| Neuroanatomy and Physiology of Memory |
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Dong Woo Yu, Seong Ho Kim |
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Department of Neurosurgery, College of Medicine, Yeungnam University, Daegu, Korea |
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| Abstract |
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The hippocampal formation and the amygdala are the key functional centers of the limbic system. Also closely associated with the limbic system is the mamillary body, which has abundant connections with the hippocampal formation and amygdaloid nucleus. The hippocampal formation plays a key role in explicit memory and learning. The amygdaloid nucleus plays an important role in behavior and emotions, and primary role in the memory of emotional reaction. Memory is the process by which that knowledge of the world is encoded, stored, and later retrieved and a phase of learning. There are two basic kinds of memory. One is explicit (or declarative) ; the other is implicit (or non-declarative). Implicit memory involves also different brain regions : fear conditioning involves amygdala ; operant conditioning involves striatum and cerebellum ; and classical conditioning, sensitization and habituation involve sensory and motor systems used in the responses. This kind of memory involves a number of processes : habituation involves decrease in synaptic strength from decreased transmitter release ; sensitization involves increase in synaptic strength due to presynaptic facilitation ; and classical conditioning involves increase in synaptic strength due to presynaptic facilitation that is dependent on activity in both pre-and postsynaptic cells. Explicit memory involves a number of brain regions : there is no general store for explicit memories ; because the subject of memories is multimodal, storage of different aspects occurs in different locations ; the hippocampal formation is important in processing information for storage as memory ; and memories are actually stored in association cortex. Right hippocampal damage produces greater deficits in memory for spatial representation, whereas left hippocampal damage produces greater deficits in memory for words, objects or people. This kind of memory probably makes use of long-term potentiation (LTP). The early phase of LTP involves glutamatergic transmission ; postsynaptic processes that produce enhanced sensitivity or receptors to glutamate as well as enhanced release of transmitter substance. In the late phase of LTP, protein synthesis leads to changes in cell structure and formation of new synapses. |
| Key Words:
Hippocampal formation, Amygdala, Explicit memory, Implicit memory. |
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