Ventral frontal cortex functions and quantified MRI in traumatic brain injury

Olfactory Dysfunction Following Moderate to Severe Traumatic Brain Injury: A Systematic Review and Meta-Analysis

OBJECTIVE

Reports of smell loss following traumatic brain injury (TBI) are a well-documented but understudied phenomenon. Given the broad consequences of olfactory loss, we characterized psychophysical olfactory dysfunction in individuals with moderate to severe TBI using systematic review and meta-analytic methods.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) protocol, five databases (PubMed, EMBASE, Cochrane Library, Web of Science, Scopus) were reviewed for studies investigating olfactory dysfunction in persons with moderate to severe TBI. Of the 5,223 studies reviewed, 19 met our inclusion criteria for the systematic review and 11 met inclusion criteria for meta-analysis. We calculated effect sizes (Hedges' g) to characterize the degree of olfactory dysfunction between patients with moderate to severe TBI and controls.

RESULTS

A total of 951 moderate-severe TBI patients from 19 studies were included in the systematic review, which largely demonstrated poorer olfactory psychophysical performances in this patient population. Meta-analysis demonstrated a large effect size for olfactory dysfunction in moderate-severe TBI relative to healthy controls (g=-2.43, 95%CI: -3.16 < δ<-1.69). The magnitude of the effect was moderated by age and patient sex, with larger effect sizes associated with older age (following exclusion of a pediatric population) and larger compositions of women in the patient group.

CONCLUSION

Moderate to severe TBI is associated with prominent olfactory dysfunction. Significant research gaps remain regarding the mechanism, recovery and natural history of olfactory dysfunction following moderate to severe TBI, which has significant clinical implications for the identification and treatment for those with post-traumatic olfactory dysfunction.

Decision-making abilities under risk and ambiguity in adults with traumatic brain injury: what do we know so far? A systematic review and meta-analysis

Traumatic brain injury (TBI) is a major health and socio-economic problem since it is one of the major sources of death and disability worldwide. TBI patients usually show high heterogeneity in their clinical features, including both cognitive and emotional/behavioral alterations. As it specifically concerns cognitive functioning, these patients usually show decision-making (DM) deficits. DM is commonly considered a complex and multistep process that is strictly linked to both hot and cold executive functioning and is pivotal for daily life functioning and patients' autonomy. However, the results are not always in agreement, with some studies that report huge alterations in the DM processes, while others do not. The present systematic review and meta-analysis aims to integrate past literature on this topic, providing a clear and handy picture both for researchers and clinicians. Thirteen studies addressing domain-general DM abilities were included from an initial N = 968 (from three databases). Results showed low heterogeneity between the studies (I2 = 7.90, Q (12) = 13.03, p = .37) supporting the fact that, overall, TBI patients showed lower performance in DM tasks as compared to healthy controls (k = 899, g = .48, 95% CI [0.33; 0.62]) both in tasks under ambiguity and under risk. The evidence that emerged from this meta-analysis denotes a clear deficit of DM abilities in TBI patients. However, DM tasks seemed to have good sensitivity but low specificity. A detailed description of patients' performances and the role of both bottom-up, hot executive functions and top-down control functions have been further discussed. Finally, future directions and practical implications for both researchers and clinicians have been put forward.

Associations of Prior Head Injury With Olfaction in Older Adults: Results From the Atherosclerosis Risk in Communities (ARIC) Study

Importance

Traumatic brain injury has been associated with short-term olfactory dysfunction, but the association of number of prior head injuries and head injury severity with both subjective and objective long-term olfactory function is less clear.

Objective

To investigate the associations of prior head injury, number of prior head injuries, and head injury severity with subjective and psychophysical (objective) olfactory function in older adults and to examine concordance between subjective and objective olfactory function among individuals with and without head injury.

Design, Setting, and Participants

This prospective cohort study included 5951 participants who attended Atherosclerosis Risk in Communities (ARIC) Study visit 5 (2011 through 2013). Data analysis was performed between November 2021 and May 2022.

Exposures

Head injury was defined by self-report and International Classification of Diseases codes.

Main Outcomes and Measures

Self-reported subjective olfactory dysfunction was assessed by the question, "Do you suffer from smell loss or a significantly decreased sense of smell?" Objective olfactory performance was assessed using the 12-item Sniffin' Sticks odor identification test.

Results

Overall, the 5951 participants were a mean (SD) age of 75.6 (5.2) years, 3501 (58.8%) were female, 1356 (22.8%) were of Black race, and 1666 (28.0%) had a history of head injury. Participants with prior head injury were more likely than individuals without prior head injury to report subjective olfactory dysfunction (24% vs 20%; difference, 4%; 95% CI, 1% to 6%) and have objective anosmia (15% vs 13%; difference, 2%; 95% CI, 0.1% to 4%) but had lower concordance between subjective and objective assessment (72% vs 77%; difference, -5%; 95% CI, -8% to -3%). In logistic regression models adjusted for sociodemographics and medical comorbidities including cognitive status, participants with a history of prior head injury, particularly individuals with 2 or more prior head injuries and more severe head injuries, were more likely to self-report subjective olfactory dysfunction and were more likely to be found to have objective anosmia compared with participants with no history of head injury.

Conclusions and Relevance

Findings of this cohort study provide evidence supporting the association between head injury and olfactory dysfunction, particularly among individuals who experienced multiple prior head injuries and among individuals with more severe head injury. The findings also suggest that individuals with prior head injury were more likely to both under-self-report and over-self-report deficits compared with objective olfactory testing; therefore, it may be important to consider objective olfactory testing in this patient population.

Selective Inhibitory Circuit Dysfunction after Chronic Frontal Lobe Contusion

Traumatic brain injury (TBI) is a leading cause of neurologic disability; the most common deficits affect prefrontal cortex-dependent functions such as attention, working memory, social behavior, and mental flexibility. Despite this prevalence, little is known about the pathophysiology that develops in frontal cortical microcircuits after TBI. We investigated whether alterations in subtype-specific inhibitory circuits are associated with cognitive inflexibility in a mouse model of frontal lobe contusion in both male and female mice that recapitulates aberrant mental flexibility as measured by deficits in rule reversal learning. Using patch-clamp recordings and optogenetic stimulation, we identified selective vulnerability in the non-fast-spiking and somatostatin-expressing (SOM+) subtypes of inhibitory neurons in layer V of the orbitofrontal cortex 2 months after injury. These subtypes exhibited reduced intrinsic excitability and a decrease in their synaptic output onto pyramidal neurons, respectively. By contrast, the fast-spiking and parvalbumin-expressing interneurons did not show changes in intrinsic excitability or synaptic output, respectively. Impairments in non-fast-spiking/SOM+ inhibitory circuit function were also associated with network hyperexcitability. These findings provide evidence for selective disruptions within specific inhibitory microcircuits that may guide the development of novel therapeutics for TBI.SIGNIFICANCE STATEMENT TBI frequently leads to chronic deficits in cognitive and behavioral functions that involve the prefrontal cortex, yet the maladaptive changes that occur in these cortical microcircuits are unknown. Our data indicate that alterations in subtype-specific inhibitory circuits, specifically vulnerability in the non-fast-spiking/somatostatin-expressing interneurons, occurs in the orbitofrontal cortex in the context of chronic deficits in reversal learning. These neurons exhibit reduced excitability and synaptic output, whereas the other prominent inhibitory population in layer V, the fast-spiking/parvalbumin-expressing interneurons as well as pyramidal neurons are not affected. Our work offers mechanistic insight into the subtype-specific function of neurons that may contribute to mental inflexibility after TBI.

Financial decision-making and self-awareness for financial decision-making is associated with white matter integrity in older adults

Financial decision-making (FDM) and awareness of the integrity of one's FDM abilities (or financial awareness) are both critical for preventing financial mistakes. We examined the white matter correlates of these constructs and hypothesized that the tracts connecting the temporal-frontal regions would be most strongly correlated with both FDM and financial awareness. Overall, 49 healthy older adults were included in the FDM analysis and 44 in the financial awareness analyses. The Objective Financial Competency Assessment Inventory was used to measure FDM. Financial awareness was measured by integrating metacognitive ratings into this inventory and was calculated as the degree of overconfidence or underconfidence. Diffusion tensor imaging data were processed with Tracts Constrained by Underlying Anatomy distributed as part of the FreeSurfer analytic suite, which produced average measures of fractional anisotropy and mean diffusivity in 18 white matter tracts along with the overall tract average. As expected, FDM showed the strongest negative associations with average mean diffusivity measure of the superior longitudinal fasciculus -temporal (SLFT; r = -.360, p = .011) and -parietal (r = -.351, p = .014) tracts. After adjusting for FDM, only the association between financial awareness and average mean diffusivity measure of the right SLFT (r = .310, p = .046) was significant. Overlapping white matter tracts were involved in both FDM and financial awareness. More importantly, these preliminary findings reinforce emerging literature on a unique role of right hemisphere temporal connections in supporting financial awareness.

Differences in Performance of ASD and ADHD Subjects Facing Cognitive Loads in an Innovative Reasoning Experiment

We aim to investigate whether EEG dynamics differ in adults with ASD (Autism Spectrum Disorders) and ADHD (attention-deficit/hyperactivity disorder) compared with healthy subjects during the performance of an innovative cognitive task, Aristotle's valid and invalid syllogisms, and how these differences correlate with brain regions and behavioral data for each subject. We recorded EEGs from 14 scalp electrodes (channels) in 21 adults with ADHD, 21 with ASD, and 21 healthy, normal subjects. The subjects were exposed in a set of innovative cognitive tasks (inducing varying cognitive loads), Aristotle's two types of syllogism mentioned above. A set of 39 questions were given to participants related to valid-invalid syllogisms as well as a separate set of questionnaires, in order to collect a number of demographic and behavioral data, with the aim of detecting shared information with values of a feature extracted from EEG, the multiscale entropy (MSE), in the 14 channels ('brain regions'). MSE, a nonlinear information-theoretic measure of complexity, was computed to extract a feature that quantifies the complexity of the EEG. Behavior-Partial Least Squares Correlation, PLSC, is the method to detect the correlation between two sets of data, brain, and behavioral measures. -PLSC, a variant of PLSC, was applied to build a functional connectivity of the brain regions involved in the reasoning tasks. Graph-theoretic measures were used to quantify the complexity of the functional networks. Based on the results of the analysis described in this work, a mixed 14 × 2 × 3 ANOVA showed significant main effects of group factor and brain region* syllogism factor, as well as a significant brain region* group interaction. There are significant differences between the means of MSE (complexity) values at the 14 channels of the members of the 'pathological' groups of participants, i.e., between ASD and ADHD, while the difference in means of MSE between both ASD and ADHD and that of the control group is not significant. In conclusion, the valid-invalid type of syllogism generates significantly different complexity values, MSE, between ASD and ADHD. The complexity of activated brain regions of ASD participants increased significantly when switching from a valid to an invalid syllogism, indicating the need for more resources to 'face' the task escalating difficulty in ASD subjects. This increase is not so evident in both ADHD and control. Statistically significant differences were found also in the behavioral response of ASD and ADHD, compared with those of control subjects, based on the principal brain and behavior saliences extracted by PLSC. Specifically, two behavioral measures, the emotional state and the degree of confidence of participants in answering questions in Aristotle's valid-invalid syllogisms, and one demographic variable, age, statistically and significantly discriminate the three groups' ASD. The seed-PLC generated functional connectivity networks for ASD, ADHD, and control, were 'projected' on the regions of the Default Mode Network (DMN), the 'reference' connectivity, of which the structural changes were found significant in distinguishing the three groups. The contribution of this work lies in the examination of the relationship between brain activity and behavioral responses of healthy and 'pathological' participants in the case of cognitive reasoning of the type of Aristotle's valid and invalid syllogisms, using PLSC, a machine learning approach combined with MSE, a nonlinear method of extracting a feature based on EEGs that captures a broad spectrum of EEGs linear and nonlinear characteristics. The results seem promising in adopting this type of reasoning, in the future, after further enhancements and experimental tests, as a supplementary instrument towards examining the differences in brain activity and behavioral responses of ASD and ADHD patients. The application of the combination of these two methods, after further elaboration and testing as new and complementary to the existing ones, may be considered as a tool of analysis in helping detecting more effectively such types of disorders.

Emotion Recognition and Traffic-Related Risk-Taking Behavior in Patients with Neurodegenerative Diseases

OBJECTIVES

Neurodegenerative diseases (NDDs), such as Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, and Huntington's disease, inevitably lead to impairments in higher-order cognitive functions, including the perception of emotional cues and decision-making behavior. Such impairments are likely to cause risky daily life behavior, for instance, in traffic. Impaired recognition of emotional expressions, such as fear, is considered a marker of impaired experience of emotions. Lower fear experience can, in turn, be related to risk-taking behavior. The aim of our study was to investigate whether impaired emotion recognition in patients with NDD is indeed related to unsafe decision-making in risky everyday life situations, which has not been investigated yet.

METHODS

Fifty-one patients with an NDD were included. Emotion recognition was measured with the Facial Expressions of Emotions: Stimuli and Test (FEEST). Risk-taking behavior was measured with driving simulator scenarios and the Action Selection Test (AST). Data from matched healthy controls were used: FEEST (n = 182), AST (n = 36), and driving simulator (n = 18).

RESULTS

Compared to healthy controls, patients showed significantly worse emotion recognition, particularly of anger, disgust, fear, and sadness. Furthermore, patients took significantly more risks in the driving simulator rides and the AST. Only poor recognition of fear was related to a higher amount of risky decisions in situations involving a direct danger.

CONCLUSIONS

To determine whether patients with an NDD are still fit to drive, it is crucial to assess their ability to make safe decisions. Measuring emotion recognition may be a valuable contribution to this judgment.

Theory of mind in adults with traumatic brain injury: A meta-analysis

Studies of abnormal theory of mind (ToM) performance in adult patients with traumatic brain injury (TBI) have reported inconsistent results. Therefore, we conducted a meta-analysis to characterize ToM performance in adult patients with TBI. Random-effects models were employed to estimate the overall effect size and the differential effect sizes across different ToM aspects. Based on a sample of 28 studies (1031 patients and 865 healthy controls), the meta-analytic findings revealed that ToM was significantly impaired in adult patients with TBI compared to healthy controls (g = -1.13). Besides, patients with TBI showed significant impairments in individual ToM tasks, as well as for different stimulus modes and contents involved in these ToM tasks. A meta-regression indicated a positive association between ToM performance and Glasgow Coma Scale score. The results of the current meta-analysis suggest that the performance in ToM tasks may be a good predictor of functional outcomes in adults with TBI, which is important for the identification of targets for cognitive interventions and the development of useful training intervention programs.

Individuals With Autism Spectrum Disorder Show Altered Event-Related Potentials in the Late Stages of Olfactory Processing

Atypical sensory reactivities are pervasive among people with autism spectrum disorder (ASD). With respect to olfaction, most previous studies have used psychophysical or questionnaire-based methodologies; thus, the neural basis of olfactory processing in ASD remains unclear. This study aimed to determine the stages of olfactory processing that are altered in ASD. Fourteen young adults with high-functioning ASD (mean age, 21 years; 3 females) were compared with 19 age-matched typically developing (TD) controls (mean age, 21 years; 4 females). Olfactory event-related potentials (OERPs) for 2-phenylethyl alcohol-a rose-like odor-were measured with 64 scalp electrodes while participants performed a simple odor detection task. Significant group differences in OERPs were found in 3 time windows 542 ms after the stimulus onset. The cortical source activities in these time windows, estimated using standardized low-resolution brain electromagnetic tomography, were significantly higher in ASD than in TD in and around the posterior cingulate cortex, which is known to play a crucial role in modality-general cognitive processing. Supplemental Bayesian analysis provided substantial evidence for an alteration in the later stages of olfactory processing, whereas conclusive evidence was not provided for the earlier stages. These results suggest that olfactory processing in ASD is altered at least at the later, modality-general processing stage.

Age, but not severity of injury, mediates decline in executive function: Validation of the rodent touchscreen paradigm for preclinical models of traumatic brain injury

Increasingly, it is being recognised that traumatic brain injury (TBI) is not just an acute event but instead results in ongoing neuronal injury that may lead to chronic impairments in multiple cognitive domains. Of these, deficits in executive function are one of the more common changes reported following TBI, and are a major predictor of well-being, social function and quality of life in individuals with a history of TBI. In order to fully understand the relationship between TBI and executive dysfunction, including brain mechanisms that may account for this, experimental models are clearly needed. However, to date, there have been a lack of preclinical studies systematically comparing the effect of injury severity on executive function, particularly at long-term timepoints post-injury. Furthermore, many previous studies have not used behavioural measures that are sensitive to the full range of executive function impairments that may manifest after injury, particularly in models of diffuse axonal injury (Lv et al.). The current study aimed to investigate the temporal profile, up to 12 months post-injury, of the evolution of executive dysfunction following different severities of injury in an experimental model of DAI. In order to do so, we utilised a rodent touchscreen paradigm to administer the 5 Choice- Continuous Performance Task (5C-CPT), an extension of the 5-choice serial reaction time task (5CSRT). Interestingly, there were no differences in learning, motivation, attention, response time or impulsivity at 1 month, 6 months or 12 months post-injury in any of the TBI groups compared to sham, regardless of the initial severity of the injury. Instead, most of the effects on executive function seen at the 12 month timepoint appeared to be a result of ageing, not injury. As even the 12-month timepoint represents middle age in the rat, future studies will be needed to further probe these effects, in order to determine whether DAI may influence the presentation of executive dysfunction in older age.

The role of conflict, feedback, and action comprehension in monitoring of action errors: Evidence for internal and external routes

The mechanisms and brain regions underlying error monitoring in complex action are poorly understood, yet errors and impaired error correction in these tasks are hallmarks of apraxia, a common disorder associated with left hemisphere stroke. Accounts of monitoring of language posit an internal route by which production planning or competition between candidate representations provide predictive signals that monitoring is required to prevent error, and an external route in which output is monitored using the comprehension system. Abnormal reliance on the external route has been associated with damage to brain regions critical for sensory-motor transformation and a pattern of gradual error 'clean-up' called conduite d'approche (CD). Action pantomime data from 67 participants with left hemisphere stroke were consistent with versions of internal route theories positing that competition signals monitoring requirements. Support Vector Regression Lesion Symptom Mapping (SVR-LSM) showed that lesions in the inferior parietal, posterior temporal, and arcuate fasciculus/superior longitudinal fasciculus predicted action conduite d'approche, overlapping the regions previously observed in the language domain. A second experiment with 12 patients who produced substantial action CD assessed whether factors impacting the internal route (action production ability, competition) versus external route (vision of produced actions, action comprehension) influenced correction attempts. In these 'high CD' patients, vision of produced actions and integrity of gesture comprehension interacted to determine successful error correction, supporting external route theories. Viewed together, these and other data suggest that skilled actions are monitored both by an internal route in which conflict aids in detection and correction of errors during production planning, and an external route that detects mismatches between produced actions and stored knowledge of action appearance. The parallels between language and action monitoring mechanisms and neuroanatomical networks pave the way for further exploration of common and distinct processes across these domains.

The influence of head injury on olfactory and gustatory function

Head injury, particularly that resulting in brain injury, is a significant public health concern. For example, annual incidence rates of traumatic brain injury, a common consequence of head injury, range from 54 to 60 million people worldwide, including 2.2-3.6 million people whose trauma is moderate to severe. Trauma to the face and brain, including blast injuries common in modern warfare, can result in alterations in the ability to both smell and taste. In the case of smell, these include total loss of function (anosmia), decreased sensitivity (hyposmia), alterations in odor quality (dysosmia), and hallucination (phantosmia). Although taste dysfunction, i.e., altered perception of such basic taste-bud-mediated sensations as sweet, sour, bitter, salty, and savory (umami), can be similarly influenced by head trauma, the effects are typically more subtle and less studied. The present review provides an up-to-date assessment of what is known about the impact of head injury on quantitative measures of taste and smell function, including the influences of severity, type of injury, location of insults, prognosis, and approaches to therapy.

Emotion recognition depends on subjective emotional experience and not on facial expressivity: evidence from traumatic brain injury

BACKGROUND

Recognizing how others feel is paramount to social situations and commonly disrupted following traumatic brain injury (TBI). This study tested whether problems identifying emotion in others following TBI is related to problems expressing or feeling emotion in oneself, as theoretical models place emotion perception in the context of accurate encoding and/or shared emotional experiences.

METHODS

Individuals with TBI (n = 27; 20 males) and controls (n = 28; 16 males) were tested on an emotion recognition task, and asked to adopt facial expressions and relay emotional memories according to the presentation of stimuli (word and photos). After each trial, participants were asked to self-report their feelings of happiness, anger and sadness. Judges that were blind to the presentation of stimuli assessed emotional facial expressivity.

RESULTS

Emotional experience was a unique predictor of affect recognition across all emotions while facial expressivity did not contribute to any of the regression models. Furthermore, difficulties in recognizing emotion for individuals with TBI were no longer evident after cognitive ability and experience of emotion were entered into the analyses.

CONCLUSIONS

Emotion perceptual difficulties following TBI may stem from an inability to experience affective states and may tie in with alexythymia in clinical conditions.

Perceived personality change after traumatic brain injury II: comparing participant and informant perspectives

OBJECTIVE

The objective of this paper was to correlate informant personality change (PC) judgements following moderate-severe traumatic brain injury with quantitative neurobehavioural measures and to contrast the neurobehavioural correlates of informant and participant judgements of PC.

PARTICIPANTS

Informant-participant pairs were recruited from a medico-legal clinic passing effort tests (N = 31) and a National Health Service clinic (N = 40).

MEASURES

Participants were assessed on Wechsler tests of general ability, tests of executive functioning (Zoo Map and Fluency) and emotional distress (Beck Depression Inventory-FastScreen, Hospital Anxiety and Depression Scale and State-Trait Anger Expression Inventory-II). Informants' expressed emotion towards participants was assessed with the family questionnaire. Both completed the DEX, the Frontal and Social Behavior Questionnaire and PC ratings.

RESULTS

The correlates of participant and informant ratings of participant PC partially overlapped. For example, participant self-reported PC was associated with self-reported dysexecutive symptoms and emotional distress. In contrast, informant report of participant PC was associated with lower perceived emotional recognition and empathy, informant report of dysexecutive symptoms and high informant expressed emotion.

CONCLUSIONS

It is argued that whilst researchers aim to exhaustively quantify specific neurobehavioural changes and their clusters, partially overlapping subsets of these changes evoke the PC judgements of participants and informants. The clinical implications of this are briefly considered.

Inter-Subject Variability of Axonal Injury in Diffuse Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of cognitive morbidity worldwide for which reliable biomarkers are needed. Diffusion tensor imaging (DTI) is a promising biomarker of traumatic axonal injury (TAI); however, existing studies have been limited by a primary reliance on group-level analytic methods not well suited to account for inter-subject variability. In this study, 42 adults with TBI of at least moderate severity were examined 3 months following injury and compared with 35 healthy controls. DTI data were used for both traditional group-level comparison and subject-specific analysis using the distribution-corrected Z-score (DisCo-Z) approach. Inter-subject variation in TAI was assessed in a threshold-invariant manner using a threshold-weighted overlap map derived from subject-specific analysis. Receiver operator curve analysis was used to examine the ability of subject-specific DTI analysis to identify TBI subjects with significantly impaired processing speed in comparison with region of interest-based fractional anisotropy (FA) measurements and clinical characteristics. Traditional group-wise analysis demonstrated widespread reductions of white matter FA within the TBI group (voxel-wise p < 0.05, corrected), despite relatively low consistency of subject-level effects secondary to widespread variation in the spatial distribution of TAI. Subject-specific mapping of TAI with the DisCo-Z approach was the best predictor of impaired processing speed, achieving high classification accuracy (area under the curve [AUC] = 0.94). In moderate-to-severe TBI, there is substantial inter-subject variation in TAI, with extent strongly correlated to post-traumatic deficits in processing speed. Significant group-level effects do not necessarily represent consistent effects at the individual level. Better accounting for inter-subject variability in neurobiological manifestations of TBI may substantially improve the ability to detect and classify patterns of injury.

The Bangor Gambling Task: Characterising the Performance of Survivors of Traumatic Brain Injury

The Bangor Gambling Task (BGT, Bowman & Turnbull, 2004) is a simple test of emotion-based decision making, with contingencies varying across five blocks of 20 trials. This is the first study to characterise BGT performance in survivors of traumatic brain injury (TBI) relative to healthy controls. The study also aimed to explore sub-groups (cluster analysis), and identify predictors of task performance (multiple regression). Thirty survivors of TBI and thirty-nine controls completed the BGT and measures of processing speed, pre-morbid IQ, working memory, and executive function. Results showed that survivors of TBI made more gamble choices than controls (total BGT score), although the groups did not significantly differ when using a cut-off score for ‘impaired’ performance. Unexpectedly, the groups did not significantly differ in their performance across the blocks; however, the cluster analysis revealed three subgroups (with survivors of TBI and controls represented in each cluster). Findings also indicated that only age and group were significant predictors of overall BGT performance. In conclusion, the study findings are consistent with an individual difference account of emotion-based decision making, and a number of issues need to be addressed prior to recommending the clinical use of the BGT.

Autobiographical memory and structural brain changes in chronic phase TBI

Traumatic brain injury (TBI) is associated with a range of neuropsychological deficits, including attention, memory, and executive functioning attributable to diffuse axonal injury (DAI) with accompanying focal frontal and temporal damage. Although the memory deficit of TBI has been well characterized with laboratory tests, comparatively little research has examined retrograde autobiographical memory (AM) at the chronic phase of TBI, with no prior studies of unselected patients drawn directly from hospital admissions for trauma. Moreover, little is known about the effects of TBI on canonical episodic and non-episodic (e.g., semantic) AM processes. In the present study, we assessed the effects of chronic-phase TBI on AM in patients with focal and DAI spanning the range of TBI severity. Patients and socioeconomic- and age-matched controls were administered the Autobiographical Interview (AI) (Levine, Svoboda, Hay, Winocur, & Moscovitch, 2002) a widely used method for dissociating episodic and semantic elements of AM, along with tests of neuropsychological and functional outcome. Measures of episodic and non-episodic AM were compared with regional brain volumes derived from high-resolution structural magnetic resonance imaging (MRI). Severe TBI (but not mild or moderate TBI) was associated with reduced recall of episodic autobiographical details and increased recall of non-episodic details relative to healthy comparison participants. There were no significant associations between AM performance and neuropsychological or functional outcome measures. Within the full TBI sample, autobiographical episodic memory was associated with reduced volume distributed across temporal, parietal, and prefrontal regions considered to be part of the brain's AM network. These results suggest that TBI-related distributed volume loss affects episodic autobiographical recollection.

To Fear Is to Gain? The Role of Fear Recognition in Risky Decision Making in TBI Patients and Healthy Controls

Fear is an important emotional reaction that guides decision making in situations of ambiguity or uncertainty. Both recognition of facial expressions of fear and decision making ability can be impaired after traumatic brain injury (TBI), in particular when the frontal lobe is damaged. So far, it has not been investigated how recognition of fear influences risk behavior in healthy subjects and TBI patients. The ability to recognize fear is thought to be related to the ability to experience fear and to use it as a warning signal to guide decision making. We hypothesized that a better ability to recognize fear would be related to a better regulation of risk behavior, with healthy controls outperforming TBI patients. To investigate this, 59 healthy subjects and 49 TBI patients were assessed with a test for emotion recognition (Facial Expression of Emotion: Stimuli and Tests) and a gambling task (Iowa Gambling Task (IGT)). The results showed that, regardless of post traumatic amnesia duration or the presence of frontal lesions, patients were more impaired than healthy controls on both fear recognition and decision making. In both groups, a significant relationship was found between better fear recognition, the development of an advantageous strategy across the IGT and less risk behavior in the last blocks of the IGT. Educational level moderated this relationship in the final block of the IGT. This study has important clinical implications, indicating that impaired decision making and risk behavior after TBI can be preceded by deficits in the processing of fear.

Improving Traumatic Brain Injury Outcomes: The Development of an Evaluation and Referral Tool at Groote Schuur Hospital

BACKGROUND

The Western Cape Province of South Africa has a great shortage of diagnostic expertise, rehabilitative infrastructure, and support services for patients with traumatic brain injury (TBI). The neurosurgical outpatient setting is busy and often chaotic, and patients are frequently lost to follow-up. This study sought to continue with the design and development of a comprehensive, yet brief tool to aid patient referrals and ensure that no consequence of TBI is left unidentified and unaddressed.

METHODS

There were 47 patients with TBI (mean age, 35 years; range, 18-75 years) assessed. The study was designed in 3 distinct phases, each representing a different stage in the tool's development.

RESULTS

The Groote Schuur Traumatic Brain Injury Evaluation was shortened and simplified. Overall, 81% of the participants indicated cognitive dysfunction. There was a high prevalence of psychological/psychiatric sequelae, with 85% of participants reporting at least 1 such problem.

CONCLUSIONS

The findings further highlight the prevalence of the cognitive, behavioral, and psychological consequences of TBI and shed additional light on the particular types of problems that patients with TBI face. Following the identified changes, the questionnaire and algorithm combination are now ready to be validated in the neurosurgical clinical setting.

Exploration of correlates of self-reported personality change after moderate-severe traumatic brain injury

OBJECTIVE

Individuals with traumatic brain injury (TBI) often express concern that their personality has changed. Factors generating that conclusion are rarely explored quantitatively. Accordingly, this study examines neurobehavioural correlates of self-reported personality change.

METHODS

Seventy-one participants and informants were interviewed M = 57.9 (SD = 46.9) months after a moderate-severe TBI. The degree of self-reported personality change was correlated with scores on measures of general cognitive functioning, executive functioning, olfaction, social-emotional behaviour, emotional distress and the Expressed Emotion close informants directed towards them.

RESULTS

As expected, self-reported personality change correlated with dysexecutive symptoms and depression. Although anosmia (a putative index of ventral frontal damage) correlated with reduced self-reported emotional recognition and empathy, against prediction, the latter measures did not correlate with self-reported personality change. Neither were the predicted positive correlations found between high Expressed Emotion (criticism and emotional over-involvement) and self-reported personality change.

DISCUSSION

These findings are discussed in the context of previous work. A need to replicate and extend the present findings is suggested. A strategy to further clarify the relationships perceived personality change have with (a) self-reported change in specific behaviours and (b) identity change is advocated. Implications for intervention are suggested.

Olfactory Function and Associated Clinical Correlates in Former National Football League Players

Professional American football players incur thousands of repetitive head impacts (RHIs) throughout their lifetime. The long-term consequences of RHI are not well characterized, but may include olfactory dysfunction. RHI has been associated with changes to brain regions involved in olfaction, and olfactory impairment is common after traumatic brain injury. Olfactory dysfunction is a frequent early sequelae of neurodegenerative diseases (e.g., Alzheimer's disease), and RHI is associated with the neurodegenerative disease, chronic traumatic encephalopathy (CTE). We examined olfaction, and its association with clinical measures, in former National Football League (NFL) players. Ninety-five former NFL players (ages 40-69) and 28 same-age controls completed a neuropsychological and neuropsychiatric evaluation as part of a National Institutes of Health-funded study. The Brief Smell Identification Test (B-SIT) assessed olfaction. Principal component analysis generated a four-factor structure of the clinical measures: behavioral/mood, psychomotor speed/executive function, and verbal and visual memory. Former NFL players had worse B-SIT scores relative to controls (p = 0.0096). A B-SIT cutoff of 11 had the greatest accuracy (c-statistic = 0.61) and specificity (79%) for discriminating former NFL players from controls. In the former NFL players, lower B-SIT scores correlated with greater behavioral/mood impairment (p = 0.0254) and worse psychomotor speed/executive functioning (p = 0.0464) after controlling for age and education. Former NFL players exhibited lower olfactory test scores relative to controls, and poorer olfactory test performance was associated with worse neuropsychological and neuropsychiatric functioning. Future work that uses more-comprehensive tests of olfaction and structural and functioning neuroimaging may improve understanding on the association between RHI and olfaction.

Frontal Lobe Contusion in Mice Chronically Impairs Prefrontal-Dependent Behavior

Traumatic brain injury (TBI) is a major cause of chronic disability in the world. Moderate to severe TBI often results in damage to the frontal lobe region and leads to cognitive, emotional, and social behavioral sequelae that negatively affect quality of life. More specifically, TBI patients often develop persistent deficits in social behavior, anxiety, and executive functions such as attention, mental flexibility, and task switching. These deficits are intrinsically associated with prefrontal cortex (PFC) functionality. Currently, there is a lack of analogous, behaviorally characterized TBI models for investigating frontal lobe injuries despite the prevalence of focal contusions to the frontal lobe in TBI patients. We used the controlled cortical impact (CCI) model in mice to generate a frontal lobe contusion and studied behavioral changes associated with PFC function. We found that unilateral frontal lobe contusion in mice produced long-term impairments to social recognition and reversal learning while having only a minor effect on anxiety and completely sparing rule shifting and hippocampal-dependent behavior.

Old wine in new bottles: validating the clinical utility of SPECT in predicting cognitive performance in mild traumatic brain injury

The neural underpinnings of cognitive dysfunction in mild traumatic brain injury (TBI) are not fully understood. Consequently, patient prognosis using existing clinical imaging is somewhat imprecise. Single photon emission computed tomography (SPECT) is a frequently employed investigation in this population, notwithstanding uncertainty over the clinical utility of the data obtained. In this study, subjects with mild TBI underwent (99m)Tc-ECD SPECT scanning, and were administered a brief battery of cognitive tests and self-report symptom scales of concussion and emotional distress. Testing took place 2 weeks (n=84) and 1 year (n=49) post-injury. Multivariate analysis (i.e., partial least squares analysis) revealed that frontal perfusion in right superior frontal and middle frontal gyri predicted poorer performance on the Stroop test, an index of executive function, both at initial and follow-up testing. Conversely, SPECT scans categorized as normal or abnormal by radiologists did not differentiate cognitively impaired from intact subjects. These results demonstrate the clinical utility of SPECT in mild TBI, but only when data are subjected to blood flow quantification analysis.

Intact alternation performance in high lethality suicide attempters

Suicide attempters often perform poorly on tasks linked to ventral prefrontal cortical (VPFC) function. Object Alternation (OA) - a VPFC probe - has not been used in these studies. In this study, currently depressed medication-free past suicide attempters whose most severe attempt was of high (n=31) vs. low (n=64) lethality, 114 medication-free depressed non-attempters, and 86 non-patients completed a computerized OA task. Participants also completed comparison tasks assessing the discriminant validity of OA (Wisconsin Card Sort), its concurrent validity relative to tasks associated with past attempt status (computerized Stroop task, Buschke Selective Reminding Test), and its construct validity as a VPFC measure (Go-No Go and Iowa Gambling Task). Against expectations, high lethality suicide attempters - the majority of whom used non-violent methods in their attempts with some planning - outperformed other depressed groups on OA, with no group differences observed on Wisconsin Card Sort. Despite intact performance on OA, past attempters exhibited deficits on the Stroop and Buschke. OA performance was associated with performance on Go-No Go and Iowa Gambling, confirming that OA measures a similar construct. VPFC dysfunction may not be a characteristic of all suicide attempters, especially those who make more carefully planned, non-violent - though potentially lethal - attempts.

The rich get richer: brain injury elicits hyperconnectivity in core subnetworks

There remains much unknown about how large-scale neural networks accommodate neurological disruption, such as moderate and severe traumatic brain injury (TBI). A primary goal in this study was to examine the alterations in network topology occurring during the first year of recovery following TBI. To do so we examined 21 individuals with moderate and severe TBI at 3 and 6 months after resolution of posttraumatic amnesia and 15 age- and education-matched healthy adults using functional MRI and graph theoretical analyses. There were two central hypotheses in this study: 1) physical disruption results in increased functional connectivity, or hyperconnectivity, and 2) hyperconnectivity occurs in regions typically observed to be the most highly connected cortical hubs, or the "rich club". The current findings generally support the hyperconnectivity hypothesis showing that during the first year of recovery after TBI, neural networks show increased connectivity, and this change is disproportionately represented in brain regions belonging to the brain's core subnetworks. The selective increases in connectivity observed here are consistent with the preferential attachment model underlying scale-free network development. This study is the largest of its kind and provides the unique opportunity to examine how neural systems adapt to significant neurological disruption during the first year after injury.

Object alternation: a novel probe of medial frontal function in frontotemporal dementia

We studied behavioral variant frontotemporal dementia (bvFTD) using object alternation (OA) as a novel probe of cognition. This task was adopted from animal models and is sensitive to ventrolateral-orbitofrontal and medial frontal function in humans. OA was administered to bvFTD patients, normal controls, and a dementia control group with Alzheimer disease (AD). Two other frontal lobe measures adopted from animal models were administered: delayed response (DR) and delayed alternation (DA). Brain volumes were measured using the semiautomatic brain region extraction method. Compared with the normal controls, bvFTD patients were significantly impaired on OA and DR. For OA and DR, sensitivities and specificities were 100% and 51.5% (cutoff=22.5 errors) and 9.5% and 98% (cutoff=1.5 errors), respectively. Negative predictive value (NPV) for OA was 100% at all prevalence rates. Comparing AD with bvFTD, there were no significant differences on OA, DR, or DA. Nevertheless, positive predictive value (PPV) and NPV were good at all prevalence rates for OA (cutoff=36.5 errors) and DA (cutoff=6 errors); PPV was good for DR (cutoff=9 errors). Error scores above cutoffs favored diagnosis of AD. Performance on OA was significantly related to medial frontal gray matter atrophy. OA, together with DR and DA, may facilitate assessment of bvFTD as a novel probe of medial frontal function.

Who benefits from treatment for executive dysfunction after brain injury? Negative effects of emotion recognition deficits

Deficits in emotion recognition, a crucial aspect of social cognition, are common after serious brain injury, as are executive deficits. Since social cognition and executive function are considered to be separate constructs, our first aim was to examine the presence of emotion recognition problems in brain injury patients with dysexecutive problems. We studied 65 brain injury patients of mixed aetiology participating in a randomised controlled trial evaluating the effects of a multifaceted treatment for executive dysfunction (Spikman, Boelen, Lamberts, Brouwer, & Fasotti, 2010 ) and 84 matched controls with a test for emotion recognition. Results showed that, in patients with acquired brain injury exhibiting executive deficits, emotion recognition deficits are also present. Male patients are more impaired than female patients, irrespective of aetiology. Our second aim was to investigate whether emotion recognition problems negatively predict the results of the treatment programme. Pre-treatment emotion recognition performance significantly predicted resumption of roles in daily life (Role Resumption List; RRL) and performance on an ecologically valid test for everyday executive functioning (Executive Secretarial Task; EST) post-treatment and, in addition, interfered negatively with treatment condition. Moreover, worse pre-treatment emotion recognition skills affect the learning of compensatory strategies for executive dysfunction negatively, whereas pre-treatment dysexecutive deficits do not.

Deficits in facial emotion recognition indicate behavioral changes and impaired self-awareness after moderate to severe traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of disability, specifically among younger adults. Behavioral changes are common after moderate to severe TBI and have adverse consequences for social and vocational functioning. It is hypothesized that deficits in social cognition, including facial affect recognition, might underlie these behavioral changes. Measurement of behavioral deficits is complicated, because the rating scales used rely on subjective judgement, often lack specificity and many patients provide unrealistically positive reports of their functioning due to impaired self-awareness. Accordingly, it is important to find performance based tests that allow objective and early identification of these problems. In the present study 51 moderate to severe TBI patients in the sub-acute and chronic stage were assessed with a test for emotion recognition (FEEST) and a questionnaire for behavioral problems (DEX) with a self and proxy rated version. Patients performed worse on the total score and on the negative emotion subscores of the FEEST than a matched group of 31 healthy controls. Patients also exhibited significantly more behavioral problems on both the DEX self and proxy rated version, but proxy ratings revealed more severe problems. No significant correlation was found between FEEST scores and DEX self ratings. However, impaired emotion recognition in the patients, and in particular of Sadness and Anger, was significantly correlated with behavioral problems as rated by proxies and with impaired self-awareness. This is the first study to find these associations, strengthening the proposed recognition of social signals as a condition for adequate social functioning. Hence, deficits in emotion recognition can be conceived as markers for behavioral problems and lack of insight in TBI patients. This finding is also of clinical importance since, unlike behavioral problems, emotion recognition can be objectively measured early after injury, allowing for early detection and treatment of these problems.

Quantified MRI and cognition in TBI with diffuse and focal damage☆

In patients with chronic-phase traumatic brain injury (TBI), structural MRI is readily attainable and provides rich anatomical information, yet the relationship between whole-brain structural MRI measures and neurocognitive outcome is relatively unexplored and can be complicated by the presence of combined focal and diffuse injury. In this study, sixty-three patients spanning the full range of TBI severity received high-resolution structural MRI concurrent with neuropsychological testing. Multivariate statistical analysis assessed covariance patterns between volumes of grey matter, white matter, and sulcal/subdural and ventricular CSF across 38 brain regions and neuropsychological test performance. Patients with diffuse and diffuse + focal injury were analyzed both separately and together. Tests of speeded attention, working memory, and verbal learning and memory robustly covaried with a distributed pattern of volume loss over temporal, ventromedial prefrontal, right parietal regions, and cingulate regions. This pattern was modulated by the presence of large focal lesions, but held even when analyses were restricted to those with diffuse injury. Effects were most consistently observed within grey matter. Relative to regional brain volumetric data, clinically defined injury severity (depth of coma at time of injury) showed only weak relation to neuropsychological outcome. The results showed that neuropsychological test performance in patients with TBI is related to a distributed pattern of volume loss in regions mediating mnemonic and attentional processing. This relationship holds for patients with and without focal lesions, indicating that diffuse injury alone is sufficient to cause significant neuropsychological disability in relation to regional volume loss. Quantified structural brain imaging data provides a highly sensitive index of brain integrity that is related to cognitive functioning in chronic phase TBI.

Implicit olfactory abilities in traumatic brain injured patients

To investigate implicit olfactory abilities in a group of anosmic traumatic brain injured (TBI) patients, an olfactomotor priming paradigm was administered. A group of matched normosmic/mildly microsmic TBI patients and a group of neurologically healthy participants served as controls. For all the groups, an interference effect was evident on the peak velocity of grip aperture when participants grasped a large target preceded by a "small" odor. The present results suggest that some form of implicit olfactory processing is preserved in TBI patients even when diagnosed as anosmic on the basis of explicit olfactory testing.

A review of magnetic resonance imaging and diffusion tensor imaging findings in mild traumatic brain injury

Mild traumatic brain injury (mTBI), also referred to as concussion, remains a controversial diagnosis because the brain often appears quite normal on conventional computed tomography (CT) and magnetic resonance imaging (MRI) scans. Such conventional tools, however, do not adequately depict brain injury in mTBI because they are not sensitive to detecting diffuse axonal injuries (DAI), also described as traumatic axonal injuries (TAI), the major brain injuries in mTBI. Furthermore, for the 15 to 30 % of those diagnosed with mTBI on the basis of cognitive and clinical symptoms, i.e., the "miserable minority," the cognitive and physical symptoms do not resolve following the first 3 months post-injury. Instead, they persist, and in some cases lead to long-term disability. The explanation given for these chronic symptoms, i.e., postconcussive syndrome, particularly in cases where there is no discernible radiological evidence for brain injury, has led some to posit a psychogenic origin. Such attributions are made all the easier since both posttraumatic stress disorder (PTSD) and depression are frequently co-morbid with mTBI. The challenge is thus to use neuroimaging tools that are sensitive to DAI/TAI, such as diffusion tensor imaging (DTI), in order to detect brain injuries in mTBI. Of note here, recent advances in neuroimaging techniques, such as DTI, make it possible to characterize better extant brain abnormalities in mTBI. These advances may lead to the development of biomarkers of injury, as well as to staging of reorganization and reversal of white matter changes following injury, and to the ability to track and to characterize changes in brain injury over time. Such tools will likely be used in future research to evaluate treatment efficacy, given their enhanced sensitivity to alterations in the brain. In this article we review the incidence of mTBI and the importance of characterizing this patient population using objective radiological measures. Evidence is presented for detecting brain abnormalities in mTBI based on studies that use advanced neuroimaging techniques. Taken together, these findings suggest that more sensitive neuroimaging tools improve the detection of brain abnormalities (i.e., diagnosis) in mTBI. These tools will likely also provide important information relevant to outcome (prognosis), as well as play an important role in longitudinal studies that are needed to understand the dynamic nature of brain injury in mTBI. Additionally, summary tables of MRI and DTI findings are included. We believe that the enhanced sensitivity of newer and more advanced neuroimaging techniques for identifying areas of brain damage in mTBI will be important for documenting the biological basis of postconcussive symptoms, which are likely associated with subtle brain alterations, alterations that have heretofore gone undetected due to the lack of sensitivity of earlier neuroimaging techniques. Nonetheless, it is noteworthy to point out that detecting brain abnormalities in mTBI does not mean that other disorders of a more psychogenic origin are not co-morbid with mTBI and equally important to treat. They arguably are. The controversy of psychogenic versus physiogenic, however, is not productive because the psychogenic view does not carefully consider the limitations of conventional neuroimaging techniques in detecting subtle brain injuries in mTBI, and the physiogenic view does not carefully consider the fact that PTSD and depression, and other co-morbid conditions, may be present in those suffering from mTBI. Finally, we end with a discussion of future directions in research that will lead to the improved care of patients diagnosed with mTBI.

Cortico-limbic morphology separates tinnitus from tinnitus distress

Tinnitus is a common auditory disorder characterized by a chronic ringing or buzzing "in the ear."Despite the auditory-perceptual nature of this disorder, a growing number of studies have reported neuroanatomical differences in tinnitus patients outside the auditory-perceptual system. Some have used this evidence to characterize chronic tinnitus as dysregulation of the auditory system, either resulting from inefficient inhibitory control or through the formation of aversive associations with tinnitus. It remains unclear, however, whether these "non-auditory" anatomical markers of tinnitus are related to the tinnitus signal itself, or merely to negative emotional reactions to tinnitus (i.e., tinnitus distress). In the current study, we used anatomical MRI to identify neural markers of tinnitus, and measured their relationship to a variety of tinnitus characteristics and other factors often linked to tinnitus, such as hearing loss, depression, anxiety, and noise sensitivity. In a new cohort of participants, we confirmed that people with chronic tinnitus exhibit reduced gray matter in ventromedial prefrontal cortex (vmPFC) compared to controls matched for age and hearing loss. This effect was driven by reduced cortical surface area, and was not related to tinnitus distress, symptoms of depression or anxiety, noise sensitivity, or other factors. Instead, tinnitus distress was positively correlated with cortical thickness in the anterior insula in tinnitus patients, while symptoms of anxiety and depression were negatively correlated with cortical thickness in subcallosal anterior cingulate cortex (scACC) across all groups. Tinnitus patients also exhibited increased gyrification of dorsomedial prefrontal cortex (dmPFC), which was more severe in those patients with constant (vs. intermittent) tinnitus awareness. Our data suggest that the neural systems associated with chronic tinnitus are different from those involved in aversive or distressed reactions to tinnitus.

Emerging imaging tools for use with traumatic brain injury research

This article identifies emerging neuroimaging measures considered by the inter-agency Pediatric Traumatic Brain Injury (TBI) Neuroimaging Workgroup. This article attempts to address some of the potential uses of more advanced forms of imaging in TBI as well as highlight some of the current considerations and unresolved challenges of using them. We summarize emerging elements likely to gain more widespread use in the coming years, because of 1) their utility in diagnosis, prognosis, and understanding the natural course of degeneration or recovery following TBI, and potential for evaluating treatment strategies; 2) the ability of many centers to acquire these data with scanners and equipment that are readily available in existing clinical and research settings; and 3) advances in software that provide more automated, readily available, and cost-effective analysis methods for large scale data image analysis. These include multi-slice CT, volumetric MRI analysis, susceptibility-weighted imaging (SWI), diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), arterial spin tag labeling (ASL), functional MRI (fMRI), including resting state and connectivity MRI, MR spectroscopy (MRS), and hyperpolarization scanning. However, we also include brief introductions to other specialized forms of advanced imaging that currently do require specialized equipment, for example, single photon emission computed tomography (SPECT), positron emission tomography (PET), encephalography (EEG), and magnetoencephalography (MEG)/magnetic source imaging (MSI). Finally, we identify some of the challenges that users of the emerging imaging CDEs may wish to consider, including quality control, performing multi-site and longitudinal imaging studies, and MR scanning in infants and children.

Are self-reported symptoms of executive dysfunction associated with objective executive function performance following mild to moderate traumatic brain injury?

BACKGROUND AND OBJECTIVE

We examined the relationship between self-reported pre- and post-injury changes in executive dysfunction, apathy, disinhibition, and depression, and performance on neuropsychological tests of executive function, attention/processing speed, and memory in relation to mood levels and effort test performance in individuals in the early stages of recovery from mild to moderate traumatic brain injury (TBI).

METHOD

Participants were 71 noncombat military personnel who were in a semiacute stage of recovery (<3 months post injury) from mild to moderate TBI. Pre- and post-TBI behaviors were assessed with the Frontal Systems Behavior Scale (FrSBe; Grace & Malloy, 2001 ) and correlated with levels of depressive symptoms, effort test performance, and performance on objective measures of attention, executive function, and memory.

RESULTS

Self-reported symptoms of executive dysfunction generally failed to predict performance on objective measures of executive function and memory, although they predicted poorer performance on measures of attention/processing speed. Instead, higher levels of depressive symptomatology best predicted poorer performance on measures of executive function and memory. However, the relationship between memory performance and TBI symptoms was no longer significant when effort performance was controlled.

CONCLUSIONS

Our findings suggest that, among individuals in early recovery from mild to moderate TBI, self-reported depressive symptoms, rather than patients' cognitive complaints, are associated with objective executive function. However, self-reported cognitive complaints may be associated with objectively measured inattention and slow processing speed.

Brain signal variability relates to stability of behavior after recovery from diffuse brain injury

Variability or noise is an unmistakable feature of neural signals; however such fluctuations have been regarded as not carrying meaningful information or as detrimental for neural processes. Recent empirical and computational work has shown that neural systems with a greater capacity for information processing are able to explore a more varied dynamic repertoire, and the hallmark of this is increased irregularity or variability in the neural signal. How this variability in neural dynamics affects behavior remains unclear. Here, we investigated the role of variability of magnetoencephalography signals in supporting healthy cognitive functioning, measured by performance on an attention task, in healthy adults and in patients with traumatic brain injury. As an index of variability, we calculated multiscale entropy, which quantifies the temporal predictability of a time series across progressively more coarse time scales. We found lower variability in traumatic brain injury patients compared to controls, arguing against the idea that greater variability reflects dysfunctional neural processing. Furthermore, higher brain signal variability indicated improved behavioral performance for all participants. This relationship was statistically stronger for people with brain injury, demonstrating that those with higher brain signal variability were also those who had recovered the most cognitive ability. Rather than impede neural processing, cortical signal variability within an optimal range enables the exploration of diverse functional configurations, and may therefore play a vital role in healthy brain function.

Brain activity patterns uniquely supporting visual feature integration after traumatic brain injury

Traumatic brain injury (TBI) patients typically respond more slowly and with more variability than controls during tasks of attention requiring speeded reaction time. These behavioral changes are attributable, at least in part, to diffuse axonal injury (DAI), which affects integrated processing in distributed systems. Here we use a multivariate method sensitive to distributed neural activity to compare brain activity patterns of patients with chronic phase moderate to-severe TBI to those of controls during performance on a visual feature integration task assessing complex attentional processes that has previously shown sensitivity to TBI. The TBI patients were carefully screened to be free of large focal lesions that can affect performance and brain activation independently of DAI. The task required subjects to hold either one or three features of a Target in mind while suppressing responses to distracting information. In controls, the multi-feature condition activated a distributed network including limbic, prefrontal, and medial temporal structures. TBI patients engaged this same network in the single-feature and baseline conditions. In multi-feature presentations, TBI patients alone activated additional frontal, parietal, and occipital regions. These results are consistent with neuroimaging studies using tasks assessing different cognitive domains, where increased spread of brain activity changes was associated with TBI. Our results also extend previous findings that brain activity for relatively moderate task demands in TBI patients is similar to that associated with of high task demands in controls.

Multivariate patterns of brain-cognition associations relating to vulnerability and clinical outcome in the at-risk mental states for psychosis

BACKGROUND

Neuropsychological deficits are a core feature of established psychosis and have been previously linked to fronto-temporo-limbic brain alterations. Both neurocognitive and neuroanatomical abnormalities characterize clinical at-risk mental states (ARMS) for psychosis. However, structure-cognition relationships in the ARMS have not been directly explored using multivariate neuroimaging techniques.

METHODS

Voxel-based morphometry and partial least squares were employed to study system-level covariance patterns between whole-brain morphological data and processing speed, working memory, verbal learning/IQ, and executive functions in 40 ARMS subjects and 30 healthy controls (HC). The detected structure-cognition covariance patterns were tested for significance and reliability using non-parametric permutation and bootstrap resampling.

RESULTS

We identified ARMS-specific covariance patterns that described a generalized association of neurocognitive measures with predominantly prefronto-temporo-limbic and subcortical structures as well as the interconnecting white matter. In the conversion group, this generalized profile particularly involved working memory and verbal IQ and was positively correlated with limbic, insular and subcortical volumes as well as negatively related to prefrontal, temporal, parietal, and occipital cortices. Conversely, the neurocognitive profiles in the HC group were confined to working memory, learning and IQ, which were diffusely associated with cortical and subcortical brain regions.

CONCLUSIONS

These findings suggest that the ARMS and prodromal phase of psychosis are characterized by a convergent mapping from multi-domain neurocognitive measures to a set of prefronto-temporo-limbic and subcortical structures. Furthermore, a neuroanatomical separation between positive and negative brain-cognition correlations may not only point to a biological process determining the clinical risk for disease transition, but also to possible compensatory or dysmaturational neural processes.

Changes in resting connectivity during recovery from severe traumatic brain injury

In the present study we investigate neural network changes after moderate and severe traumatic brain injury (TBI) through the use of resting state functional connectivity (RSFC) methods. Using blood oxygen level dependent functional MRI, we examined RSFC at 3 and 6 months following resolution of posttraumatic amnesia. The goal of this study was to examine how regional off-task connectivity changes during a critical period of recovery from significant neurological disruption. This was achieved by examining regional changes in the intrinsic, or "resting", BOLD fMRI signal in separate networks: 1) regions linked to goal-directed (or external-state) networks and 2) default mode (or internal-state) networks. Findings here demonstrate significantly increased resting connectivity internal-state networks in the TBI sample during the first 6 months following recovery. The most consistent finding was increased connectivity in both internal and external state networks to the insula and medial temporal regions during recovery. These findings were dissociable from repeat measurements in a matched healthy control sample.

Parcellating the neuroanatomical basis of impaired decision-making in traumatic brain injury

Cognitive dysfunction is a devastating consequence of traumatic brain injury that affects the majority of those who survive with moderate-to-severe injury, and many patients with mild head injury. Disruption of key monoaminergic neurotransmitter systems, such as the dopaminergic system, may play a key role in the widespread cognitive dysfunction seen after traumatic axonal injury. Manifestations of injury to this system may include impaired decision-making and impulsivity. We used the Cambridge Gambling Task to characterize decision-making and risk-taking behaviour, outside of a learning context, in a cohort of 44 patients at least six months post-traumatic brain injury. These patients were found to have broadly intact processing of risk adjustment and probability judgement, and to bet similar amounts to controls. However, a patient preference for consistently early bets indicated a higher level of impulsiveness. These behavioural measures were compared with imaging findings on diffusion tensor magnetic resonance imaging. Performance in specific domains of the Cambridge Gambling Task correlated inversely and specifically with the severity of diffusion tensor imaging abnormalities in regions that have been implicated in these cognitive processes. Thus, impulsivity was associated with increased apparent diffusion coefficient bilaterally in the orbitofrontal gyrus, insula and caudate; abnormal risk adjustment with increased apparent diffusion coefficient in the right thalamus and dorsal striatum and left caudate; and impaired performance on rational choice with increased apparent diffusion coefficient in the bilateral dorsolateral prefrontal cortices, and the superior frontal gyri, right ventrolateral prefrontal cortex, the dorsal and ventral striatum, and left hippocampus. Importantly, performance in specific cognitive domains of the task did not correlate with diffusion tensor imaging abnormalities in areas not implicated in their performance. The ability to dissociate the location and extent of damage with performance on the various task components using diffusion tensor imaging allows important insights into the neuroanatomical basis of impulsivity following traumatic brain injury. The ability to detect such damage in vivo may have important implications for patient management, patient selection for trials, and to help understand complex neurocognitive pathways.