Carrillo-Mora P

Language: Spanish
References: 63
Page: 85-93
PDF size: 130.17 Kb.

ABSTRACT

Memory is a fascinating brain function by means of which the nervous system can codify, store, organize, and recover a variety of information relevant to the subject. The formal study of memory started more than a century ago, providing in this time a considerable amount of scientific information on memory functioning. The actual knowledge of memory allow us to consider it far from being unique, isolated or static function, but more as a complex net of memory systems working in parallel for a common goal. Historic evolution of memory concepts and their classifications have progressed simultaneously to our knowledge on these systems. The first empiric approaches to memory description were found in ancient Greece by authors like Plato and Aristoteles, and were based on philosophy, thinking, and introspection and logic methods. However, the first real scientific approaches appeared in the XIX century, by authors such as Ebbinghaus and Lashley, who initiated the experimental study of memory in humans and animals, respectively. The contribution of the intellectual group known as «behaviorist» in the beginning of XX century, was also relevant during this period, and was represented by scientists like Pavlov, Watson, Skinner, and Thorndike, who detailed a variant of learning recognized in our days as associative learning. In turn, this variant can be divided into classic conditioning (associates a stimulus with a response) and instrumental or operant conditioning (associates a stimulus with a specific behavior). Behaviorists claimed that only on observational basis of behavior is possible to know processes linked to learning. However, these authors clearly made a mistake when they stated that knowledge on processes occurring in the brain will always be far of the understanding of the investigator. Later on, one of the hardest evidences for the study of memory processes came from clinic studies of patients with focal cerebral lesions. Penfield, Scoville, and Milner, during the 60’s, documented the effects of surgical lesions of temporal lobe on declarative memory, finding selective alterations, such as severe anterograde amnesia and retrograde amnesia with temporal gradient. These findings were accompanied also by a description of memory subsystems remaining intact, despite of those temporal lobe lesions (procedural memory, long-term memory, etc.). Based on these findings, medial temporal lobe was described as a key structure for the acquisition of declarative information. In parallel to clinic studies, a first attempt to coordinate psycho-psychiatric research with the knowledge and scientific protocol of biology occurred in the 60’s, thus allowing the emergence of disciplines known as cognitive neuroscience and cognitive psychology or psychophysiology, both created in an effort to explore the cellular and molecular mechanisms responsible for the storage of memory information. The list of significant findings provided by these two scientific disciplines is extensive, but among the most important are probably those derived from the study of the most elementary memory processes (i.e. habituation and sensitization) in invertebrate animal models, such as Aplysia spp. These researches established the basis for the basic cellular requirements for elementary learning, as well as the molecular basis for short-and long-term memory. The conjugation of these clinical descriptions together with experimental evidence led to the postulation of the first classifications of memory systems during the 80’s. One of these classifications divided memory processes in two categories: declarative memory — the one containing information consciously acquired and easy to verbalize or transmit to other persons (this type of memory is also divided in semantic and episodic memories)—, and non-declarative —including that information not easy to verbalize or which acquisition is unconscious (this type of memory implies heterogeneous information in which the role of consciousness is complex and remains in discussion, and includes procedural memory, priming, classic, and operant conditioning, as well as the most elementary forms of learning, such as habituation and sensitization). To conceptualize these memory systems in an isolated form is a mistake since is results clear enough that all of them work together most of the time, and they work independently only very seldom, some other times cooperating, or even functioning in a competitive manner. Experimental studies have shown that the role of memory systems is different each time, even when two subjects perform exactly the same learning task, thus suggesting that codification, motivation and initial handling of information may determine whether this is processed as procedural, spatial or semantic information. The recent description of competitive relationships among the different memory systems (declarative vs. procedural) resulted to be an outstanding finding, although at the present there is hard clinical and experimental evidence indicating that a decrease of functions in procedural, spatial or declarative systems may induce the activation of another memory system. Initial studies in this field suggest that transient inactivation of striatal dorsal structures (implicated in performance of motor skills) or those from the hippocampus (implicated in the performance of spatial skills) facilitate learning in that system remaining active after pharmacological challenge. The real meaning of this competition among systems still remains unclear, although it has been proposed that both systems have evolved separately in response to distinct needs, which in turn might explain why eventually these systems can compete for the handling of information. Unfortunately, several studies have demonstrated that relationships among memory systems are complicated and poorly understood until now. Semantic memory

Semantic memory mainly refers to information stored on characteristics defining concepts (facts lacking a well-defined spatial/ temporal frame), as well as processes allowing its efficient recovery for further util ization in language and thought. Knowledge about the anatomic location of semantic representations has gained attention with the use of new functional neuroimaging techniques. These studies have shown that the information about the features of specific objects needed to create concepts is stored in the same neuronal systems that remain active during the perception of different stimuli. The way in which this conceptual information is organized remains unclear so far, but there is evidence suggesting that its organization proceeds on the basis of grouped categories of concepts. Pathological studies in patients suffering semantic dementia have also demonstrated that some areas, such as temporal pole and perirhinal cortex, are relevant for semantic processing.

REFERENCES

1. Rains, Dennis G. Sistemas de memoria. En: Principios de neuropsicología humana. Primera edición. México: Mc Graw Hill; 2004; pp: 241-286.

2. Squire LR. Memory systems of the brain: A brief history and current perspective. Neurobiol Learn Mem 2004;82:171-177.

3. Aristoteles. Metafísica de Aristoteles. Segunda edición. Madrid: Edit. Gredos; 1997.

4. Ebbinghaus H. Memory. A contribution to experimental psychology.New York: Columbia University; 1885.

5. James W. The principles of psychology. Tercera edición. United Kingdom: Courier Dover Publications; 1950.

6. Shacter DL. Implicit memory: History and current status. J Exp Psychol:Learn Mem Cog 1987;13:501-518.

7. Zubaran C, Fernandes JG, Rodnight R. Wernicke-Korsakoff Syndrome. Postgrad Med 1997;73:27-31.

8. Schacter DL. Forgotten ideas, neglected pioneers: Richard Semon and the history of memory. Philadelphia: Psychology Press; 2001.

9. von Bekhterev M. Demonstration eines gehirns mit zerstörung der vorderen und inneren theile der hirnrinde beider schläfenlappen. Neurologisches Zeitblatt 1900;19:990-1.

10. Milner B. The medial temporal-lobe amnesic syndrome. Psychiatr Clin N Am 2005;28:599-611.

11. Thorndike EL. Memory for paired associates. Psychological Rev 1909;15:122-138.

12. Pavlov IP. Conditioned reflex. London: Oxford University Press; 1927.

13. Skinner BF. Drive and reflex strength: I J Gen Psychol 1932;6:22-37.

14. Epstein R. Consciousness, art, and the brain: Lessons from Marcel Proust. Consciousness Cognition 2005;13:213-240.

15. Lashley KS. Brain mechanism and intelligence: A Quantitative study of injuries to the brain. Chicago: Univ of Chicago Press; 1929.

16. Victor M, Angevine JB, Mancall EL, Fisher CM. Memory loss with lesions of hippocampal formation. Arch Neurol 1961;5:244-263.

17. Rose FC. Persistent memory defect following encephalitis. Brain 1960;83:195-212.

18. Hebb DO. The organization of behavior. New York: Wiley; 1949.

19. Penfield W, Milner B. Memory deficits induced by bilateral lesions in the hippocampal zone. Arch Neurol Psychiatry 1958;79:475-97.

20. Scoville WB, Milner B. Loss of recent memory after bilateral hippocampal lesions. J Neurol Neurosurg Psychiatry 1957;20:11-21.

21. Sawa M, Ueki Y, Arita M, Harada T. Preliminary report on the amygdaloidectomy on the psychotic patients, with interpretation of oral-emotional manifestation in schizophrenics. Folia Psychiatrica Neurologica Japonica 1954;7:309-29.

22. Scoville WB. The limbic lobe in man. J Neurosurg 1954;11:64-6.

23. Milner B. The memory defect in bilateral hippocampal lesions. Psychiatric Research Report 1959;11:43-58.

24. Milner B. Disorders of learning and memory after temporal lobe lesions in man. Clin Neurosurg 1972;19:421-46.

25. Milner B, Corkin S, Teuber HL. Further analysis of the hippocampal amnesic syndrome 14-year follow-up study of HM. Neuropsychologia 1968;6:215-34.

26. Scoville WB, Correll RE. Memory and the temporal lobe. Acta Neurochirurgica 1973;28:251-258.

27. Drachman DA, Arbit S. Memory and the hippocampal complex II. Is the memory a multiple process? Arch Neurol 1966;15:52-61.

28. Corkin S. Acquisition of motor skills after bilateral temporal-lobe excision. Neuropsychologia 1968;6:255-65.

29. Warrington E, Weiskrantz L. New method for testing long-term retention with special reference to amnesic patients. Nature 1968;4:217:972.

30. Gollin ES. Developmental studies of visual recognition of incomplete objects. Percept Mot Skills 1960;11:289-98.

31. Mishkin M. Memory in monkeys severely impaired by combined but not by separate removal of amygdala and hippocampus. Nature 1978;273:297-298.

32. Zola-Morgan S, Squire LR. Preserved learning in monkeys with medial temporal lesions: Sparing of motor and cognitive skills. J Neurosci 1984;4:1072-1085.

33. Squire LR. Mechanisms of memory. Science 1986;232:1612-1619.

34. Tulving E. How many memory systems are there? American Psychologist 1985;40:385-398.

35. Tulving E, Schacter DL. Priming and human memory systems. Science 1990;247:301-306.

36. Milner B, Squire LR, Kandell ER. Cognitive neuroscience and the study of memory. Neuron 1998;20: 445-468.

37. Cajal SR. La fine structure des centres nerveux. Proc R Soc Lond 1894;55:444-468.

38. Mountcastle V. Modality and topographic properties of single neurons of cat somatosensory cortex. J Neurophysiol 1957;20:408–434.

39. Wurtz RH. Steady potential shifts during arousal and sleep in the cat. Electroencephalograp Clin Neurophysiol 1965;18:649-662.

40. Brownell GL, Sweet WH. Localization of brain tumors with positron emitters. Nucleonics 1953;11:40-45.

41. Kandell ER, Tauc L. Mechanism of prolonged heterosynaptic facilitation. Nature 1964;2002:145.

42. Routtenberg A, Rekart JL. Post-translational modification as the substrate for long-lasting memory. Trends Neurosci 2005;28:12-19.

43. Gold PE. Protein synthesis inhibition and memory: Formation vs. amnesia. Neurobiol Learn Mem 2008;89:201-211.

44. Hernandez PJ, Abel T. The role of protein synthesis in memory consolidation. Progress amid decades of debate. Neurobiol Learn Mem 2008;89:293-311.

45. Bailey CH, Barco A, Hawkins RD, Kandell ER. Molecular studies of learning and memory in Aplysia and the hippocampus: A comparative analysis of implicit and explicit memory storage. En: Byrne JH (ed.) Learning and memory: A comprehensive reference. EUA: Academic Press; 2008; vol. 2; pp.11-29.

46. Roediger III HL, Zaromb FM, Goode MK. A typology of memory terms. En: Byrne JH (ed.). Learning and memory: A comprehensive reference. EUA: Academic Press; 2008; vol. 1; pp.11-24.

47. Poldrack RA, Packard MG. Competition among multiple memory systems: converging evidence from animal and human brain studies. Neuropsychol 2003;1497:1-7.

48. Packard MG, Hirsh R, White NM. Differential effects of fornix and caudate nucleus lesions on two radial maze task: evidence for multiple memory systems. J Neurosci 1989;9:1465-72.

49. Packard MG, McGaugh JL. Double dissociation of fornix and caudate nucleus lesions on acquisition of two water maze tasks: further evidence for multiple memory systems. Behav Neurosci 1992;106:439-46.

50. Packard MG, McGaugh JL. Inactivation of hippocampus or caudate nucleus with lidocaine differentially affects expression of place and response learning. Neurobiol Learn Mem 1996;65:65-72.

51. Poldrack RA, Prabakharan V, Seger C, Gabrieli JDE. Striatal activation during cognitive skill learning. Neuropsychol 1999;13:564-74.

52. Packard MG. Exhumed from thought: Basal ganglia and response learning in the plus maze. Behav Brain Res 2009 (en prensa).

53. Wingard JC, Packard MG. The amygdala and emotional modulation of competition between cognitive and habit memory. Behav Brain Res 2008;193:126-131.

54. Martin A Chao LL. Semantic memory and the brain: Structure and processes. Curr Neurobiol 2001;11:194-201.

55. Martin A, Haxby JV, Lalonde FM, Wiggs CL, Ungerleider LG. Discrete cortical regions associated with knowledge of color and knowledge of action. Science 1995;379:649-652.

56. Caramazza A, Shelton JR. Domain specific knowledge systems in the brain: the animate-inanimate distinction. J Cog Neurosci 1998;10:1-34.

57. Kreiman G, Koch C, Fried I. Category-specific visual responses of single neurons in the human medial temporal lobe. Nat Neurosci 2000;3:946-953.

58. Ishai A, Ungerleider LG, Martin A, Schouter JL, Haxby JV. Distributed representation of objects in the ventral visual pathway. Proc Natl Acad Sci USA 1999;96:9379-9384.

59. Poldrack RA, Wagner DA, Prull MW, Desmond JE, Glover GH et al. Functional specialization for semantic and phonological processing in the left inferior frontal cortex. Neuroimage 1999;10:15-35.

60. Faust M, Ben-Artzi E, Harel I. Hemispheric asymmetries in semantic processing: Evidence from false memories for ambiguous words. Brain Lang 2008;105:220-228.

61. Smith CN, Squire L. Medial temporal lobe activity during retrieval of semantic memory is related to the age of memory. J Neurosci 2009;29:930-938.

62. Davies RR, Halliday GM, Xuereb JH, Kril JJ, Hodges JR. The neural basis of semantic memory: Evidence from semantic dementia. Neurobiol Aging 2008 (en prensa).

63. Leonard B, de Partz MP, Grandin C, Pillon A. Domain-specific reorganization of semantic processing after extensive damage to the left temporal lobe. NeuroImage 2009;45:572-586.