Content memory and temporal order memory for performed activities after severe closed-head injury

Thirty severe closed-head injured (CHI) participants (more than 1 year postinjury) and 30 matched controls completed eight different cognitive activities. Participants' free recall and recognition of the activities provided a measure of content memory. Temporal order memory was assessed with a reconstruction task. CHI participants recalled and recognized fewer activities than did controls. However, the CHI and control groups did not differ in temporal order memory. For both groups, recognition memory was not correlated with temporal order memory. These results demonstrate intact temporal order memory for performed activities in a severe CHI population, and support the notion of separate processing of content memory and order information. Issues related to automaticity and the roles of the frontal lobes in temporal order memory are also discussed.     

Absolute and relative temporal order memory for performed activities following stroke

Reconstructing the temporal order of events is a crucial part of episodic memory. The temporal dimension, however, is often discarded in clinical settings, and measurements of true temporal aspects of episodic memory are scarce. The present study assessed temporal memory in stroke patients and in age- and education-matched healthy controls. Both groups underwent a standardized neuropsychological examination. We asked participants afterwards to reconstruct the order of tests they had performed, measured in absolute temporal order (event placed on correct moment in sequence) and relative temporal order (event placed correctly relative to directly preceding and following events). The aim of the study was to examine how serial-position curve effects (measuring absolute temporal order anchored in exact time) and how relative temporal order memory (anchored to other events) may differ in a group of cerebral stroke patients. Another aim was to link temporal order memory deficits with established neuropsychological measures of cognitive functioning. Although item identification was comparable in both groups, absolute temporal order memory was impaired in patients: A total of 43% of the patients lacked the expected primacy and recency effects (serial position effect). In addition, relative temporal order memory was affected in this group as well, F(1, 70) = 4.08, p < .05; 25% of the patients were impaired in reconstructing the relative temporal order (p = .019, Fisher’s Exact Test). Both absolute and relative temporal order memory performance related to the domains of executive functioning and memory. Our results suggest that it is important to test both absolute and relative temporal order memory, especially because these types of memory depend on different anchors, either on time or on adjacent events.     

Memory for performed and observed activities following traumatic brain injury

Traumatic brain injury (TBI) is associated with deficits in memory for the content of completed activities. However, TBI groups have shown variable memory for the temporal order of activities. We sought to clarify the conditions under which temporal order memory for activities is intact following TBI. Additionally, we evaluated activity source memory and the relationship between activity memory and functional outcome in TBI participants. Thus, we completed a study of activity memory with 18 severe TBI survivors and 18 healthy age- and education-matched comparison participants. Both groups performed eight activities and observed eight activities that were fashioned after routine daily tasks. Incidental encoding conditions for activities were utilized. The activities were drawn from two counterbalanced lists, and both performance and observation were randomly determined and interspersed. After all of the activities were completed, content memory (recall and recognition), source memory (conditional source identification), and temporal order memory (correlation between order reconstruction and actual order) for the activities were assessed. Functional ability was assessed via the Community Integration Questionnaire (CIQ). In terms of content memory, TBI participants recalled and recognized fewer activities than comparison participants. Recognition of performed and observed activities was strongly associated with social integration on the CIQ. There were no between- or within-group differences in temporal order or source memory, although source memory performances were near ceiling. The findings were interpreted as suggesting that temporal order memory following TBI is intact under conditions of both purposeful activity completion and incidental encoding, and that activity memory is related to functional outcomes following TBI.     

Predictions of episodic memory following moderate to severe traumatic brain injury during inpatient rehabilitation

We examined memory self-awareness and memory self-monitoring abilities during inpatient rehabilitation in participants with moderate to severe traumatic brain injury (TBI). A total of 29 participants with moderate to severe TBI and 29 controls matched on age, gender, and education completed a performance prediction paradigm. To assess memory self-awareness, participants predicted the amount of information they would remember before completing list-learning tasks and visual-spatial memory tasks. Memory self-monitoring was assessed by participants' ability to increase accuracy of their predictions after experience with the tests. Although the TBI participants performed more poorly than controls on both episodic memory tasks, no significant group differences emerged in memory self-awareness or memory self-monitoring. The TBI participants predicted that their memory performances would be poorer than that of controls, accurately adjusted their predictions in accordance with the demands of the tasks, and successfully modified their predictions following experience with the tasks. The results indicate that moderate to severe TBI individuals in the early stages of recovery can competently assess the demands of externally driven metamemorial situations and utilize experience with task to accurately update their knowledge of memory abilities.     

Prospective evaluation of first and last memory reports following moderate to severe traumatic brain injury

Prospective monitoring of posttraumatic amnesia (PTA) status is recommended following traumatic brain injury (TBI). Use of patients’ subjective reports is, however, still common and necessary in some circumstances. It is therefore important to understand how patients’ self-reported first memories relate to prospective measures and how reliable these reports remain over time. In the present study, patients with moderate–severe TBI in PTA were asked about their first and last memories surrounding the injury daily and were administered the Westmead Post-Traumatic Amnesia Scale (WPTAS). Following PTA emergence, a semistructured interview was used to ascertain participants’ reports of return of continuous memory after the injury, as well as their last preinjury memory. This interview was repeated six months later, along with the Community Integration Questionnaire to measure functional outcome and the Rey Auditory Verbal Learning Test to measure anterograde memory. The temporal order of recovery of WPTAS variables and subjective reports was determined, and consistency of subjective reports over time was examined using bivariate correlation and intraclass correlation coefficients (ICCs). Findings suggested that patients’ reports of return of continuous memory aligned most closely with return of consistent orientation, and occurred significantly earlier than attainment of criterion on the WPTAS. Reported first memories were significantly later at follow-up (i.e., greater days post injury) and the ICC was not suggestive of adequate clinical reliability. Last memory reports were slightly more reliable, with 71% of cases remaining in the same band at follow-up. Demographic and injury-related variables were not significantly associated with the discrepancy between reports. The variability in patients’ reports over time highlights the importance and value of prospective PTA monitoring.     

Working memory brain activation following severe traumatic brain injury

Functional magnetic resonance imaging (fMRI) has shown that brain activation during performance of working memory (WM) tasks under high memory loads is altered in adults with severe traumatic brain injury (TBI) relative to uninjured subjects (Perlstein et al., 2004; Scheibel et al., 2003). Our study attempted to equate TBI patients and orthopedically injured (OI) subjects on performance of an N-Back task that used faces as stimuli. To minimize confusion in TBI patients that was revealed in pilot work, we presented the memory conditions in two separate tasks, 0- versus 1-back and 0- versus 2-back. In the 0- versus 1-back task, OI subjects activated bilateral frontal areas more extensively than TBI patients, and TBI patients activated posterior regions more extensively than OI subjects. In the 0- versus 2-back task, there were no significant differences between the groups. Analysis of changes in activation over time on 1-back disclosed that OI subjects had decreases in bilateral anterior and posterior regions, while TBI patients showed activation increases in those and other areas over time. In the 2-back condition, both groups showed decreases over time in fusiform and parahippocampal gyri, although the OI group also showed increases over time in frontal, parietal, and temporal areas not seen in the TBI patients. The greatest group differences were found in the 1-back condition, which places low demand on WM. Although the extent of activation in the 2-back condition did not differ between the two groups, deactivation in the 2-back condition was seen in the OI patients only, and both groups' patterns of activation over time varied, suggesting a dissociation between the TBI and OI patients in recruitment of neural areas mediating WM.     

Recovery of memory and learning functions following traumatic brain injury.

Twenty-four traumatically brain-injured males, of whom eight had sustained right-sided, eight left-sided, and eight bilateral or diffuse closed head injuries, took a battery of neuropsychological tests within the first six months, the second six months, the second year and the third year post injury. Performances on WAIS Digits Forward and Backward and Rey's Auditory-Verbal Learning Test were classified as within or below normal range. Comparisons were made (1) between time periods and tests and (2) between subgroups formed by severity, site of lesion, and age. The findings give an overall picture of wide performance variability with consistent improvement in immediate memory span and learning. Recovery varied with the specific nature of the tested function, task complexity, and severity of injury. Neither age, site of injury, not recency were associated with improvement.     

Assessment of impulsivity after moderate to severe traumatic brain injury

The aim of the study was to develop and validate a short questionnaire assessing four dimensions of impulsivity (urgency, lack of premeditation, lack of perseverance, sensation seeking) in patients with traumatic brain injury (TBI). To this end, 82 patients with TBI and their caregivers completed a short questionnaire adapted from the UPPS Impulsive Behavior Scale designed to assess impulsivity changes after TBI. Confirmatory factor analyses (CFAs) performed on the version of the scale completed by the relatives revealed that a hierarchical model holding that lack of premeditation and lack of perseverance are facets of a higher order construct (lack of conscientiousness), with urgency and sensation seeking as separate correlated factors, fit the data best. Urgency, lack of premeditation, and lack of perseverance increased after the TBI, whereas sensation seeking decreased. CFA failed to reveal a satisfactory model in the version of the scale completed by the patients. The psychological processes related to these impulsivity changes and the discrepancy observed between self-report and informant-report are discussed. This short questionnaire opens up interesting prospects for better comprehension and assessment of behavioural symptoms of TBI.     

Endothelial cell activation following moderate traumatic brain injury

Traumatic brain injury (TBI) initiates a cascade of acute and chronic injury responses which include disturbances in the cerebrovasculature that may result in the activation of the microvascular endothelial development of a dysfunction endothelium. The present study examines endothelial cell (EC) activation in a percussion model of moderate TBI. The criteria for endothelial activation used in these studies was surface expression of a number of markers collectively termed endothelial activation antigens. Temporal induction of the major histocompatibility (MHC) class II molecules, E-selectin (CD62E), vascular cell adhesion molecule (VACM-1) (CD106) as well as altered expression of constitutively expressed intercellular adhesion molecule-1 (ICAM-1) (CD54), the glucose transporter protein (glut-1), the transferrin receptor (tfR) (CD71), and MHC class I molecules was examined at various times following impact. Induction of E-selectin and increased expression of ICAM-1 was seen by 2 h post-impact (PI) and was sustained through 24 h PI. Decreased expression of immunologically reactive glut-1 and tfR was observed by 2-4 h PI and remained low up to 24 h PI. No induction of VCAM-1, MHC class II molecules or altered constitutive expression or MHC class I molecules was seen. Changes in EC activation were observed predominantly at the site of impact and were diminished temporarily. These results indicate that mild concussive injury to the brain results in activation of the endothelium.     

Working memory after severe traumatic brain injury.

The aim of the present study was to assess the functioning of the different subsystems of working memory after severe traumatic brain injury (TBI). A total of 30 patients with severe chronic TBI and 28 controls received a comprehensive assessment of working memory addressing the phonological loop (forward and backward digit span; word length and phonological similarity effects), the visuospatial sketchpad (forward and backward visual spans), and the central executive (tasks requiring simultaneous storage and processing of information, dual-task processing, working memory updating). Results showed that there were only marginal group differences regarding the functioning of the two slave systems, whereas patients with severe TBI performed significantly poorer than controls on most central executive tasks, particularly on those requiring a high level of controlled processing. These results suggest that severe TBI is associated with an impairment of executive aspects of working memory. The anatomic substrate of this impairment remains to be elucidated. It might be related to a defective activation of a distributed network, including the dorsolateral prefrontal cortex.     

Effects of severe traumatic brain injury on visual memory

The study aimed to clarify the effects of severe traumatic brain injury (TBI) on visual memory. Three groups of participants (14 late-recovery and 14 early-recovery TBI individuals and 18 controls) were administered the following: The Shum Visual Learning Test (SVLT), a test that measures the ability to remember visual patterns, an electronic maze test, a test that measures the ability to remember spatial positions, and the Rey Auditory Verbal Learning Test (RAVLT), a test of verbal memory and learning. The individuals with TBI (late- and early-recovery) were found to be impaired on the SVLT and the RAVLT but not on the electronic maze. Specifically, on the SVLT, they were found to learn at a slower rate and make more false-positive errors than the controls. The advantages of the SVLT over visual memory tests used in previous studies and the significance of findings of the present study were discussed.     

Time estimation and episodic memory following traumatic brain injury

The ability to accurately estimate the passage of time plays an important role in helping to structure daily activities. In this study, we used a prospective verbal time estimation paradigm to investigate time perception in 27 moderate to severe traumatic brain injury (TBI) participants and 27 controls. Verbal time estimations were made for filled intervals both within (i.e., <30 s) and beyond the time frame of working memory. We found that the TBI participants exhibited normal or near-normal estimates of time passage for duration up to 25 s. In contrast, for durations that exceeded working memory, the TBI group perceived less time as having passed than actually had passed as the TBI group significantly underestimated time when compared to controls. This pattern of data was interpreted as being due to episodic memory dysfunction.     

Recovery of educational skills following paediatric traumatic brain injury

Academic success in the classroom is often dependent upon a child's ability in the areas of literacy, such as reading and spelling, and arithmetic. Following traumatic brain injury these skills are often compromised. The present study examined the recovery of educational skills (reading accuracy, reading comprehension, spelling and arithmetic) over 24 months post-injury, in a group of children who had sustained a mild, moderate or severe TBI. Results showed that the severe TBI group exhibited greater deficits on reading comprehension and arithmetic, while the moderate and severe TBI groups performed similarly in the areas of reading accuracy and spelling. Future research is required to further investigate predictors of educational outcome post-TBI.     

Verbal learning patterns in moderate and severe traumatic. brain injury

Abstract

Previous studies that have examined performances on the California Verbal Learning Test (CVLT) among individuals with traumatic brain injury (TBI) have found differing levels of performance. Differential patterns of performance, however, have only been inferred. The present investigation sought to determine empirically if differential patterns of performance could be discerned in a TBI sample of 65 subjects with CVLT variables. The CVLT variables were selected based on the instrument's factor structure. Cluster analysis yielded four distinct subtypes of brain-injured individuals. The Active subtype demonstrated impaired unassisted retrieval, but used active encoding strategies and showed relatively intact ability to store novel information. The Disorganized subtype demonstrated an inconsistent, haphazard learning style along with deficits in encoding. The Passive subtype was marked by an overreliance on a serial clustering strategy as well as impaired encoding and/or consolidation. The Deficient subtype was the most impaired of all groups, exhibiting a slowed rate of acquisition, passive learning style, and significant impairment in encoding. Implications for rehabilitation are discussed.     

Family impact and influence following severe traumatic brain injury

Negotiating is the core variable or central concern of families who have a close relative in a state of post-comatose unawareness or minimal responsiveness following a severe traumatic brain injury. Family members negotiate with each other, with members of the health care team, and with others such as insurance agents, case managers, and representatives of the justice system on behalf of the injured individual. Family members also negotiate the intricacies of the health care system. These are the findings of a 16-month grounded theory study conducted on two acute neurosurgical units in Toronto, with 25 family members from 11 families who had a close family member who suffered a severe traumatic brain injury and who was in a state of post-comatose unawareness or minimal responsiveness. An extensive review of the scholarly literature related to family research methodology and family research related to families following the brain injury of a family member is also provided in this paper.     

Vulnerability of the anterior commissure in moderate to severe pediatric traumatic brain injury

In relation to the adult brain, the immature brain might be more vulnerable to damage during and following traumatic brain injury, particularly in white-matter tracts. Given well-established evidence of corpus callosum atrophy, we hypothesized that anterior commissure volume (using quantitative magnetic resonance imaging [MRI]) in this structure would be decreased in children with moderate to severe traumatic brain injury relative to typically developing children. Second, given the purported role of the anterior commissure in interhemispheric axon conveyance between temporal lobes, we hypothesized that temporal lobe white matter, temporal lesion volume, and injury severity (Glasgow Coma Scale score) would be predictive of decreased anterior commissure cross-sectional volume in patients with traumatic brain injury. Finally, we wished to establish the relationship between the anterior commissure and the temporal stem, a major white-matter tract into the temporal lobes, using diffusion tensor imaging fiber-tracking maps for each patient. We also hypothesized that children with traumatic brain injury would exhibit decreased fractional anisotropy in relation to typically developing children in a fiber system including the anterior commissure and the temporal lobes. Decreased anterior commissure cross-sectional volume was observed in patients with traumatic brain injury, and, as predicted, anterior commissure and temporal white-matter volumes were positively related to each other and to higher Glasgow Coma Scale scores. Lesion volume was not independently predictive of anterior commissure volume in the overall model. Diffusion tensor imaging fractional anisotropy values differed between the groups for the temporal stem-anterior commissure system, with the traumatic brain injury group exhibiting decreased fractional anisotropy. The anterior commissure, like the corpus callosum, appears to be highly vulnerable to white-matter degenerative changes resulting from mechanisms such as the direct impact of trauma, progressive axonal injury as tissue in other brain regions atrophies, or myelin degeneration. This is the first systematic examination of anterior commissure atrophy following traumatic brain injury using in vivo quantitative MRI and diffusion tensor imaging fiber tracking in pediatric subjects.     

Pre-injury assessment of everyday executive function in moderate to severe traumatic brain injury

Executive dysfunction is frequently observed in moderate to severe traumatic brain injury (TBI) and is commonly assessed with objective measures or subjective rating scales. Given the variability in executive function in the normal population, a reliable measure of pre-injury executive function would be of considerable value. In this study we examined pre-injury self and collateral (relative or friend) ratings on the Frontal Systems Behavior Rating Scale (FrSBe). Fifty-one persons with moderate to severe TBI and their collaterals provided before- and after-TBI ratings at 3 months post injury. A subset of 36 dyads were retested at 6 and 12 months; 26 neurologically intact controls and their collaterals also provided FrSBe ratings. At 3 months post injury, the difference between patient and collateral ratings of current status was larger than the difference relating to premorbid status, suggesting that patients were able to rate themselves from a pre-injury perspective. However, pre-injury ratings from collaterals were more reliable over time compared with patients’ self-ratings. For all sets of ratings – before injury, after injury, and status of healthy controls – collateral ratings indicated more abnormality, overall, than comparable self-ratings. Evaluating one’s own executive behaviour may be a difficult task even without TBI, with the difficulty exacerbated by the effects of injury.     

Benefits of order: the influence of item sequencing on metacognition in moderate and severe traumatic brain injury

The ability to appraise one's own ability has been found to have an important role in the recovery and quality of life of clinical populations. Examinee and task variables have been found to influence metacognition in healthy students; however the effect of these variables on the metacognitive accuracy of adults with neurological insult, such as traumatic brain injury (TBI), remains unknown. Twenty-two adults with moderate and severe TBI and a matched sample of healthy adults participated in this study examining the influence of item sequencing on metacognitive functioning. Retrospective confidence judgments were collected while participants completed a modified version of the Matrix Reasoning subtest. Significant influence of item sequence order was found, revealing better metacognitive abilities and performance when participants completed tasks where item difficulty progressed in order from easy to difficult. We interpret these findings to suggest that the sequencing of item difficulty offers "anchors" for gauging and adjusting to task demands.