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PSYCH 2TT3 (28)


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Brett Beston

February 4 , 2013 Psych 2TT3: Animal Behaviour Learning Behaviour - Behaviour can be shaped by innate activity or learning Learning - what is learning? - Learning is the ability to acquire a neuronal representation of new information - An individual may use that information to determine subsequent behaviour - Learning is represented on a neuronal scale - Donald Hebb – Hebb’s law: first describe learning on a synaptic scale  Idea that cells that fire together wire together; cells that don’t won’t - what is learning at the neuronal level?  Learning depends on the persistent change in connectivity in the brain  A stimulus from a neuron produces a typical response from the neuron to which it connects  If an input is large enough it will generate a response = action potential, producing stereotype pattern  We can record the magnitude of the curve and show that it increases or decreases based on how well it is connected  If the stimulus reliably produces a response, the strength of the physiological response increases  Over several repeated parings there is a change in the magnitude of an action potential response  Reliable stimulation results in a strengthening of a connection  The opposite is true in forgetting  If the stimulus doesn’t reliably produce a response, the strength of the physiological response decreases  We get a weakening of the connection Dr. Eric Kandel - study of memory and learning in Aplysia (sea slug) - idea of Hebbian rule and related it to learning in an animal - strength of a connection or a response could change through learning Why Study the Memory of a Sea Slug? - capable of learning about environment - what do Aplysia have to focus on in their environment: basic defensive reflexes - have same kinds of basic reflexes as humans - slow therefore must have good strategies - main predators: crabs and lobsters - what do sea slugs have to remember: how to survive with these predators - able to modify some of their basic reflexes in response to predators Non-Associative Learning - sensitization: increased response to stimuli following the presentation of a prominent stimulus (e.g. loud sound, strong smell) - habituation: decreased response to a stimulus following the repeated presentation of that stimulus (e.g. loud sound, strong smell) - involves single stimulus and response - how do those responses change over time? Habituation and Sensitization in Humans - habituation:  bright light  clothes  alarm clock - sensitization:  your name  red light - they can be the exact same thing but the context shapes how we react to it Aplysia and its Role in Understanding the Neural Basis of Learning - Gill siphon withdrawal reflex (GSWR) - Siphon is a delicate organ used to sense the environment and gather food, protected by skin, in presence of stimulation retracts its gill withdrawing the siphon and becoming more protected - Reflex can tell scientist if the Aplysia has learned - Aplysia thought to be on guard are more alert and remains withdrawn longer - Process of sensitization was an increase in duration of the gill siphon withdraw reflex - The longer the reflex the more salient is the response - If the animal is habituate they are more likely to ignore the stimulus and response would decrease Gigantic Neurons - sea slugs are the most often used model organism in neuroscience as they have extremely distinctive neurons - nervous system is simple and consist of 20 000 neurons organized into 9 ganglia - therefore it is easy to figure out the pathway, the connection between neurons, and locate the neurons - GSWR is mediate by a single connection between sensory neuron (siphon) which triggers a reaction in the motor neuron inducing a change in the gill muscle - Sensory mechanical connection Aplysia and its Role in Understanding the Neural Basis of Learning - large neurons allow you to (more) easily record/monitor activity - simple connectivity between connections - can demonstrate simple forms of learning (non-associative learning in particular) Habituation in Applysia - touch the siphon and gill withdraws - small stimulus Hypothetical Data of Aplysia Gill Withdrawal Response - habituation - extracted neurons that connected between siphon and gill, how does weak stimulation affect neuron overtime:  stimulates sensory neuron (presynaptic) and records consistent stimulation  stimulation is the same  records output of postsynaptic neuron (amount of current) the response decreases Sensitization in Aplysia - using a stronger stimuli - change in response Hypothetical Data of Aplysia Gill Withdrawal Response After Shock - same set of connections had increased the amount of current - able to relate behavioural changes to changes in connectivity Hypothetical Data of Aplysia GSWR after Shock - sensitization increases in magnitude Pavlov’s Drooling Dogs - not a psychologist - study of digestion - discovered psychic secretions: noticed that every time dogs were fed they started to salivate before food was actually presented to them, food should be the stimulus, so what was triggering the salvation, dogs cued in to presents of the white lab coats Basic Principles of Classical Conditioning - fundamental building block of learning - happens in virtually all animals Classical Conditioning - stimulus elicits reflex: salvation at the sight of food - unconditional stimulus elicits unconditional responses: demonstrates a relationship exist, every time the stimulus is presented the response will follow (non associative conditioning) - how could stimulus that had nothing to do with the response still elicit the response - conditional stimulus: any kind of a stimulus that initially does not elicit a response but over time comes to do so when it is paired with the unconditional stimulus - we could eventually only present the conditional stimulus that still elicit the response even when the unconditional stimulus is presented, the conditional response - through experience unrelated environmental stimulus develop a relationship In Associative Learning - following pairings with an unconditioned stimulus, a neutral stimulus can come to control a new response: conditioned stimulus (CS) - after a number of pairings, the conditioned stimulus produces a new response: conditioned response (CR) - ex.: salivation to the sound of a bell is the new learned response Preparing for an Important Event - can we demonstrate classical conditioning on ourselves: balloon experiment - What did you observe: response was the greatest on trial 1 and decreases over the next three trials, in trial 5 it increases as the stimulus was not presented under the same conditions - Can you identify the US, UR, CS, and CR?  US: sound of balloon popping  UR: fear or startled response  CS: countdown  CR: preparing or readiness for stimulus  Response we generate need to be relevant to the current context  How do we know that this is classical conditioning and not habituation: in trial 5 the conditioned stimulus was not presented in the same sequence of timing with the unconditioned stimulus, change in contingency shows us that this is a learned association  Graph  is consistent, happens in a reliable manner, we can describe the rate and the amount of learning, and how much learning happens from one trial to the next  relevance of the response: CR and UR don’t have to be the same but are related therefore there is some relevant response  allows us to understand the basis of some very complex behaviour: for example, phobia, drug addiction Understanding the Basis of Physiological Responses - learned drug tolerance:  overdose case studies: failures of tolerance  over time, the effect of the drug decreases as a result of learned compensatory responses  we supress our responses  over repeated pairings our response changes (decreases) over time to the same stimulus  this is not a result of habituation both the result of a learnt compensatory response Behavioural Indication of Tolerance in Rats - giving rats morphine and measuring the change in response over time - measure analgesic effect - rat is on a hot plate: if rat is aware of heat they tend to lick their paws to cool it, measure the amount of time it takes before they lick their paws - average delay of 30s with rats on morphine, normal rats take about 10s - over time rat develops tolerance - tolerance decreases over time: rats develop tolerance to morphine - we can also measure this physiologically Physiological Indication of Tolerance in Rats - consuming alcohol decreases core body temperature - body temperature dips when you inject rat with alcohol - hypothermic effect changes over repeated trials - effect isn’t as great and does not last as long Understanding the Basis of Physiological Responses - more drug is needed to achieve the same effect - typical response in heroine users - average dose for beginner: 5-10mg - non tolerant dose, lethal dose would be around: 2mg - if we look at addicts: 1800mg without even feeling any negative effects or suffering overdose - Pavlovian conditioning is related to this tolerance - Withdrawal symptoms - Treatment difficulties - Environment and context of drugs, e.g. return of American soldiers from Vietnam - For a drug user the cues may be several and they may be related to taking the drug, the environment, preparatory cues - Changing contextual cues can change the apparent tolerance to a drug Conditional Hyperthermia - a conditioned response to the cues previously paired with drug administration - give animal saline, in an animal with previous experience under the same contextual cues, their body temperature will increase - responding in opposite way of unconditioned response Situational-Specificity of Tolerance - room with yellow light, then test the drug in two different environments that had yellow light present (same) and red light (different) - animals in different context were no longer tolerant - rats were given a high dose of heroin - 96% of control group died - tolerant rats, given heroin in the same room (ST, yellow) were more likely to survive than in a different room (DT, blue) - same holds true for other drugs - without preparatory response (CS) people will suffer from overdose Understanding the Basis of Physiological Responses - prediction: subjects drinking an unfamiliar drink (green peppermint) will exhibit stronger intoxication than subjects drinking a familiar drink (favourite beer) - test:  tracking a rapidly moving circle with a mouse  word search in a 16x16 grid of jumbled letters  subjective intoxication Stronger Effects of Alcohol with the Unfamiliar Drink Situational-Specificity of Tolerance - effect of Caffeine on blood pressure - small effect (tolerant response): drinking coffee - large effect (non-tolerant response): injecting coffee Four Loko Lawsuit: Did Caffenated Alcohol Cause Death –or- Was it Situational Specificity - alcohol, caffeine and sugar - since caffeine was removed they introduced a new drink: different flavours for a limited amount of time - individuals constantly drinking a beverage in which they are unfamiliar with it will disrupt the learned tolerance cues to your learned drinking Conditioned Toelrance to the Heart Rate Effects of Smoking - H.R. for subjects who smoked in the same context showed tolerance from trials 1 to 5 - In the changing cues condition, heart rates for subjects remained stable Pavlov, Siegel & Four Loko - see limited decrease in the tolerance to alcohol The Relevance of Conditioned Associations - Ivan Pavlov: if our hypothesis as to the origin of the conditioned reflex is correct, it follows that nay natural phenomenon chosen at will may be converted into a conditioned stimulus - We can take any stimulus and we could come to form a conditioned response - Historical consensus: aside from the details, the process of conditioning is the same for any two stimuli - But learning should be under strong selective pressure, favouring individuals who learn the appropriate cues that are useful in their particular environment - Question: is there any bias to learn the appropriate cues that are useful in their particular environment? - Animals tend to associate things that are essential to their survival Biases in Aversion Learning - Linking nausea and taste is an evolutionary successful strategy - Some stimulus that associate in pairs more easily - Present rats with compact stimuli: tasty water cue + A/V cues - Water was flavoured Bright, Noisy, Tasty Water - When rats lick the spout:  They get flavoured water,  A relay clicks, and  A lamp is lighted - half of rats have their feet shocked when they lick the spout - the other half are poisoned and get sick - rats were either made sick or given a shock when drinking “bright-noisy- tasty” water during training - what kind of associations are created?$ - some of the rats were made ill after drinking in the presence of “bright-nosy- tasty water” - when tested with the stimuli alone, they show a greater aversion to drinking to the taste of water if they have been made sick - some of the rats were shocked after drinking in the presence of bright-noisy- tasty water - when tested with the stimuli alone, they show a greater aversion to drinking to the audio-visual stimuli Biases in Aversion Learning - why:  animals have innate pre-dispositions for associating certain stimuli (CS) with certain states (US
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