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Biomedical subjects

J Dywan

Publications and source records attributed to J Dywan.

16 recordsLinked to original sources
PubMed2005

Life satisfaction and distress in family caregivers as related to specific behavioural changes after traumatic brain injury.

PRIMARY OBJECTIVE: To predict long-term outcome of those caring for family members who have sustained a traumatic brain injury (TBI). METHODS AND PROCEDURES: A multivariate approach was used to examine the effectiveness of caregiver coping strategies in the context of TBI-related behavioural change. Self-administered questionnaire packages were collected from 72 adult survivor and family-member pairs who provided information on survivors' altered executive function, behavioural control and emotional sensitivity as well as caregivers' methods of coping, attitudes toward caregiving, indices of distress, mood ratings and quality of life. MAIN OUTCOMES AND RESULTS: Family members generally reported higher levels of satisfaction than dissatisfaction with their caregiving role. The type of neurobehavioural deficit and the approaches taken to cope with stress had specific effects on each dimension of caregiver outcome. CONCLUSIONS: Adequate family support requires finely tuned assessment of factors relevant to successful coping.

Adaptation, Psychological↗
PubMed2001

Error-negativity and positivity as they relate to other ERP indices of attentional control and stimulus processing.

We compared individual differences in the ERP associated with incorrect responses in a discrimination task with other ERP components associated with attentional control and stimulus discrimination (N2, P3, CNV). Trials with errors that are detected by the subject normally produce a negativity (N(E)) immediately following the response followed by a positivity (P(E)). The morphology of the N(E) and the P(E) is similar to that of the standard N2-P3 complex on correct discrimination trials. Our findings suggest that the P(E) is a P3 response to the internal detection of errors. The N(E), however, appears to be distinct from the N2. Finally, even though both the contingent negative variation (CNV) and the N(E) are associated with prefrontal cortex and the allocation of attention to response accuracy, the N(E) and CNV did not relate to one another.

Adult↗
PubMed2001

Event-related potential evidence for age-related differences in attentional allocation during a source monitoring task.

Event-related potentials (ERPs) were recorded while older and younger adults were engaged in a source monitoring task. After studying a list of words, participants were presented with a recognition test during which some of the new words were repeated, rendering them as familiar as the study words. Instructions at test indicated whether the goal was to select the previously studied words or the repeated test items. Behaviorally, the younger adults were less likely to make source monitoring errors. ERPs, averaged only for correct trials, indicated that younger adults produced late positivities of greatest amplitude in response to whichever word type was designated as target irrespective of its familiarity. The ERPs of the older adults were generally less differentiated and their late positivities greater for recently repeated words irrespective of target designation. These results suggest that source monitoring in young adults is facilitated by their ability to allocate and withdraw attention from stimuli on the basis of task relevance rather than familiarity alone, and that this attentional flexibility declines with age.

Adult↗
PubMed1998

Source monitoring: ERP evidence for greater reactivity to nontarget information in older adults.

Event-Related Potentials (ERPs) were collected concurrently with stimulus presentation during a source monitoring task. Younger adults were less likely than older adults to make source monitoring errors and their ERP records showed far greater discrimination between target stimuli and familiar but nontarget foils. Older adults not only made more source errors but produced high amplitude late positivities to the nontarget foils even when these foils were correctly rejected. Under divided attention conditions, younger adults performance was similar to that of the older adults both behaviorally and electrophysiologically. These data illustrate the role that attentional resources play in the ability to inhibit response tendencies and suggest that age differences in source monitoring may be more related to attentional control than inefficiencies in the encoding of contextual information. As well, they suggest that the ERP late positivity may represent a more general response to item salience rather than serve as an index of recollection as is the current view.

Aged↗
PubMed1998

Toward a neurophysiological model of hypnotic memory effects.

In the early 1980s the use of hypnosis of "refresh" eyewitness memory was increasing with little opposition. While there was some evidence that hypnosis could produce confabulation, the mechanisms underlying this effect were poorly understood. A central hypothesis was that hypnosis simply altered response criterion such that hypnotized individuals were more likely to report as memories information in which they had little confidence. It was in this context that Dywan and Bowers first approached the topic of hypnosis and memory. Paying attention to the importance of experiential data in the experimental context allowed for the development of an alternate perspective, i.e., the "illusion of familiarity." Meanwhile, factors involved in the fallibility of recollection have received considerable research attention and these data are consistent with the view that the experience of remembering can be altered in ways far more complex than can be captured by a simple report criterion perspective.

Attention↗
PubMed1997

The ERP late positivity: a graduated response to stimulus repetition.

The late positive component of the event-related potential (ERP) is sensitive to stimulus repetition but evidence to date is ambiguous regarding whether it is differentially sensitivity to multiple repetitions, ERPs were monitored in a running recognition paradigm while participants indicated whether a series of test words had been presented earlier. In study 1, some words were repeated up to three times, at lags of 15, 30 and 45. In study 2, words were repeated only once but interstimulus intervals were varied. As expected, the late positivity was sensitive to previous occurrence and although it did not vary reliably in response to the size of interstimulus interval, it did provide a reliable graded reflection of the number of stimulus repetitions.

Adult↗
PubMed1997

Attentional factors in response time variability after traumatic brain injury: an ERP study.

Reaction time (RT) is often used in the assessment of patients with traumatic brain injury (TBI), presumably because it reflects either information processing speed or attentional capacity. To clarify this distinction, we examined behavioral RT and the within-subject variability of RT as they relate to electrophysiological measures of attention and information processing. These include the P300 latency, which reflects stimulus evaluation time, P300 amplitude, which reflects attentional allocation, and the preresponse component of the contingent negative variation (CNV), which reflects sustained attention. We found that the latency and variability in behavioral RT were not correlated with the latency or variability of the P300, suggesting that stimulus evaluation time is not a major contributor to RT and its variability in this paradigm. However, among normal controls, RT was related to P300 amplitude, and therefore to attentional allocation. For the TBI subjects, it was the variability, not the speed, of RT that was related to P300 amplitude and to the preresponse component of the CNV. These data suggest that, while in normal controls RT reflects attentional allocation, among TBI subjects it is the variability in RT that is sensitive to the ability to allocate and sustain attention.

Adult↗
PubMed1996

Aging and inhibitory control in text comprehension.

The degree to which inhibitory regulation is related to the initial perception of information or to the control of response tendencies was examined by asking participants to read paragraphs that included italicized, to-be-ignored words. Older adults were more likely than younger adults to begin vocalization of the italicized words and to make text comprehension errors involving the to-be-ignored information. However, younger adults were subsequently more likely to recognize the words they had apparently ignored, suggesting that inhibitory regulation controls selectivity in response rather than initial perception. Commonalities between inhibitory regulation and source monitoring paradigms are demonstrated, and discussion focuses on the degree to which on-line monitoring of goal-relevant response underlies age-related deficits in both domains.

Adult↗
PubMed1995

The illusion of familiarity: an alternative to the report-criterion account of hypnotic recall.

Hypnosis increases the likelihood that participants will report incorrect material at higher levels of confidence. One interpretation of such data is that hypnosis induces individuals to lower the criterion they use to make memory reports. A lowered report criterion could account for the increase in items that participants are willing to report as memories but not for the increase in confidence that typically accompanies hypnotic retrieval. Although some participants may indeed lower their report criterion, this alone should not result in the highly confident confabulation so often observed. An alternative perspective is that for some participants, hypnosis alters the experience of retrieval such that items generated during retrieval attempts are more likely to have the qualities (e.g., perceptual fluency, vividness) usually associated with remembering. This illusion of familiarity would account for the higher levels of confidence that are so frequently observed in hypnotic recall, and adopting this perspective should lead to even greater caution in the use of hypnosis as an aid to retrieval.

Attention↗
PubMed1994

Source monitoring during name recognition in older adults: psychometric and electrophysiological correlates.

The hypothesis that source monitoring in older adults is specifically related to frontal lobe function was tested. In a fame-judgment task, older adults' ability to monitor the source of name familiarity was independent of their short-term recognition ability. Source errors were not related to performance on the Wisconsin Card Sorting Test, a psychometric index of frontal function, or to the initial orienting response of the contingent negative variation (CNV), a frontally based electrophysiological measure, even though these "frontal" measures were reliably related to each other. Source error was predicted by the latter portion of the CNV, the expectancy response, and by the Benton Facial Recognition Test, a visuoperceptual task not typically linked to frontal function. These data suggest that the accuracy of source attribution in older adults depends on various attentional control processes, not all of which may be frontally based.

Aged↗
PubMed1993

Memory for source after traumatic brain injury.

A fame judgment task was used to distinguish subjects' ability to recognize previously presented information from their ability to recognize the source of that information. Traumatic brain injured (TBI) subjects were impaired relative to controls with respect to verbal recall and recognition as well as memory for source. However, memory for source was demonstrated to be independent of explicit indices of recall and recognition ability. It was also found to be an extremely sensitive index of coma duration in the TBI subjects. The anticipated relationship between source memory and a putative index of frontal function (Wisconsin Card Sorting Test) was modest relative to the relationship between source memory and subjects' performance on a complex visual pattern matching task (Benton Facial Recognition), raising questions about hypothesized cognitive and neurophysiological mechanisms underlying memory for source.

Accidents, Traffic↗
PubMed1992

CNV evidence for the distinctiveness of frontal and posterior neural processes in a traumatic brain-injured population.

The association between certain behavioral tests of executive functions in humans and the integrity of the prefrontal lobes has rested primarily on studies comparing subjects with frontal versus other loci of damage. Another approach is to compare the within-group variation on a physiological index of frontal functioning with the behavioral tests of interest. In the present study, subjects with traumatic brain injury (TBI) were given four behavioural measures of executive function, two measures of posterior nonexecutive function, and a Contingent Negative Variation (CNV) task, a proposed electrophysiological index of frontal-lobe functioning. We found that three of the four executive function tests were significantly related to the CNV, accounting for 23-52% of the variance, while the CNV did not correlate at all with the posterior tasks.

Adolescent↗
PubMed1990

Effects of aging on source monitoring: differences in susceptibility to false fame.

Older adults were less likely than young adults to spontaneously recollect the source of familiarity for previously read nonfamous names. Older adults were more likely to call old nonfamous names famous when subsequently encountered in a fame judgment task. Poor source monitoring by the elderly could not be accounted for by inability to recognize earlier read nonfamous names when specifically asked to do so. Both source-monitoring errors and recognition memory performance were based on attributions made about the experience of familiarity. Elderly subjects most prone to making familiarity errors recalled fewer items on a verbal learning task and were less likely to chunk information into semantic categories as it was recalled. This finding suggests that a decline in the tendency to spontaneously organize and integrate information underlies the poor source monitoring observed.

Adolescent↗
PubMed1983

The use of hypnosis to enhance recall.

The forensic use of hypnosis is increasing. A hypermnesic procedure was used in an experiment that calls this practice into question. Subjects tried for a week to recall 60 previously presented pictures. They were then either hypnotized or not and encouraged to recall even more pictures. Most of the newly recalled material was incorrect, especially for highly hypnotizable subjects in the hypnosis condition. Such errors in recall can have profound implications for forensic investigations.

Forensic Psychiatry↗