments is _ and must _ before _ can occur again
temporarily ‘blinded’ by a bright light (e.g. camera flash)
your entire supply of pigments is depleted and must regenerate before transduction can occur again
gradual improvement that we experience as we dark adapt has a lot to do with
pigments being regenerated at a faster rate than they’re being used
Spectral sensitivity refers to
Monochromatic light (_____) can be used to determine ____ at different wavelengths
the sensitivity of rods and cones to different parts of the visible spectrum
Monochromatic light (containing only one ‘type’ of wavelength, e.g. 400 nm) can be used to determine threshold at different wavelengths
Threshold and sensitivity are
reciprocal
Humans are most sensitive to the _ part of the visible spectrum (/ light)
This corresponds to the part of the spectrum that they have the lowest/highest threshold for
Humans are most sensitive to the middle part of the visible spectrum (greenish/yellow light)
lowest
Rods and cones are similar/differ in their spectral sensitivity
differ
Rods are more sensitive to _-wavelength light (most sensitivity at 500 nm)
Cones are most sensitive at _ nm
Rods are more sensitive to short-wavelength light (most sensitivity at 500 nm)
Cones are most sensitive at 560 nm on average
The difference in spectral sensitivity across rods/cones is due to a
difference in their absorption spectra of visual pigments
Purkinje shift:
enhanced sensitivity to short wavelengths during dark adaptation when the shift from cone to rod vision occurs
purkinje shift results in
Results in blue ‘seeming’ brighter to a dark-adapted eye, as compared to how it appears to a light-adapted eye (and can also shift our perception of colour)
Rods and cones send signals vertically through: (2)
Bipolar cells
Ganglion cells
Signals are sent horizontally: (2)
Between receptors by horizontal cells
Between bipolar and between ganglion cells by amacrine cells
_ million rods and cones converge to 1 million _ cells
Higher/lower convergence of rods than cones
Average of _ rods to one ganglion cell
Average of _ cones to one ganglion cell
Cones in fovea have - relation to ganglion cells
126 million rods and cones converge to 1 million ganglion cells
Higher convergence of rods than cones
Average of 120 rods to one ganglion cell
Average of six cones to one ganglion cell
Cones in fovea have one to one relation to ganglion cells
Rods (as compared to cones)… (3)
Are more sensitive to light, Take less light to respond, greater convergence
greater convergence of rods results in…
trade off?
summation of the inputs of many rods into ganglion cells, increasing the likelihood of a response
rods cannot distinguish detail as well
more convergence of rods = more/less sensitive
more
compared to rods are cones sensitive enough to register a response to a faint stimulus
no
All-cone foveal vision results in __ _ _
This relates to the difference in convergence, in which more/fewer cones are connected to any one ganglion cell (i.e. have more/less convergence)
T/F: This kind of wiring allows cones to better discriminate detail (as compared to rods)
high visual acuity
fewer, less
T
The trade-off for cones due to wiring
need more light to respond than rods
explain firing pattern of ganglion that’s connected to multiple roods when it is stimulated in two different patterns
explain firing pattern of ganglion that’s connected to one cone when it is stimulated in two different patterns (1:1 connection)
same firing pattern in ganglion, cell can’t differentiate
different firing pattern that can be differentiated
different firing pattern of cones indicate
greater acuity
t/f: humans can perceive uv like bees
f
Visual receptive fields refer to the
retinal region over which a given cell in the visual system can be influenced (excited or inhibited) by light
visual receptive fields Can be determined by monitoring
single cell responses
single cell responses
They cover a greater/smaller area than that associated with a single rod/cone, and do/do not overlap with each other
(stimulus is presented to retina and response of cell is measured by an electrode)
greater, do
hartline based work of single cell responses on
frog eyes
unlike frog eyes, cat (and human) eyes can demonstrate both _ and _ effects associated with receptive fields
excitatory and inhibitory
2 basic forms of retinal vision
Excitatory-centre-inhibitory surround
Inhibitory-centre-excitatory surround
Output of centre-surround receptive fields changes depending on area stimulated:
Highest response when only the___ area is stimulated
Lowest response when only the___ area is stimulated
Intermediate responses when both areas are stimulated (- antagonism)
excitatory
inhibitory
centre-surround
implication of excitatory-inhibitory layout of eye
neural mechanism that allows the neuron to respond ‘best’ to one particular type of stimuli
excitatory-inhibitory layout of eye demonstrates
‘tuning’, or specialization for a particular kind of stimulus
Signals from retina exit the eye through the _ _ then…
Arrive first at the __
sent along to the _ in the_ lobe
Are then sent through two pathways to the_ lobe and the_ lobe (the dorsal and ventral streams)
And finally arrive at the_ lobe
optic nerve
lateral geniculate nucleus (LGN)
primary visual receiving area, occipital
temporal, parietal
frontal
primary visual receiving area located in
striate cortex, beginning with area V1
_ _ also receives some signals form the eye and and is important for controlling -
Accounts for ~_% nerve fibres leaving the eye
superior colliculus
eye-movements
10
The __accounts for ~ 90% nerve fibres leaving the eye
LGN
LGN cells have ___ (like in the retina)
centre-surround receptive fields
More ‘information’ (a larger signal) is sent from the eye to the LGN, as compared to what is passed along from the LGN to_
what does this suggest?
V1
(suggesting the LGN may regulate, or filter, what information is passed along to V1)
The LGN also receives more/less information from the cortex than it sends to the cortex
what does this suggest?
more
backward flow of information that may constitute a feedback mechanism
Neurons that fire in response to specific features of a stimulus are called
feature detectors
feature detectors have receptive fields with both _ and _ areas (like the receptive fields in the retina and LGN)
They are oriented _ - _ (rather than the centre-surround receptive fields seen in the retina and LGN)
inhibitory and excitatory
side-by-side
Major types of feature detectors in V1: (3) (sec)
Simple cortical cell
Complex cortical cell
End-stopped cortical cell
___ plot the response of a simple cortical cell to line stimuli of varying orientations
Orientation tuning curves
Complex cortical cells
respond best to movement across the receptive field of particularly oriented bar
what happened when Hubel and Wiesel dropped a slide into their slide projector, the image of the edge of the slide moving down
triggered activity in complex cortical cells
simple cortical cells
excitatory and inhibitory areas arranged side by side, responds best to particular orientation
end stopped cortical cells
responds to corners, angles, bars of a particular length moving in a particular direction
optic nerve fibre (ganglion cell)
center surround receptive system
responds best to small spots but will recognize other stimuli