Biomedical subjects

D L Schacter

Publications and source records attributed to D L Schacter.

At least 73 records · Page 4Linked to original sources

PubMed1997

False recollection induced by photographs: a comparison of older and younger adults.

Looking at photographs constitutes an important everyday memory activity for older adults. The authors found that reviewing photographs of events seen earlier in a videotape increases the likelihood that both older and younger adults remember specific details from the reviewed event (W. Koutstaal, D. L. Schacter, M. K. Johnson, K. E. Angell, & M. S. Gross, 1977). In the present study, the authors report 2 experiments demonstrating that photo review can also produce false recollection in elderly adults: After reviewing photos of events that had not been shown earlier in a videotape, older but not younger adults were later more likely to "remember" that those events had been shown in the videotape. False recollection induced by photo review appears to reflect an age-related deficit in source-monitoring abilities.

Adolescent↗

PubMed1997

Illusory memories in amnesic patients: conceptual and perceptual false recognition.

Little is known about the neuropsychology of false recognition. D.L. Schacter, M. Verfaellie, and D. Pradere (1996) induced false recognition in amnesic patients and normal controls by exposing them to numerous semantic associates of a nonstudied word and found that amnesics showed significantly reduced levels of false recognition. To determine whether this outcome is specific to the semantic domain, the authors examined false recognition after exposure to lists of conceptually and perceptually related words. In the control group, conceptual false recognition was associated with "remember" responses and perceptual false recognition was associated with "know" responses. Amnesic patients showed reduced levels of conceptual and perceptual false recognition that were approximately equally divided between remember and know responses.

Age Factors↗

PubMed1997

Illusory recall of vocal affect.

Illusions of memory occur when a person recalls something that did not take place, and may result from processes that systematically bias recall. This paper reports three experiments exploring a novel form of memory bias that can occur when a person is attempting to recall the affective tone of voice in which someone spoke previously. Subjects first studied photographs of faces while listening to sentences spoken in a positive or negative tone of voice. At test, subjects saw brief presentations of faces and were asked to recall the tone of voice in which the pictured person had spoken earlier. Across a variety of study and test conditions a strong recall bias was observed: when faces conveyed either subtle positive or negative affect, subjects tended to recall the pictured person as having spoken with a matching affective tone, regardless of the tone of voice in which the person had actually spoken. It is proposed that this affective recall bias may be the product of a retrieval mechanism that relies on a combination of information from the memory trace and retrieval environment to guide responding.

Adolescent↗

PubMed1997

False recognition in younger and older adults: exploring the characteristics of illusory memories.

Roediger and McDermott (1995) demonstrated that when subjects hear a list of associates to a "theme word" that has itself not been presented, they frequently claim to recollect having heard the nonpresented theme word on the study list. In Experiment 1, we found that asking subjects to explain their remember responses, by writing down exactly what they remembered about the item's presentation at study, did not significantly diminish the rate of remember false alarms to nonpresented theme words. We also found that older adults were relatively more susceptible than younger adults to this false-recognition effect. Subjects' explanations suggested that both veridical and illusory memories were predominantly composed of associative information as opposed to sensory and contextual detail. In Experiment 2, we obtained quantitative evidence for this conclusion, using a paradigm in which subjects were asked focused questions about the contents of their recollective experience. Lastly, we found that both younger and older adults recalled more sensory and contextual detail in conjunction with studied items than with nonpresented theme words, although these differences were less pronounced in older adults.

Adult↗

PubMed1996

Illusory memories: a cognitive neuroscience analysis.

Memory illusions and distortions have long been of interest to psychology researchers studying memory, but neuropsychologists and neuroscientists have paid relatively little attention to them. This article attempts to lay the foundation for a cognitive neuroscience analysis of memory illusions and distortions by reviewing relevant evidence from a patient with a right frontal lobe lesion, patients with amnesia produced by damage to the medial temporal lobes, normal aging, and healthy young volunteers studied with functional neuroimaging techniques. Particular attention is paid to the contrasting roles of prefrontal cortex and medial temporal lobe structures in accurate and illusory remembering. Converging evidence suggests that the study of illusory memories can provide a useful tool for delineating the brain processes and systems involved in constructive aspects of remembering.

Aged↗

PubMed1996

The role of hippocampus and frontal cortex in age-related memory changes: a PET study.

The purpose of this study was to examine the neuroanatomical correlates of explicit retrieval of episodic memories in older and young adults. We used an experimental paradigm that allowed us to separate the effort involved in attempting to retrieve a recently studied word from the actual recollection of the item. Both older and younger adults showed hippocampal blood flow increases in association with recollection of a studied word. In contrast, younger but not older adults showed bilateral blood flow increases in anterior prefrontal cortex during retrieval attempts: older adults showed more posterior frontal lobe activations during attempted retrieval. We conclude that the hippocampus activations may reflect a commonality in the way that older and younger adults remember past events, whereas differences in frontal activation may reflect age-related changes in their retrieval strategies.

Adult↗

PubMed1996

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

We used positron emission tomography (PET) to examine the role of the hippocampal formation in implicit and explicit memory. Human volunteers studied a list of familiar words, and then they either provided the first word that came to mind in response to three-letter cues (implicit memory) or tried to recall studied words in response to the same cues (explicit memory). There was no evidence of hippocampal activation in association with implicit memory. However, priming effects on the implicit memory test were associated with decreased activity in extrastriate visual cortex. On the explicit memory test, subjects recalled many target words in one condition and recalled few words in a second condition, despite trying to remember them. Comparisons between the two conditions showed that blood-flow increases in the hippocampal formation are specifically associated with the conscious recollection of studied words, whereas blood-flow increases in frontal regions are associated with efforts to retrieve target words. Our results help to clarify some puzzles concerning the role of the hippocampal formation in human memory.

Adult↗

PubMed1996

False recognition and the right frontal lobe: a case study.

We described a patient, BG, who exhibited a striking pattern of false recognition after an infarction of the right frontal lobe. Seven experiments document the existence of the phenomenon, explore its characteristics, and demonstrate how it can be eliminated. BG showed pathologically high false alarm rates when stimuli were visual words (experiments 1 and 4), auditory words (experiment 2), environmental sounds (experiment 3), pseudowords (experiment 5), and pictures (experiment 7). His false alarms were not merely attributable to the semantic or physical similarity of studied and non-studied items (experiments 4 and 5). However, BG's false recognitions were virtually eliminated by presenting him with categorized stimuli and testing him with new stimuli from non-studied categories (experiments 6 and 7). The results suggest that BG's false alarms may be attributable to an over-reliance on memory for general characteristics of the study episode, along with impaired memory for specific items. The damaged right frontal lobe mechanisms may normally support the monitoring and/or retrieval processes that are necessary for item-specific recognition.

Aged↗

PubMed1996

Neuroanatomical correlates of veridical and illusory recognition memory: evidence from positron emission tomography.

Memory distortions and illusions have been thoroughly documented in psychological studies, but little is known about the neuroanatomical correlates of true and false memories. Vivid but illusory memories can be induced by asking people whether they recall or recognize words that were not previously presented, but are semantically related to other previously presented words. We used positron emission tomography to compare brain regions involved in veridical recognition of printed words that were heard several minutes earlier and illusory recognition of printed words that had not been heard earlier. Veridical and illusory recognition were each associated with blood flow increases in a left medial temporal region previously implicated in episodic memory; veridical recognition was distinguished by additional blood flow increases in a left temporoparietal region previously implicated in the retention of auditory/phonological information. This study reveals similarities and differences in the way the brain processes accurate and illusory memories.

Acoustic Stimulation↗

PubMed1996

Can cognitive neuroscience illuminate the nature of traumatic childhood memories?

Recent findings from cognitive neuroscience and cognitive psychology may help explain why recovered memories of trauma are sometimes illusory. In particular, the notion of defective source monitoring has been used to explain a wide range of recently established memory distortions and illusions. Conversely, the results of a number of studies may potentially be relevant to forgetting and recovery of accurate memories, including studies demonstrating reduced hippocampal volume in survivors of sexual abuse, and recovery from functional and organic retrograde amnesia. Other recent findings of interest include the possibility that state-dependent memory could be induced by stress-related hormones, new pharmacological models of dissociative states, and evidence for 'repression' in patients with right parietal brain damage.

Amnesia, Retrograde↗

PubMed1996

Visual specificity effects on word stem completion: beyond transfer appropriate processing?

An important, but poorly understood, aspect of memory retrieval concerns the conditions under which priming is influenced by perceptual changes in the form of target items. According to transfer appropriate processing perspectives, perceptual specificity effects on priming require a study task that focuses attention on the perceptual, rather than semantic, features of the items. Other research suggests that perceptual specificity effects are enhanced by conditions yielding high levels of explicit memory. The present experiments manipulated encoding tasks and other variables known to influence explicit memory (repetition and retention interval) in order to gain insight into the determinants of perceptual specificity effects on visual word-stem completion. In Experiment 1 we found that perceptual specificity (letter case) effects on stem completion priming depend on perceptual encoding when subjects' awareness of the study-test relationship is limited. In Experiments 2-4 we found that perceptual specificity effects can be obtained after semantic encoding--especially when the study-test retention interval is short. Perceptual specificity effects after short retention intervals were independent of encoding task, and may reflect a form of involuntary explicit memory.

Adult↗

PubMed1996

Form-specific visual priming for new associations in the right cerebral hemisphere.

In three experiments, we examined the internal processing mechanisms of relatively independent visual-form subsystems. Participants first viewed centrally presented word pairs and then completed word stems presented beneath context words in the left or right visual field. Letter-case-specific priming in stem completion was found only when the context word was the same word that had previously appeared above the primed completion word and the items were presented directly to the right cerebral hemisphere. This pattern of results was not found when participants deliberately recollected previously presented words when completing the stems. Results suggest that holistic processing, not parts-based processing as assumed in many contemporary theories of visual-form recognition, is performed in a subsystem that distinguishes specific instances in the same abstract category of form and that operates more effectively in the right hemisphere than in the left hemisphere.

Adult↗

PubMed1995

Brain regions associated with retrieval of structurally coherent visual information.

An object's global, three-dimensional structure may be represented by a specialized brain system involving regions of inferior temporal cortex. This system's role in object representation can be understood by experiments in which people study drawings of novel objects with possible or impossible three-dimensional structures, and later make either possible/impossible object decisions or old/new recognition decisions about briefly flashed studied and non-studied objects. Although object decisions about possible objects are facilitated by prior study, there is no corresponding facilitation for impossible objects, thereby implicating a system that is specifically involved in the representation of structurally coherent visual objects. Here we show, by positron emission tomography (PET), that increases in blood flow in inferior temporal regions are associated with object decisions about possible but not impossible objects, and that there are increases in the vicinity of the hippocampal formation associated with episodic recognition of possible objects.

Brain Mapping↗

PubMed1995

Auditory priming for nonverbal information: Implicit and explicit memory for environmental sounds.

Three experiments examined repetition priming for meaningful environmental sounds (e.g., clock ticking, tooth brushing, toilet flushing, etc.) in a sound stem identification paradigm using brief sound cues. Prior encoding of target sounds together with their associated names facilitated subsequent identification of sound stems relative to nonstudied controls. In contrast, prior exposure to the names alone in the absence of the environmental sounds did not prime subsequent sound stem identification performance at all (Experiments 1 and 3). Explicit and implicit memory were dissociated such that sound stem cued recall was higher following semantic than nonsemantic encoding, whereas sound priming was insensitive to manipulations of depth of encoding (Experiments 2 and 3). These results extend the findings of long-term repetition priming into the auditory nonverbal domain and suggest that priming for environmental sounds is mediated primarily by perceptual processes.

Acoustic Stimulation↗

PubMed1995

Implicit memory in amnesic patients: when is auditory priming spared?

Amnesic patients often exhibit spared priming effects on implicit memory tests despite poor explicit memory. In previous research, we found normal auditory priming in amnesic patients on a task in which the magnitude of priming in control subjects was independent of whether speaker's voice was same or different at study and test, and found impaired voice-specific priming on a task in which priming in control subjects is higher when speaker's voice is the same at study and test than when it is different. The present experiments provide further evidence of spared auditory priming in amnesia, demonstrate that normal priming effects are not an artifact of low levels of baseline performance, and provide suggestive evidence that amnesic patients can exhibit voice-specific priming when experimental conditions do not require them to interactively bind together word and voice information.

Alcohol Amnestic Disorder↗

PubMed1995

Bias in the priming of object decisions: logic, assumption, and data.

R. Ratcliff and G. McKoon (1995) describe 7 experiments that led them to conclude that priming of possible but not impossible objects on the object decision task introduced by D.L. Schacter, L.A. Cooper, & S.M. Delaney (1990) is attributable to explicit memory processes that offset a bias to call studied objects "possible." On the basis of this point, Ratcliff and McKoon (1995) claim to have undermined our hypothesis that a structural description system plays an important role in object decision priming. Ratcliff and McKoon (1995) also offer a general critique of multiple memory systems accounts of priming and explicit memory. Ratcliff and McKoon's (1995) arguments are based on an inaccurate characterization of Schacter et al.'s theoretical position; the evidence for Ratcliff and McKoon's (1995) idea that explicit memory offsets bias is weak, and the central assumptions that underlie both Ratcliff and McKoon's (1995) specific experimental manipulations and their general conclusions are questionable.

Decision Making↗

PubMed1994

Varieties of priming.

Recent data from brain-damaged and normal subjects converge to suggest several characteristics of repetition priming: firstly, it is sensitive to the physical and structural properties of input; secondly, it is unaffected by semantic processing at encoding; thirdly, it is frequently preserved in amnesic patients with impaired explicit memory; fourthly, it depends upon perceptual representations processed and stored by modality-specific cortical memory systems; and, finally, it is subject to constraints particular to the task employed and the type of information that is primed.

Auditory Perception↗

PubMed1994

Perceptual specificity of auditory priming: implicit memory for voice intonation and fundamental frequency.

Five experiments explored the effect of acoustic changes between study and test on implicit and explicit memory for spoken words. Study-test changes in the speaker's voice, intonation, and fundamental frequency produced significant impairments of auditory priming on implicit tests of auditory identification and stem completion but had little or no effect on explicit recall and recognition tests (Experiments 1-4). However, study-test changes in overall decibel level had no effect on priming on an auditory stem-completion test or on cued-recall performance (Experiment 5). The results are consistent with the idea that fundamental frequency information is represented in a perceptual representation system that plays an important role in auditory priming.

Acoustic Stimulation↗