Intact and impaired conceptual memory processes in amnesia.

To examine the status of conceptual memory processes in amnesia, a conceptual memory task with implicit or explicit task instructions was given to amnesic and control groups. After studying a list of category exemplars, participants saw category labels and were asked to generate as many exemplars as possible (an implicit memory task) or to generate exemplars that had been in the prior study list (an explicit memory task). After incidental deep or shallow encoding of exemplars, amnesic patients showed normal implicit memory performance (priming), a normal levels-of-processing effect on priming, and impaired explicit memory performance. After intentional encoding of exemplars, amnesic patients showed impaired implicit and explicit memory performance. Results suggest that although amnesic patients can show impairments on implicit and explicit conceptual memory tasks, their deficit does not generalize to all conceptual memory tasks.

Normal perceptual priming of orthographically illegal nonwords in amnesia.

This study examined priming in perceptual identification of orthographically illegal nonwords in control subjects and patients with global amnesia. Subjects studied a list of orthographically illegal nonwords and then performed a perceptual identification task in which half of the stimuli were from the prior study list and half were new (unstudied) stimuli. Priming was reflected in enhanced identification accuracy of studied compared to unstudied nonwords. Amnesic patients showed significant and normal priming despite impaired recognition memory performance. Because the experimental stimuli were dissimilar to real words in terms of orthography and phonology, it is unlikely that this priming effect was mediated by activation of pre-existing representations of orthographically or phonologically similar words, morphemes, or syllables. These results demonstrate that intact perceptual priming in amnesia is not limited to stimuli that are premorbidly represented in long-term knowledge, nor to novel stimuli that conform to the rules that characterize familiar items. Further, because the experimental stimuli comprised novel letter assemblies, the results suggest that amnesic patients can show normal priming for new perceptual associations. These findings demonstrate that processes spared in amnesia can support the creation and subsequent retrieval of novel stimulus representations.