Central executive system impairment in traumatic brain injury

Joint analysis of frontal theta synchrony and white matter following mild traumatic brain injury

Some of the most disabling aspects of mild traumatic brain injury (mTBI) include lingering deficits in executive functioning. It is known that mTBI can damage white matter tracts, but it remains unknown how this structural brain damage translates into cognitive deficits. This experiment utilized theta band phase synchrony to identify the dysfunctional neural operations that contribute to cognitive problems following mTBI. Sub-acute stage (< 2 weeks) mTBI patients (N = 52) and healthy matched controls (N = 32) completed a control-demanding task with concurrent EEG. Structural MRI was also collected. While there were no performance-specific behavioral differences between groups in the dot probe expectancy task, the degree of theta band phase synchrony immediately following injury predicted the degree of symptom recovery two months later. Although there were no differences in fractional anisotropy (FA) between groups, joint independent components analysis revealed that a smaller network of lower FA-valued voxels contributed to a diminished frontal theta phase synchrony network in the mTBI group. This finding suggests that frontal theta band markers of cognitive control are sensitive to sub-threshold structural aberrations following mTBI.

BRAINSTORMING: A study protocol for a randomised double-blind clinical trial to assess the impact of concurrent brain stimulation (tDCS) and working memory training on cognitive performance in Acquired Brain Injury (ABI)

Background

Acquired Brain Injury (ABI) admissions have an incidence of 385 per 100,000 of the population in the UK, and as brain injury often involves the frontal networks, cognitive domains affected are likely to be executive control, working memory, and problem-solving deficits, resulting in difficulty with everyday activities. The above observations make working memory, and related constructs such as attention and executive functioning attractive targets for neurorehabilitation. We propose a combined home-based rehabilitation protocol involving the concurrent administration of a working memory training program (adaptive N-back task) with non-invasive transcranial direct current stimulation (tDCS) of the right dorsolateral prefrontal cortex to promote long-lasting modification of brain areas underlying working memory function.

Method

Patients with a working memory deficit will be recruited and assigned to two age-matched groups receiving working memory training for 2 weeks: an active group, receiving tDCS (2 mA for 20 min), and a control group, receiving sham stimulation. After the end of the first 2 weeks, both groups will continue the working memory training for three more weeks. Outcome measures will be recorded at timepoints throughout the intervention, including baseline, after the 2 weeks of stimulation, at the end of the working memory training regimen and 1 month after the completion of the training.

Discussion

The aim of the study is to assess if non-invasive tDCS stimulation has an impact on performance and benefits of a working memory training regimen. Specifically, we will examine the impact of brain stimulation on training gains, if changes in gains would last, and whether changes in training performance transfer to other cognitive domains. Furthermore, we will explore whether training improvements impact on everyday life activities and how the home-based training regimen is received by participants, with the view to develop an effective home healthcare tool that could enhance working memory and daily functioning.

Trial registration

This study was registered with clinicaltrials.gov: NCT04010149 on July 8, 2019.

Off-road assessment of cognitive fitness to drive

Road safety is a major issue in every society. The assessment of driving ability with a real vehicle is a lengthy and costly process; therefore, there is a growing need for the development of a neuropsychological battery that can provide a fast and reliable evaluation of a person's cognitive fitness to drive. In the present study, we examined the relationship of an off-road lab-type test, namely, the Driving Scenes test, with performance on a driving simulator, as well as the influence of cognitive factors on driving ability as evaluated by Driving Scenes. Our results demonstrated a relationship between Driving Scenes and driving simulator performance. They also showed that some cognitive factors (namely, selective attention and verbal memory), were predictive of driving ability (as determined by the Driving Scenes test), but not others (namely visuospatial perception/memory, working memory, and visuospatial recognition). In addition, age strongly predicted performance on this test (younger age was associated with better performance). The conclusions derived from the present study highlight the need to identify off-road tools with high predictive value in assessing driving ability.

Detection of text-based social cues in adults with traumatic brain injury

OBJECTIVES

Written text contains verbal immediacy cues-word form or grammatical cues that indicate positive attitude or liking towards an object, action, or person. We asked if adults with moderate-severe traumatic brain injury (TBI) would respond to these cues, given evidence of TBI-related social communication impairments.

METHODS

Sixty-nine adults with TBI and 74 healthy comparison (HC) peers read pairs of sentences containing different types of immediacy cues (e.g., speaker A said "these Canadians" vs. B said "those Canadians.") and identified which speaker (A or B) had a more positive attitude towards the underlined entity (Task 1); and pairs of sentences comprised of a context sentence (e.g., Fred is asked, "Did you visit Joan and Sue?") and a statement sentence (Fred says, "I visited Sue and Joan.") and were asked to indicate how much Fred liked or disliked the underlined words (Task 2).

RESULTS

HC group scores were significantly higher on Task 1, indicating more sensitivity to cues. On Task 2, TBI and HC group ratings differed across cue types and immediacy types, and the TBI group appeared to have less sensitivity to these cues.

CONCLUSIONS

Findings suggest that TBI-related impairments may reduce sensitivity to subtle social cues in text.

Cognitive Load Affects Speech Motor Performance Differently in Older and Younger Adults

Purpose The aim of this study was to determine the impact of cognitive load imposed by a speech production task on the speech motor performance of healthy older and younger adults. Response inhibition, selective attention, and working memory were the primary cognitive processes of interest. Method Twelve healthy older and 12 healthy younger adults produced multiple repetitions of 4 sentences containing an embedded Stroop task in 2 cognitive load conditions: congruent and incongruent. The incongruent condition, which required participants to suppress orthographic information to say the font colors in which color words were written, represented an increase in cognitive load relative to the congruent condition in which word text and font color matched. Kinematic measures of articulatory coordination variability and movement duration as well as a behavioral measure of sentence production accuracy were compared between groups and conditions and across 3 sentence segments (pre-, during-, and post-Stroop). Results Increased cognitive load in the incongruent condition was associated with increased articulatory coordination variability and movement duration, compared to the congruent Stroop condition, for both age groups. Overall, the effect of increased cognitive load was greater for older adults than younger adults and was greatest in the portion of the sentence in which cognitive load was manipulated (during-Stroop), followed by the pre-Stroop segment. Sentence production accuracy was reduced for older adults in the incongruent condition. Conclusions Increased cognitive load involving response inhibition, selective attention, and working memory processes within a speech production task disrupted both the stability and timing with which speech was produced by both age groups. Older adults' speech motor performance may have been more affected due to age-related changes in cognitive and motoric functions that result in altered motor cognition.

Patterns of cognitive deficits in persons with spinal cord injury as compared with both age-matched and older individuals without spinal cord injury

Context/Objective: Cognitive deficits can impact as many as 60% of individuals with spinal cord injury (SCI). In an effort to identify the nature of cognitive deficits in SCI, we examined neuropsychological test performance in individuals with SCI, age matched healthy controls and older healthy controls.Design: Participants completed a motor-free neuropsychological test battery assessing attention, working memory, information processing speed, new learning /memory and executive control.Setting: Outpatient rehabilitation research facility.Participants: Participants included 60 individuals with chronic spinal cord injury [SCI; 32 with paraplegia (T2-T12) and 28 with tetraplegia (C3-T1)], 30 age-matched healthy controls (AMHC; 30-40 years old) and 20 older healthy controls (OHC; 50-60 years old).Outcome Measures: Wechsler Intelligence Scale - 3^rd edition (WAIS-III) Digit Span and Letter-Number Sequencing; Symbol Digit Modalities Test (SDMT) - oral version; California Verbal Learning Test-II; Paced Auditory Serial Addition Test (PASAT); Wechsler Abbreviated Scale of Intelligence (WASI); Delis-Kaplan Executive Function System; Verbal Fluency subtest.Results: Significant differences were noted between the SCI and AMHC groups on measures of information processing speed, new learning and memory, and verbal fluency. No significant differences were noted between the groups on tests of attention or working memory.Conclusion: The current study documented differences in specific realms of cognitive functioning between a chronic SCI sample and AMHC. Implications for cognitive rehabilitation and overall quality of life are discussed. Additional research is needed utilizing a more comprehensive battery of motor-free neuropsychological tests that avoid the confound of upper limb motor limitations on cognitive performance.

Impaired theory of mind in adults with traumatic brain injury: A replication and extension of findings

OBJECTIVE

To replicate a previous study of Theory of Mind (ToM) task performance in adults with traumatic brain injury (TBI) under different working memory (WM) demands, and determine if there are sex-based differences in effects of WM load on ToM task performance.

METHOD

58 adults with moderate-severe TBI (24 females) and 66 uninjured adults (34 females) matched group-wise for age, sex, and education viewed a series of video vignettes from the Video Social Inference Task (VSIT) (Turkstra, 2008) and answered ToM questions. Vignette presentation format required updating and maintenance of information, and WM load was manipulated by varying presence of distracters.

RESULTS

There were main effects of group and WM load, no significant effect of sex, and a marginal interaction of group by WM load, with larger between-group differences in conditions with higher WM load. VSIT scores for the condition with the highest WM load were significantly correlated with scores on the first trial of the California Verbal Learning Test.

CONCLUSIONS

We replicated findings of lower scores in adults with TBI on a video-based ToM task, and provided additional evidence of the effect of WM load on social cognition task performance. There were no significant accuracy differences between men and women, inconsistent with prior evidence - including our own data using the same test. There is strong evidence of a female advantage on other social cognition tasks, and the parameters of this advantage remain to be discovered.

Speed of processing and executive functions in adults with phenylketonuria: Quick in finding the word, but not the ladybird

A reduction in processing speed is widely reported in phenylketonuria (PKU), possibly due to white matter pathology. We investigated possible deficits and their relationships with executive functions in a sample of 37 early-treated adults with PKU (AwPKUs). AwPKUs were not characterized by a generalized speed deficit, but instead their performance could be explained by two more specific impairments: (a) a deficit in the allocation of visuo-spatial attention that reduced speed in visual search tasks, in some reading conditions and visuo-motor coordination tasks; and (b) a more conservative decision mechanism that slowed down returning an answer across domains. These results suggest that the impairments in executive functions seen in AwPKUs are not the consequence of a generalized speed deficit. They also suggest that processing speed is linked to the efficiency of a particular cognitive component and cannot be considered a general function spanning domains. Similarities with patterns in ageing are discussed.

Does processing speed mediate the effect of pediatric traumatic brain injury on working memory?

OBJECTIVE

Processing speed (PS) and working memory (WM), core abilities that support learning, are vulnerable to disruption following traumatic brain injury (TBI). Developmental increases in WM are related to age-related changes in PS. The purpose of this study was to investigate whether WM deficits in children with TBI are mediated by PS.

METHOD

The performance of children with complicated mild, moderate, and severe TBI (n = 77) was examined relative to an orthopedic injury (n = 30) and a healthy comparison group (n = 40) an average of 4 years after injury (range 8 months to 12 years). Coding was utilized as a measure of PS, while the WM measures included complex verbal and visual-spatial span tasks with parallel processing requirements. Mediation analysis examined whether TBI might have an indirect effect on WM through PS.

RESULTS

Children in the TBI group performed more poorly than the combined comparison groups on coding and visual-spatial WM. Verbal WM scores were lower in TBI and the healthy comparison relative to the orthopedic group. TBI severity group differences were found on coding, but not WM measures. The relation between coding and both the WM tasks was similar. Bootstrap regression analyses suggested that PS, as measured by coding, might partially mediate the effect of group performance on WM.

CONCLUSIONS

TBI disrupts core PS and WM abilities that scaffold more complex abilities. Importantly, slowed PS was associated with WM deficits commonly identified following pediatric TBI. Implications of our findings regarding the relation between PS and WM may suggest interventions for children and adolescents following TBI.

Relationships between risky sexual behaviour, dysexecutive problems, and mental health in the years following interdisciplinary TBI rehabilitation

Little is known about the long-term consequences of traumatic brain injury (TBI) regarding risky sexual behaviour. The objectives of the study were (1) to compare risky sexual behaviour in a sample of individuals with TBI having received interdisciplinary rehabilitation with that of healthy controls, and (2) to explore the relationships between risky sexual behaviour, executive functions, and mental health in individuals with TBI. The study group consisted of 42 individuals with TBI with a mean age of 37.9 years (SD = 9.7), 12.8 years of education (SD = 3.3), and 3.3 years post-injury (SD = 4.3). Healthy controls consisted of 47 participants, with a mean age of 37.6 years (SD = 10.7), and 13 years of education (SD = 3). Risky sexual behaviour was measured with the Sexual Risk Survey and executive function with the Dysexecutive Questionnaire. Mental health measures included the Generalised Anxiety Disorder Scale, and the Patient Health Questionnaire for depression. Compared to healthy controls, individuals with TBI reported more dysexecutive and mental health problems, without differences in risky sexual behaviour. In individuals with TBI, risky sexual behaviour was associated with behavioural, cognitive and emotional dysexecutive problems, but not with anxiety or depression. It was concluded that special attention should be given to individuals with TBI showing difficulties in executive functions given their association with risky sexual behaviour.

Traumatic brain injury and cognition

Traumatic brain injury (TBI) is a major cause of death and disability, and therefore an important health and socioeconomic problem for our society. Individuals surviving from a moderate to severe TBI frequently suffer from long-lasting cognitive deficits. Such deficits include different aspects of cognition such as memory, attention, executive functions, and awareness of their deficits. This chapter presents a review of the main neuropsychological and neuroimaging studies of patients with TBI. These studies found that patients evolve differently according to the severity of the injury, the mechanism causing the injury, and the lesion location. Further research is necessary to develop rehabilitation methods that enhance brain plasticity and recovery after TBI. In this chapter, we summarize current knowledge and controversies, focusing on cognitive sequelae after TBI. Recommendations from the Common Data Elements are provided, with an emphasis on diagnosis, outcome measures, and studies organization to make data more comparable across studies. Final considerations on neuroimaging advances, rehabilitation approaches, and genetics are described in the final section of the chapter.

White matter integrity in veterans with mild traumatic brain injury: associations with executive function and loss of consciousness

OBJECTIVE

We investigated using diffusion tensor imaging (DTI) and the association between white matter integrity and executive function (EF) performance in postacute mild traumatic brain injury (mTBI). In addition, we examined whether injury severity, as measured by loss of consciousness (LOC) versus alterations in consciousness (AOC), is related to white matter microstructural alterations and neuropsychological outcome.

PARTICIPANTS

Thirty Iraq and Afghanistan War era veterans with a history of mTBI and 15 healthy veteran control participants.

RESULTS

There were no significant overall group differences between control and mTBI participants on DTI measures. However, a subgroup of mTBI participants with EF decrements (n = 13) demonstrated significantly decreased fractional anisotropy of prefrontal white matter, corpus callosum, and cingulum bundle structures compared with mTBI participants without EF decrements (n = 17) and control participants. Participants having mTBI with LOC were more likely to evidence reduced EF performances and disrupted ventral prefrontal white matter integrity when compared with either mTBI participants without LOC or control participants.

CONCLUSIONS

Findings suggest that altered white matter integrity contributes to reduced EF in subgroups of veterans with a history of mTBI and that LOC may be a risk factor for reduced EF as well as associated changes to ventral prefrontal white matter.

A new adaptive videogame for training attention and executive functions: design principles and initial validation

A growing body of evidence suggests that action videogames could enhance a variety of cognitive skills and more specifically attention skills. The aim of this study was to develop a novel adaptive videogame to support the rehabilitation of the most common consequences of traumatic brain injury (TBI), that is the impairment of attention and executive functions. TBI patients can be affected by psychomotor slowness and by difficulties in dealing with distraction, maintain a cognitive set for a long time, processing different simultaneously presented stimuli, and planning purposeful behavior. Accordingly, we designed a videogame that was specifically conceived to activate those functions. Playing involves visuospatial planning and selective attention, active maintenance of the cognitive set representing the goal, and error monitoring. Moreover, different game trials require to alternate between two tasks (i.e., task switching) or to perform the two tasks simultaneously (i.e., divided attention/dual-tasking). The videogame is controlled by a multidimensional adaptive algorithm that calibrates task difficulty on-line based on a model of user performance that is updated on a trial-by-trial basis. We report simulations of user performance designed to test the adaptive game as well as a validation study with healthy participants engaged in a training protocol. The results confirmed the involvement of the cognitive abilities that the game is supposed to enhance and suggested that training improved attentional control during play.

Reduced amygdala volume is associated with deficits in inhibitory control: a voxel- and surface-based morphometric analysis of comorbid PTSD/mild TBI

A significant portion of previously deployed combat Veterans from Operation Enduring Freedom and Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) are affected by comorbid posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI). Despite this fact, neuroimaging studies investigating the neural correlates of cognitive dysfunction within this population are almost nonexistent, with the exception of research examining the neural correlates of diagnostic PTSD or TBI. The current study used both voxel-based and surface-based morphometry to determine whether comorbid PTSD/mTBI is characterized by altered brain structure in the same regions as observed in singular diagnostic PTSD or TBI. Furthermore, we assessed whether alterations in brain structures in these regions were associated with behavioral measures related to inhibitory control, as assessed by the Go/No-go task, self-reports of impulsivity, and/or PTSD or mTBI symptoms. Results indicate volumetric reductions in the bilateral anterior amygdala in our comorbid PTSD/mTBI sample as compared to a control sample of OEF/OIF Veterans with no history of mTBI and/or PTSD. Moreover, increased volume reduction in the amygdala predicted poorer inhibitory control as measured by performance on the Go/No-go task, increased self-reported impulsivity, and greater symptoms associated with PTSD. These findings suggest that alterations in brain anatomy in OEF/OIF/OND Veterans with comorbid PTSD/mTBI are associated with both cognitive deficits and trauma symptoms related to PTSD.

17β-estradiol confers protection after traumatic brain injury in the rat and involves activation of G protein-coupled estrogen receptor 1

Abstract Traumatic brain injury (TBI) is a significant public health problem in the United States. Despite preclinical success of various drugs, to date all clinical trials investigating potential therapeutics have failed. Recently, sex steroid hormones have sparked interest as possible neuroprotective agents after traumatic injury. One of these is 17β-estradiol (E2), the most abundant and potent endogenous vertebrate estrogen. The goal of our study was to investigate the acute potential protective effects of E2 or the specific G protein-coupled estrogen receptor 1 (GPER) agonist G-1 when administered in an intravenous bolus dose 1 hour post-injury in the lateral fluid percussion (LFP) rodent model of TBI. The results of this study show that, when assessed at 24 hours post-injury, E2 or G-1 confers protection in adult male rats subjected to LFP brain injury. Specifically, we found that an acute bolus dose of E2 or G-1 administered intravenously 1 hour post-TBI significantly increases neuronal survival in the ipsilateral CA 2/3 region of the hippocampus and decreases neuronal degeneration and apoptotic cell death in both the ipsilateral cortex and CA 2/3 region of the hippocampus. We also report a significant reduction in astrogliosis in the ipsilateral cortex, hilus, and CA 2/3 region of the hippocampus. Finally, these effects were observed to be chiefly dose-dependent for E2, with the 5 mg/kg dose generating a more robust level of protection. Our findings further elucidate estrogenic compounds as a clinically relevant pharmacotherapeutic strategy for treatment of secondary injury following TBI, and intriguingly, reveal a novel potential therapeutic target in GPER.

The Effect of Choice on Compliance Using Telerehabilitation for Direct Attention Training: A Comparison of “Push” Versus “Pull” Scheduling

Home practice, a type of asynchronous telerehabilitation, is an integral component of most rehabilitation regimens. Exercise drills conducive to home practice have been shown to be beneficial in remediating acquired impairments in attention, speech, language, and voice. A variety of interacting psychological, cognitive, and socioenvironmental factors contribute to short- and long-term exercise adherence. There has been little research evaluating the personal characteristics most likely to motivate clients to engage in their rehabilitation and follow through with prescribed activities. In this project, we were interested in using telerehabilitation to learn more about factors that might increase clients' adherence to home exercise; we used direct attention training as our experimental domain. The study used a single-subject, alternating treatment experimental design with 2 participants to compare compliance on home attention exercises under two conditions. The Attention Process Training-3 (APT-3, 2010) direct attention training program, delivered via the Televised Assistance Program (TAP) system, allowed us to compare compliance under (a) conditions when the client had no control over the start-up of the program (push) versus (b) conditions when the client had to initiate turning on the program to do the home program (pull). Results showed that home exercise adherence was higher for both participants under the nonautonomous push condition. This ran counter to our hypothesis, based on the therapy literature, that suggested patients are more likely to follow through with home assignments when practice is under their control. We discuss our findings with respect to the interaction between self-efficacy, therapy beliefs, and autonomy for patients with acquired brain injury.

Therapeutic targets for neuroprotection and/or enhancement of functional recovery following traumatic brain injury

Traumatic brain injury (TBI) is a significant public health concern. The number of injuries that occur each year, the cost of care, and the disabilities that can lower the victim's quality of life are all driving factors for the development of therapy. However, in spite of a wealth of promising preclinical results, clinicians are still lacking a therapy. The use of preclinical models of the primary mechanical trauma have greatly advanced our knowledge of the complex biochemical sequela that follow. This cascade of molecular, cellular, and systemwide changes involves plasticity in many different neurochemical systems, which represent putative targets for remediation or attenuation of neuronal injury. The purpose of this chapter is to highlight some of the promising molecular and cellular targets that have been identified and to provide an up-to-date summary of the development of therapeutic compounds for those targets.

Consequences of cognitive impairments following traumatic brain injury: Pilot study on visual exploration while driving

PRIMARY OBJECTIVE

The aim was to assess the visual exploration of a person suffering from traumatic brain injury (TBI). It was hypothesized that visual exploration could be modified as a result of attentional or executive function deficits that are often observed following brain injury.

RESEARCH DESIGN

This study compared an analysis of eyes movements while driving with data from neuropsychological tests.

METHODS AND PROCEDURES

Five participants suffering from TBI and six control participants took part in this study. All had good driving experience. They were invited to drive on a fixed-base driving simulator. Eye fixations were recorded using an eye tracker. Neuropsychological tests were used to assess attention, working memory, rapidity of information processing and executive functions.

MAIN OUTCOMES AND RESULTS

Participants with TBI showed a reduction in the variety of the visual zones explored and a reduction of the distance of exploration. Moreover, neuropsychological evaluation indicates that there were difficulties in terms of divided attention, anticipation and planning.

CONCLUSIONS

There is a complementarity of the information obtained. Tests give information about cognitive deficiencies but not about their translation into a dynamic situation. Conversely, visual exploration provides information about the dynamic with which information is picked up in the environment but not about the cognitive processes involved.

Changes to articulation following LSVT(R) and traditional dysarthria therapy in non-progressive dysarthria

The present study aimed to evaluate the effects of the Lee Silverman Voice Treatment (LSVT(R)) on acoustic and perceptual measures of articulation in non-progressive dysarthria in comparison to traditional dysarthria therapy. The study involved 26 individuals with non-progressive dysarthria who were randomly allocated to receive either LSVT(R) or traditional dysarthria therapy (TRAD), both of which were administered for 16 hourly sessions over 4 weeks. Participants' speech samples were collected over a total of six testing sessions during three assessment phases: (1) prior to treatment, (2) immediately post-treatment, and (3) 6 months post-treatment (FU). Speech samples were analysed perceptually to determine articulatory precision and intelligibility as well as acoustically using vowel space (and vowel formant measures) and first moment differences. Results revealed short and long-term significant increases in vowel space area following LSVT(R). Significantly increased intelligibility was also found at FU in the LSVT(R) group. No significant differences between groups for any variables were found. The study reveals that LSVT(R) may be a suitable treatment option for improving vowel articulation and subsequent intelligibility in some individuals with non-progressive dysarthria.

Can measures of cognitive function predict locomotor behaviour in complex environments following a traumatic brain injury?

PRIMARY OBJECTIVE

To determine the relationships between clinical measures of executive function and attention, and laboratory measures of anticipatory locomotor adaptations with dual tasks following a TBI.

METHODS AND PROCEDURES

Ten people with moderate or severe TBI were compared to 10 healthy subjects for neuropsychological measures in the clinic, as well as locomotor patterns and reading time in the laboratory for adapted Stroop tasks (Bar and Word) during unobstructed and obstructed walking.

MAIN OUTCOMES AND RESULTS

As previously found 1 (Vallee M, McFadyen BJ, Swaine B, Doyon J, Cantin JF, Dumas D. Effects of environmental demands on locomotion after traumatic brain injury. Archives of Physical Medicine Rehabilitation 2006;87:806--813) during the locomotor activities, subjects with TBI walked slower, had higher clearance margins and took longer to read during the Stroop tasks than healthy subjects. In general, subjects with TBI also showed deficits in executive functions and attention. Significant relationships were specifically observed between scores on Trail Making B and clearance margins for subjects with TBI, but not for healthy subjects. Alternatively, significant relationships between clinical scores on Stroop and dual task Stroop reading times were obtained for healthy subjects but not for subjects with TBI.

CONCLUSIONS

These results suggest that measures of executive functioning and attention may be associated to locomotor behaviour in complex environments following a moderate to severe TBI.

A pilot study for rehabilitation of central executive deficits after traumatic brain injury

PRIMARY OBJECTIVE

An impairment of the central executive system (CES) of working memory (WM) is a common consequence of traumatic brain injury (TBI), and may also explain deficits in divided attention, long-term memory and executive functions. Here we investigated the efficacy of a rehabilitative program (working memory training: WMT) targeting the CES in improving WM and other cognitive functions dependent on this system.

METHODS AND PROCEDURES

Nine TBI patients with severe WM deficits underwent the WMT (experimental training). The WMT was preceded by a general stimulation training (GST; control training). Patients' cognitive performance was evaluated at the admission, after the GST and at the end of the WMT.

MAIN OUTCOMES AND RESULTS

Whereas the GST had no effect on patients' performance, after the WMT patients improved in all the cognitive functions dependent on the CES, but not in those functions not thought to tap this system. Importantly, a beneficial WMT effect was found on patients' everyday life functioning.

CONCLUSIONS

The results support the efficacy of the WMT in recovering CES impairments.

Validation of the Behavioral Dyscontrol Scale-Electronic Version: Sensitivity to subtle sequelae of mild traumatic brain injury

PRIMARY OBJECTIVE

To determine whether a new computer-administered battery (Behavioral Dyscontrol Scale-Electronic Version; BDS-EV) can detect subtle executive weaknesses among individuals with a self-reported history of mild head trauma (MHT), and to compare the utility of this battery to the original, non-electronic BDS and other traditional executive measures. Both BDS-EV and BDS are comprised of three factors (motor programming, environmental independence, and fluid intelligence).

METHOD

Participants with (n = 19) and without (n = 24) MHT were compared on their performance on the BDS-EV, the non-electronic BDS, and three traditional measures of executive abilities.

RESULTS

Participants with MHT differed from those without MHT on the BDS-EV motor programming and environmental independence, but not on any other measures.

CONCLUSION

The results show that electronic administration improved the sensitivity of the battery, and support prior findings that traditional executive measures are generally insensitive to subtle executive deficits associated with chronic MHT.

Making decisions and advising decisions in traumatic brain injury

OBJECTIVE AND BACKGROUND

Decision under ambiguity and decision under risk are fundamental in every-day life.

METHODS

We investigated these 2 types of decision in traumatic brain injury (TBI) patients through the Iowa Gambling Task (IGT), the Probability-Associated Gambling (PAG) task, and a counsel version of the PAG task. Although in the IGT rules for gain and losses are implicit and probability information is missing, in the PAG task and the counsel task rules are explicit and probabilities are well-defined.

RESULTS

In the IGT, TBI patients selected more disadvantageously than healthy controls and failed to develop an advantageous strategy over time. Patients also made less advantageous choices than controls in the PAG task and the counsel task. Compared with controls, TBI patients gambled more frequently with low probabilities and less frequently with high probabilities. Overall, participants decided more advantageously in the counsel task, which does not provide feedback, than in the PAG task. Importantly, our results indicate that TBI patients' performance on all decision tasks correlated with executive functions.

CONCLUSIONS

Our study shows that TBI patients have difficulties in decision under risk and decision under ambiguity. Difficulties may be attributed to deficient learning from feedback and to reduced risk estimation, but not to impulsive risk taking behavior.

White matter and neurocognitive changes in adults with chronic traumatic brain injury

Diffusion tensor imaging was used to investigate white matter (WM) integrity in adults with traumatic brain injury (TBI) and healthy adults as controls. Adults with TBI had sustained severe vehicular injuries on the average of 7 years earlier. A multivariate analysis of covariance with verbal IQ as the covariate revealed that adults with TBI had lower fractional anisotropy and higher mean diffusivity than controls, specifically in the three regions of interest (ROIs), the centrum semiovale (CS), the superior frontal (SPF), and the inferior frontal (INF). Adults with TBI averaged in the normal range in motor speed and two of three executive functions and were below average in delayed verbal recall and inhibition, whereas controls were above average. Time since injury, but not age, was associated with WM changes in the SPF ROI, whereas age, but not time since injury, was associated with WM changes in the INF ROI, suggesting that the effects of WM on time since injury may interact with age. To understand the utility of WM changes in chronic recovery, larger sample sizes are needed to investigate associations between cognition and WM integrity of severely injured individuals who have substantial cognitive impairment compared to severely injured individuals with little cognitive impairment. (JINS, 2009, 15, 130-136.).

Behavioral pre-conditioning enhances angiogenesis and cognitive outcome after brain trauma

OBJECTIVES

In this study, we used Marmarou's model of traumatic brain injury (TBI) and sought to determine: (1) the effect of TBI on cognitive outcome measured on a radial arm maze; (2) the effect of behavioral conditioning before TBI, i.e. pre-conditioning, on cognitive outcome; (3) the effect of pre-conditioning on angiogenesis.

METHODS

Cognitive outcome was measured by performance on an eight-arm radial maze. Behavioral conditioning consisted of daily exposure of animals to the radial arm maze. Latency and number of errors were recorded as an index of overall performance and acquisition of the test. Extent of angiogenesis was measured by vascular endothelial growth factor receptor 2 (VEGFR2) immunofluorescence and by determining capillary density.

RESULTS

Our results indicated that trauma alone causes significant cognitive impairments. Pre-conditioning caused a marked improvement in radial arm maze performance following injury. These results coincide with both a significant increase in VEGFR2 expression and increased capillary density within the cortex and hippocampus.

DISCUSSION

TBI causes significant impairments in cognition. These deficits can be ameliorated using a pre-conditioning paradigm. While the precise mechanism has yet to be elucidated, our results indicate that angiogenesis may underlie the cognitive sparing seen in pre-conditioned animals.