Perceptual and conceptual memory processes in global amnesia.

Abstract

To determine whether global amnesia reflects a selective deficit in conceptual processing, amnesic and control subjects performed 4 memory tasks that varied processing and retrieval requirements. A study-phase modality (auditory/visual) manipulation validated the nature of processing (perceptual and conceptual) engaged by each task. Amnesic patients were impaired on perceptual and conceptual explicit memory tasks (word-fragment and word-associate cued recall) and were intact on perceptual and conceptual implicit memory tasks (word-fragment completion and word association). These results are consistent with the view that limbic-diencephalic structures damaged in amnesia mediate, in part, processes typically engaged during explicit retrieval. The results are inconsistent, however, with the characterization of that deficit as being one of conceptual processing per se.Amnesia is associated with bilateral damage to medial temporal or diencephalic brain regions and is characterized by the failure to remember new facts and events, despite preserved perceptual, motoric, and intellectual functions (for reviews, see Cermak, 1982;Hirst, 1982;Squire, 1986). Amnesic patients perform poorly on explicit tests of memory, such as recall and recognition tasks, which require intentional recollection of prior study episodes. These patients may perform normally, however, on implicit tests of memory, which make no reference to prior study episodes but infer memory by a change in performance (Graf & Schacter, 1985).

The role of explicit memory processes in cross-modal priming: An investigation of stem completion priming in amnesia

“…Blum and Yonelinas (2001) recently provided evidence suggesting that cross-modal priming in fragment completion may be mediated differently from cross-modal priming in stem completion, since only participants who claimed to have used explicit retrieval processes showed cross-modal priming in the fragment completion task. At odds with their data, however, is the f inding of intact cross-modal fragment completion priming in a group of amnesic patients (Vaidya, Gabrieli, Keane, & Monti, 1995; but see Kohler et al, 1997, for evidence of impairment in a single case). Clearly, future studies will be needed to analyze the nature of cross-modal priming in fragment completion and to compare cross-modal priming in the fragment completion task and the stem completion task.…”

Convergent behavioral and neuropsychological evidence for a distinction between identification and production forms of repetition priming.

“…Most fragments have only one answer, so there is little or no response competition. Word-fragment completion is a test of perceptual priming (e.g., Roediger et al, 1989Roediger et al, ,1992Vaidya et al, 1995) that is not reduced by auditory division of attention at study (Experiment 2 in the present study; Gabrieli et al, 1999;Mulligan & Hartman, 1996). The older individuals in the study by Winocur et al (1996) were either high functioning and community dwelling or less high functioning and living in institutions; the latter group did not, however, have AD.…”

“…Conceptual priming is often enhanced by conceptual elaboration at study (e.g., Keane et al, 1997;Monti et al, 1996;Srinivas & Roediger, 1990;Vaidya et al, 1997) and is often intact in global amnesia (e.g., Keane et al, 1997;Shimamura & Squire, 1984;Vaidya, Gabrieli, Keane, & Monti, 1995). Perceptual and conceptual forms of priming are often dissociable because modality and notation manipulations affect perceptual but not conceptual priming, whereas manipulation of conceptual encoding affects conceptual but not perceptual priming.…”

Neural correlates of conceptual implicit memory and their contamination of putative neural correlates of explicit memory

“…Effective connectivity analyses might also provide relevant evidence. However, compelling dissociations between conceptual priming and explicit memory have been provided by neuropsychological studies in amnesic patients (Graf et al 1985;Vaidya et al 1995;Keane et al 1997;Levy et al 2004). Research that might verify such dissociations in healthy individuals by directly examining putative functional relationships can now be pursued by making use of neural correlates of memory as characterized in the present study.…”