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Chapter 13

Chapter 13- Learning and Memory.pdf

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University of Waterloo
Britt Anderson

Chapter 13 Learning and Memory The Nature of LearningLearning refers to the process by which experiences change our nervous system and hence our behaviourWe refer to these changes as memoriesExperiences are not stored rather they change the way we perceiveperform think and plan4 Basic forms of learning Perceptual learning stimulusresponse learning motor learning and relational learningPerceptual learningLearning to recognize a particular stimulus that had been perceived beforeThe primary function of this type of learning is the ability to identify and categorize objects including other members of our own species and situationsEach of the sensory systems is capable of perceptual learningPerceptual learning appears to be accomplished primarily by changes in the sensory association cortex eg visual and auditory association cortexStimulusresponse learningLearning to automatically make a particular response in the presence of a particular stimulus includes classical and instrumental conditioningThus involves the establishment of connections between circuits involved in perception and those involved in movementThe behaviour can be an automatic response defensive reflex or it could be a complicated sequence of movements Two major categories classical conditioning and instrumental conditioningClassical conditioning A form of learning in which an unimportant stimulus acquires the properties of an important one A learning procedure when a stimulus that initially produces no particular response is followed several times by an unconditional stimulus USUnconditional stimulusUS that produces a defensive or appetitive response the Unconditional responseUR the first stimulus now called a Conditional stimulusCS itself evokes the response now called a Conditional responseCR It involves an association between two stimuli A stimulus that previously had little effect on behaviour becomes able to evoke a reflexive species typical behaviourEg a defensive eyeblink response can be conditioned to a tone If we direct a brief puff of air toward a rabbits eye the eye will automatically blink This is an unconditional response UR because it occurs unconditionally without any special training The stimulus that 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 rabbits 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 eyeblinkDonald Hebb proposed a rule that might explain how neurons are changed by experience in a way that would cause changes in behaviourHebb rule The hypothesis proposed by Donald Hebb that the cellular basis of learning involves strengthening of synapses that is repeatedly active when the postsynaptic neuron firesif 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 itHow 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 TAfter 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 occurredInstrumental conditioning 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 conditioningThe second major class of stimulusresponse learning Whereas classical conditioning involves automatic speciestypical responses instrumental conditioning involves behaviours that have been learnedclassical conditioning involves an association between 2 stimuli whereas instrumental conditioning involves an association between a response and a stimulusInstrumental conditioning is a more flexible form of learning it permits an organism to adjust its behaviour according to the consequences of that behaviour 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 frequentlyReinforcing stimuli An appetitive stimulus that follows a particular behaviour and thus makes the behaviour become more frequentFavourable consequencesPunishing stimuli An aversive attitude that follows a particular behaviour and thus makes the behaviour become less frequentUnfavourable consequencesRat and leverfood experiment Reinforcement causes the sight of the lever to serve as the stimulus that elicits the leverpressing response It is not accurate to say simply that a particular behaviour becomes more frequentIf 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 Thus the process of reinforcement strengthens a connection between neural circuits involved in perception the sight of the lever and those involved in movementthe act of lever pressing The third major category of learning motor learning is actually a component of stimulusresponse learningEg we can think of perceptual learning as the establishment of changes within the sensory systems of the brain stimulusresponse learning as the establishment of connections between sensory systems and motor systems and motor learning as the establishment of changes within motor systemsMotor learning Learning to make a new responseMotor learning cannot occur without sensory guidance from the environment Eg most skilled movements involve interactions with objects bicycles video game controllers knitting needles 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 floorMotor 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 modifiedA particular learning situation can involve varying amounts of all 3 types of learning that I have described so far Perceptual stimulusresponse and motor Eg 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 stimulusresponse learning 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 placeThe 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 Learning is more complex than thatOther Forms of Learning
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