46-333 Lecture Notes - Retina, Trichromacy, Proprioception

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Published on 19 Apr 2013
School
University of Windsor
Department
Psychology
Course
PSYC 3330
Professor
Perception*
!
Thresholds*
threshold!(or!limen)‐‐the!point!when!a!psychological!and/or!physiological!effect!is!produced!
absolute!threshold‐‐the!least!amount!of!a!stimulus!needed!to!trigger!a!sensory!perception!(e.g.!
a!candle!at!one!mile!away)!
difference!threshold1(or!just1noticeable1difference)‐‐the!least!amount!of!difference!between!two!
stimuli!for!perception!to!occur!
!
Gustav!Fechner!elaborated!on!Ernst!Weber’s!work!to!create!Weber’s1Law!
–! Weber’s!Law!states,!to!be!perceptibly!different,!two!stimuli!must!differ!by!a!constant!
proportion,!not!a!constant!amount!of!the!original!stimulus!
this!is!related!to!difference1thresholds1
1
David!Hubel!and!Torsten!Wiesel!are!best!known!for!feature1detection1theory!
the!visual!cortex!has!feature1detector1neurons1that!receive!information!from!individual!
ganglion!cells!in!the!visual!field!and!respond!to!a!scene’s!specific!features!
feature!detection!cells!in!the!visual!cortex!pass!on!information!to!other!cortical!cells!that!
respond!only!to!more!complex!patterns!
the!visual!cortex!has!feature!detectors!for!a!variety!of!images;!what!we!perceive!is!a!
combination!of!these!features!
!
•!! our!brain!naturally!engage!in!parallel1processing—processing!many!things!at!once!
•!! the!visual!scene!is!divided!by!the!brain!into!sub‐dimensions—movement,!color,!depth,!form!
•!! visual!perception!requires!integrating!these!separate!pieces!
–! the!process!of!facial!recognition!requires!the!combined!efforts!of!about!30%!of!the!cortex!
–! interrupting!facial!recognition!with!magnetic!pulses!will!disrupt!this!process!and!people!are!
unable!to!recognize!the!face!
–! magnetic!pulses!do!not!work!with!object!recognition,!however!
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The*Eye*Diagram*p.*205*
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The*Eye*
the!structures!of!the!eye!from!the!diagram!are!as!follows:!
lens:!focuses!the!image!onto!the!retina;!the!image!is!focused!upside‐down!on!the!retina!
pupil:!regulates!the!amount!of!light!entering!the!eye;!full!dark!adaptation!takes!about!30!
minutes!and!light!adaptation!about!1!minute!
iris:!the!colored!part!of!the!eye!
cornea:!the!soft,!outer,!protective!covering!of!the!eye!
retina:!contains!photoreceptor!cells,!rods!(which!detect!brightness!contrasts)!and!cones!
(which!detect!color)!
fovea:!an!area!of!the!retina!that!contains!all!cones!and!no!rods!
optic!nerve:!relays!visual!information!to!the!brain!
blind!spot:!where!the!optic!nerve!connects!to!the!back!of!the!eye!
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How*We*See*
gathering!light!
light!reflected!off!objects!
color!is!collected!through!both!light!intensity!(brightness)!and!light!wavelength!(color)!
within!the!eye!
reflected!light!enters!the!eye!through!the!cornea!and!pupil!
the!iris!muscles!regulate!the!pupil!to!open!or!close!
the!light!is!focused!by!the!lens!onto!the!retina1
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transduction!
transduction‐‐translating!incoming!stimuli!into!neural!signals!
rods!and!cones!fire!in!an!area!of!the!retina1
these!photoreceptor!cells!activate!the!next!layer!of!bipolar1cells!
these!bipolar!cells!activate!ganglion1cells!
axons!of!these!ganglion!cells!make!up!the!optic!nerve!
the!optic!nerve!sends!these!impulses!to!the!lateral1geniculate1nucleus!of!the!thalamus!
these!impulses!are!sent!to!the!visual1cortex!in!the!occipital!lobe!
feature!detectors!are!activated!to!determine!lines,!curves,!motion!and!other!features!of!the!
object!
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Transduction*Diagram*p.*207*
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