Inattentive behavior after traumatic brain injury

The Association of Traumatic Brain Injury, post-traumatic stress disorder, and criminal recidivism

BACKGROUND

The purpose of the study was to assess the prevalence of traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) and to determine whether TBI or PTSD is associated with an increase in general or violent criminal recidivism among a representative sample of released prisoners. In-person interviews were conducted with a stratified random sample of individuals incarcerated with the South Carolina Department of Corrections approximately 90 days prior to the prisoners' releases. In addition to a variety of items and scales, respondents were screened for TBI and were asked whether they had received a current diagnosis of PTSD. Data were merged with arrest data that provided measures of past criminal involvement and indicators of post-release recidivism (arrest). Arrests were coded as "general" for any arrest charge and "violent" for any violent offense charge.

RESULTS

Survival analyses indicate that neither TBI nor PTSD predicts time to general recidivism. PTSD (p < 0.01) and age at first arrest (p < 0.01) are significant predictors for violent recidivism and TBI is non-significant at p = 0.09. Results from the negative binomial models indicate that TBI (p < 0.05) and PTSD (p < 0.05) are significantly associated with more post-release violent arrests, but not general arrests.

CONCLUSIONS

TBI and PTSD were found to predict violent offending but not general criminal behavior. These findings demonstrate the need for prison officials to identify individuals with a history of TBI and PTSD and to develop appropriate interventions that could be provided during incarceration to reduce the post-release likelihood of violence.

Rehabilitation of executive function in chronic paediatric brain injury: a randomized controlled trial

BACKGROUND

Impaired executive functions (EFs, i.e., purposeful, goal-directed behaviour) cause significant disability after paediatric acquired brain injury (pABI) warranting efficient interventions. Goal Management Training (GMT) is a metacognitive protocol proven effective for executive dysfunction in adults. This pre-registered, blinded, parallel-randomized controlled trial evaluated efficacy of a paediatric adaptation (pGMT) compared to a psychoeducative control (paediatric Brain Health Workshop, pBHW) to improve EF.

METHODS

Children aged 10 to 17 years with pABI (e.g., traumatic brain injury, brain tumour), ≥ 1 year post-onset or ended treatment, with parent-reported EF complaints were eligible. Participants were randomized (computer-algorithm) to either group-based pGMT (n = 38) or pBHW (n = 38). The active control was tailored to keep non-specific factors constant. Thus, both treatments comprised of 7 sessions at hospitals over 3 consecutive weeks, followed by 4 weeks of telephone counselling of participants, parents, and teachers. Parent-reported daily life EF, assessed by the questionnaire Behavior Rating Inventory of Executive Function (BRIEF; Behavioral Regulation Index (BRI) and Metacognition Index (MI)), were co-primary outcomes 6 months post-intervention. Secondary outcomes included neuropsychological tests and a complex naturalistic task (Children's Cooking Task).

RESULTS

Seventy-three participants (96%) completed allocated interventions and 71 (93%) attended the 6-month follow-up. The results demonstrated no significant difference in effectiveness for the two interventions on parent-reported EF: For BRIEFBRI, mean (SD) raw score for pGMT was 42.7 (8.8) and 38.3 (9.3) for pBHW. Estimated difference was - 2.3 (95% CI - 5.1 to 0.6). For BRIEFMI, the corresponding results were 80.9 (20.4) for GMT and 75.5 (19.3) for pBHW. Estimated difference was - 1.4 (95% CI -8.5 to 5.8). In performance-based tests, pGMT was associated with improved inhibition and executive attention, while pBHW was associated with fewer errors in the naturalistic task.

CONCLUSIONS

In pABI, metacognitive training (pGMT) did not demonstrate additional effectiveness on parent-reported daily life EF at 6-month follow-up, when compared to a psychoeducative control. Both interventions were well-tolerated and demonstrated distinct improvements at different EF assessment levels. To conclude on pGMT efficacy, larger studies are needed, including further investigation of appropriate assessment levels and possible differences in effect related to treatment duration, developmental factors, and injury characteristics.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT0321534211, 11 July 2017.

Cognitive, Behavioral, and Functional Impairments among Traumatic Brain Injury Survivors: Impact on Caregiver Burden

Background  The burden of cognitive, behavioral, and functional impairments after traumatic brain injury (TBI) is still not highlighted much, but its impact on caregivers is socio-economically relevant. The objectives of the study were to assess cognitive, behavioral, and functional impairments in patients of TBI and its impact on caregiver burden. Materials and Methods  A descriptive cross-sectional study was conducted using a total enumeration sampling technique. Mini-mental status examination, neuropsychiatric inventory and Rappaport's disability rating scale were used to assess patients' cognitive, behavioral, and functional impairments, respectively. Zarit Caregiver Burden Scale was executed to quantify the caregiver burden. Results  Fifty patients of TBI and their caregivers were enrolled. Among these, 24% had moderate cognitive impairments. Among behavioral symptoms, 40% had agitation, 24% had depression, 18% had anxiety, and 16% had irritability. Moderate functional disability was reported by 18% of the patients, while 2% reported severe functional disability. Moderate to severe caregiver burden was reported by 8% of caregivers. Patients' behavioral ( r = 0.507, p < 0.001), functional ( r = 0.473, p = 0.001), and cognitive ( r = -0.438, p = 0.001) impairments had significant correlations with caregiver burden. Conclusion  Patients develop cognitive, behavioral, and functional disability after TBI. The caregiver burden increases significantly with cognitive dysfunction, behavioral symptoms, and impaired functional status of patients. Therefore, appropriate support is to be provided to caregivers as well as patients.

Relationship Between Physiologically Measured Attention and Behavioral Task Engagement in Persons With Chronic Aphasia

Purpose Persons with aphasia (PWAs) have been shown to have impaired attention skills that may interfere with their ability to successfully participate in speech and language therapy. Fluctuations in attention can be detected using physiological measures such as electroencephalography (EEG), but these measures can be impractical for clinical use. The primary purpose of this study was to investigate observable behavioral signs of attention as a means of measuring within-session fluctuations in attention by comparing behavioral ratings to physiological changes. Other aims were to understand the relationship between observable behaviors and task performance and to determine whether syntactic complexity influences behavioral attention. Method Ten PWAs and 10 neurologically healthy adults underwent a sentence-reading task with 45 active and 45 passive sentences while video/audio and EEG data were recorded continuously. EEG data for each trial were classified into one of four levels of attention using a classification algorithm (Berka et al., 2004), and video/audio data were scored for accuracy and behavioral engagement by two trained speech-language pathologist students using a behavioral rating scale of inattention (Whyte et al., 1996). Results Results showed that behavioral engagement was significantly correlated with task performance, with higher engagement scores associated with fewer errors. Behavioral engagement did not differ based on syntactic complexity for either group, but PWAs had significantly lower behavioral engagement scores when they were in lower/distracted states of physiologically measured vigilant attention. Conclusion Behavioral observation may provide an alternative means of detecting clinically significant lapses in attention during aphasia therapy.

Transplantation of Mesenchymal Stem Cells Overexpressing Fibroblast Growth Factor 21 Facilitates Cognitive Recovery and Enhances Neurogenesis in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a progressive and complex pathological condition that results in multiple adverse consequences, including impaired learning and memory. Transplantation of mesenchymal stem cells (MSCs) has produced limited benefits in experimental TBI models. Fibroblast growth factor 21 (FGF21) is a novel metabolic regulator that has neuroprotective effects, promotes remyelination, enhances angiogenesis, and elongates astrocytic processes. In this study, MSCs were genetically engineered to overexpress FGF21 in order to improve their efficacy in TBI. MSCs overexpressing FGF21 (MSC-FGF21) were transplanted to mouse brain by intracerebroventricular injection 24 h after TBI was induced by controlled cortical impact (CCI). Hippocampus-dependent spatial learning and memory, assessed by the Morris water maze test, was markedly decreased 3-4 weeks after TBI, a deficit that was robustly recovered by treatment with MSC-FGF21, but not MSC-mCherry control. Hippocampus-independent learning and memory, assessed by the novel object recognition test, was also impaired; these effects were blocked by treatment with both MSC-FGF21 and MSC-mCherry control. FGF21 protein levels in the ipsilateral hippocampus were drastically reduced 4 weeks post-TBI, a loss that was restored by treatment with MSC-FGF21, but not MSC-mCherry. MSC-FGF21 treatment also partially restored TBI-induced deficits in neurogenesis and maturation of immature hippocampal neurons, whereas MSC-mCherry was less effective. Finally, MSC-FGF21 treatment also normalized TBI-induced impairments in dendritic arborization of hippocampal neurons. Taken together, the results indicate that MSC-FGF21 treatment significantly improved TBI-induced spatial memory deficits, impaired hippocampal neurogenesis, and abnormal dendritic morphology. Future clinical investigations using MSC-FGF21 to improve post-TBI outcomes are warranted.

Cross-cultural adaptation and psychometric properties of the MMSE and MoCA questionnaires in Tanzanian Swahili for a traumatic brain injury population

BACKGROUND

Traumatic Brain Injury (TBI) is the most common cause of injury-related death and disability globally, and a common sequelae is cognitive impairment. Addressing post-TBI cognitive deficits is crucial because they affect rehabilitation outcomes, but doing this requires valid and reliable cognitive assessment measures. However, no such instrument has been validated in Tanzania's TBI population. Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) are two commonly used instruments to measure cognitive impairment, and there have been a few studies reporting their use in post-TBI cognitive assessment. Our aim was to report the psychometric properties of the Swahili version of both scales amongst the TBI population in Tanzania.

METHODS

A cross-cultural adaptation committee participated in the translation and content validation process for both questionnaires. Our patient sample consisted of 192 adults with TBI who were admitted to Kilimanjaro Christian Medical Center (KCMC) in Tanzania. Confirmatory factor analysis, reliability and external validity were evaluated.

RESULTS

MoCA showed adequate factor loadings (values > 0.50 for all items except items 7 & 10) and adequate reliability (values > 0.70). Factor loadings for most of the MMSE items were below 0.5 and internal consistency was medium (< 0.7). Polychoric correlation between MMSE and MoCA was strong, positive and statistically significant (r = 0.68, p = 0.001); correlation with the cognitive subscale of FIM indicated moderately positive relationships - MMSE (r = 0.35, p = 0.001) and MoCA (r = 0.43, p = 0.001).

CONCLUSIONS

With the exception of the language and memory items, MoCA is a valid and reliable instrument for cognitive impairment screening in Tanzania's adult TBI population. On the other hand, MMSE does not appear to be an appropriate tool in this patient group, but its positive correlations with MoCA and cFIM indicate similar theoretical concepts. Both instruments require further validation studies to prove their predictive ability for screening cognitive impairment before they are considered suitable for clinical use.

Assessing Executive Function in Adolescence: A Scoping Review of Existing Measures and Their Psychometric Robustness

Background: There is much research examining adolescents' executive function (EF) but there is little information about tools that measure EF, in particular preference of use, their reliability and validity. This information is important as to help both researchers and practitioners select the most relevant and reliable measure of EF to use with adolescents in their context. Aims: We conducted a scoping review to: (a) identify the measures of EF that have been used in studies conducted among adolescents in the past 15 years; (b) identify the most frequently used measures of EF; and (c) establish the psychometric robustness of existing EF measures used with adolescents. Methods: We searched three bibliographic databases (PsycINFO, Ovid Medline, and Web of Science) using key terms "Adolescents," "Executive Functions," and "measures". The search covered research articles published between 1st January 2002 and 31st July 2017. Results: We identified a total of 338 individual measures of EF from 705 eligible studies. The vast majority of these studies (95%) were conducted in high income countries. Of the identified measures, 10 were the most used frequently, with a cumulative percent frequency accounting for nearly half (44%) the frequency of usage of all reported measures of EF. These are: Digit Span (count = 160), Trail Making Test (count = 158), Behavior Rating Inventory of Executive Function (count = 148), Wisconsin Card Sorting Test (count = 140), Verbal Fluency Tasks (count = 88), Stroop Color-Word Test (count = 78), Classical Stroop Task (count = 63), Color-Word Interference Test from Delis-Kaplan battery (count = 62), Rey-Osterrieth Complex Figure Test (count = 62), and Original Continuous Performance Test (count = 58). In terms of paradigms, tasks from Span (count = 235), Stroop (count = 216), Trails (count = 171), Card sorting (count = 166), Continuous performance (count = 99), and Tower (count = 94) paradigms were frequently used. Only 48 studies out of the included 705 reported the reliability and/or validity of measures of EF used with adolescents, but limited to studies in high income countries. Conclusion: We conclude that there is a wide array of measures for assessing EF among adolescents. Ten of these measures are frequently used. However, the evidence of psychometric robustness of measures of EF used with adolescents remains limited to support the validity of their usage across different contexts.

Exploring the relationship between boredom proneness and self-control in traumatic brain injury (TBI)

Characterized as an agitated state in which the individual is motivated to engage in their environment but all attempts to do so fail to satisfy, boredom represents a disengaged attentional state that is associated with negative affect and poor self-control. There have been anecdotal reports of increased levels of boredom post-traumatic brain injury (TBI). For the first time, we provide objective evidence that TBI patients do indeed experience higher levels of boredom proneness. Hierarchical regression analyses showed that the presence and severity of head injury were a significant positive predictor of levels of boredom proneness and a negative predictor of self-control. As with healthy controls, TBI patients showed a strong negative correlation between boredom proneness and self-control-those with lower levels of self-control exhibited higher levels of boredom proneness. This was despite the fact that our TBI patients reported higher overall levels of self-control (probably concomitant with their older mean age). The TBI patients also showed strong positive correlations between boredom proneness and measures of physical aggression and anger. Together, this suggests that patients with TBI may be more susceptible to increased levels of boredom proneness and other negative affective states that arise as a consequence of failures of self-control.

Disrupted Intrinsic Connectivity among Default, Dorsal Attention, and Frontoparietal Control Networks in Individuals with Chronic Traumatic Brain Injury

OBJECTIVES

Individuals with chronic traumatic brain injury (TBI) often show detrimental deficits in higher order cognitive functions requiring coordination of multiple brain networks. Although assessing TBI-related deficits in higher order cognition in the context of network dysfunction is promising, few studies have systematically investigated altered interactions among multiple networks in chronic TBI.

METHOD

We characterized disrupted resting-state functional connectivity of the default mode network (DMN), dorsal attention network (DAN), and frontoparietal control network (FPCN) whose interactions are required for internally and externally focused goal-directed cognition in chronic TBI. Specifically, we compared the network interactions of 40 chronic TBI individuals (8 years post-injury on average) with those of 17 healthy individuals matched for gender, age, and years of education.

RESULTS

The network-based statistic (NBS) on DMN-DAN-FPCN connectivity of these groups revealed statistically significant (p NBS2.58) reductions in within-DMN, within-FPCN, DMN-DAN, and DMN-FPCN connectivity of the TBI group over healthy controls. Importantly, such disruptions occurred prominently in between-network connectivity. Subsequent analyses further exhibited the disrupted connectivity patterns of the chronic TBI group occurring preferentially in long-range and inter-hemispheric connectivity of DMN-DAN-FPCN. Most importantly, graph-theoretic analysis demonstrated relative reductions in global, local and cost efficiency (p<.05) as a consequence of the network disruption patterns in the TBI group.

CONCLUSION

Our findings suggest that assessing multiple networks-of-interest simultaneously will allow us to better understand deficits in goal-directed cognition and other higher order cognitive phenomena in chronic TBI. Future research will be needed to better understand the behavioral consequences related to these network disruptions.

Alcohol exposure after mild focal traumatic brain injury impairs neurological recovery and exacerbates localized neuroinflammation

Traumatic brain injury (TBI) represents a leading cause of morbidity and mortality among young individuals. Alcohol abuse is a risk factor associated with increased TBI incidence. In addition, up to 26% of TBI patients engage in alcohol consumption after TBI. Limited preclinical studies have examined the impact of post-injury alcohol exposure on TBI recovery. The aim of this study was to determine the isolated and combined effects of TBI and alcohol on cognitive, behavioral, and physical recovery, as well as on associated neuroinflammatory changes. Male Sprague-Dawley rats (∼300g) were subjected to a mild focal TBI by lateral fluid percussion (∼30PSI, ∼25ms) under isoflurane anesthesia. On day 4 after TBI, animals were exposed to either sub-chronic intermittent alcohol vapor (95% ethanol 14h on/10h off; BAL∼200mg/dL) or room air for 10days. TBI induced neurological dysfunction reflected by an increased neurological severity score (NSS) showed progressive improvement in injured animals exposed to room air (TBI/air). In contrast, TBI animals exposed to alcohol vapor (TBI/alcohol) showed impaired NSS recovery throughout the 10-day period of alcohol exposure. Open-field exploration test revealed an increased anxiety-like behavior in TBI/alcohol group compared to TBI/air group. Additionally, alcohol-exposed animals showed decreased locomotion and impaired novel object recognition. Immunofluorescence showed enhanced reactive astrocytes, microglial activation, and HMGB1 expression localized to the injured cortex of TBI/alcohol as compared to TBI/air animals. The expression of neuroinflammatory markers showed significant positive correlation with NSS. These findings indicated a close relationship between accentuated neuroinflammation and impaired neurological recovery from post-TBI alcohol exposure. The clinical implications of long-term consequences in TBI patients exposed to alcohol during recovery warrant further investigation.

Decoding hippocampal signaling deficits after traumatic brain injury

There are more than 3.17 million people coping with long-term disabilities due to traumatic brain injury (TBI) in the United States. The majority of TBI research is focused on developing acute neuroprotective treatments to prevent or minimize these long-term disabilities. Therefore, chronic TBI survivors represent a large, underserved population that could significantly benefit from a therapy that capitalizes on the endogenous recovery mechanisms occurring during the weeks to months following brain trauma. Previous studies have found that the hippocampus is highly vulnerable to brain injury, in both experimental models of TBI and during human TBI. Although often not directly mechanically injured by the head injury, in the weeks to months following TBI, the hippocampus undergoes atrophy and exhibits deficits in long-term potentiation (LTP), a persistent increase in synaptic strength that is considered to be a model of learning and memory. Decoding the chronic hippocampal LTP and cell signaling deficits after brain trauma will provide new insights into the molecular mechanisms of hippocampal-dependent learning impairments caused by TBI and facilitate the development of effective therapeutic strategies to improve hippocampal-dependent learning for chronic survivors of TBI.

Decreased level of olfactory receptors in blood cells following traumatic brain injury and potential association with tauopathy

Traumatic brain injury (TBI) is a leading cause of death and disability among children and young adults in the United States. In this study, we explored whether changes in the gene expression profile of peripheral blood mononuclear cells (PBMC) may provide a clinically assessable "window" into the brain, reflecting molecular alterations following TBI that might contribute to the onset and progression of TBI clinical complications. We identified three olfactory receptor (OR) TBI biomarkers that are aberrantly down-regulated in PBMC specimens from TBI subjects. Down-regulation of these OR biomarkers in PBMC was correlated with the severity of brain injury and TBI-specific symptoms. A two- biomarker panel comprised of OR11H1 and OR4M1 provided the best criterion for segregating the TBI and control cases with 90% accuracy, 83.3% sensitivity, and 100% specificity. We found that the OR biomarkers are ectopically expressed in multiple brain regions, including the entorhinal-hippocampus system known to play an important role in memory formation and consolidation. Activation of OR4M1 led to attenuation of abnormal tau phosphorylation, possibly through JNK signaling pathway. Our results suggested that addition of the two-OR biomarker model to current diagnostic criteria may lead to improved TBI detection for clinical trials, and decreased expression of OR TBI biomarkers might be associated with TBI-induced tauopathy. Future studies exploring the physiological relevance of OR TBI biomarkers in the normal brain and in the brain following TBI will provide a better understanding of the biological mechanisms underlying TBI and insights into novel therapeutic targets for TBI.

Advancing the evidence base of rehabilitation treatments: a developmental approach

Translational research refers to the development of new scientific discoveries into evidence-based treatments for human diseases and conditions. This developmental process requires that a number of scientific, as well as social and psychological obstacles, be overcome during a sequence of research stages that address different goals. Rehabilitation, like other biomedical disciplines, requires this kind of developmental process. For a variety of reasons, however, development of rehabilitation treatments is less linear than the familiar phases of pharmaceutical research. In addition, research on treatments intended to address impairments (body structure/function, in terms of the International Classification of Functioning, Disability and Health), faces the challenge of determining the likely impact of an impairment-level treatment on the multifaceted activities and aspects of participation that are the typical goals of rehabilitation treatments. This article describes the application of treatment theory and enablement theory to the development of new impairment-based treatments, and examines similarities and differences between the developmental sequence needed for rehabilitation treatment research versus pharmaceutical research in other areas of medicine.

Neurobiological consequences of traumatic brain injury

Traumatic brain injury (TBI) is a worldwide public health problem typically caused by contact and inertial forces acting on the brain. Recent attention has also focused on the mechanisms of injury associated with exposure to blast events or explosions. Advances in the understanding of the neuropathophysiology of TBI suggest that these forces initiate an elaborate and complex array of cellular and subcellular events related to alterations in Ca⁺⁺ homeostasis and signaling. Furthermore, there is a fairly predictable profile of brain regions that are impacted by neurotrauma and the related events. This profile of brain damage accurately predicts the acute and chronic sequelae that TBI survivors suffer from, although there is enough variation to suggest that individual differences such as genetic polymorphisms and factors governing resiliency play a role in modulating outcome. This paper reviews our current understanding of the neuropathophysiology of TBI and how this relates to the common clinical presentation of neurobehavioral difficulties seen after an injury.

Neurobehavioral sequelae of traumatic brain injury: evaluation and management

Traumatic brain injury (TBI) is a worldwide public health problem. Over the last several decades, improvements in acute care have resulted in higher survival rates. Unfortunately, the majority of survivors of moderate and severe TBI have chronic neurobehavioral sequelae, including cognitive deficits, changes in personality and increased rates of psychiatric illness. These neurobehavioral problems are understandable in the context of the typical profile of regional brain damage associated with trauma. This paper presents an overview of the neurobehavioral sequelae of TBI and outlines issues to consider in the evaluation and management of these challenges.

Activation of calcium/calmodulin-dependent protein kinases after traumatic brain injury

A prominent cognitive impairment after traumatic brain injury (TBI) is hippocampal-dependent memory loss. Although the histopathologic changes in the brain are well documented after TBI, the underlying biochemical mechanisms that contribute to memory loss have yet to be thoroughly delineated. Thus, we determined if calcium/calmodulin-dependent protein kinases (CaMKs), known to be necessary for the formation of hippocampal-dependent memories, are regulated after TBI. Sprague-Dawley rats underwent moderate parasagittal fluid-percussion brain injury on the right side of the parietal cortex. The ipsilateral hippocampus and parietal cortex were Western blotted for phosphorylated, activated alpha-calcium/calmodulin-dependent protein kinase II (alpha-CaMKII), CaMKIV, and CaMKI. alpha-Calcium/calmodulin-dependent protein kinase II was activated in membrane subcellular fractions from the hippocampus and parietal cortex 30 mins after TBI. CaMKI and CaMKIV were activated in a more delayed manner, increasing in phosphorylation 1 h after TBI. The increase in activated alpha-CaMKII in membrane fractions was accompanied by a decrease in cytosolic total alpha-CaMKII, suggesting redistribution to the membrane. Using confocal microscopy, we observed that alpha-CaMKII was activated within hippocampal neurons of the dentate gyrus, CA3, and CA1 regions. Two downstream substrates of alpha-CaMKII, the AMPA-type glutamate receptor GluR1, and cytoplasmic polyadenylation element-binding protein, concomitantly increased in phosphorylation in the hippocampus and cortex 1 h after TBI. These results demonstrate that several of the biochemical cascades that subserve memory formation are activated unselectively in neurons after TBI. As memory formation requires activation of CaMKII signaling pathways at specific neuronal synapses, unselective activation of CaMKII signaling in all synapses may disrupt the machinery for memory formation, resulting in memory loss after TBI.

Selective attention deficits following severe closed head injury: the role of inhibitory processes

Heightened distractibility following severe closed head injury (sCHI) may result from a deficit in selective attention. The integrity of inhibitory processes involved in selective attention was assessed through use of a negative priming paradigm, allowing dissociation of inhibitory and episodic retrieval processes. In this task, inhibitory processes are elicited under intact stimulus conditions, whereas episodic retrieval is elicited when target stimuli are degraded. Despite inconsistent evidence of inhibitory deficits following sCHI in the literature, long-term survivors of sCHI showed no negative priming under intact stimulus conditions, providing evidence of compromised inhibitory processing. The sCHI participants' demonstration of negative priming when target stimuli were degraded provides evidence that automatic retrieval processes are intact following sCHI, results that are consistent with prior findings.

Pathophysiology of traumatic injury in the developing brain: an introduction and short update

Current understanding about the main peculiarities in pathophysiology of immature brain traumatic injury involves marked developmental discrepancy of biomechanical properties, aspects of altered features in water and electrolyte homeostasis as well as maturation dependent differences in structural and functional responses of major transmitter systems. Based on the fact that traumatic brain injury (TBI) is one of the major causes of morbidity and mortality in infants and children, the currently available epidemiological data are reviewed in order to gain insights about scope and dimension of health care engagement and derive the requirements for reinforced pathogenetic research. To this end, the main aspects of peculiarities in primary and secondary TBI mechanisms in the immature/developing brain are discussed, including structural and functional conditions resulting in a markedly diminished shear resistance of the immature brain tissue. As such, the immature brain tissue appears to be more susceptible to mechanical alterations, because similar mechanical load induces a more intense brain tissue displacement. Furthermore, available indications for increased incidence of brain swelling in the immature brain after TBI are reviewed, focusing on the interrelationship between the age-dependent differences in extracellular space and aquaporin-4 expression during brain maturation. The developmental differences of TBI induced cerebrovascular response as well as some relevant aspects of altered neurotransmission following TBI of the immature brain in regard to the glutamatergic and dopaminergic transmitter system are assessed. Thus, this mini-review highlights some progress but also an increased necessity for expanded pathogenetic research on a clinical scale in order to develop a solid foundation for adequate therapeutic strategies for the different life-threatening consequences of TBI in infancy and childhood, which mainly have failed up to now.

Neuropsychological and Information Processing Performance and Its Relationship to White Matter Changes Following Moderate and Severe Traumatic Brain Injury: A Preliminary Study

Reductions in information processing speed have frequently been reported following moderate and severe traumatic brain injuries (TBIs), consistent with the effects of diffuse white matter damage. Although the corpus callosum (CC) is a common site for diffuse damage following TBI, the effects of this damage on information processing speed have not been adequately examined. This study assessed a TBI group and a matched control group on tests of attention, memory, fluency, and set shifting ability, together with reaction time (RT) tasks requiring the inter- and intrahemispheric processing of visual and tactile information. The RT tasks were designed to target the cognitive functions that are likely to be affected by diffuse white matter damage, including damage to the CC. The TBI group demonstrated deficits in verbal and visual fluency and verbal memory. They were also slower on the visual and tactile RT tasks, were more affected by task complexity, and slower on RT tasks requiring the interhemispheric transfer of information. In fact, one of the interhemispheric tactile RT tasks proved to be the most discriminating of all the cognitive and RT measures. MRIs completed on a subset of TBI participants indicated that the mean CC measurements were 5% to 19% smaller than a normative control group, with the most atrophied areas being the isthmus and anterior midbody. Although white matter atrophy was moderately related to visual and tactile RT performance, and total hippocampal volume related to memory performance, CC area was not related to many of the tasks that were designed to tap interhemispheric processing. None of the standard cognitive tests correlated with outcome in the TBI group, but 1 of the tactile RT measures was significantly related to 2 measures of outcome.

Age-Dependent Effects of Severe Traumatic Brain Injury on Cerebral Dopaminergic Activity in Newborn and Juvenile Pigs

There is evidence that the dopaminergic system is sensitive to traumatic brain injury (TBI). However, the age-dependency of this sensitivity has not been studied together with brain oxidative metabolism. We postulate that the acute effects of severe TBI on brain dopamine turnover are age-dependent. Therefore 18F-labelled 6-fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) together with Positron-Emission-Tomography (PET) was used to estimate the activity of the aromatic amino acid decarboxylase (AADC) in the brain of 11 newborn piglets (7-10 days old) and nine juvenile pigs (6-7 weeks old). Six newborn and five juvenile animals were subjected to a severe fluid-percussion (FP) induced TBI. The remaining animals were used as sham operated untreated control groups. Simultaneously, the regional cerebral blood flow (CBF) was measured with colored microspheres and the cerebral metabolic rates of oxygen and glucose were determined. At 1 h after FP-TBI, [18F]FDOPA was infused and PET scanning was performed for 2 h. At 2 h after FP-TBI administration, a second series of measurements of physiological values including CBF and brain oxidative metabolism data had been obtained. Severe FP-TBI elicited a marked increase in the rate constant for fluorodopamine production (k3FDOPA) in all brain regions of newborn piglets studied by between 97% (mesencephalon) and 143% (frontal cortex) (p < 0.05). In contrast, brain hemodynamics and cerebral oxidative metabolism remained unaltered after TBI. Furthermore, the permeability-surface area product of FDOPA (PSFDOPA) was unchanged. In addition, regional blood flow differences between corresponding ipsi- and contralateral brain regions did not occur after TBI. Thus, it is suggested that severe FP-TBI induces an upregulation of AADC activity of newborn piglets that is not related to alterations in brain oxidative metabolism.

Effects of Methylphenidate on Attention Deficits After Traumatic Brain Injury

OBJECTIVE

To evaluate the effects of methylphenidate on a variety of aspects of attention, ranging from laboratory-based impairment measures to caregiver ratings and work productivity, in individuals after traumatic brain injury.

DESIGN

A total of 34 adults with moderate to severe traumatic brain injury and attention complaints in the postacute phase of recovery were enrolled in a 6-wk, double-blind, placebo-controlled, repeated crossover study of methylphenidate, administered in a dose of 0.3 mg/kg/dose, twice a day. A wide range of attentional measures was gathered weekly, including computerized and paper-and-pencil tests of attention, videotaped records of individual work in a distracting environment, real-time observational scoring of attentiveness in a classroom environment, and caregiver and clinician rating scales of attentiveness. Participants also attempted to guess their drug condition each week. Data from the first ten participants were used for pilot purposes, to develop attentional factors for composite scoring, and to identify attentional dimensions suggestive of a treatment effect for independent replication. The remaining 24 participants' results were used to confirm potential treatment effects seen in the pilot sample, using Wilcoxon's signed-ranks test on composite factor scores and individual variables.

RESULTS

A total of 54 dependent variables were reduced to 13 composite factors and 13 remaining individual variables. Of the 13 attentional factors, five showed suggestive treatment effects in the pilot sample. Of these, three showed statistically significant treatment effects in the replication sample: speed of information processing (effect sizes, -0.06 to 0.48; P < 0.001), attentiveness during individual work tasks (effect sizes, 0.15-0.62; P = 0.01), and caregiver ratings of attention (effect sizes, 0.44-0.50; P = 0.01). Of the individual variables, four showed suggestive treatment effects in the pilot sample, but only one showed significant treatment effects in the replication sample: reaction time before errors in the Sustained Attention to Response Task (effect size, 0.20; P = 0.03). No treatment-related improvement was seen in divided attention, sustained attention, or susceptibility to distraction. None of the variables showed suggestive or definite negative treatment effects. Effect sizes for those performance measures positively affected by methylphenidate were in the small to medium range and included both impairment and activity level measures. Improvements in processing speed did not seem to come at the expense of accuracy.

CONCLUSIONS

Methylphenidate, at 0.3 mg/kg/dose, given twice a day to individuals with attentional complaints after traumatic brain injury, seems to have clinically significant positive effects on speed of processing, caregiver ratings of attention, and some aspects of on-task behavior in naturalistic tasks. Further research is needed to identify the optimal dose and to extend these findings to less carefully selected individuals.

Working memory deficits after traumatic brain injury: catecholaminergic mechanisms and prospects for treatment -- a review

PRIMARY OBJECTIVE

To review the neural circuitry and neurochemistry of working memory and outline the evidence for working memory deficits after traumatic brain injury, and the evidence for the use of catecholaminergic agents in the amelioration of these deficits. Current knowledge gaps and research needs are identified.

MAIN OUTCOMES AND RESULTS

Impairments in working memory are a core component of the cognitive deficits associated with traumatic brain injury. Recent progress in understanding the neural circuitry and neurochemistry of working memory suggests that catecholamines play a central role in the activation and regulation of working memory and thus lays a framework in which to consider the use of catecholaminergic agents (dopaminergic and alpha-2 adrenergic agonists) in the treatment of specific cognitive deficits after traumatic brain injury.

CONCLUSIONS

The combined methods of cognitive neuroscience, functional brain imaging and neuropharmacology are proposed as an excellent method for studying working memory deficits. A strong rationale exists for the targeted use of catecholaminergic agonists in the treatment of working memory deficits after traumatic brain injury.

Light deprivation soon after frontal brain trauma accelerates recovery from attentional deficits and promotes functional normalization of basal ganglia

BACKGROUND

Light deprivation significantly accelerates recovery from attention deficits (neglect) after cortical ablation in rats. We hypothesized that light deprivation would improve recovery after traumatic contusive brain injury (TBI) and do so by enhancing dopaminergic function in the ipsilateral basal ganglia.

METHODS

Adult rats received left frontal contusion injury and were placed into darkness or standard light/dark cycling for 48 hours. Neurologic evaluation included attentional and sensorimotor tasks. Amphetamine-induced production of the immediate early gene protein product Fos was quantified to determine neuronal dopaminergic response in caudate-putamen (striatum).

RESULTS

Unilateral frontal TBI produced severe contralateral deficits in all tasks. Postoperative light deprivation resulted in improved recovery from attentional but not sensorimotor deficits. Five days after injury, ipsilateral striatal Fos expression was reduced by 51% in TBI rats experiencing normal light cycling (p < 0.006). In contrast, postoperative light deprivation normalized striatal Fos expression. By 6 weeks, all TBI rats demonstrated nearly full recovery and striatal Fos expression was symmetrical between the two striata.

CONCLUSION

Postoperative light deprivation may improve recovery from TBI-induced attention deficits by normalizing basal ganglia function.

Effects of methylphenidate on attentional function after traumatic brain injury. A randomized, placebo-controlled trial

Attention deficits after traumatic brain injury (TBI) are common and disabling. Many pharmacologic agents have been used to ameliorate attention deficits, and considerable interest has focused on methylphenidate (MP) because of its documented efficacy in attention deficit disorder. However, clinical studies of MP in subjects with TBI have yielded mixed results. We examined the effects of MP on attentional function in individuals with TBI referred specifically for attentional assessment and treatment. Subjects were studied in a double-blind, placebo-controlled, repeated crossover design, using five different tasks designed to measure various facets of attentional function. MP produced a significant improvement in the speed of mental processing. Orienting to distractions, most aspects of sustained attention, and measures of motor speed were unaffected. These results suggest that MP may be a useful treatment in TBI but is primarily useful for symptoms that can be attributed to slowed mental processing.

Phasic arousal in response to auditory warnings after traumatic brain injury

Traumatic brain injury (TBI) is believed to have adverse effects on attention, but because of the multifaceted nature of the arousal and attentional network, the precise impact of TBI on various subcomponents of this network remains controversial. As part of a larger program of research on attention in TBI, we studied the effects of auditory warning signals on accuracy, reaction time, and response bias, as indices of phasic arousal in a visual go/no-go task. Warnings were presented randomly at various pre-stimulus intervals to a sample of recently injured patients and control subjects. For each subject and performance index, we examined the time interval required to reach maximal phasic arousal, the degree of performance change occurring at this maximal point, and the ability to maintain this state of increased arousal over longer warning intervals. After adjustment for baseline differences, there were no significant differences between patients and controls in any aspect of performance. Examination of effect sizes suggested that this was not due to limited statistical power, but that any differences between groups, if present, must have been small. In contrast, in our prior research on sustained attention and observable behaviors related to attention, large group differences have been found. These data suggest that mechanisms responsible for auditorily-induced phasic arousal responses are largely preserved in severe TBI.