Talking about Memory
	Voices on the nature of recall
	(revised 20 November 2000)

Contents and Links
"The key process of memory is retrieval": Interview with Endel Tulving
"Memory is a distributed system": Excerpts from Richard Cytowic
Aspects of memory: Cytowic's classification
Reality monitoring: Excerpts from Johnson (separate file)
Bibliography of memory research

"Of course memories are not stored at synapses. But I think it is useful to contemplate the possibility that they are not stored anywhere else in the brain either. The whole issue of where or, more important, how memories are stored in the brain may turn out to be an incorrect formulation of the problem, despite its seductively enticing allure. And the sournce of such an incorrect formulation may lie in the single-minded preoccupation with the storage, or the engram, and sometimes even identification of storage with memory. This preoccupation with the physical changes that follow from an experience that can be remembered seems to be accompanied by a rather conspicuous neglect of retrieval processes." (97)

"As a scientist I am compelled to the conclusion—not postulation, not assumption, but conclusion—that there must exist certain physical-chemical changes in the nervous tissue that correspond to the storage of information, or to the engram, changes that constitute the necessary conditions of remembering. (The alternative stance, that it may be possible for any behavior or any thought to occur independently of physical changes in the nervous system, as all your good readers know, is sheer mysticism.) However, if the engram is a kind of entity that manifests itself only in activity, or retrieval, then we might conjecture that the physical changes resulting from experience do not exist as an engram in the absence of that activity. And we can also imagine that the engram, qua engram, is not detectable in its quiescent state, that is, in the absence of retrieval, with any physical technique." (98-99).

"Even if you could somehow identify the total pattern of physical/chemical aftereffects of an experienced event, in all of its intricate and elaborate detail and full-blown complexity, you would nhave no way of knowing or predicting what kind of a memory (in the sense of experience) that engram is going to produce: that depends on the retrieval process, and that process has not yet occurred." (104).

"It is not only useful but important to distinguish between the storage metaphor, on the one hand, and the idea of the physical indeterminacy of the engram, on the other." (106).

"The approach of cognitive psychology and the approach of neurobiology are complementary, and there is no problem whatever. The problem arises only if one assumes that the physical approach is the only one, or the most essential one, or the fundamental one, that is, the old die-hard reductionist position. Remembering is a completely emergent, biological-psychological process of the brain." (108).
 
 

Table of content for Gazzaniga's book

Gazzaniga, Michael S. (ed.)  Conversations in the Cognitive Neurosciences Cambridge, MA: MIT Press, 1997

• "The explanation of memory that is now popular, but not definitively proven, is that an event is somehow stored in the same neural configurations that participate in its perception and understanding" (318). (Cf. mental images.)
• "So, we can say that memory storage is localized in the sense that a given distributed system represents specific aspects of an event, but memory is also diffuse in the sense that there is no generic memory center, nothing that represents an entire event at a singular locus" (318).
• "No focal memory center exists, but many brain parts each contributes something different to the memory of a singular event" (319).
• "multiple areas of neocortex, activated through limbic structures, participate in representing the memories and thoughts that give rise to evoked mental experiences" (Squire 1987, p. 84; quoted in Cytowic, p. 319).
• The amygdala does not participate in explicit or declarative memory, which depends on the medial temporal lobe system. "Rather, the amygdala plays an important but not exclusive role in cross-modal associations and the attachment of affect to neutral stimuli (Squire & Zola-Morgan, 1991)" (319).

On the Amygdala

• "The amygdala can be regarded as a neural crossroads since it has direct and extensive connections to all sensory modalities in cortex and thalamus. Sites of amygdalar multisensory convergence themselves project fibers deeper to the hippocampus, possibly thereby associating memories from diverse senses" (319-320).
• "the amygdala associates a familiar stimuli with emotional valence" (320).
• Somewhat more speculatively, "the amygdala not only enables sensory-sensory and sensory-emotional cross-modal associations, but also it may well enable emotion to influence one's perception of events and subsequent memory of them. Anatomy shows that sensory cortices not only project to the amygdala, but receive projections back from it" (320, italics in original).
• "Finally, the amygdala is rich in endogenous opiates," especially in the terminal processing areas (320).
• "The reciprocal amygdalar projections to sensory cortices together with its projections to hypothalamus may explain why, in both animals and humans, emotional experiences are so well remembered" (320).

• "the role of the cortex is to analyze the external world and house our models (representations) of reality. It is the limbic brain, however, that decides questions of salience and relevance and so determines how we act on the information we have" (102)
• "it is an emotional calculus, more than a logical one, that animates us" (102)
• The neocortex is "a detour interposed between brainstem nuclei and limbic entities. The neocortex provides analytic space, as suggested by its structure, and contains our model of reality. However, it is the limbic brain that is primarily involved in determining what we do with the analysis that the neocortex has carried out" (103).
• A large cortex alone is not enough, as seen in the example of the Australian anteater--a prosimian on a very low branch of the mammalian family tree
• It has a tremendously developed frontal cortex, much more developed than monkeys; however, it did not develop a robust limbic system
• Its cognitive limitations may have something to do with the fact that it is the only mammal that appears not to dream

• A major challenge of a complex brain is the prioritizing of informational processing
• Some of this processing appears to be taking place in sleep, during periods of intense mental activity, marked by rapid eye movements (REM)
• The REM phase is associated with an EEG signal called the theta rhythm
• Theta is particularly prominent in the hippocampus, which is part of the limbic system; the theta rhythm appears to signal an integrative activity, one of setting priorities
• "When any sensory signal comes into the human cortex, the hippocampal theta rhythm becomes active only if the stimulus is evaluated as relevant and we attend to it" (104)
• "All sensory inputs, external and visceral, must pass through the emotional limbic brain before being redistributed to the cortex for analysis, after which they return to the limbic system for a determination of whether the highly transformed, multisensory input is salient" (104-5)
• The neocortex receives more input from the limbic system than it provides to it
• "the volume and nature of recursive feedback suggests that the limbic influence may be greater than the neocortical one" (105)
• Temporal lobe epilepsy can cause "episodes in which one cannot distinguish between dreaming and reality" (106)
• The limbic system is "for integrating one's internal and external worlds" (108)
• In conclusion, it seems likely that dreaming performs a significant computational task related to integrating the computational results of the neocortex with the emotional values of the limbic system.

Richard E. Cytowic, MD  The Neurological Side of Neuropsychology Cambridge, MA: MIT Press, 1996

Bibliography of Memory Research Top

Abel, T., C. Alberini, M. Ghirardi, Y-Y. Huang, P. Nguyen, and E.R. Kandel (1995). Steps toward a molecular definition of memory consolidation. In Schacter 1995: 298-325.

Baddeley, Alan (2000). The episodic buffer: A new component of working memory? Trends in Conitive Sciences 4. 12 (2000): 417-423. Abstract.

Cho, Kwangwook (2001). Chronic 'jet lag' produces temporal lobe atrophy and spatial cognitive deficits. Nature Neuroscience 4: 567-568 (external link). BBC news report (external).

Goldman-Rakic, Patricia S. et al. (eds.) (2000). Memory. A section in The New Cognitive Neurosciences (2nd ed.). Edited by Michael S. Gazzaniga et al. Cambridge, MA: MIT Press.  Abstract.

Larsen, Steen Folke. Memorable Books: Recall of Reading and Its Personal Context. Empirical Approaches to Literature and Aesthetics. Norwood, NJ. 1996.

Mayes, Andrew R., Patricia A. Gooding and Rob van Eijk (1997). A New Theoretical Framework For Explicit and Implicit Memory. Psyche: An Interdisciplinary Journal of Research on Consciousness 3(2). The paper has an excellent up-do-date bibliography on memory research, and  a detailed discussion of possible mechanisms of reality monitoring (external file).

Miyake, Akira and Priti Shah (eds) (1999). Models of working memory: Mechanisms of active maintenance and executive control. New York, NY: Cambridge University Press. Abstracts.

Moscovitch, M. (1995) Recovered consciousness: A hypothesis concerning modularity and episodic memory. Journal of Clinical and Experimental Neuropsychology 17: 276-290.

Nyberg, Lars, Jonas Persson, Reza Habib, Endel Tulving, Anthony R. McIntosh, Roberto Cabeza, and Sylvian Houle (2000). Large Scale Neurocognitive Networks Underlying Episodic Memory. Journal of Cognitive Neuroscience 12. 1 (January 2000).

Rajaram, S. (1993). Remembering and knowing: Two means of access to the personal past. Memory and Cognition 21: 89-12.

Roediger, H. (1990). Implicit memory: Retention without remembering. American Psychologist 45: 1043-1056.

Rolls, Edmund T. (2000). Memory Systems in the Brain. Annu. Rev. Psychol. 2000. 51:599-630. Abstract (external).

Rose, S. (1992). The Making of Memory. London: Bantam Press.

Schacter, D.L., M. Verfaellie, and D. Pradere (1996) The neuropsychology of memory illusions: False recall and recognition in amnesic patients. Journal of Memory and Language 35: 319-334.

Schacter, D.L. and E. Tulving (eds) (1994). Memory Systems. London: MIT Press.

Schacter, D.L. (ed) (1995). Memory Distortion: How Minds, Brains, and Societies Reconstruct the Past. Cambridge, MA: Harvard University Press.

Sirigu, Angela; Grafman, Jordan. Selective impairments within episodic memories. Cortex, 1996 Mar, v32 (n1):83-95. Abstract. Dissociation between episodic memory of time and person vs place and content.

Squire, L.R. (1992). Memory and the Hippocampus: A synthesis from findings with rats, monkeys and humans. Psychological Review 99: 195-231.

Squire, L.R. (1994). Declarative and Nondeclarative memory : Multiple brain systems supporting learning and memory. In Schacter and Tulving.

Tulving, Endel (1983) Elements of Episodic Memory. Oxford: Oxford University Press.

Tulving, Endel (1985). Memory and consciousness. Canadian Psychology 26: 1-12.

Tulving, Endel (1993). What is episodic memory? Current Directions in Psychological Science 2: 67-68.

Ungerleider, L.G. (1995) Functional brain imaging studies of cortical mechanisms for memory.
Science 270: 769-775.

Wiggs, C.L., J. Weisberg, S. Garber, and A. Martin (1996). Brain regions associated with semantic and episodic memory. Neuroimaging 3: 568-.
 

For web sites and general works on neuroscience, see Bibliography on Neuroscience.
 
 

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