Dissociations between Word Priming Effects in Normal Subjects and Patients with Memory Disorders: Multiple Memory Systems or Retrieval?

Abstract

Repetition priming was measured in two different tasks within a single experiment--one in which subjects named briefly (tachistoscopically) presented words, and one requiring naming of visually fragmented/degraded words. Thirteen amnesic patients, 12 patients with Alzheimer's disease (AD), and 15 normal control subjects were tested under 4 experimental conditions involving the factorial combination of two variables: delay of test (10 minutes and 24 hours), and number of prior occurrences of the primed items (1 and 4). The two tasks produced very different patterns of priming effects, despite the fact that common study phases were employed. In one task the priming effect showed no decay and virtually no effect of the number of prior occurrences of the primed items, whereas both these variables affected priming in the other task. The AD patients evidenced impaired priming in both tasks. However, in the degraded-word-naming task the deficit was only apparent under some experimental conditions. The amnesics produced priming effects that in absolute terms were similar to those produced by control subjects. However, when group differences in overall performance level were taken into account in the tachistoscopic task, these patients also showed clear evidence of impaired priming. It is argued that the complex pattern of priming effects obtained is best explained by the characteristics of the retrieval cues provided in the tasks, and, generally, that such characteristics may determine whether or not experimental variables will affect measured priming.

The effects on priming of word frequency, number of repetitions, and delay depend on the magnitude of priming

“…This relationship between baseline performance and measured priming is important when memory-impaired patients are compared with normal control subjects. If the patients have deficits that affect their baseline identification performance, then these have to be taken into account when evaluating the priming effects (see Hamann, Squire, & Schacter, 1995;Ostergaard, 1994;, 1995.…”

“…Ostergaard (1994) obtained similarly conflicting evidence in a direct comparison between two perceptual word-priming tasks. Delay of the priming test and the number ofrepetitions of the primed items affected the magnitude of priming in a tachistoscopic word-identification task, but not in a task of identifying visually fragmented words.…”

“…Delay of the priming test and the number ofrepetitions of the primed items affected the magnitude of priming in a tachistoscopic word-identification task, but not in a task of identifying visually fragmented words. Ostergaard (1994) illustrated how the characteristics of the retrieval cues provided in the priming task could produce such divergent results. Different information-processing tasks may not be equally sensitive to, or facilitated by, a given level of encoded information.…”

Implicit and explicit memory for odors: Hemispheric differences

“…The evidence comes, for instance, from finding different patterns of outcome for more or less parallel explicit and implicit tasks. The former asks for recall or recognition of previously presented information and the latter does not, but assesses how the previously presented information reflects itself otherwise (e.g., Hayman & Tulving, 1989;Jacoby, 1991;La Voie & Light, 1994;Ostergaard, 1993). In some cases, the comparison of explicit and implicit processing has entailed a contrast between the right and left hemispheres.…”

Controlled and Automatic Memory Process in Alzheimer's Disease

“…patient characteristics can account for discrepancies in the findings (e.g., Burke, Knight and Partridge, 1994;Ostergaard, 1994). Furthermore, differences in the psychometric characteristics of the tests of memory used in experimental studies can also be important.…”