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PSYC 102 - sensory > Perception > Flashcards

Flashcards in Perception Deck (110)
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what is sensation

the process of transforming physical stimuli to electrical (neuronal) signals


what is transduction

turning one signal into another


what is perception

the process of interpreting these signals for conscious awareness or for action


explain retinal implant

for macual degeneration / retinitis pigmentosa
silicone microelectrode array implanted in damaged retina
sends electrical signals directly into the cells that carry info to the brain


explain neural prosthesis

treatment of quadriplegia
96 electrodes implanted into motor cortex = can think about moving and machine will then move


why do we study vision so heavily

its what we know the most about


explain the major theme of perception

it is an inference
your brain is doing its best to figure out whats going on given the limited input
percetion is ongoing and more than just a passive sensation
perception is rarely ambiguous - the brain jumps to conclusions, or tries to force an interpretation on a scene (eg the necker cube - we see one or the other, never both simulataneously)


how do we see (ideas not specific)

with our brain not our eyes
often the interpretation imposed by the brain is based on prior experience on what is most likely


what part of the electromagnetic spectrum do we see

the visible spectrum
400nm to 700 nm in waelenght (blue to red)


explain the four receptors in the retina

blue cones - absorb blue light
green cones - absorb green light
red cones - absorb red light
cones support colour vision


whats special about matis shrimp

12 photoreceptors
but they are rubbish at colour vision
shrimp brain cant process it all
we are much better at seeing with our brains


vision (and perception in general) is always.....

constructive and filtered through your own experience
perception is always dependent on a combination f bottom-up sensory information and top-down knowledge


why do we study perception

think about natural vs aritificial images
our ultimate goal is to undersatnd the visual system - go from light to perception in a step by step process
this is tough so instead we take a reductionist approach - how does the brain understand the smaller pieces


natural image vs artifical stimuli

natural - what we actually see
artificial - what we use in the lab


why do we use artificial stimuli in the lab

we can ask much more systematci questions
for example whats the smallest change in orinetation of lines we can perceive


what is threshold and what does it tell us

threshold is the smallest change the observer notices
is tells us how sensitive the observer is to a particular feature
these thresholds inform us about perceptual capabilities
eg colour code different bits of brain cells to different types of stimuli


how to study perception (3 ways and goal)

1 behavioural measurements - psychophysics
2 physiological and behavioural measurements in animals
3 physiological and behavioural measurements in humans
goal - link neural activity with perception and behaviour


what is psychophysics

performing behavioural measurements to determine how well stimuli are perceived


go through magnitude estimation psychophysics example

stimuli are above the threshold
observer is given a standard stimulus and a value for its intensity
observer compares the standard stimulus to test stimuli by assigning numbers relative to the standard
response expansion - as intensty increases, the perceived magnitude increases more quikcly than the stimulus intensity eg shock
response compression - as intensity increases the perceived magnitude increases more slowly than the intensity eg brightness


explain the two types of threshold estimation

absolute threshold - the minimum intensity of stimulation required to produce a detectable sensory experience 50% of the time - detection
difference threshold - the minimum chnage in intensity required to produce a detectable change in sensory experience about 80% of the time (this is also known as the just noticeable difference) - discrimination


explain graphs for creating a psychometric function for absolute threshold by method of constant stimuli

plot 6 values of light intensity against percentage stimuli detected
now can find the 50% threshold point where the light at that intensity would be detected 50% of the time through interpolation


explain frequency vs pitch in auditory perception

the psychological experinece of pitch is related to the temporal frequency of vibrations of air hitting the eardrum
so double the frequency = double the octave of the pitch


how to measure someones JND between two auditory pitches

lets use method of constant stimuli
pick baseline value
pick a set of increments
sequentially present baseline and baseline +increment
randomly chose which one comes first and ask subject for the higher frequency (chance = 50%)
plot the psychometric function
the difference threshold is the value that gives 80% correct (80% here is just a typicla value)


what is the weber fraction

the fractional increase above a baseline value that can be reliably detected
it is the ration difference threshold over the baseline value


what is weber's law

detectable change n a stimulus varies as a function of baseline stimulus value
-constant ration (difference threshol / baseline value)


how did Fulton 1928 study walters brain

listened with a stethescope to walter's buldge on the back of his head
heard nothing when eyes closed
but lots when reading a newspaper


how does fMRI work

takes advantage of hemodynamic (blood flow, blood oxygenation)
magnetic properties of blood to indirectly track neural activity
blood oxygenation level dependent (BOLD) signals - oxygenated and deoxygenated hemoglobin have different magnetic properties and so the change in relative concentration can be measuredusing MRI


uses of functional meuroimaging

functional brain mapping
relative neural activity behabiour
-intact humans
-patients with brain damage
presurgical planning - eg epilepsy or tumour resection


problem with fMRI

no temporal resolution - spike appears around 6 seconds after stimulation
but its really safe in humans


when do we use single unit recording and what does it measure

as usually surgical normally in non-humans
occasionally used in humans for presurgical mapping
measures firing in one neuron