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D L Schacter

Publications and source records attributed to D L Schacter.

At least 109 records · Page 6Linked to original sources
PubMed1990

Toward a cognitive neuropsychology of awareness: implicit knowledge and anosognosia.

Although a systematic cognitive neuropsychology of awareness has not yet emerged, a number of phenomena reported in the literature provide an empirical basis for developing it. The present discussion focusses on two such phenomena: implicit knowledge, which refers to knowledge that is expressed in task performance unintentionally and with little phenomenal awareness; and anosognosia, which refers to unawareness of neuropsychological deficits. Two types of theoretical accounts of these phenomena are discussed. A first order theoretical account entails postulating damage to, or disconnection of, a system or process that generates awareness across multiple domains. A second-order account does not postulate disruption of a cross-domain awareness mechanism, but instead appeals to difficulties in gaining access to particular kinds of domain-specific information that are associated with aware expressions of knowledge in individual domains. Instances of first- and second-order accounts are illustrated with examples from studies of memory and amnesia. The relation between implicit knowledge and anosognosia is also discussed.

Agnosia↗
PubMed1989

Extending the limits of complex learning in organic amnesia: computer training in a vocational domain.

This study explored the limits of learning that could be achieved by an amnesic patient in a complex real-world domain. Using a cuing procedure known as the method of vanishing cues, a severely amnesic encephalitic patient was taught over 250 discrete pieces of new information concerning the rules and procedures for performing a task involving data entry into a computer. Subsequently, she was able to use this acquired knowledge to perform the task accurately and efficiently in the workplace. These results suggest that amnesic patients' preserved learning abilities can be extended well beyond what has been reported previously.

Adult↗
PubMed1989

Autobiographical memory in a case of multiple personality disorder.

Previous research on multiple personality disorder (MPD) has been concerned with between-personalities amnesia, and little attention has been paid to within-personality memory function. This study examined the autobiographical memory of a multiple personality patient, I.C., with cueing procedures that have proven useful in previous studies of normal and abnormal memory. Results indicated that I.C. was able to retrieve autobiographical episodes from the recent past, although her performance differed in several respects from that of matched controls. The study also revealed a striking deficit in I.C.'s autobiographical memory for childhood: She was unable to recall a single episode from prior to the age of 10 in response to various retrieval cues, whereas control subjects had no difficulty recalling numerous childhood episodes. This phenomenon of extended childhood amnesia has not been reported previously in studies of MPD.

Adult↗
PubMed1989

Modality specificity of implicit memory for new associations.

In previous research we demonstrated that newly acquired associations between unrelated word pairs influence the magnitude of priming effects on word-completion tests. This phenomenon of implicit memory for new associations is observed only following semantic study elaboration. The present experiments reveal that implicit memory for new associations, though elaboration dependent, is also modality specific: Associative effects on a visual word-completion test were consistently reduced by study-test modality shifts. In contrast, explicit memory for new associations, as indexed by cued-recall performance, was uninfluenced by modality shifts. The modality effect on completion performance was eliminated when subjects were given brief visual preexposures to, or were required to construct visual images of, word pairs presented in auditory study conditions. The results pose a theoretical puzzle insofar as they indicate that within the domain of implicit memory, access to the products of elaborative processing depends on modality-specific, sensory-perceptual processing.

Association↗
PubMed1989

Unawareness of deficits in neuropsychological syndromes.

Damage to different regions of the brain can cause a variety of neuropsychological deficits, including specific disturbances of language, memory, perception and motor function. A significant number of brain-damaged patients are unaware of their deficits, even when they are profound and have debilitating effects on patients' performance. This article reviews clinical observations and experimental investigations concerning unawareness of deficits, considers methodological issues, and critically evaluates different interpretations of the phenomenon. An integrative theoretical framework is proposed to account for unawareness of deficits in diverse neuropsychological syndromes. Possible directions for future research are outlined.

Agnosia↗
PubMed1988

Long-term retention of computer learning by patients with memory disorders.

Previous research has demonstrated that patients with memory disorders resulting from closed-head injury can acquire the complex knowledge and skills necessary for the use of a microcomputer. The present paper extends the generality of those findings by showing that (1) amnesic patients with other etiologies could similarly learn how to operate a computer and (2) the knowledge and skills acquired were retained over intervals of up to 9 months.

Adult↗
PubMed1988

Priming of semantic autobiographical knowledge: a case study of retrograde amnesia.

The case of a 36-year-old man who suffers dense retrograde and anterograde amnesia as a result of closed-head injury that caused extensive damage to his left frontal-parietal and right parieto-occipital lobes is described. Patient K.C. has normal intelligence and relatively well-preserved perceptual, linguistic, short-term memory, and reasoning abilities. He possesses some fragmentary general knowledge about his autobiographical past, but he does not remember a single personal event or happening from any time of his life. He has some preserved expert knowledge related to the work he did for 3 years before the onset of amnesia, although he has no personal recollections from that period. Some features of K.C.'s retrograde amnesia can be interpreted in terms of the distinction between episodic and semantic memory, and in terms of the distinction between episodic and semantic autobiographical knowledge. K.C.'s semantic knowledge, but not his episodic knowledge, showed progressive improvement, or priming, in the course of the investigation.

Adult↗
PubMed1988

Memory and awareness in a patient with multiple personality disorder.

We studied an individual with multiple personality disorder in whom each of several personalities claimed to have no direct awareness of the others and to be unable to consciously remember the experiences of other personalities. A broad selection of implicit and explicit memory tests was used to determine the extent to which one personality had access to knowledge acquired by another and the circumstances in which that knowledge would be expressed. The implicit assessment of memory was a necessary but not sufficient condition for demonstrating interpersonality access. The degree of compartmentalization of knowledge in this patient depended largely on whether the interpretation of presented information was likely to differ across personalities.

Awareness↗
PubMed1987

When priming persists: long-lasting implicit memory for a single episode in amnesic patients.

This experiment investigated the durability of implicit memory for a single episode in normal and amnesic subjects. The target materials consisted of sentence puzzles that were difficult to comprehend in the absence of a key word or phrase. Sentences were re-presented at delays ranging from one minute to one week, and implicit memory was indicated by facilitation in solving previously incomprehensible sentences on subsequent exposures. Patients with severe memory impairments on tests of explicit recall and recognition showed substantial and robust facilitation, or priming, from a single prior presentation and there was no evidence of a systematic decay of facilitation over retention intervals up to one week. The long-lasting implicit memory observed in the sentence puzzle task contrasts with previous findings of rapid decay of priming effects in amnesic patients.

Adult↗
PubMed1987

Neurochemical dissociation of memory systems.

The administration of scopolamine, an anticholinergic drug, reduced the ability to recall and recognize stimuli presented previously--abilities thought to require declarative memory. In contrast, measures of procedural memory were unaffected by scopolamine: performance on a serial reaction time task incorporating a repeating stimulus and response sequence showed no difference in acquisition and retention of the sequence after scopolamine or saline. These results suggest that the cholinergic system is required for declarative but not procedural memory.

Adult↗
PubMed1987

Implicit expressions of memory in organic amnesia: learning of new facts and associations.

Organic amnesia is a selective impairment of memory that occurs as a consequence of various types of brain damage. Although amnesic patients typically have severe difficulties remembering recent events and acquiring new information, it has been demonstrated that some of their learning abilities are spared. Amnesic patients can retain and express some aspects of a learning experience, despite their inability to recollect the experience in a conscious or explicit manner. This phenomenon is referred to as an implicit expression of memory. The present article considers whether amnesic patients show implicit memory for new facts and associations. Three relevant kinds of evidence are considered: source amnesia, priming effects, and learning of computer vocabulary and commands. It is concluded that (a) amnesic patients do show some implicit memory for new facts and associations, and (b) this type of memory is not entirely spared. Implications for multiple memory system views of amnesia are discussed.

Amnesia↗
PubMed1986

Computer learning by memory-impaired patients: acquisition and retention of complex knowledge.

Several investigators have shown that memory-impaired patients are capable of learning relatively simple information in both the laboratory and everyday life. The present research explored whether patients with memory disorders could also acquire complex knowledge--the domain-specific knowledge needed for operating and interacting with a microcomputer. The results indicated that patients with memory disorders of varying severity could learn to manipulate information on the computer screen, to write, edit and execute simple computer programs, and to perform disk storage and retrieval operations. The learning process, however, was slow relative to controls and the knowledge acquired appeared to be qualitatively different. Theoretical and practical implications of these findings are discussed.

Adult↗
PubMed1986

Learning and retention of computer-related vocabulary in memory-impaired patients: method of vanishing cues.

Several investigators have suggested that microcomputers might serve as useful external aids for memory-impaired patients. However, knowledge of basic computer vocabulary may be necessary for patients to use and benefit from a microcomputer. The present paper describes a procedure, the method of vanishing cues, which facilitated the acquisition of computer-related vocabulary in four memory-impaired patients. The method involves the systematic reduction of letter fragments of to-be-learned words across trials. Although learning was slow and strongly dependent on first-letter cues, all patients acquired a substantial amount of the vocabulary and eventually were able to produce the target words in the absence of fragment cues. Further, they retained the vocabulary over a 6-week interval and showed some transfer of the knowledge they had acquired. These findings suggest that memory-impaired patients may eventually be able to use a microcomputer as a prosthetic device.

Adult↗
PubMed1986

Preserved learning in amnesic patients: perspectives from research on direct priming.

An important source of evidence for preserved learning ability in amnesic patients is provided by the phenomenon of repetition or direct priming: the facilitative effect of an encounter with an item on subsequent processing of the same item. In this article we consider a series of experiments that have attempted to clarify the nature of priming in amnesic patients and normal subjects. The experiments indicate that there may be two varieties of priming, one dependent upon the activation of preexisting memory representations, the other dependent upon newly formed memory representations. We suggest that the former type of priming is preserved even in severely amnesic patients, whereas the latter may be preserved only in mildly-to-moderately amnesic patients. Implications of research on preserved learning for the development of remedial strategies are also discussed.

Adult↗
PubMed1986

Mnemonic precedence in amnesic patients: an analogue of the AB error in infants?

Amnesic patients were able to retrieve an object hidden at an initial location after a brief delay, but subsequently failed to retrieve an object at a new location, and instead searched for it at the old place. This phenomenon, which we call mnemonic precedence, resembles the AB error that has been observed in 8-10-month-old infants. The parallel performance of amnesics and infants on object search tasks is consistent with the hypothesis that memory deficit, rather than defective object concept, plays a major role in the AB error. The influence of memory processes on tests of symbolic representation is discussed.

Adult↗
PubMed1985

Implicit and explicit memory for new associations in normal and amnesic subjects.

Two experiments examined whether repetition priming effects on a word completion task are influenced by new associations between unrelated word pairs that were established during a single study trial. On the word completion task, subjects were presented with the initial three letters of the response words from the study list pairs and they completed these fragments with the first words that came to mind. The fragments were shown either with the paired words from the study list (same context) or with other words (different context). Both experiments showed a larger priming effect in the same-context condition than in the different-context condition, but only with a study task that required elaborative processing of the word pairs. This effect was observed with college students and amnesic patients, suggesting that word completion performance is mediated by implicit memory for new associations that is independent of explicit recollection.

Adult↗