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Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001.

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Neuroscience. 2nd edition.

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Brain Systems Underlying Declarative and Procedural Memories

Three extraordinary clinical cases of amnesia have been especially revealing about the brain systems responsible for the short-term storage of declarative information and are now familiar to neurologists and neurobiologists as patients H.M., N.A., and R.B. (see Box C). Taken together, these cases provide dramatic evidence of the importance of midline diencephalic and medial temporal lobe structures—the hippocampus, in particular—in establishing new declarative memories (Figure 31.6). These patients also demonstrate that there is a different anatomical substrate for anterograde and retrograde amnesia, since in each of these individuals, memory for events prior to the precipitating injury was retained. The devastating deficiency is (or was in the case of R.B.) the inability to establish new memories. Retrograde amnesia—the loss of memory for events preceding an injury or illness—is more typical of the generalized lesions associated with head trauma and neurodegenerative disorders, such as Alzheimer's disease (Box D). Although a degree of retrograde amnesia can occur with the more focal lesions that cause anterograde amnesia, the long-term storage of memories is presumably distributed throughout the brain (see next section). Thus, the hippocampus and related diencephalic structures indicated in Figure 31.6 form and consolidate declarative memories that are ultimately stored elsewhere. Finally, it is important to emphasize that H.M., N.A., and R.B. had no problems establishing (or recalling) procedural memories, indicating that procedural memories are laid down by means of a different anatomical substrate.

Figure 31.6. Brain areas that, when damaged, tend to give rise to declarative memory disorders.

Figure 31.6

Brain areas that, when damaged, tend to give rise to declarative memory disorders. By inference, declarative memory is based on the physiological activity of these structures. (A) Studies of amnesic patients have shown that the formation of declarative (more...)

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Box D

Alzheimer's Disease.

Other causes of amnesia have also provided some insight into the parts of the brain relevant to various aspects of memory (see Table 31.2). Korsakoff's syndrome, for example, occurs in chronic alcoholics as a result of thiamine (vitamin B1) deficiency. In such cases, loss of brain tissue occurs bilaterally in the mammillary bodies and the medial thalamus, for reasons that are not well understood.

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2001, Sinauer Associates, Inc.
Bookshelf ID: NBK10940

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