学习与记忆宏观英文课件.ppt

Learning and Memory,1. The basic concepts of learning&memory classification of learning&memory brain structures hosting learning&memory learning&memory in behavioral study learning&memory and neural plasticity2. The molecular basis of learning& memory studies in Aplysia studies in mouse, LTP, LTD and long term memory,Basic concepts of Learn&Mem,Learning：the process of acquiring ability or knowledge that is not born learned: reading;,writing, driving etc born: sucking milk, yelling, blinking etcMemory：the retaining/maintaining of learned ability or knowledgeActually, the studies on learning and memory include learning, repeating, memory, and forgetting as well,Steps of memory processing,Acquisition is the process of bringing knowledge into the brain and into a first-stage memory buffer via sensory organs and primary sensory corticesConsolidation is the process of rehearsing and building a robust representation of it in the brainStorage is the creation of a relatively stable memory trace or record of knowledge in the brainRetrieval is the process of reactivating knowledge in a way that will allow it to become an image in consciousness or translated into motor output,Amnesia,Retrograde amnesia: memory loss for events before the trauma; you forget things you already knewAnterograde amnesia: an inability to form new memories following brain trauma.,Classification of memories,According to time course: Working memory Short term memory Long term memoryAccording to appearance: non-declarative memory (implicit memory) declarative memory (explicit memory),Working memory: information held “in mind.”Short-term memory: memories that last on the order of seconds to hours and are vulnerable to disruption.Long-term memory: memories that you can recall days, months, or years after they were originally stored.,Implicit and explicit memory,Non-declarative memory (implicit memory): Perceptual memory: acquired through the sense. Procedure learning: representation of a series of actions or perceptual processing functions that occur unconsciously and repetitions typically result in increased speed or accuracy Fear memory:Declarative memory (explicit memory): Episodic memory: a system that collects temporarily and spatially encoded events in a subjects life, such as recalls of particular experiences or episodes Semantic memory: an organization of factual information independent of specific episodes during which that information was acquired.Its knowledge of the world.,Declarative and non-declarativememory,1. The basic concepts of learning&memory classification of learning&memory brain structures hosting learning&memory learning&memory in behavioral study learning&memory and neural plasticity,Brain structures hosting learning&memory,General theories about memory engramLocalization of declarative memory: temporal lobe diencephalonLocalization of procedure memory striatumLocalization of working memory frontal cortex,The search for engram- Where is the engram?,Engram- the physical representation or location of memory, also called memory traceStrategy/Methods: 1. lesion or ablation of certain brain regions 2. recording the response of specific neurons,Effect of brain lesions on Maze learning in rats- Karl Lashley,rats given brain lesions before learning needed more trials to run the maze without going down blind alleysrat given brain lesions after learning made mistakes and went down blind alleys it had previously learned to avoid.,a rat run through a maze to get food,The greater the percentage of cortex destroyed, the more errors made while the rats learn to run the maze. The number of errors shown is cumulative across trials, suggesting that rats with larger lesions had difficulty remembering which arms of the maze were blind alleys.,Karl Lashleys conclusions,all cortical areas contribute equally to learning and memory it is simply a matter of getting poorer performance on the maze task as the lesion gets bigger and the ability to remember the maze worsens.,It is wrong that all areas are equal, but it true that the memories are distributed,Brain structures hosting learning&memory,General theories about memory engramLocalization of declarative memory: medial temporal lobe diencephalon brainLocalization of procedure memory striatumLocalization of working memory frontal cortex,Localization of declarative memories to neocortex,Studied in humanStudies in monkeys,The brain lesion in patient H.M. that produced severe anterograde amnesia.(a) The medial temporal lobe was removed from both hemispheres in H.M.s brain to alleviate severe epileptic seizures. (b) A normal brain, showing the location of the hippocampus and cortex that were removed from H.M.sbrain.,H.M. has partial retrograde amnesia for the years preceding the operation. Much more serious is his extreme anterograde amnesia. While he can remember a great deal about his childhood, he is unable to remember someone he met just a few minutes earlier.,Case study- H.M.,Declarative memories in neocortex -studies in monkeys,Responses to faces in inferotemporal cortex. (a) The location of area IT in the inferior temporal lobe of a macaque monkey. (b) Responses of a face cell.The histograms show the response of a neuron in area IT to different views of a monkeys head. The horizontal bar under each histogram indicates when the stimuluswas presented. (c) Changing responses of a cell to unfamiliar faces.,Diencephalon and memory,Components of the diencephalon involved in memory. The thalamus and mammillary bodies receive afferents from structures in the medial temporal lobe.,Case study of NA and Kosakoffs syndrome,Case study- N.A.,The only obvious damage was a lesion in his left dorsomedial thalamus.N.A.s cognitive ability was normal but his memory was impaired. He had relatively severe anterograde amnesia and retrograde amnesia for a period of about 2 years preceding the accident. While he could remember some faces and events from the years following his accident, even these memories were sketchy. He had difficulty watching television because during commercials, hed forget what was previously happening.,Korsakoffs syndrome-,lesions in the dorsomedial thalamus and mammillary bodiesNo strong correlation exists between the severity of anterograde amnesia and retrograde amnesia in Korsakoffs syndrome. The mechanisms involved in consolidation (disrupted in anterograde amnesia) are largely distinct from processes used to recall memories (disrupted in retrograde amnesia). Anterograde amnesia may be associated with diencephalic lesions results from damage to the thalamus and mammillary bodies. Retrograde amnesia, may invovles diencephalon, the cerebellum, brain stem, and neocortex.,Brain structures hosting learning&memory,General theories about memory engramLocalization of declarative memory:Localization of procedure memory striatumLocalization of working memory,An eight-arm radial arm maze. If a rat learns that four of the eight arms never contain food, it will ignore these and follow a path to only thebaited arms.,Hippocampus and declarative memory,Two versions of radial arm maze task -declarative/procedure memory,The first was the standard, in which the rat must move as efficiently as possible retrieving the food from each of the baited arms of the maze.In the second version, small lights were illuminated above the arms containing food, and the unlit arms had no food. The lights could be turned on or off at any timeThe standard maze task was designed to require the use of declarative memory. The “light” version of the task was intended to draw on procedural memory because of the consistent association between the presence of food and illuminated lights.,If the hippocampal system was damaged, performance was degraded on the standard maze task but was relatively unaffected on the light version.Conversely, a lesion in the striatum impaired performance of the light task but had little effect on the standard task. This “double dissociation” of the lesion site and the behavioral deficit suggests that the striatum is part of a procedural memory system but is not crucial for the formation of declarative memories.,Brain structures hosting learning&memory,General theories about memory engramLocalization of declarative memory: temporal lobe diencephalon brainLocalization of procedure memory striatumLocalization of working memory frontal cortex, area LIP,Area LIP and working memory,LIP: lateral intraparietal cortex (顶内沟外侧区),(a) The monkey fixates on a central point while a peripheral target flashes on and off. When the fixation point disappears, and the animal knows to move its eyes to the remembered location of the target. (b) The histogram shows the response of an LIP neuron.,1. The basic concepts of learning&memory classification of learning&memory brain structures hosting learning&memory learning&memory in behavioral study learning&memory and neural plasticity2. The molecular basis of learning& memory studies in Aplysia studies in mouse, LTP, LTD and long term memory,Non-associative learning,Sensitization progressive amplification of a response after repeated administrations of a stimulus Gill Withdraw Reflex in AplysiaHabituation decrease in response to a stimulus after repeated presentations Probscis extension response in Drosophila “wolf-coming”,Associative learning- Classical conditioning,CS: conditioned stimulus A signaling stimulus that does not elicit a response by itself US: unconditioned stimulus: A stimulus is a factor that causes a response in an organismConditioning: coupling of CS and US to elicit a response,Associative learning-operant conditioning,Learning by doing,Operant conditioning differs from classical conditioning in that the animal can control the presence of the unconditioned stimulus.,1. The basic concepts of learning&memory classification of learning&memory brain structures hosting learning&memory learning&memory in behavioral study learning&memory and neural plasticity2. The molecular basis of learning& memory studies in Aplysia studies in mouse, LTP, LTD and long term memory,Neural basis of learning and memory: general thinking,Information can be stored in the nervous system in forms of molecular, synaptic, and cellular eventsNeuroplasticity (or neural plasticity) is the ability of neurons and neural circuits to be remodeled by experience or environment.,Memory Storage Requires Neuronal Remodeling,Changes can be presynaptic (such as increased neurotransmitter), or postsynaptic (such as altered effectiveness of receptors), or both.Structural changes at the synapse may provide long-term storage.,Pre- and Post-synaptic Changes That May Store Memories,Structural Changes That May Store Memories,