Jane Dywan

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.

Error negativity and response control

Error trials are associated with faster responses than correct trials in simple discrimination tasks suggesting that errors result from impulsive responding. We investigated the relationship between error negativity (Ne/ERN), an event-related potential associated with error detection, and two behavioral indices of response control: response time (RT) differences between incorrect and correct trials (an index of impulsivity) and percentage of errors. Response-locked ERPs were collected from 17 young adults during a visual flanker task. Consistent with previous findings, participants were significantly faster on error trials. However, participants who exhibited larger Ne/ERN peak amplitudes had significantly smaller RT differences, suggesting a more controlled response strategy. Furthermore, Ne/ERN latencies were positively associated with percentage of errors. These findings are consistent with the view that the Ne/ERN reflects the activity of a monitoring system that is closely linked to remedial systems responsible for individual differences in response control or impulsive behavior.

Brain bases of error-related ERPs as influenced by age and task

Age effects in the error negativity (Ne) and error positivity (Pe) were examined in a standard letter flanker task and an age-sensitive source memory exclusion task. Older adults made more errors and produced Ne and Pe components of lower amplitude in both tasks. The Ne was insensitive to task and error rate. The Pe, however, was reduced in the source memory relative to the flanker task and was correlated with error rate in both tasks. Ne and Pe dipoles were generally localized to anterior cingulate cortex, but dipoles associated with the Pe were more frontal for flanker errors and, for young adults, more posterior for source errors. These data suggest that the Ne reflects an automatic response to error as it occurs whereas the Pe, being more sensitive to age and task demands, and more closely linked to accuracy, reflects the allocation of attention to an error that has been made.

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.

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.

Altered electrodermal response to facial expression after closed head injury

Summary : The objective was to determine whether diffuse damage to orbital and ventromedial regions of the prefrontal cortex usually associated with moderate-to-severe closed head injury (CHI) would affect the ability to perceive and respond to socially relevant information. Methods : Participants with CHI and age-matched non-injured controls were presented with faces that varied with respect to emotional expression while electrodermal activity (EDA) was monitored. Cognitive and general adaptive functioning was also assessed. Results : CHI was associated with a failure to increase EDA in response to negative facial expressions and with reduced ability to identify negative expressions, especially fear. The groups differed on other signs of orbital/medial prefrontal damage such as anosmia and in general social adaptability and awareness-of-deficit as measured by the Brock Adaptive Functioning Questionnaire. Conclusions : CHI affected the ability to identify and respond to negative facial expression. Addressing these deficits may enhance rehabilitative efforts within the social domain.

ERN varies with degree of psychopathy in an emotion discrimination task

It is hypothesized that anterior cingulate cortex (ACC) function may be disrupted in psychopathy. Since ACC is considered the generator of the error-related negativity (ERN), we expected the ERN to be sensitive to the degree of psychopathy among violent offenders. EEG was collected while offenders and controls responded to a standard letter flanker task and to a face flanker task that required discrimination between angry and fearful expressions. Offenders were as accurate as controls on the letter flanker task but made more errors in emotion discrimination on the face flanker task. ERNs elicited by letter flanker errors did not differ across groups but were markedly reduced in the offenders in the face flanker condition. These effects were related to the degree of psychopathy within the offender group. Source modelling of the ERN also indicated an atypical response for psychopaths when error monitoring required the discrimination of affectively based information.

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.

Response inhibition in psychopathy: The frontal N2 and P3

Psychopathy has been associated with atypical function of the anterior cingulate cortex (ACC) and adjacent brain regions and with abnormalities in performance monitoring, which is thought to rely on these structures. The ACC and adjacent regions are also involved in the generation of two characteristic components of the event-related potential: the frontal N2 and P3. Both components are enhanced when a response is withheld (NoGo trial) within a series of positive-responses (Go trials) and are considered an index of response inhibition. We recorded event-related potentials while violent offenders who varied on the dimension of psychopathy and non-offender controls performed a Go/NoGo task. The offenders made more errors of commission on NoGo trials but this effect was unrelated to level of psychopathy within the group and, inconsistent with a previous report, they produced the enhanced frontal N2 and P3 effect in response to NoGo relative to Go conditions. We conclude that the neural processes involved in response inhibition are not abnormal in psychopaths when both stimuli and context are affectively neutral and suggest that a more nuanced perspective regarding impulsivity in this population be considered.

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.