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Amnesia

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A. Evaluate evidence that non-declarative long-term memory is preserved in amnesia.

Amnesic patients tend to suffer from permanent or temporal, normally partial or total loss of episodic memory and an impaired capacity to form and store new memories. On the other hand, they seem to demonstrate unimpaired performance of behaviours involving prior experiences on tests which do not require any intentional or conscious recollection of those experiences (Schacter, 1992). Hence, most amnesic patients demonstrate the ability to retain and learn new behaviours through priming and conditioning, and acquire new perceptual, cognitive, motor and emotional skills which cannot be traced back to an explicit memory but can be demonstrated implicitly.
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The combined findings provide the foundation for the hypothesis that there is more than one kind of memory, or rather that skill-based memories must be organised differently from fact-based memories since the former seem to be preserved in amnesia as opposed to the latter.
Further supportive evidence comes from priming studies; priming refers to the improved capacity for detecting or processing a novel or familiar stimuli based on recent experience (Tulving & Schater, 1990). In a famous study by Heist et al. (1991) amnesic patients and control subjects studied words and non-words. They were then given a perceptual identification test with briefly presented previously studied and unstudied items. Perceptual priming was measured as the increase in the probability of identifying the former versus the letter items. Amnesic patients exhibited entirely normal priming for both old words and non-words. On the other hand, they showed significant impairment in recognizing items that had appeared on the administered test. Priming of non-words did not appear to be based on the activation of words that were phonologically or orthographically similar to the non-words. The non-word results suggest that priming can involve the acquisition of new information, rather than simply the activation of pre-existing representations. Researchers concluded that intact perceptual priming in amnesic patients reflects specific changes
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