PSYCH261 Chapter Notes - Chapter 13: Limbic System, Striatum, Nucleus Accumbens

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Learning!refers!to!the!process!by!which!experiences!change!our!nervous!system!and!hence!our!
behaviour.!
9 We!refer!to!these!changes!as!memories.!
9 Experiences!are!not!“stored”;!rather,!they!change!the!way!we!perceive!,!perform,!think,!and!
plan.!
9 4!Basic!forms!of!learning:!Perceptual!learning,!stimulus9response!learning,!motor!learning,!and!
relational!learning.!
!
9&':&$%7#;(;&#'-.-/!Learning!to!recognize!a!particular!stimulus!that!had!been!perceived!before<!
9 The!primary!function!of!this!type!of!learning!is!the!ability!to!identify!and!categorize!objects!
(including!other!members!of!our!own!species)!and!situations.!
9 Each!of!the!sensory!systems!is!capable!of!perceptual!learning.!
9 Perceptual!learning!appears!to!be!accomplished!primarily!by!changes!in!the!sensory!
association!cortex!e.g!visual!and!auditory!association!cortex.!
!
=%.27;7>+'&>$3->&(;&#'-.-/!Learning!to!automatically!make!a!particular!response!in!the!presence!of!a!
particular!stimulus;!includes!classical!and!instrumental!conditioning.!
9 Thus,!involves!the!establishment!of!connections!between!circuits!involved!in!perception!and!
those!involved!in!movement.!
9 The!behaviour!can!be!an!automatic!response!(defensive!reflex),!or!it!could!be!a!complicated!
sequence!of!movements.!
!
9 Two!major!categories:!classical!conditioning!and!instrumental!conditioning!
!
!;#>>.:#;(:3-0.%.3-.-/9!A!form!of!learning!in!which!an!unimportant!stimulus!acquires!the!properties!of!
an!important!one!!
9 A!learning!procedure;!when!a!stimulus!that!initially!produces!no!particular!response!is!
followed!several!times!by!an!unconditional!stimulus!(US)!
!
?-:3-0.%.3-#;(>%.27;7>@?=A9!that!produces!a!defensive!or!appetitive!response!(the!?-:3-0.%.3-#;(
'&>$3->&B?C),!the!first!stimulus!(now!called!a!!3-0.%.3-#;(>%.27;7>B!=)!itself!evokes!the!response!
(now!called!a!!3-0.%.3-#;('&>$3->&B!C).!
!
9 It!involves!an!association!between!two!stimuli.!A!stimulus!that!previously!had!little!effect!on!
behaviour!becomes!able!to!evoke!a!reflexive,!species!typical!behaviour.!
9 E.g.!a!defensive!eyeblink!response!can!be!conditioned!to!a!tone.!If!we!direct!a!brief!puff!of!
air!toward!a!rabbit’s!eye,!the!eye!will!automatically!blink.!This!is!an!unconditional!response!
(UR)!because!it!occurs!unconditionally,!without!any!special!training.!The!stimulus!that!
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produces!it!(the!puff!of!air)!is!the!unconditional!stimulus.!Now!we!begin!training.!We!
present!a!series!of!brief!1000Hz!tones,!each!followed!by!500ms!later!by!a!puff!of!air.!After!
several!trials!the!rabbit’s!eye!begins!to!close!even!before!the!puff!of!air!occurs.!Classical!
conditioning!has!occurred;!the!conditional!stimulus!(the!1000Hz!tone)!now!elicits!the!
conditional!response!(the!eyeblink).!
9 Donald!Hebb!proposed!a!rule!that!might!explain!how!neurons!are!changed!by!experience!in!
a!way!that!would!cause!changes!in!behaviour.!
(
D&EE('7;&!!The!hypothesis!proposed!by!Donald!Hebb!that!the!cellular!basis!of!learning!involves!
strengthening!of!synapses!that!is!repeatedly!active!when!the!postsynaptic!neuron!fires.!–!if!a!synapses!
repeatedly!becomes!active!at!about!the!same!time!that!the!postsynaptic!neuron!fires,!changes!will!take!
place!in!the!structure!or!chemistry!of!the!synapse!that!will!strengthen!it.!!
!
9 How!does!the!Hebb!rule!apply!to!our!circuit?!If!the!1000Hz!tone!is!presented!first,!then!
weak!synapse!T!becomes!active.!If!the!puff!is!presented!immediately!afterward,!then!strong!
synapse!P!becomes!active!and!makes!the!motor!neuron!fire.!The!act!of!firing!then!
strengthens!any!synapse!with!the!motor!neuron!that!has!just!been!active!(synapse!T).!
9 After!several!pairing!of!the!two!stimuli!and!after!several!increments!of!strengthening,!
synapse!T!becomes!strong!enough!to!cause!the!motor!neuron!to!fire!by!itself.!Learning!has!
occurred.!
!
F->%'72&-%#;(:3-0.%.3-.-/!!A!learning!procedure!whereby!the!effects!of!a!particular!behavior!in!a!
particular!situation!increase!(reinforce)!or!decrease!(punish)!the!probability!of!the!behaviour;!also!
called!operant!conditioning.!
9 The!second!major!class!of!stimulus9response!learning!
Whereas!classical!conditioning!involves!automatic,!species9typical!responses,!instrumental!
conditioning!involves!behaviours!that!have!been!learned.!
9 classical!conditioning!involves!an!association!between!2!stimuli!whereas!instrumental!
conditioning!involves!an!association!between!a!response!and!a!stimulus.!
9 Instrumental!conditioning!is!a!more!flexible!form!of!learning;!it!permits!an!organism!to!
adjust!its!behaviour!according!to!the!consequences!of!that!behaviour.!!
9 when!a!behaviour!is!followed!by!favourable!consequences,!the!behaviour!tends!to!occur!
more!frequently;!when!it!is!followed!by!unfavourable!consequences,!it!tends!to!occur!less!
frequently.!
!
C&.-83':.-/(>%.27;.!!An!appetitive!stimulus!that!follows!a!particular!behaviour!and!thus!makes!the!
behaviour!become!more!frequent.!
9 Favourable!consequences!
!
97-.>".-/(>%.27;.!!An!aversive!attitude!that!follows!a!particular!behaviour!and!thus!makes!the!
behaviour!become!less!frequent.!
9 Unfavourable!consequences:!
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!
Rat$and$lever+food$experiment:!Reinforcement!causes!the!sight!of!the!lever!to!serve!as!the!stimulus!
that!elicits!the!lever9pressing!response.!It!is!not!accurate!to!say!simply!that!a!particular!behaviour!
becomes!more!frequent.!
9 If!no!lever!is!present,!a!rat!that!has!learned!to!press!one!will!not!wave!its!paw!around!in!the!
air.!The!sight!of!a!lever!is!needed!to!produce!the!response.!!
9 Thus,!the!process!of!reinforcement!strengthens!a!connection!between!neural!circuits!
involved!in!perception!(the!sight!of!the!lever)!and!those!involved!in!movement!(!the!act!of!
lever!pressing).!!
!
The!third!major!category!of!learning,!motor$learning,!is!actually!a!component!of!stimulus9response!
learning.!
9 E.g.!we!can!think!of!perceptual!learning!as!the!establishment!of!changes!within!the!sensory!
systems!of!the!brain,!stimulus9response!learning!as!the!establishment!of!connections!
between!sensory!systems!and!motor!systems,!and!motor!learning!as!the!establishment!of!
changes!within!motor!systems.!
!
13%3'(;&#'-.-/!!Learning!to!make!a!new!response.!
9 Motor!learning!cannot!occur!without!sensory!guidance!from!the!environment.!!
9 E.g.!most!skilled!movements!involve!interactions!with!objects;!bicycles,!video!game!
controllers,!knitting!needles.!!
9 Even!skilled!movements!that!we!make!by!ourselves,!such!as!solitary!dance!steps,!involve!
feedback!from!our!joints,!muscles,!vestibular!apparatus,!eyes!and!contact!between!the!feet!
and!the!floor.!
9 Motor!learning!differs!from!other!forms!of!learning!primarily!in!the!degree!to!which!new!
forms!of!behaviour!are!learned;!the!more!novel!the!behaviour,!the!more!the!neural!circuits!
in!the!motor!systems!of!the!brain!must!be!modified.!
!
A!particular!learning!situation!can!involve!varying!amounts!of!all!3!types!of!learning!that!I!have!
described!so!far:!Perceptual,!stimulus<response,!and!motor.!
!
9 E.g.!if!we!teach!an!animal!to!make!a!new!response!whenever!we!present!a!stimulus!is!has!
never!seen!before,!the!animal!must!learn!to!recognize!the!stimulus!(perceptual!learning)!
and!make!the!response!(motor!learning),!and!a!connection!must!be!established!between!
these!two!new!memories!(stimulus9response!learning).!!
9 If!we!teach!the!animal!to!make!a!response!that!it!has!already!learned!whenever!we!present!
a!new!stimulus,!only!perceptual!learning!and!stimulus!response!learning!will!take!place.!
9 The!3!forms!of!learning!described!so!far!consist!primarily!of!changes!in!one!sensory!system,!
between!one!sensory!system!and!motor!system,!or!in!the!motor!system.!!
9 Learning!is!more!complex!than!that!
!
Other$Forms$of$Learning$
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