神经生物学课件：11 学习与记忆-宏观2-4-5

1、Learning and Memory,Zhefeng Gong (龚哲峰) Institute of Neuroscience, Zhejiang University,1. The basic concepts of learning,writing, driving etc born: sucking milk, yelling, blinking etc Memory：the retaining/maintaining of learned ability or knowledge Actually, the studies on learning and memory include

2、 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 cortices Consolidation is the process of rehearsing and building a robust repres

3、entation of it in the brain Storage is the creation of a relatively stable memory trace or record of knowledge in the brain Retrieval 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: m

4、emory loss for events before the trauma; you forget things you already knew Anterograde amnesia: an inability to form new memories following brain trauma.,Classification of memories,According to time course: Working memory Short term memory Long term memory According to appearance: non-declarative m

5、emory (implicit memory;”knowing how”) declarative memory (explicit memory; “knowing what”),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,

6、 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 typ

7、ically 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 infor

8、mation 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

9、 learning&memory and neural plasticity,Brain structures hosting learning&memory,General theories about memory engram Localization of declarative memory: temporal lobe diencephalon Localization of procedure memory striatum Localization of working memory frontal cortex,The search for engram- Where is

10、the engram?,Engram- the physical representation or location of memory, also called memory trace Strategy/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 befor

11、e learning needed more trials to run the maze without going down blind alleys rat 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

12、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 sim

13、ply 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 engram Locali

14、zation of declarative memory: medial temporal lobe diencephalon brain Localization of procedure memory striatum Localization of working memory frontal cortex,Localization of declarative memories to neocortex,Studied in human Studies in monkeys,The brain lesion in patient H.M. that produced severe an

15、terograde 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.s brain.,H.M. has partial retrograde amnesia for the years preced

16、ing 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 inferotemp

17、oral 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 stimulus was presented. (

18、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

19、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

20、 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 bodies No strong correlation exists between the severity of a

21、nterograde 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

22、 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 engram Localization of declarative memory: Localization of procedure memory str

23、iatum Localization 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 the baited arms.,Hippocampus and declarative memory,Two versions of radial arm maze task -declarative/procedure memory,The

24、 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 an

25、y time. The 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, performanc

26、e 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

27、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 engram Localization of declarative memory: temporal lobe diencephalon brain Localization of procedure memory striatu

28、m Localization 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 re

29、membered 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 plasticity 2. The molecular basis

30、 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 Aplysia Habituation decrease in response to a stimulus after rep

31、eated 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 organism Conditioning: coupling of CS and US to elicit a response,Associative learning-operant conditioning,Learning by doing,Operant condit