Chapter13 Power Point Lecture

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  • Chapter13 Power Point Lecture

    1. 1. Chapter 13: Biology of Learning and Memory
    2. 2. Learning, Memory, Amnesia, and Brain Functioning <ul><li>An early influential idea regarding localized representations of memory in the brain suggested physical changes occur when we learn something new. </li></ul><ul><li>One popular idea was that connections grow between areas of the brain. </li></ul>
    3. 3. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Ivan Pavlov researched classical conditioning in which pairing of two stimuli changes the response to one of them. </li></ul><ul><ul><li>Presentation of a conditioned stimulus (CS) is paired with an unconditioned stimulus (UCS). </li></ul></ul><ul><ul><li>Automatically results in an unconditioned response (UCR ). </li></ul></ul><ul><li>After several pairings, response can be elicited by the CS without the UCS, which is known as a conditioned response (CR ). </li></ul>
    4. 4. Learning, Memory, Amnesia, and Brain Functioning <ul><li>In operant conditioning , responses are followed by reinforcement or punishment that either strengthen or weaken a behavior. </li></ul><ul><ul><li>Reinforcers are events that increase the probability that the response will occur again. </li></ul></ul><ul><ul><li>Punishment are events that decrease the probability that the response will occur again. </li></ul></ul>
    5. 5. Fig. 13-1, p. 385
    6. 6. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Pavlov believed that conditioning strengthened connections between the CS center and UCS center in the brain. </li></ul><ul><li>Karl Lashley set out to prove this by searching for such engrams , or physical representations of what had been learned. </li></ul><ul><ul><li>Believed that a knife cut should abolish the newly learned response. </li></ul></ul>
    7. 7. Fig. 13-2, p. 386
    8. 8. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Lashley’s studies attempted to see if disrupting certain connections between cortical brain areas would disrupt abilities to learn associations. </li></ul><ul><li>Found that learning and memory did not depend on connections across the cortex </li></ul><ul><li>Also found that learning did not depend on a single area of the cortex. </li></ul>
    9. 9. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Lashley proposed two key principles about the nervous system: </li></ul></ul><ul><ul><ul><li>Equipotentiality – all parts of the cortex contribute equally to complex functioning behaviors (e.g. learning) </li></ul></ul></ul><ul><ul><ul><li>Mass action – the cortex works as a whole, not as solitary isolated units. </li></ul></ul></ul>
    10. 10. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Modern day research by Richard F. Thompson and colleagues has suggested that the engram for classical conditioning is located in the cerebellum, not the cortex. </li></ul><ul><li>During conditioning, changes occur in cells of one nucleus of the cerebellum called the lateral interpositus nucleus (LIP) . </li></ul><ul><li>However, a change in a brain area does not necessarily mean that learning necessarily took place in that area. </li></ul>
    11. 11. Fig. 13-4, p. 388
    12. 12. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Suppression of activity in the LIP led to a condition in which the subject displayed no previous learning. </li></ul><ul><li>As suppression wore off, the animal began to learn at the same speed as animals that had no previous training. </li></ul><ul><li>But suppression of the red nucleus also led to a similar condition. </li></ul><ul><li>Later assumed that the learning did occur in the LIP, as it was the last structure that needed to be awake for learning to occur. </li></ul>
    13. 13. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Hebb (1949) differentiated between two types of memory: </li></ul><ul><ul><ul><li>Short-term memory – memory of events that have just occurred. </li></ul></ul></ul><ul><ul><ul><li>Long-term memory – memory of events from previous times. </li></ul></ul></ul>
    14. 14. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Differences between STM and LTM </li></ul><ul><ul><li>Short-term memory has a limited capacity; long-term memory does not. </li></ul></ul><ul><ul><li>Short-term memory fades quickly without rehearsal; long-term memories persist. </li></ul></ul><ul><ul><li>Memories from long-term memory can be stimulated with a cue/ hint; retrieval of memories lost from STM do not benefit from the presence of a cue. </li></ul></ul>
    15. 15. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Later research has weakened the distinction between STM and LTM. </li></ul><ul><ul><li>Some memories do not qualify as distinctly short-term or long-term. </li></ul></ul><ul><li>Working Memory </li></ul><ul><ul><li>Proposed by Baddeley & Hitch as an alternative to short-term memory. </li></ul></ul><ul><ul><li>Emphasis on temporary storage of information to actively attend to it and work on it for a period of time. </li></ul></ul>
    16. 16. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Three major components of working memory include: </li></ul><ul><ul><ul><li>Phonological loop – Stores auditory input </li></ul></ul></ul><ul><ul><ul><li>Visuospatial sketchpad – Stores visual input. </li></ul></ul></ul><ul><ul><ul><li>Central Executive – Directs attention and determines which items to store. </li></ul></ul></ul>
    17. 17. Learning, Memory, Amnesia, and Brain Functioning <ul><li>The delayed response task is a test of working memory which requires responding to a stimulus that one heard or saw a short while earlier. </li></ul><ul><ul><ul><li>Increased activity in the prefrontal cortex during the delay indicates storing of the memory. </li></ul></ul></ul><ul><ul><ul><li>The stronger the activation, the better the performance. </li></ul></ul></ul>
    18. 18. Fig. 13-7, p. 394
    19. 19. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Older people often have impairments in working memory. </li></ul><ul><li>Changes in the prefrontal cortex assumed to be the cause. </li></ul><ul><li>Declining activity of the prefrontal cortex in the elderly is associated with decreasing memory. </li></ul><ul><li>Increased activity is indicative of compensation for other regions in the brain. </li></ul>
    20. 20. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Amnesia is the loss of memory. </li></ul><ul><li>Studies on amnesia help to clarify the distinctions between and among different kinds of memories and their mechanisms. </li></ul><ul><li>Different areas of the hippocampus are active during memory formation and retrieval. </li></ul><ul><ul><li>Damage results in amnesia. </li></ul></ul>
    21. 21. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Patient HM is a famous case study in psychology who had his hippocampus removed to prevent epileptic seizures. </li></ul><ul><li>Afterwards Patient HM had great difficulty forming new long-term memories. </li></ul><ul><li>STM or working memory remained intact. </li></ul><ul><li>Suggested that the hippocampus is vital for the formation of new long-term memories. </li></ul>
    22. 22. Fig. 13-5ab, p. 391
    23. 23. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Patient HM showed massive anterograde amnesia after the surgery. </li></ul></ul><ul><ul><li>Two major types of amnesia include: </li></ul></ul><ul><ul><ul><li>Anterograde amnesia – the loss of the ability to form new memory after the brain damage occurred. </li></ul></ul></ul><ul><ul><ul><li>Retrograde amnesia – the loss of memory events prior to the occurrence of the brain damage. </li></ul></ul></ul>
    24. 24. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Patient HM had difficulty with declarative and episodic memory. </li></ul><ul><ul><li>Episodic memory: ability to recall single events. </li></ul></ul><ul><ul><li>Declarative memory: ability to put a memory into words. </li></ul></ul><ul><li>Patient HM’s procedural memory remained intact. </li></ul><ul><ul><li>Procedural memory : ability to develop motor skills (remembering or learning how to do things). </li></ul></ul>
    25. 25. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Patient HM also displayed greater “implicit” than “explicit” memory. </li></ul><ul><ul><ul><li>Explicit memory – deliberate recall of information that one recognizes as a memory. </li></ul></ul></ul><ul><ul><ul><li>Implicit memory – the influence of recent experience on behavior without realizing one is using memory. </li></ul></ul></ul>
    26. 26. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Research in differences in hippocampus size has revealed conflicting results. </li></ul><ul><li>Some evidence suggests that a smaller hippocampus is associated with better memory performance. </li></ul><ul><ul><li>Hypothesis is that apoptosis improves hippocampus functioning. </li></ul></ul><ul><li>Generally, hippocampus activity is more associated with memory performance than is the size. </li></ul>
    27. 27. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Research of the function of the hippocampus suggests the following: </li></ul><ul><ul><li>The hippocampus is critical for declarative (especially episodic) memory functioning. </li></ul></ul><ul><ul><li>The hippocampus is especially important for spatial memory. </li></ul></ul><ul><ul><li>The hippocampus is especially important for configural learning and binding. </li></ul></ul>
    28. 28. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Research in the role of the hippocampus in episodic memory shows damage impairs abilities on two types of tasks: </li></ul></ul><ul><ul><ul><li>Delayed matching-to-sample tasks – a subject sees an object and must later choose the object that matches. </li></ul></ul></ul><ul><ul><ul><li>Delayed non-matching-to-sample tasks – subject sees an object and must later choose the object that is different than the sample. </li></ul></ul></ul>
    29. 29. Fig. 13-7, p. 394
    30. 30. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Damage to the hippocampus also impairs abilities on spatial tasks such as: </li></ul><ul><ul><ul><li>Radial mazes – a subject must navigate a maze that has eight or more arms with a reinforcer at the end. </li></ul></ul></ul><ul><ul><ul><li>Morris search task – a rat must swim through murky water to find a rest platform just underneath the surface. </li></ul></ul></ul>
    31. 31. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Hippocampus damage also impairs configural learning and binding. </li></ul><ul><ul><li>Configural learning – learning in which the meaning of a stimulus depends on what other stimuli are paired with it. </li></ul></ul><ul><ul><li>Animals with damage can learn configural tasks but learning is slow. </li></ul></ul><ul><ul><ul><li>Indicates hippocampus is not necessary for configural learning, but is involved. </li></ul></ul></ul>
    32. 32. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Evidence suggests that the hippocampus is important in the process of “consolidation”. </li></ul><ul><li>Consolidation is the process of strengthening short-term memories into long-term memories. </li></ul><ul><li>Damage to the hippocampus impairs recent learning more than older learning. </li></ul><ul><ul><li>The more consolidated a memory becomes, the less it depends on the hippocampus. </li></ul></ul>
    33. 33. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Reverberating circuits of neuronal activity were thought to be the mechanisms of consolidation. </li></ul><ul><li>Consolidation is also influenced by the passage of time and emotions. </li></ul><ul><ul><li>Small to moderate amounts of cortisol activate the amygdala and hippocampus where they enhance storage and consolidation of recent experiences. </li></ul></ul><ul><ul><li>Prolonged stress impairs memory. </li></ul></ul>
    34. 34. Fig. 13-11, p. 398
    35. 35. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Different kinds of brain damage result in different types of amnesia. </li></ul></ul><ul><ul><li>Two common types of brain damage include: </li></ul></ul><ul><ul><ul><li>Korsakoff’s syndrome </li></ul></ul></ul><ul><ul><ul><li>Alzheimer’s disease </li></ul></ul></ul>
    36. 36. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Korsakoff’s syndrome – prolonged thiamine (vitamin B1) deficiency impedes the ability of the brain to metabolize glucose. </li></ul></ul><ul><ul><li>Leads to a loss of or shrinkage of neurons in the brain. </li></ul></ul><ul><ul><li>Often due to chronic alcoholism. </li></ul></ul><ul><ul><li>Symptoms include apathy, confusion, and forgetting and confabulation (taking guesses to fill in gaps in memory). </li></ul></ul>
    37. 37. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Alzheimer’s disease is associated with a gradually progressive loss of memory often occurring in old age. </li></ul></ul><ul><ul><li>Affects 50% of people over 85. </li></ul></ul><ul><ul><li>Early onset seems to be influenced by genes, but 99% of cases are late onset. </li></ul></ul><ul><ul><li>About half of all patients with late onset have no known relative with the disease. </li></ul></ul>
    38. 38. Fig. 13-13, p. 401
    39. 39. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Alzheimer’s disease is associated with an accumulation and clumping of the following brain proteins: </li></ul></ul><ul><ul><ul><li>Amyloid beta protein 42 which produces widespread atrophy of the cerebral cortex, hippocampus and other areas. </li></ul></ul></ul><ul><ul><ul><li>An abnormal form of the tau protein, part of the intracellular support system of neurons. </li></ul></ul></ul>
    40. 40. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Accumulation of the tau protein results in: </li></ul><ul><ul><li>Plaques – structures formed from degenerating neurons. </li></ul></ul><ul><ul><li>Tangles – structures formed from degenerating structures within a neuronal body. </li></ul></ul>
    41. 41. Learning, Memory, Amnesia, and Brain Functioning <ul><li>A major area of damage is the basal forebrain and treatment includes enhancing acetylcholine activity. </li></ul><ul><li>One experimental treatment includes the stimulation of cannabinoid receptors that limits overstimulation by glutamate. </li></ul><ul><li>Research with mice suggests the possibility of immunizing against Alzheimer’s by stimulating the production of antibodies against amyloid beta protein. </li></ul>
    42. 42. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Lessons from studying amnesiac patients include: </li></ul><ul><ul><li>There can be deficiencies of very different aspects of memory. </li></ul></ul><ul><ul><li>There are independent kinds of memory. </li></ul></ul><ul><ul><li>Various kinds of memory depend on different brain areas. </li></ul></ul>
    43. 43. Storing Information in the Nervous System <ul><li>(con’t) </li></ul><ul><li>Activity in the brain results in physical changes. </li></ul><ul><li>Patterns of activity leave a path of physical changes. </li></ul><ul><li>Not every change is a specific memory as was once originally believed. </li></ul>
    44. 44. Storing Information in the Nervous System <ul><li>A Hebbian synapse occurs when the successful stimulation of a cell by an axon leads to the enhanced ability to stimulate that cell in the future. </li></ul><ul><ul><li>Increases in effectiveness occur because of simultaneous activity in the presynaptic and postsynaptic neurons. </li></ul></ul><ul><ul><li>Such synapses may be critical for many kinds of associative learning. </li></ul></ul>
    45. 45. Storing Information in the Nervous System <ul><li>Studies of how physiology relates to learning often focus on invertebrates and try to generalize to vertebrates. </li></ul><ul><li>The aplysia is a slug-like invertebrate that is often studied due to its large neurons. </li></ul><ul><li>This allows researchers to study basic processes such as: </li></ul><ul><ul><li>Habituation. </li></ul></ul><ul><ul><li>Sensitization. </li></ul></ul>
    46. 46. Storing Information in the Nervous System <ul><li>Habituation is a decrease in response to a stimulus that is presented repeatedly and accompanied by no change in other stimuli. </li></ul><ul><ul><li>Results in a change in the synapse between the sensory neurons and the motor neurons. </li></ul></ul><ul><ul><li>Sensory neurons fail to excite motor neurons as they did previously. </li></ul></ul>
    47. 47. Storing Information in the Nervous System <ul><li>Sensitization is an increase in response to a mild stimulus as a result to previous exposure to a more intense stimulus. </li></ul><ul><li>Changes at identified synapses include: </li></ul><ul><ul><li>Serotonin released from a facilitating neuron blocks potassium channels in a presynaptic neuron. </li></ul></ul><ul><ul><li>Prolonged release of transmitter from that neuron results in prolonged sensitization. </li></ul></ul>
    48. 48. Storing Information in the Nervous System <ul><li>Long-term Potentiation (LTP) occurs when one or more axons bombard a dendrite with stimulation. </li></ul><ul><ul><li>Leaves the synapse “potentiated” for a period of time and the neuron is more responsive. </li></ul></ul>
    49. 49. Storing Information in the Nervous System <ul><li>Properties of LTP that suggest it as a cellular basis of learning and memory include: </li></ul><ul><ul><li>Specificity </li></ul></ul><ul><ul><li>Cooperativity </li></ul></ul><ul><ul><li>Associativity </li></ul></ul>
    50. 50. Storing Information in the Nervous System <ul><ul><li>Specificity – only synapses onto a cell that have been highly active become strengthened. </li></ul></ul><ul><ul><li>Cooperativity – simultaneous stimulation by two or more axons produces LTP much more strongly than does repeated stimulation by a single axon. </li></ul></ul><ul><ul><li>Associativity – pairing a weak input with a strong input enhances later responses to a weak input. </li></ul></ul>
    51. 51. Storing Information in the Nervous System <ul><li>Long-term depression (LTD ) is a prolonged decrease in response at a synapse that occurs when axons have been active at a low frequency. </li></ul><ul><ul><li>The opposite of LTP </li></ul></ul>
    52. 52. Storing Information in the Nervous System <ul><li>Biochemical mechanisms of LTP are known to depend on changes in glutamate synapses primarily in the postsynaptic neuron </li></ul><ul><li>This occurs at several types of receptor sites including the ionotropic receptors: </li></ul><ul><ul><ul><ul><li>AMPA receptors. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>NMDA receptors. </li></ul></ul></ul></ul>
    53. 53. Fig. 13-21, p. 409
    54. 54. Storing Information in the Nervous System <ul><li>LTP in hippocampal neurons occurs as follows: </li></ul><ul><ul><li>Repeated glutamate excitation of AMPA receptors depolarizes the membrane. </li></ul></ul><ul><ul><li>The depolarization removes magnesium ions that had been blocking NMDA receptors. </li></ul></ul><ul><ul><li>Glutamate is then able to excite the NMDA receptors, opening a channel for calcium ions to enter the neuron. </li></ul></ul>
    55. 55. Storing Information in the Nervous System <ul><ul><li>Entry of calcium through the NMDA channel triggers further changes. </li></ul></ul><ul><ul><li>Activation of a protein that sets in motion a series of events occurs. </li></ul></ul><ul><ul><li>More AMPA receptors are built and dendritic branching is increased. </li></ul></ul><ul><li>These changes increase the later responsiveness of the dendrite to incoming glutamate. </li></ul>
    56. 56. Storing Information in the Nervous System <ul><li>Changes in presynaptic neuron can also cause LTP. </li></ul><ul><li>Extensive stimulation of a postsynaptic cell causes the release of a retrograde transmitter that travels back to the presynaptic cell to cause the following changes: </li></ul><ul><ul><li>Decrease in action potential threshold </li></ul></ul><ul><ul><li>Increase neurotransmitter release of </li></ul></ul><ul><ul><li>Expansion of the axons. </li></ul></ul><ul><ul><li>Transmitter release from additional sites. </li></ul></ul>
    57. 57. Storing Information in the Nervous System <ul><li>LTP changes behavior by creating changes in multiple synapses and complex networks of neurons. </li></ul><ul><li>Understanding the mechanisms of changes that enhance or impair LTP may lead to drugs that improve memory. </li></ul><ul><ul><li>Example: Mice with genes that cause abnormalities in the NMDA receptor learn slowly and extra NMDA receptors result in faster learning. </li></ul></ul>

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