Time estimation and episodic memory following traumatic brain injury

Time Perception in Prodromal Alzheimer's Dementia and in Prodromal Dementia With Lewy Bodies

Background: Time perception is a subjective experience or sense of time. Previous studies have shown that Alzheimer's dementia (AD) patients have time perception deficits compared to a cognitively unimpaired control group (CU). There are only a few studies on dementia with Lewy bodies (DLB) patients' time perception in comparison with CU and AD patients. Early intervention and prescription of the right medicine may delay the deterioration of AD and DLB, moreover, knowing how prodromal AD (prAD) and prodromal DLB's (prDLB) time perception differ from each other might be helpful for future understanding of these two dementias. Therefore, the purpose of this study is to explore the difference in time perception performance between prodromal AD and prodromal DLB. Methods: We invited people diagnosed with prAD, prDLB, and CU to participate in this study. Tests of verbal estimation of time and time interval production were used to assess their time perception. We analyzed the average time estimation (ATE), absolute error score (ABS), coefficient of variance (CV), and subjective temporal unit (STU) within the three groups. Results: A total of 40 prAD, 30 prDLB, and 47 CU completed the study. In the verbal estimation test, the CV for the prAD was higher than both prDLB and CU at the 9 s interval, and the CV of prAD was higher than CU at the 27 s interval. In the time interval production test, the subjective time units of prDLB were higher than prAD at the 10 s interval, while those of both prDLB and CU were higher than prAD at the 30 s interval. The percentage of subjects with STU < 1.0 s, indicating overestimation, was higher in prAD than both prDLB and CU. Conclusion: Time perception of prAD patients showed imprecision and overestimation of time, while prDLB tended to underestimate time intervals. No significant difference was found in accuracy among the three groups. It is speculated that the clinical and pathological severity of the two prodromal dementia stages may be different, and some patients have not yet had their time perception affected.

A review of prospective memory in individuals with acquired brain injury

OBJECTIVE

Prospective memory (PM) deficits have emerged as an important predictor of difficulty in daily life for individuals with acquired brain injury (BI). This review examines the variables that have been found to influence PM performance in this population. In addition, current methods of assessment are reviewed with a focus on clinical measures. Finally, cognitive rehabilitation therapies are reviewed, including compensatory, restorative and metacognitive approaches.

METHOD

Preferred reporting items for systematic reviews and meta-analyses guidelines were used to identify studies. Studies were added that were identified from the reference lists of these.

RESULTS

Research has begun to elucidate the contributing variables to PM deficits after BI, such as attention, executive function and retrospective memory components. Imaging studies have identified prefrontal deficits, especially in the region of BA10 as contributing to these deficits. There are now several clinical measures available with good psychometric properties. Rehabilitation techniques have mostly focused on compensatory strategies, but, in addition, some restorative and metacognitive approaches have shown preliminary promise.

CONCLUSIONS

PM deficits are a common and important deficit after BI. Clinical evaluation is recommended and further understanding of rehabilitation techniques is needed.

Memory and executive functions correlates of self-awareness in traumatic brain injury

OBJECTIVE

The purpose of this study was to investigate the contribution of executive functions (EF) components and episodic and working memory variables, as well as clinical and demographic factors, to awareness of cognitive ability in traumatic brain injury (TBI).

METHODS

Sixty-five TBI patients (mild: n = 26; moderate/severe: n = 39) took part in the study. Independent stepwise regression models were calculated for EF and memory predictors, with awareness being measured by patient/informant discrepancy in the Patient Competency Rating Scale.

RESULTS

Models with EF variables indicated that semantic verbal fluency and age are the best predictors of awareness, whereas models including mnemonic functions suggested verbal delayed episodic recall and TBI severity as predictors.

CONCLUSIONS

These results are discussed in relation to clinical implications, such as the need to focus efforts of rehabilitation in the cognitive abilities related to awareness, and theoretical models.

Focused and divided attention abilities in the acute phase of recovery from moderate to severe traumatic brain injury

PRIMARY OBJECTIVE

Impairments in attention following traumatic brain injury (TBI) can significantly impact recovery and rehabilitation effectiveness. This study investigated the multi-faceted construct of selective attention following TBI, highlighting the differences on visual nonsearch (focused attention) and search (divided attention) tasks.

METHODS AND PROCEDURES

Participants were 30 individuals with moderate to severe TBI who were tested acutely (i.e. following emergence from PTA) and 30 age- and education-matched controls. Participants were presented with visual displays that contained either two or eight items. In the focused attention, nonsearch condition, the location of the target (if present) was cued with a peripheral arrow prior to presentation of the visual displays. In the divided attention, search condition, no spatial cue was provided prior to presentation of the visual displays.

MAIN OUTCOMES AND RESULTS

The results revealed intact focused, nonsearch, attention abilities in the acute phase of TBI recovery. In contrast, when no spatial cue was provided (divided attention condition), participants with TBI demonstrated slower visual search compared to the control group.

CONCLUSIONS

The results of this study suggest that capitalizing on intact focused attention abilities by allocating attention during cognitively demanding tasks may help to reduce mental workload and improve rehabilitation effectiveness.

Level of agreement of occupational titles between persons with traumatic brain injury and their informants

BACKGROUND

Returning to work is one of the most important goals cited by individuals with traumatic brain injury (TBI). However, they may have difficulty evoking past work history. The ability to recall work history is integral to the rehabilitation process of return to work.

OBJECTIVE

The aim of this study was to determine 1) the level of agreement on the reporting of occupations and 2) if agreement is affected when specific occupational details are required in recall between adults with traumatic brain injury and their informants.

METHODS

This is a retrospective cohort study of 259 individuals, with moderate to severe traumatic brain injury, and their selected informants (e.g. spouse, parent). Interviews were conducted separately for the individual and respective informant to gather information on type of occupation at time of injury and at time of interview. Reported occupations were coded using a standard classification system. Level of agreement was analyzed by interclass correlation coefficients and percent agreement, and the significance of bias was calculated.

RESULTS

Participants were a mean age of 44.5 at time of study with 40% employed compared to 77% at time of injury. Agreement between participants and their informants for occupational title was high for both time periods though more so at the time of injury compared to current status. Level of agreement for specificity was moderate to high however, decreased as need for specificity of detail increased.

CONCLUSION

While participant-informant responses appear to be reliable for occupational classification, when detailed information is required corroborating information is likely needed.

Time Perception in Mild Cognitive Impairment: Interval Length and Subjective Passage of Time

OBJECTIVES

Patients with mild cognitive impairment (MCI) may have difficulties in time perception, which in turn might contribute to some of their symptoms, especially memory deficits. The aim of this study was to evaluate perception of interval length and subjective passage of time in MCI patients as compared to healthy controls.

METHODS

Fifty-five MCI patients and 57 healthy controls underwent an experimental protocol for time perception on interval length, a questionnaire for the subjective passage of time and a neuropsychological evaluation.

RESULTS

MCI patients presented no changes in the perception of interval length. However, for MCI patients, time seemed to pass more slowly than it did for controls. This experience was significantly correlated with memory deficits but not with performance in executive tests, nor with complaints of depression or anxiety.

CONCLUSIONS

Memory deficits do not affect the perception of interval length, but are associated with alterations in the subjective passage of time. (JINS, 2016, 22, 755-764).

Tendency to overestimate the explicit time interval in relation to aging and cognitive decline

Age-related deficits in explicit time perception has been reported by some studies. However, the findings are inconsistent about the preference of older adults to over/underestimate the observed interval as well as the relationship between the time estimation and the participant's cognitive status. In this study, we used a verbal estimation task for the rotation time of a virtual building (40 seconds) to assess the explicit interval timing of participants. The performance of a cohort of 250 cognitively-healthy adults and 10 Alzheimer's patients was analyzed in relation to their age and cognitive scale, measured by Montreal Cognitive Assessment (MoCA) score. The participants' performances were evaluated based on three measurements: Coefficient of variation (CV) for measuring stability, Absolute Error (AE) for measuring accuracy and Directional Error (DE) for measuring the degree of over/under-estimation. A significant difference was observed between the participants who overestimated the interval and those who underestimated it in terms of age, cognitive status and Absolute Error. We also found a significant effect of time estimation, with underestimation by cognitively healthy participants to mild over-estimation by 70+ year old and low-MoCA (MoCA score <; 26) participants as well as severe overestimation by Alzheimer's disease patients. The result of regression analysis for predicting MoCA score based on the dependent variables (AE, DE and CV) support the superiority of Directional Error to Absolute Error and Coefficient of Variation that are commonly used in the time perception studies.

Percept of the duration of a vibrotactile stimulus is altered by changing its amplitude

There have been numerous studies conducted on time perception. However, very few of these have involved tactile stimuli to assess a subject’s capacity for duration discrimination. Previous optical imaging studies in non-human primates demonstrated that increasing the duration of a vibrotactile stimulus resulted in a consistently longer and more well defined evoked SI cortical response. Additionally, and perhaps more interestingly, increasing the amplitude of a vibrotactile stimulus not only evoked a larger magnitude optical intrinsic signal (OIS), but the return to baseline of the evoked response was much longer in duration for larger amplitude stimuli. This led the authors to hypothesize that the magnitude of a vibrotactile stimulus could influence the perception of its duration. In order to test this hypothesis, subjects were asked to compare two sets of vibrotactile stimuli. When vibrotactile stimuli differed only in duration, subjects typically had a difference limen (DL) of approximately 13%, and this followed Weber’s Law for standards between 500 and 1500 ms, as increasing the value of the standard yielded a proportional increase in DL. However, the percept of duration was impacted by variations in amplitude of the vibrotactile stimuli. Specifically, increasing the amplitude of the standard stimulus had the effect of increasing the DL, while increasing the amplitude of the test stimulus had the effect of decreasing the DL. A pilot study, conducted on individuals who were concussed, found that increasing the amplitude of the standard did not have an impact on the DL of this group of individuals. Since this effect did not parallel what was predicted from the optical imaging findings in somatosensory cortex of non-human primates, the authors suggest that this particular measure or observation could be sensitive to neuroinflammation and that neuron-glial interactions, impacted by concussion, could have the effect of ignoring, or not integrating, the increased amplitude.

Self-awareness and traumatic brain injury outcome

PRIMARY OBJECTIVE

Impaired self-awareness following a traumatic brain injury (TBI) can reduce the effectiveness of rehabilitation, resulting in poorer outcomes. However, little is understood about how the multi-dimensional aspects of self-awareness may differentially change with recovery and impact outcome. Thus, this study examined four self-awareness variables represented in the Dynamic Comprehensive Model of Awareness: metacognitive awareness, anticipatory awareness, error-monitoring and self-regulation.

RESEARCH DESIGN

This study evaluated change of the self-awareness measures with recovery from TBI and whether the self-awareness measures predicted community re-integration at follow-up.

METHODS AND PROCEDURES

Participants were 90 individuals with moderate-to-severe TBI who were tested acutely following injury and 90 age-matched controls. Forty-nine of the TBI participants and 49 controls were re-tested after 6 months.

MAIN OUTCOME AND RESULTS

Results revealed that the TBI group's error-monitoring performance was significantly poorer than controls at both baseline and follow-up. Regression analyses revealed that the self-awareness variables at follow-up were predictive of community re-integration, with error-monitoring being a unique predictor.

CONCLUSIONS

The results highlight the importance of error-monitoring and suggest that interventions targeted at improving error-monitoring may be particularly beneficial. Understanding the multi-dimensional nature of self-awareness will further improve rehabilitation efforts and understanding of the theoretical basis of self-awareness.

The stability of time estimation in older adults

The ability to correctly estimate time is important for many daily activities, such as cooking and driving. This study investigated the stability time estimation in healthy older adults and compared them to healthy younger adults. Participants were tested and retested across the duration of 1 year. Using a prospective paradigm, verbal estimates were provided for intervals of 10, 25, 45, and 60 seconds. Although the older adults demonstrated a greater magnitude of error in their time estimates than younger adults, their time estimates remained stable across the 1-year duration. This suggests that instability in time estimates across two time points is unlikely to account for the discrepant task findings in the aging and verbal time estimation literature.

Temporal dysfunction in traumatic brain injury patients: primary or secondary impairment?

Adequate temporal abilities are required for most daily activities. Traumatic brain injury (TBI) patients often present with cognitive dysfunctions, but few studies have investigated temporal impairments associated with TBI. The aim of the present work is to review the existing literature on temporal abilities in TBI patients. Particular attention is given to the involvement of higher cognitive processes in temporal processing in order to determine if any temporal dysfunction observed in TBI patients is due to the disruption of an internal clock or to the dysfunction of general cognitive processes. The results showed that temporal dysfunctions in TBI patients are related to the deficits in cognitive functions involved in temporal processing rather than to a specific impairment of the internal clock. In fact, temporal dysfunctions are observed when the length of temporal intervals exceeds the working memory span or when the temporal tasks require high cognitive functions to be performed. The consistent higher temporal variability observed in TBI patients is a sign of impaired frontally mediated cognitive functions involved in time perception.

Time dysperception perspective for acquired brain injury

Distortions of time perception are presented by a number of neuropsychiatric illnesses. Here we survey timing abilities in clinical populations with focal lesions in key brain structures recently implicated in human studies of timing. We also review timing performance in amnesic and traumatic brain injured patients in order to identify the nature of specific timing disorders in different brain damaged populations. We purposely analyzed the complex relationship between both cognitive and contextual factors involved in time estimation, as to characterize the correlation between timed and other cognitive behaviors in each group. We assume that interval timing is a solid construct to study cognitive dysfunctions following brain injury, as timing performance is a sensitive metric of information processing, while temporal cognition has the potential of influencing a wide range of cognitive processes. Moreover, temporal performance is a sensitive assay of damage to the underlying neural substrate after a brain insult. Further research in neurological and psychiatric patients will clarify whether time distortions are a manifestation of, or a mechanism for, cognitive and behavioral symptoms of neuropsychiatric disorders.

A neuropsychological approach to time estimation

Time estimation, within a range of seconds, involves cognitive functions which depend on multiple brain regions. Here we report on studies investigating the reproduction and production of three durations (5, 14, and 38 seconds) in four groups of patients. The amnesic patient underproduced the length of the long durations because of episodic memory deficit following bilateral medial temporal lesions. Epileptic patients (n = 9) with right medial temporal lobe resections underproduced the three durations because of a distorted representation of time in long-term memory. Traumatic brain injury patients (n = 15) made more variable duration productions and reproductions because of working memory deficits following frontal-lobe dysfunction. Patients with Parkinson's disease (n = 18) overproduced the short duration and underproduced the long duration because of a possible increase in internal clock speed following levodopa treatment, as well as working memory deficits associated with frontal-lobe damage. Further research, in neurological and psychiatric patients, is required to better understand the underlying mechanisms of time estimation.

Time discrimination in traumatic brain injury patients

Time management skills are required for most daily activities. Traumatic brain injury (TBI) patients often present with cognitive dysfunction, but few studies have investigated temporal impairment. The aim of the present study was to assess temporal abilities in TBI patients using a time discrimination task. Twenty-seven TBI patients (ages = 18-60 years) and 27 controls (ages = 20-60 years) were asked to discriminate between two time intervals presented sequentially. The standard intervals were 500 ms or 1,300 ms long followed by a comparison stimulus that was 25% shorter or longer than the standard one. Participants were also asked to perform two tasks to assess attention, speed-of-processing (the Stroop task), and working memory (the n-back task) abilities. The TBI patients were less accurate than the controls on the time discrimination task and showed greater time-order error effects. In fact, TBI patients pressed the "short" key more times when the standard time interval was 500 ms and the "long" key more times when the standard interval was 1,300 ms. Significant correlations were found between time discrimination, working memory, and speed of processing in both TBI and controls when the standard time interval was 1,300 ms. Attention appeared to be involved in different ways in the two groups. Working memory and speed of processing were involved in time processing only in TBI patients when the standard time interval was 500 ms. These data lend additional support to the notion that two different systems are responsible for elaborating time durations shorter or longer than a second.

Time-based prospective memory in severe traumatic brain injury patients: the involvement of executive functions and time perception

Prospective memory (PM) is the ability to remember to perform a future action at a specified later time, which is investigated through the use of event-based and time-based tasks. Prior investigations have found that PM is impaired following traumatic brain injury (TBI). However, there is limited information regarding the cognitive functions that mediate TBI and PM performance. Thus, this study investigated time-based PM in TBI patients, and the relationship among time-based PM, time perception, and executive functions. To accomplish this objective, 18 severe TBI patients and 18 healthy matched controls performed a time-based PM task, a time reproduction task, and two executive functions (Stroop and n-back) tasks. While both groups increased their monitoring frequency close to the target time, TBI patients monitored more and were less accurate than healthy controls at the target time confirming the time-based PM dysfunction in these patients. Importantly, executive functions, particularly inhibition and updating abilities, were strongly related to time-based PM performance; both time perception and executive functions are involved in time-based prospective memory in controls, whereas, only executive functions appear to be involved in TBI time-based prospective memory performance.

Recovery of time estimation following moderate to severe traumatic brain injury

OBJECTIVE

Accurate time estimation abilities are thought to play an important role in efficient performance of many daily activities. This study investigated the role of episodic memory in the recovery of time estimation abilities following moderate to severe traumatic brain injury (TBI).

METHOD

Using a prospective verbal time estimation paradigm, TBI participants were tested in the early phase of recovery from TBI and then again approximately one year later. Verbal time estimations were made for filled intervals both within (i.e., 10 s, 25 s) and beyond (i.e., 45 s 60 s) the time frame of working memory.

RESULTS

At baseline, when compared to controls, the TBI group significantly underestimated time durations at the 25 s, 45 s and 60 s intervals, indicating that the TBI group perceived less time as having passed than actually had passed. At follow-up, despite the presence of continued episodic memory impairment and little recovery in episodic memory performance, the TBI group exhibited estimates of time passage that were similar to controls.

CONCLUSION

The pattern of data was interpreted at suggesting that episodic memory performance did not play a noteworthy role in the recovery of temporal perception in TBI participants.

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.

Task switching in mild cognitive impairment: switch and nonswitch costs

The ability to switch rapidly and fluidly between tasks is an important component of many everyday activities. In this study, we used a predictable, externally cued task-switching paradigm to investigate executive control processes in individuals with mild cognitive impairment (MCI). Participants were 26 individuals with amnestic MCI and 26 healthy older adult (OA) controls. In the mixed-task trials, participants switched between classifying whether a digit was odd/even or a letter was a consonant/vowel on every fourth trial. In the single-task trials, participants completed only the digit task or letter task throughout the entire block. Task switching costs were decomposed into nonswitch costs, which reflect the dual nature of the task, and switch costs, which reflect set-shifting abilities. The results revealed that the MCI group was not affected more than the healthy OAs by the requirement of keeping two tasks sets active in working memory (nonswitch costs). In contrast, the cost of switching between the two tasks was significantly greater for the MCI group compared with the OA controls (switch costs). Future research is needed to better understand the nature and implications for daily living of the greater switch costs found for individuals with MCI. (JINS, 2009, 15, 103-111.).