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Retrograde amnesia (RA) is a loss of memory-access to events that occurred, or information that was learned, before an injury or the onset of a disease〔.〔 RA is often temporally graded, consistent with Ribot's Law: subjects are more likely to lose recent memories that are closer to the traumatic incident than more remote memories.〔Wixted, J. T. (2004). The psychology and neuroscience of forgetting, ''Annual Review of Psychology'', ''55'', 235-269. 〕 ==Brain structures== The most commonly affected areas are associated with episodic and declarative memory such as the hippocampus,〔Cipolotti, L., Shallice, T., Chan, D., Fox, N., Scahill, R., Harrison, G., Stevens, J., & Rudge, P. (2001). Long-term retrograde amnesia...the crucial role of the hippocampus, ''Neuropsychologia'', ''39''(2), 151–172.〕 the diencephalon,〔 and the temporal lobes.〔Buccione, I., Fadda, L., Serra, L., Caltagirone, C., & Carlesimo, G. (2008). Retrograde episodic and semantic memory impairment correlates with side of temporal lobe damage, ''Journal of the International Neuropsychological Society'', ''14''(6), 1083-1094.〕 * The hippocampus deals largely with memory consolidation,〔 in particular episodic memory. Its main responsibility is making information go from short-term memories into long-term stores. Amnesic patients with damage to the hippocampus are able to demonstrate some degree of unimpaired semantic memory, despite loss of episodic memory, due to spared parahippocampal cortex.〔Nadel, L., & Moscovitch, M. (1997). Memory consolidation, retrograde amnesia and the hippocampal complex, ''Current Opinion in Neurobiology'', ''7''(2), 217-227. 〕 * The diencephalon and the surrounding areas' role in memory is not well understood. However, this structure appears to be involved in episodic memory recall.〔Dusoir, H., Kapur, N., Byrnes, D. P., McKinstry, S., & Hoare, S. D. (1990). The role of diencephalic pathology in human memory disorder: Evidence from a penetrating paranasal brain injury, ''Brain'', ''113''(6), 1695-1706. 〕 * The temporal lobes are essential for semantic and factual memory processing. Aside from helping to consolidate memory with the hippocampus,〔 the temporal lobes are extremely important for semantic memory. Damage to this region of the brain can result in impaired organization and categorization of verbal material, disturbance of language comprehension, and impaired long-term memory. Right side lesions in particular, result in impaired recall of non-verbal material, such as music and drawings.〔Milner, B. (1968). Visual recognition and recall after right temporal lobe excision in man, ''Neuropsychologia'', ''6'', 191-209.〕 Difficulties in studying this region of the brain extend to its duties in comprehension, naming objects, verbal memory, and other language functions.〔Kolb, B., & Whishaw, I. (1990). Fundamentals of human neuropsychology. W.H. Freeman and Co., New York.〕 Plasticity of the brain is when rewiring occurs because of brain damage, finding different neural pathways and not relying on the damaged structures.〔Kolb, B., & Gibb, R. (2003). Brain plasticity and behavior, ''Current Directions in Psychological Science'', ''12''(1), 1-5. 〕 Thus, the brain can learn to be independent of the impaired hippocampus, but only to a certain extent.〔 For example, older memories are consolidated over time and in various structures of the brain, including Wernicke's area and the neocortex, making retrieval through alternate pathways possible.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「retrograde amnesia」の詳細全文を読む スポンサード リンク
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