Learning & memory. Phenomenon:

Transcription

1 Learning & memory Phenomenon: 9/11/2001 Where were you on the following day? Your 10th birthday? What did you do? Do you remember when you had an accident? How did it happen? Can you remember a Skill you used to do well that you don't anymore? 1

2 Learning & memory Knowing that Vs. Knowing how Gilbert Ryle, Oxford philosopher of mind,

3 The four C s Eichenbaum's themes Connectivity memory in the dynamics Cognition Representation vs process Compartmentalization-local vs distributed Consolidation- fragile memory to permanent 3

4 Themes of the course (tensions) (1) Involuntary vs voluntary (unconscious - conscious, procedural - declarative, implicit - explicit, incidental - intentional, automatic- controlled) (2) functional mapping to neurophysiological processes (3) representation (i.e., content) in the brain (MEMORY) (4) relation between acquiring and accessing information (encoding-retrieval) LEARNING (5) constraints on memory (e.g., duration, capacity/size, physiological) costs. (6) memory system or systems? 4

5 Ebbinghaus: The Psychology of Learning (1913) Chapter II Using process to classify memories (e.g., observational, associative,rational) Using content to classify memory (e.g., sensory vs motor memory) Immediate vs permanent retention (STM / LTM) W. James reports Ebbinghaus's results as reflecting a short-term and long-term memories

6 Bartlett: Remembering (1932) Elements comprising memory Constructive character of remembering Consciousness in memory (beyond behaviorism)

7 MEMORY MODEL ATKINSON & SHIFFRIN (1968) 7

8 Rapid consolidation: synaptic mechanisms Three overlapping time courses for consolidation proposed by McGaugh 8

9 Multiple memory systems 9

10 Baddeley and Hitch model Working memory Visualspatial sketchpad Central Executive Phonological Loop 13

11 Central executive Attentional control Making changes to practiced routine. (Example: Altering driving to work routine when there is a traffic accident) Dividing attention Multitasking Switching attention from one task to another 20

12 Baddeley

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15 Why is the brain made of GOO? The brain cost us almost nothing to run... Best Computer technology at present has efficiency JOULES work for 10 MILLION OPERATIONS in 1 SEC! The BRAIN JOULES of work for 10 MILLION OPERATIONS in 1 SEC! The brain is ~100 MILLION times more efficient then the best computer technology

16 Evolution and the Brain From the inside out... from the simplest most primitive responses

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18 Scientific American

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23 Networks: Associationism James, 1890

24 Actual Neural Networks

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26 Semantic Network: Neural Networks

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28 Core concepts Modularity assumption Localisation of function Transparency assumption about interpreting brain lesions.--tube radio Lashley (1950) - misleading concepts of mass-action and equipotentiality. Representation How do neurons of a particular bit of the brain represent something? object recognition--categorization Single-cells and neural networks Grandmother cells Emergent properties of networks (e.g. distributed associative memories). Plasticity Brain circuits show varying degrees of hard-wiring and susceptibility to change.

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30 Face Recognition Fusiform Face Area (FFA)...bilateral.. but RH FFA seems more active.

31 FACE RECOGNITION: Uncanny Valley 41

32 Object Recognition Areas throughout the Brain?

33 Memory and Learning Memory can be defined as a lasting representation that is reflected in thought, experience, or behavior. Learning is the acquisition of such representations -involving a wide range of brain areas and activities. Memory storage is believed to involve widespread synaptic alterations in cortex. 43

34 Prefrontal cortex, consciousness and working memory Different types of working memory In his seminal work on working memory, Baddeley proposed that there were differing types of working memory: a visuospatial sketchpad for visual inputs and a phonological loop for sound-based inputs. Neuroimaging studies have shown differing brain areas for visual and verbal working memory processes, with the DL-PFC (D) interacting with Broca s area (B), a phonological loop (P) and with the frontal eye fields (F). 44

35 Important brain structures in the study of memory are the cortex and the medial temporal lobes (MTL), which contain the two hippocampi and their surrounding tissue. The MTL encodes information across sensory domains such as smell, vision, and touch. The MTL is a highly interactive crossroads, well-placed for integrating multiple brain inputs, and for coordinating learning and retrieval in many parts of the cortex. It is a hub of hubs. H. M. B.Milner 1960s, M.N.I. 46

36 Penfield and Olds 1940s Electrically evoked autobiographical memories For more than 50 years, neurosurgeons have reported that awake patients report vivid, specific conscious recollections during temporal lobe stimulation. Electrode grids are typically placed on the surface of the temporal lobe and areas are systematically stimulated and the patient s reported memories are noted. 49

37 Learning & memory: Single Events During scanning of medial temporal lobe and frontal lobe regions, subjects viewed complex, color photographs. Subjects later received a test of memory for the photos. The magnitudes of focal activations in right prefrontal cortex and in bilateral parahippocampal cortex predicted which photographs were later remembered well, remembered less well, or forgotten. Brewer J, Science 1998; Wagner A, Science

38 The limbic system: Memory & emotion 51

39 Varieties of memory Memory is not unitary: the Schacter-Tulving classification of memory types 60

40 Striatum The grouping formed by the caudate nucleus (orange) and the putamen (g reen) is called the striatum. It constitutes the major target for the cortical afferents of the basal ganglia. The efferents from the basal ganglia to the thalamus arise in the globus pallidus. The part of the ventrolateral nucleus of the thalamus that then projects to Area 6 is called "pars oralis" and usually designated by the symbol VLo. The other structures of the basal ganglia form various internal loops that modulate the activity of the main loop, in which information passes through the following brain structures in succession: cortex striatum globus pallidus VLo cortex (supplementary motor area, or SMA). 61

41 The Striatum and Implicit Memory Two elements of basal ganglia Striatum Caudate nucleus Putamen Rodent Recordings and Lesions in the Striatum Lesions to striatum: Disrupts procedural memory (classical conditioning/implicit) Damaged hippocampal system: Degraded performance on standard maze task-spatial memory.. (Operant conditioning/explicit) 63

42 Temporal Difference Learning Sutton (1988).. predicting the weather.. environment Reward (Rt) State (St) Action agent 64

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44 Systems for Learning Most of what has been presented has been cortical processes for memory, but there are other kinds of memory and brain areas that have not been discussed: 66

45 Lets stop here for now... Format of class: White papers due at class time. This should be 1 page of your view of the issues in the papers you read. Papers will be assigned for student presentation and Discussion. Papers will available on the course website: Final paper and presentation due in the last session (12/5). 67

46 Discussion Points 1890: What was Ebbinhaus's concept of Memory? What is it now? Learning and Memory? Same? Are these different processes? Same process different phases? Is a habit memory? Is a reflex memory? How do we reconcile Associative learning with other implicit memory? Ebbinghaus seems to be investigating Eichenbaum's "Consolidation" feature of memory and Bartlett Eichenbaum's "Cognition". What, if anything do Ebbinghaus and Bartlett have to say about Eichenbaum's "Connection" and "Compartmentalization"? Can Bartlett's idea of memory be reconciled wtih that of Ebbinghaus? How does the biological basis of memory (Squire and Kandel) relate to something like Ebbinghaus' traces or Bartlett's "schema"? Can memory be both localized and distributed? 68

47 Complexity and the threshold for implicit learning.. Categorization and Learning Depending on how complex the rules Are to learn.. the more the memory system tends towards implicit encoding/learning. 69

48 Bruner Goodnow & Austin (1956) RULE Learning

49 Concepts & Categories: Bruner Goodnow & Austin, (1956)

50 Spared functions in amnesia: implicit / procedural learning and memory A way to investigate implicit and explicit learning was developed by Knowlton and colleagues. The patterns on the cards predict either rainy or sunny weather with an 80% probability. Healthy individuals implicitly extract the rules in this weather task before they are aware of them explicitly. 72

51 Spared functions in amnesia: implicit / procedural learning and memory Spared functions in PD: Explicit Learning Amnesia patients perform as well as the controls in the early trials that involve implicit rule extraction, but perform worse in the later trials when explicit rule learning is involved. PD patients perform poorly implicit early trials, but eventually learn rule. 73

52 The Striatum and Procedural Memory Amnesic-- poor in Explicit memory PD-- poor in Implicit memory 74

53 How does (explicit) memory work? MTL-- both episodic and semantic information whats the relationship? 75

54 The sight of a coffee cup activates visual cortex up to the level of object perception 76

55 Memory storage: MTL coordinates widespread memory traces throughout cortex 77

56 When the episodic memory -- the sight of the coffee cup -- is cued the following day, MTL is once again involved in retrieving and organizing widespread memory traces 78

57 Varieties of memory Episodic and semantic memory: Remembering versus knowing Remembering autobiographical episodes involves an active reconstruction of the original (conscious) episode 79

58 Varieties of memory Episodic and semantic memory: Remembering versus knowing Knowing semantic memories does not require active reconstruction of the original episode, it is assessed by a feeling of knowing. 80

59 Varieties of memory Episodic memories may turn into semantic memories over time A model for how semantic and episodic memories may be related: semantic memories may be the cortical residue of many episodic memories. 81

60 Consolidation: interaction between the medial temporal lobes and cortex Two kinds of consolidation are through to exist: cellular and systems consolidation. Both are evoked by activation of the MTL and cortex. 82

61 LTM modulating factors Long term memory modulating factors improves all performance except for recency (eg Sumby 1963) Slower list presentation More familiar words 83

62 Atkinson and Shiffrin (1968) 84

63 Problems with Atkinson and Shiffrin Model says STS required for entry into LTS A neurological patient with defective short term memory (as measured by digit span) showed normal long term learning. (Shallice and Warrington 1970) Model says length of time in STS determines likelihood of LTM storage Length of time in STM does not necessarily result in transfer to LTM. Depth of processing is more important (Craik and Tulving 1975) 85

64 The Temporal Lobes and Deficits The Diencephalon and Memory Processing Korsakoff s Syndrome Symptoms: Confusion, confabulations, severe memory impairment, and apathy Alcoholics: Develop thiamin deficiency Leads to symptoms: Abnormal eye movements, loss of coordination, tremors Treatment: Supplemental thiamin Thiamin deficiency: Structural brain damage 86

65 Prefrontal Interactions Short Term/Working Memory 87

66 Prefrontal cortex, consciousness and working memory The delayed-match-to-sample task is widely used in studies investigating the role of the PFC in working memory. In the classic experiment, a monkey is trained to delay responding to a stimulus ( sample, typically a red, blue, or white light). The monkey shows recognition of the stimulus after the delay by correctly pressing the light that matched the sample. Neurons active during the delay period are shown in red at the bottom of the panel. 88

67 Prefrontal cortex, consciousness and working memory Working with memory: the frontal lobe works purposefully with memory The prefrontal cortex (PFC) plays a critical role in working memory. The macaque monkey has been the primary experimental animal if many studies of working memory. PFC in monkeys (top) and humans (bottom). The most common division is between upper and lower halves of the PFC, called the dorsolateral prefrontal cortex (DL-PFC, purple shading) and the ventrolateral prefrontal cortex (VL-PFC, green shading). 89

68 Retrieval and metacognition Metacognition is the ability to know our own cognitive functions, and to be able to use that knowledge. Many neurological patients who are severely impaired have no metacognitive insight that anything is wrong. Healthy individuals use metacognition in memory retrieval. For example, semantic memories may be retrieved by using episodic cues and vice versa 90

69 Retrieval and metacognition Theta rhythms may coordinate memory retrieval: theta oscillations may coordinate MTL and the prefrontal lobe during retrieval 91

70 Retrieval and metacognition Hemispheric lateralization in retrieval Do the two hemispheres play differing roles in memory encoding and retrieval? Tulving and colleagues found that the left hemisphere showed greater activity in episodic learning (encoding), while the right hemisphere showed more activity in episodic retrieval. 92

71 Learning & memory: Working memory & sleep deprivation After full night sleep After sleep deprivation N-back task 93 Drummond SP, Nature 2004

72 Memories are made of this Long-term potentiation and long-term depression: excitatory and inhibitory memory traces These two processes are thought to occur in long-term potentiation (LTP) for excitatory cells and long-term depression (LTD) for inhibitory cells. Recording from a cell in the hippocampus showing long lasting (90 minutes) activity in an excitatory cell (center). 94

73 Coordination of the Brain Functions 95 Figure 9-19: The diffuse modulatory systems modulate brain function