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Biomedical subjects

A P Shimamura

Publications and source records attributed to A P Shimamura.

At least 19 recordsLinked to original sources
PubMed2000

Toward a cognitive neuroscience of metacognition.

The relationship between metacognition and executive control is explored. According to an analysis by Fernandez-Duque, Baird, and Posner (this issue), metacognitive regulation involves attention, conflict resolution, error correction, inhibitory control, and emotional regulation. These aspects of metacognition are presumed to be mediated by a neural circuit involving midfrontal brain regions. An evaluation of the proposal by Fernandez-Duque et al. is made, and it is suggested that there is considerable convergence of issues associated with metacognition, executive control, working memory, and frontal lobe function. By integrating these domains and issues, significant progress could be made toward a cognitive neuroscience of metacognition.

Attention↗
PubMed2000

Differential effects of cue dependency on item and source memory.

The authors investigated the cue dependency of source and item memory. Individuals listened to words spoken by a man or a woman and later determined whether a test word was previously presented by a man or by a woman, or whether it was a new word. Cue dependent effects were assessed by presenting test words with (a) the same voice (match condition) that originally presented the word, (b) a different but familiar voice (mismatch condition), (c) a novel test voice (novel condition), and (d) no test voice (control condition). Compared with the control condition, source recollection was facilitated in matching-context conditions, disrupted in mismatching-context conditions, and not affected in novel test conditions. By contrast, item recognition was not affected by the match-mismatch manipulation but was significantly worse in novel test voice conditions. The authors propose an associative source interference view to account for the voice match-mismatch effects observed in source recollection.

Cues↗
PubMed1999

Retrieval-induced forgetting in episodic memory.

Participants learned the locations of 12 stimuli that were uniquely colored but could be grouped by shape (4 circles, 4 triangles, 4 crosses). Following the study, a retrieval-practice phase required participants to recall the colors of a subset of the stimuli (i.e., 2 circles, 2 triangles) using shape and location as cues. In a final test, participants recalled the colors of all 12 stimuli. Compared with the control set of stimuli (i.e., 4 crosses), memory was facilitated for practiced items but impaired for related items, which were not practiced but shared the same shape group. Across experiments, retrieval-induced forgetting was observed for different perceptual groupings and for different cuing procedures. The effect, however, required retrieval of information during the interpolated phase. Providing extra presentations did not disrupt memory for related items.

Humans↗
PubMed1999

Monitoring item and source information: evidence for a negative generation effect in source memory.

Item memory and source memory were assessed in a task that simulated a social conversation. Participants generated answers to questions or read statements presented by one of three sources (faces on a computer screen). Positive generation effects were observed for item memory. That is, participants remembered topics of conversation better if they were asked questions about the topics than if they simply read statements about topics. However, a negative generation effect occurred for source memory. That is, remembering the source of some information was disrupted if participants were required to answer questions pertaining to that information. These findings support the notion that item and source memory are mediated, as least in part, by different processes during encoding.

Adult↗
PubMed1998

On the recollection of specific- and partial-source information.

Memory judgments can be based on information that is more or less specific with respect to the source of an item. The authors introduce a procedure and multinomial model for measuring specific- and partial-source information. In 2 experiments, participants heard words spoken by 4 different voices: 2 male voices and 2 female voices. During the test, participants were required to remember who spoke the test items (e.g., Male 1, Male 2, Female 1, Female 2, or new word). Participants often remembered information about the gender of the source (i.e., partial-source information) when they did not remember information that identified the source itself (i.e., specific-source information). Dividing attention during retrieval impaired participants' memory for specific-source information (i.e., voice information) but did not affect memory for partial-source information (i.e., gender information).

Attention↗
PubMed1998

Letter and category fluency in patients with frontal lobe lesions.

This study examines the hypothesis that patients with frontal lobe lesions are impaired on tests of letter but not category fluency. This hypothesis was proposed by Moscovitch (1994), based on a series of cognitive studies with young, normal participants. A group of patients with lateral prefrontal lesions and age-matched controls were tested on 2 tests of verbal fluency, the FAS task and a category fluency task that used semantic categories as cues (e.g., animals). Patients with frontal lobe lesions generated fewer items than controls on both letter and category fluency. This effect did not interact with the type of fluency test, suggesting that the frontal lobes are more generally involved in verbal fluency. Moreover, this pattern of findings, along with previous results of impaired free recall and remote retrieval in this patient group, suggests that patients with frontal lobe lesions do not efficiently organize and develop retrieval strategies.

Aged↗
PubMed1998

Mapping symbols to response modalities: interference effects on Stroop-like tasks.

Response compatibility effects were assessed with a Stroop-like task which involved arrow and word stimuli. The subjects were required to respond to one stimulus--an arrow (e.g.,-->) or a word (e.g., left)--and ignore the other. It was shown that response compatibility played a significant role in generating Stroop-like interference. Robust interference effects were observed when the subjects responded manually to word stimuli (ignoring irrelevant arrows) and when they responded vocally to arrow stimuli (ignoring irrelevant words). Smaller interference effects were observed under response-compatible conditions, namely, responding manually to arrows and vocally to words. In the second experiment, within-dimension displays (e.g., arrow-arrow or word-word displays) yielded a pattern of interference that did not interact with response modality. These findings indicate that both stimulus-response compatibility effects and target-distractor similarity are crucial for understanding Stroop-like interference.

Humans↗
PubMed1997

Impaired word-stem priming in patients with temporal-occipital lesions.

In the word-stem priming test, words are presented (e.g., MOTEL, PARADE), and later subjects are shown three-letter word stems (e.g., MOT, PAR) and asked to complete each stem with the first word that comes to mind. Word-stem priming, as well as other aspects of implicit memory, are intact in amnesic patients with medial temporal lesions. However, this form of priming has been shown to be impaired in patients with Alzheimer's disease, suggesting that damage to neocortical areas outside the medial temporal lobe contributes to impaired priming in these patients. To examine the role of posterior cortical areas on word-stem priming, we administered the test to patients with unilateral temporal-occipital lesions. Patients with temporal-occipital lesions exhibited significantly impaired priming on this test. The findings suggest a critical role of the inferior posterior neocortex in the expression of this form of implicit memory.

Aged↗
PubMed1995

Impaired use of organizational strategies in free recall following frontal lobe damage.

Free recall, use of organizational strategies, and interference effects were assessed in patients with frontal lobe lesions and control subjects. In three experiments, patients with frontal lobe lesions exhibited impaired free recall and reduced use of organizational strategies in tests of memory. Reduced use of strategies was observed on tests of recall of unrelated items, as measured by subjective organization, and on tests of recall of related items, as measured by both category clustering and subjective organization. Frontal patients benefited from strategy instruction at either study or test, suggesting that both encoding and retrieval processes are impaired by frontal lobe damage. These findings indicate that the free recall impairments exhibited by patients with frontal lobe lesions may be caused at least in part by deficits in the use of organizational strategies. In addition, when first-list learning was matched for patients and control subjects, patients with frontal lobe lesions exhibited relatively increased sensitivity to proactive interference during second-list learning.

Aged↗
PubMed1994

Serial position effects in implicit and explicit tests of memory.

The effects of serial position at study on implicit and explicit tests of memory were investigated. Both primary and recency effects were observed in implicit tests of word-stem completion. These effects, however, were transient. No serial position effects were found in the second half of testing (Experiments 1 and 3) or when testing followed a 1-min, filled delay (Experiment 2). Serial position effects were also examined in explicit tests of cued recall. When performance on explicit cued recall was below ceiling levels, a primacy effect persisted throughout testing (Experiment 3). Similarly, in explicit tests of free recall, primacy effects were consistently observed, both with immediate testing (Experiments 1 and 3) and when testing followed a filled delay (Experiment 2).

Humans↗
PubMed1993

Cognitive neuropsychology is more than single-case studies.

S. M. Sokol et al. (1991) claim that "The Cognitive Neuropsychology Approach" (p. 355) is limited to the single-case study design. The present article takes issue with this claim. Contrary to the beliefs of Sokol et al., we argue (a) that cognitive modularity is best studied by group design, (b) that the possibility of neural reorganization in patients should be tested through converging evidence from different populations using various methods, and (c) that cognitive neuropsychology can benefit from being a part of cognitive neuroscience where both neural and cognitive mechanisms underlying normal cognition are relevant.

Bias↗
PubMed1992

Intact implicit memory in patients with frontal lobe lesions.

Patients with frontal lobe lesions and control subjects were administered tests of word-stem completion priming. In this implicit memory test, subjects are first presented words (e.g. MOTEL, PARADE) in an incidental learning paradigm. Following word presentation, subjects are shown word stems (e.g. MOT, PAR) and asked to produce the first word that comes to mind. Patients with frontal lobe lesions exhibited normal levels of word-stem completion. These findings indicate that implicit memory can operate normally despite damage to the prefrontal cortex. The present results substantiate previous neuropsychological and positron emission tomography findings which indicate that word priming depends critically on posterior cortical areas.

Brain Damage, Chronic↗
PubMed1992

On the relationship between recall and recognition memory.

The relationship between recall and recognition has been a central topic for the study of memory. A test of alternative views about recall and recognition was arranged by studying amnesic patients. In amnesia, damage has occurred to a brain system important for declarative (conscious) memory, but skill learning, priming, and other forms of nonconscious memory are intact. Recall and recognition were found to be proportionately impaired in amnesic patients, and confidence ratings for the recognition judgments were commensurate with the level of impaired performance. The results are contrary to views that either recognition memory or associated confidence judgments are ordinarily supported significantly by nonconscious memory. The results favor the view that recall and recognition are related functions of declarative memory and equivalently dependent on the brain system damaged in amnesia.

Aged↗
PubMed1990

Memory for the temporal order of events in patients with frontal lobe lesions and amnesic patients.

Patients with frontal lobe lesions, amnesic patients with Korsakoff's syndrome, other (non-Korsakoff) amnesic patients, and control subjects were given tests of memory for temporal order. In the first experiment, subjects were presented with a list of 15 words and then asked to reproduce the list order from a random array of the words. In the second experiment, they were asked to arrange in chronological order a random display of 15 factual events that occurred between 1941 and 1985. In both experiments, patients with frontal lobe lesions were impaired in placing the items in the correct temporal order, despite normal item memory (i.e. normal recall and recognition memory for the words and facts). The two groups of amnesic patients exhibited impaired memory for temporal order as well as impaired item memory. Patients with Korsakoff's syndrome exhibited poorer temporal order memory than the other amnesic patients, despite similar levels of item memory. These findings demonstrate that patients with frontal lobe lesions have difficulty organizing information temporally. Patients with Korsakoff's syndrome, who have both diencephalic and frontal damage, have memory impairment together with a disproportionate deficit in memory for temporal order.

Alcohol Amnestic Disorder↗
PubMed1990

Intact text-specific reading skill in amnesia.

Amnesic patients were studied to determine whether the acquisition and retention of item-specific skills can be supported by nondeclarative (implicit) memory. In Experiment 1, subjects read 2 different passages 3 times in succession. Reading speed improved at a similar rate in both amnesic patients and normal subjects and was specific to the text that was read. In Experiment 2, amnesic patients and normal subjects read a passage 3 successive times and then reread the same passage after a 0-s, 10-min, 2-hr, or 1-day delay. In both groups, facilitation persisted for at least 10 min and disappeared within 2 hr. It is suggested that facilitated reading speed depends importantly on both semantic and perceptual information and that such information can be supported by nondeclarative memory.

Aged↗
PubMed1989

Source memory impairment in patients with frontal lobe lesions.

In two experiments, we investigated memory for recently learned facts and memory for the source of the facts (i.e. where and when the facts were learned) in patients with frontal lobe lesions, age-matched elderly control subjects, and younger subjects. In both experiments, patients with frontal lobe lesions recalled as many facts as their age-matched subjects and the younger subjects, but they frequently attributed facts to incorrect sources. In the second experiment, both patients with frontal lobe lesions and their age-matched subjects committed more source errors than younger subjects. These findings suggest that the frontal lobes may play a special role in associating facts to the context in which they were learned. The results are also discussed in the light of the source memory impairment that occurs in amnesic patients.

Adult↗