Ppt Chap 13

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Ppt Chap 13

  1. 1. Chapter 13: Biology of Learning and Memory
  2. 2. Learning, Memory, Amnesia, and Brain Functioning <ul><li>An early influential idea was that physical changes occur when something new is learned or a memory is formed. </li></ul><ul><li>Explanations was that connections grew between areas of the brain. </li></ul><ul><ul><li>Led to the search for localized representations of memory </li></ul></ul>
  3. 3. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Ivan Pavlov pioneered classical conditioning in which pairing of two stimuli changes the response to one of them. </li></ul><ul><ul><li>A conditioned stimulus (CS) is paired with an unconditioned stimulus (UCS) which 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, </li></ul><ul><ul><li>New response is now called a conditioned response (CR ). </li></ul></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 the 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. 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>
  6. 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 entirely 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>
  7. 10. 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>
  8. 11. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Richard F. Thompson et. al. suggested that the engram for classical conditioning is located in the cerebellum, not the cortex. </li></ul><ul><li>During conditioning, changes occur in the lateral interpositus nucleus (LIP) of the cerebellum </li></ul><ul><ul><li>Responses increase as learning proceeds </li></ul></ul><ul><ul><li>necessary for learning and retention </li></ul></ul><ul><li>However, a change in a brain area does not necessarily mean that learning took place in that area. </li></ul>
  9. 13. 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>
  10. 14. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Psychologist differentiate between learning and memory. </li></ul><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 times further back. </li></ul></ul></ul>
  11. 15. 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>
  12. 16. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Researchers propose all information enters STM where the brain consolidates it into LTM. </li></ul><ul><li>Later research has weakened the distinction between STM and LTM </li></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>
  13. 17. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Common test of working memory is the delayed response task. </li></ul><ul><ul><li>Requires responding to something you heard or saw a short while ago. </li></ul></ul><ul><li>Research points to the prefrontal cortex for the storage of this information </li></ul><ul><li>Brain may use elevated levels of calcium to potentiate later responses </li></ul>
  14. 18. 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>
  15. 19. 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>
  16. 20. Learning, Memory, Amnesia, and Brain Functioning <ul><li>H.M. is a famous case study in psychology who had his hippocampus removed to prevent epileptic seizures. </li></ul><ul><li>Afterwards H.M. 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>
  17. 22. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>H.M. 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 </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>
  18. 23. 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>
  19. 24. Learning, Memory, Amnesia, and Brain Functioning <ul><li>H.M. had difficulty with episodic memory and declarative memory. </li></ul><ul><ul><li>Episodic memory: ability to recall single events. </li></ul></ul><ul><ul><li>Declarative memory: ability to state a memory into words. </li></ul></ul><ul><li>H.M.’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>
  20. 25. 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 memory functioning (especially episodic). </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>
  21. 26. 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>
  22. 28. 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 water maze task – a rat must swim through murky water to find a rest platform just underneath the surface. </li></ul></ul></ul>
  23. 31. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Hippocampus may also be important for contextual learning </li></ul><ul><li>Remembering the detail and context of an event </li></ul><ul><li>suggests that the hippocampus is important in the process of “consolidation”. </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>
  24. 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>
  25. 34. 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>
  26. 35. Learning, Memory, Amnesia, and Brain Functioning <ul><ul><li>Korsakoff’s syndrome – brain damage caused by prolonged thiamine (vitamin B1) deficiency </li></ul></ul><ul><ul><li>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>
  27. 36. 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>
  28. 38. 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>
  29. 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>
  30. 42. 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>
  31. 43. 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>
  32. 44. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Other subcortical brain areas and the cortex important in learning: </li></ul><ul><li>Amygdala associated with fear learning </li></ul><ul><li>Parietal lobe associated with piecing information together </li></ul><ul><li>anterior and inferior region of the temporal lobe and semantic memory </li></ul><ul><ul><li>semantic dementia (loss of semantic memory) </li></ul></ul>
  33. 45. Learning, Memory, Amnesia, and Brain Functioning <ul><li>Other areas of the cortex important in learning (con’t): </li></ul><ul><li>Prefrontal cortex and learning about rewards and punishments </li></ul><ul><ul><li>Basal ganglia, anterior cingulate cortex also involved </li></ul></ul>
  34. 47. Storing Information in the Nervous System <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><ul><li>Many ideas originally believed to be true have been refined. </li></ul>
  35. 48. 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>
  36. 49. 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>
  37. 52. 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>Depends upon 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>
  38. 53. 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 more intense stimuli. </li></ul><ul><li>Changes at identified synapses include: </li></ul><ul><ul><li>Serotonin released from a facilitating neuron blocks potassium channels in the presynaptic neuron. </li></ul></ul><ul><ul><li>Prolonged release of transmitter from that neuron results in prolonged sensitization. </li></ul></ul>
  39. 54. 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>
  40. 55. 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>
  41. 56. 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>
  42. 57. 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>
  43. 58. Storing Information in the Nervous System <ul><li>Biochemical mechanisms of LTP are known to depend on changes at glutamate and GABA 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>
  44. 60. 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>
  45. 61. 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>
  46. 63. 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>
  47. 65. Storing Information in the Nervous System <ul><li>LTP reflects increased activity by the presynaptic neuron and increased responsiveness by the postsynaptic neuron </li></ul><ul><li>Understanding the mechanisms of changes that enhance or impair LTP may lead to drugs that improve or block memory. </li></ul><ul><ul><li>Increasing production of hormones increased by LTP </li></ul></ul><ul><ul><li>Ginkgo biloba </li></ul></ul><ul><ul><li>Etc. </li></ul></ul>

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