Introduction to memory systems

1. Introduction to memory systems

2. 1. L. Squire, Memory systems of the brain: A brief history and current perspective, Neurobiology of Learning and Memory, Vol 82, pp. 171-177, 2004 2. J. D. E. Gabrieli, Cognitive Neuroscience of Human Memory, Annual Reviews Psychology, Vol 49, pp.87-115, 1998 3. R. Cabeza, L Nyberg, Neural Bases of learning and memory: functional neuroimaging evidence, Current opinion in neurology, Vol 13, pp. 415-421, 2000 4. Moscovitch et al. Functional Neuranatomy of remote episodic, semantic and spatial memory: an account based on multiple trace theory, Journal of Anatomy, Vol 207, pp 35-66, 2005 5. Martin A, Chao LL, Semantic memory and the brain: structure and processes, Current Opinion in Neurobiology, Vol 11. pp.194-201, 2001 6. Thompson-Scill S, Neuroimaging studies of semantic memory: Inferring how from where, Neuropsychologia, Vol 41, pp. 280-292, 2003 7. Tulving E, Episodic memory: from mind to brain, Annual Reviews of psychology, Vol 53, pp 1-25, 2002 8. Hwang D, Golby A, The brain bases of episodic memory: insights from fMRI intracranial eeg and patients with epilepsy, Epilepsy and behaviour, Vol 8, pp115-126, 2006 9. Curtis C, Despozito M, Persistent activity in the prefrontal cortex during working memory, Vol 7, pp 415-423, Trends in Cognitive Science, 2003 10. Smith E, Jonides J, Neuroimaging analyses of human working memory, PNAS, Vol 95, pp 12061-12068, 1998 References

3. Hwang 2006

4. Hwang, 2006 Squire, 2004 Attributes of declarative memory * representational * remembered material can be compared and contrasted * memories can be encoded in terms of relationships of multiple items and events * stored representations are flexible Attributes of non-declarative memory * dispositional * guided through performance

5. intact in amnesia ex: motor skills ex: word priming studies Working Memory DLPFC Parietal Squire, 2004 (striatum=caudate+putamen diencephalon=thalamus and vicinity)

6. Multiple memory systems work independently and in parallel Example: associated words in sentences Medicine cured hiccups Differently encoded in normals versus amnesics * Structure and function go hand in hand in the memory 'System' * Contrary to the psychological view which says there is one memory storage but different memory processes, neurobiology has clarified that there are multiple memory 'systems' BUT Squire, 2004

7. Semantic memory

8. Consistent activity during semantic processing: MTL: Medial Temporal lobe A. Ventral Temporal Cortex B. Prefrontal Cortex Thompson-Schill, 2003

9. A. VENTRAL TEMPORAL CORTEX How does semantic info get represented: 1. Taxonomy: categorical specificity 2. Attributes: sensory versus function Filing clerk Filing cabinet Martin and Chao, 2001

10. 1. Taxonomy: categorical specificity Tasks producing these activations: * object-naming * picture matching * word-reading Martin and Chao, 2001

11. Controversies 1. Faces versus objects (or Animate/inanimate) organization versus Expertise organization The Haxby, Kanwisher, Gauthier debates The Clinton and Angelina Jolie neurons Christoph Koch

12. 2. Attributes: sensory versus function Martin and Chao, 2001

13. Activity during: Mental imagery Naming tools > animals Viewing tools > animals Generating action words to tools Imagining tool manipulation Activity during: viewing static objects that imply motion Basic versus subordinate levels: For ex: human versus Marilyn Monroe Task: picture-word matching Martin and Chao, 2001

14. Function: * action Visual attr: * color * size * motion IFG IPC STS (dynamic obj attrib) Activity in primate brain: STS, OCC M.E. Sereno et. al., 2002 Thompson-Schill, 2003 ON periods: 3d rotating objects

15. Thompson-Schill, 2003

16. B. PREFRONTAL CORTEX LIFG = BROCA Thompson-Schill, 2003

17. Abstract 'objects' No brain areas overlapped across studies Bookheimer, 2002

18. Episodic memory

19. Thompson-Schill, 2003 3 necessary components of episodic memory: * subjective time * autonoetic awareness * time traveler Episodic memory is about happenings at particular places at particular times: - what - where - when Episodic memory develops late Not found in children younger than 4 years old (Give example from self)

20. Tulving, 2002

21. Brain bases for episodic memory Tulving, 2002

22. Hwang, 2006

23. Working memory

24. Working memory Defn.: Maintanence or manipulation of a limited amount of information (1-10 items) in an active state for a brief amount of time (0-60 sec). Ex: Maintanence: telephone number Manipulation: mental map of an area when you ask for directions Online manipulation of this type of information engages similar processes involved in reasoning, decison-making, problem solving, language understanding There are separate WM systems for verbal and spatial information processing Smith and Jonides, 1998

25. Modules/Components: • storage (decays rapidly) • rehearsal (can reactivate storage) • executive processing (may be same in both verbal and spatial WM) • For maintanence, only storage & rehearsal needed • For manipulation, executive processing is also necessary Processes: * selection * rehearsal WM performance parameters: * Delay * Load

26. Curtis and D'esposito 2003

27. Role of PFC from temporal storage perspective visual cuse response delay interval task Curtis and D'esposito 2003

28. Role of PFC from top-down control perspective Curtis and D'esposito 2003

29. Role of PFC from action-perception perspective Curtis and D'esposito 2003

30. Selection Rehearsal BROCA Curtis and D'esposito 2003 Curtis and D'esposito 2003 Smith and Jonides, 1998

31. POSTERIOR PARIETAL CORTEX Storage Smith and Jonides, 1998

32. Smith and Jonides, 1998

33. Verbal working memory no delay Task: respond Y or N if the probe letter is identical in name to the previosly seen 4 target letters Control Task: respond Y or N if the probe letter is identical in name to the previosly seen 4 target letters (no memory required since no delay) Localization: Control Task - Task: all L hemisphere storage = post parietal (BA40) rehearsal = Broca's (BA 44), pre-motor (BA6), SMA (BA 6) no executive processing activity in left hemisphere

34. Verbal working memory Task: Control Task1:Single target letter specified at the beginning. Decide whether each given letter matches it. (subtract out perceptual processing) Control Task2: Letter seen, press a button, rehearse the letter, repeat. (subtract out rehearsal as well) subtract Localization: Control Task1 - Task: Verbal WM = L Broca's + L premotor + L post. parietal cortex Control Task2 - Task: Reveals only storage = L post. parietal Control Task2 - Control Task1: Reveals only rehearsal = SMA + Broca's Control Task1 - Control Task2: Reveals just a little storage = L post. Parietal

35. Performance parameters: Load * Conduction aphasia (Wernicke's): Lesion in L posterior parietal area - subject cannot repeat a word even immediately, when rehearsal is not needed (L parietal = WM storage) * Broca's aphasia: Lesion in L Broca's area - when there is significant delay, subject's forgetting curve drops sharply. storage rehearsal N-back task, N=0,1,2,3 Smith and Jonides, 1998

36. Spatial working memory no delay Task: respond Y or N if the probe position is identical to the previosly seen target spots Control Task: respond Y or N if the probe position is identical to the previosly seen target spots Localization: Control Task - Task: all R hemisphere storage = inf. post. parietal (BA40), ant. occipital (BA19) rehearsal = superior post. parietal, pre-motor (BA6) executive processes: Inferior frontal (BA47) Rehearsal in spatial WM requires selectively attending to target locations. In selective attention experiments, superior post. parietal and premotor areas activate. activity in right hemisphere

37. The top-down model Smith and Jonides, 1997 Curtis and D'esposito 2003

38. Overall

39. Cabeza, 2000

40. * How to study memory from this table & structures: - Local approach: Relate each brain region to a process within cognitive domain - Global approach: Associate each brain region an operation that is recruited by a variety of tasks - Network approach: Interpret the role of each brain region in relation to other regions engaged by the same task Neocortex is the ultimate repository for consolidated long-term memory, which is category specific: name of objects, name of people, proper nouns, living things, manufactured things (tools), food (fruits and veg.) (see N. Kanwisher) The differential cortical geography of knowledge in healthy brain is still a mystery.

41. Last but not least: Hippocampus and MTL Structures

42. Hwang 2006

43. Hippocampus and other players Entorhinal cortex gets input from amygdala, all association areas of cortex, Fornix Outputs of hippocampus: from field CA1 and subiculum to entorhinal and association cortex

44. Moscovitch, 2005

45. Fornix • Several studies have shown that damage to the fornix causes anterograde amnesia • Amount of damage is correlated to the severity of symptoms • Fornix: • carries outflow of info from hippocampal formation to diencephalon • carries axons into hippocampus • Amnesia can be caused by interrupting either of these processes.

46. Mammillary Bodies • Mammillary bodies are related with Korsakoff’s syndrome. • In patients with this syndrome, there is almost always severe degeneration of mammillary bodies. • Therefore, shrinkage of this region is positively correlated with memory deficits.

47. Moscovitch, 2005

48. !!!! wrong Gabrieli, 1998 LTP, the long lasting enhancement of synaptic transmission , has long been regarded, along with it's counterpart LTD, as a potential mechanism for memory formation and learning.

49. Hebbian learning • Learning depends on the pre and postsynaptic cells being depolarized at the same time. • “Neurons that fire together wire together”. • A synapse that undergoes a long term change in strength is called a Hebbian synapse

50. LTP similar to kind of change that was postulated by Hebb in 1949 to underlie memory In vitro, brief period of intense high frequency stimulation (of perforant path) enhances the subsequent response of postsynaptic neurons granule cells in dentate gyrus to low-intensity stimulation of the presynaptic neuron. This enhancement can last for weeks. LTP requires co-occurance of activation of pre- and post-synaptic neurons. Increased number of synapses that exist between pre- and post-synaptic neurons following induction of LTP Consolidation: Process which results in transfer of information into LTM