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Psychology 205
Perception
06 Feb 03
Day 06
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Three Kinds of Adaptation
definition: "Modify to suit new conditions"
biology: Darwin -- change in the genome so that the phenomebetter fits its ecological niche; better --> reproduction;change random with selection
perception:1. Responding to constant stimuli
sensory neurons2. Accommodating different ranges of stimulation
sensory systems3. Accommodating different patterns of stimulation
cortex
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1. Response to constant stimuli neuronal
touch, olfaction, gustation, visionnot audition, pain, or kinesthesis
response decrement, spontaneous recovery
cross-adaptationadaptation (d') vs. habituation ()
stabilized imagesPurkinje's tree
saccades & fixationspursuit movementsphysiological nystagmus (eye tremors)
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slowlyadapting
rapidlyadapting
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for conveniencelook at rapidlyadapting systems
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how to test?
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one testinterval
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2nd testinterval
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3rd testinteval
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Result byconnectingdata points
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no cross-adaptation
adapt withone stimulus
test with adifferentstimulus
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some crossadaptation
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adaptation (d')change in the sensitivityd' decreases with increased neural
adaptation but adaptation is not the only cause for a change in d'
habituation ()change in ones bias;
possible increase in boredom,or simply tuning out
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stabilized images ----->Purkinje's tree
3 basic eye movements
1. saccades & fixations: endogenous control
2. pursuit movements: exogenous control
3. physiological nystagmus eye tremors, automatic,uncontrolled
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eye movements
1. saccades & fixations:3-4/s in reading, watching cinema, often less elsewhere
fixations ~200-300 ms; saccades ~50-100 mssaccades up to 600 /s
2. pursuit movements:up to 80/s, lowered acuity (tracking not perfect)
3. physiological nystagmusup to 150 cycles/s; amplitude = half diameter of cone
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classicalmethod
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Process of perception:
1. One sees the content of the slide perfectly2. Then content fades3. Then content fades to neutral gray, not black
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Approximation:
stare atblack dot
overtimerings
willfade
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alternativemethod, notquite asgood
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Stabilized edges (Krauskopf, 1963)
Filling in of color, despitethe fact thatthe receptorsarestimulateddifferently
Importanceof edges!
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Are there any stabilized images inthe real world of our natural experience?
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9 of 10 photons enteringthe eye are absorbedbefore nearing thereceptors; many receptorsare beneath blood vessels
and arteries
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Purkinjes
tree
optic diskfovea
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2. Accommodating different ranges of stimulationsensory systems
light & dark adaptationphotopic & scotopic cones & rodsmesopic
ossicular dampening
signal-to-noise ratiosoptimality in sensory systems
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light & dark adaptation:light --> quick; dark --> slow
two light-catching systems
photopicday vision, color, cones
scotopicnight vision, black and white, rods ~500 times as sensitive after complete dark adaptation
mesopic both, room light
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Is there an analog in audition?
partial
ossicular dampening
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Ossiculardampening causedby muscles aroundossicles
When in the midst of constant loudnoise, they clench and dampen the
sound by about 6 dB, ~3x
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Why not simply build a supersensitive system?avoid the necessity of needing two (or more) systems
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1. Range of neural spikes/unit time is relatively small maximal firing = 1000 s
2. The system should avoid firing near maximal ratefor too long. Possible tissue damage; ossicular dampening.
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3. Accommodating different patterns of stimulationcortical
re-learning usingMolyneux's paradox in animals and humans
Roger Sperryneural regeneration in amphibians
George Stratton, Ivo Kohler, and others inverting lenses body schema
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William Molyneux, Dioptrica Nova, 1692
Molyneuxs Paradox - the orientation of thevisual fieldRelevant to M ller VIII
Molyneuxs Premise - depth perception
Moylneuxs Conjecture - the blind given sight
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upside downand backwards;rotated 180
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Neuroplasticity and behavior
Roger Sperry
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rotate the eyes
upside down,backwards,depth wrong
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switchopticnerves
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Snyder &Pronko
Dolezal
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In responseto Molyneux
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upside down;
swinging;coordination
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gradualimprovement
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still moreimprovement;
left-right;swinging
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gradual build up of unifiedsense of body and sight
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Ivo Kohler
after a 30-day period of adaptation toinverting lenses
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Ivo Kohler
after a 30-day period of adaptation toinverting lenses
able to drive a Vespa rapidly, weaving in an out of traffic, indowntown Innsbruck
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slow adaptation to new state of affairs;old schema suppressed, not changed
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wedgeprisms
sensorimotoradaptation
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people adapt;chicks dont
adaptation to spatialinversion anddisplacements are cortical,and beyond V1
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Three Kinds of Adaptation
definition: "Modify to suit new conditions
biology:
perception:1. Responding to constant stimulisensory neurons --> Purkinjes tree & lab phenomena
2. Accommodating different ranges of stimulationsensory systems --> light/dark adaptation
ossicular dampening3. Accommodating different patterns of stimulation
cortical --> inverting & wedge lenses