Brain activation while thinking about the self from another person's perspective after traumatic brain injury in adolescents

Abnormal Functional Network Topology and Its Dynamics during Sustained Attention Processing Significantly Implicate Post-TBI Attention Deficits in Children

Traumatic brain injury (TBI) is highly prevalent in children. Attention deficits are among the most common and persistent post-TBI cognitive and behavioral sequalae that can contribute to adverse outcomes. This study investigated the topological properties of the functional brain network for sustained attention processing and their dynamics in 42 children with severe post-TBI attention deficits (TBI-A) and 47 matched healthy controls. Functional MRI data during a block-designed sustained attention task was collected for each subject, with each full task block further divided into the pre-, early, late-, and post-stimulation stages. The task-related functional brain network was constructed using the graph theoretic technique. Then, the sliding-window-based method was utilized to assess the dynamics of the topological properties in each stimulation stage. Relative to the controls, the TBI-A group had significantly reduced nodal efficiency and/or degree of left postcentral, inferior parietal, inferior temporal, and fusiform gyri and their decreased stability during the early and late-stimulation stages. The left postcentral inferior parietal network anomalies were found to be significantly associated with elevated inattentive symptoms in children with TBI-A. These results suggest that abnormal functional network characteristics and their dynamics associated with the left parietal lobe may significantly link to the onset of the severe post-TBI attention deficits in children.

Challenges and opportunities for neuroimaging in young patients with traumatic brain injury: a coordinated effort towards advancing discovery from the ENIGMA pediatric moderate/severe TBI group

Traumatic brain injury (TBI) is a major cause of death and disability in children in both developed and developing nations. Children and adolescents suffer from TBI at a higher rate than the general population, and specific developmental issues require a unique context since findings from adult research do not necessarily directly translate to children. Findings in pediatric cohorts tend to lag behind those in adult samples. This may be due, in part, both to the smaller number of investigators engaged in research with this population and may also be related to changes in safety laws and clinical practice that have altered length of hospital stays, treatment, and access to this population. The ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Pediatric Moderate/Severe TBI (msTBI) group aims to advance research in this area through global collaborative meta-analysis of neuroimaging data. In this paper, we discuss important challenges in pediatric TBI research and opportunities that we believe the ENIGMA Pediatric msTBI group can provide to address them. With the paucity of research studies examining neuroimaging biomarkers in pediatric patients with TBI and the challenges of recruiting large numbers of participants, collaborating to improve statistical power and to address technical challenges like lesions will significantly advance the field. We conclude with recommendations for future research in this field of study.

Theory of Mind after Pediatric Traumatic Brain Injury: A Scoping Review

This scoping review aims to synthesize existing literature regarding theory of mind (ToM) outcomes, the neuropathology associated with ToM outcomes, and the relationship between ToM outcomes and social functioning in children and adolescents with traumatic brain injury (TBI). We searched MEDLINE^® and PsycINFO databases to identify all literature that examined ToM following pediatric TBI until July 2019. A total of 29 articles met inclusion and exclusion criteria and were included in the results. These articles examined a variety of aspects of ToM, which could be broadly grouped into those focused on cognitive, cognitive-affective, and pragmatic factors. The existing literature suggests that children and adolescents with TBI, compared with their typically developing peers and peers with orthopedic injuries, are more likely to have deficits in ToM. The evidence further shows that the age at which brain injury occurs contributes to ToM disruption. Neuroimaging techniques have offered crucial insights into how TBI may impact ToM performance in children and adolescents. Finally, this review provides evidence that disruption in ToM plays a role in the difficulties in social functioning demonstrated by children and adolescents with TBI. Limitations and gaps in the existing literature warrant future research in this field.

The effect of severe traumatic brain injury on social cognition, emotion regulation, and mood

This chapter provides a review of the emotional and psychosocial consequences of moderate to severe traumatic brain injury (TBI). Many of the disorders affecting socioemotional function arise from damage to frontotemporal systems, exacerbated by white matter injury. They include disorders of social cognition, such as the ability to recognize emotions in others, the ability to attribute mental states to others, and the ability to experience empathy. Patients with TBI also often have disorders of emotion regulation. Disorders of drive or apathy can manifest across cognitive, emotional, and behavioral domains. Likewise, disorders of control can lead to dysregulated emotions and behavior. Other disorders, such as loss of self-awareness, are also implicated in poor psychosocial recovery. Finally, this chapter overviews psychiatric disorders associated with TBI, especially anxiety and depression. For each kind of disorder, the nature of the disorder and its prevalence, as well as theoretical considerations and impact on every day functions, are reviewed.

Altered resting-state functional connectivity within the developing social brain after pediatric traumatic brain injury

Traumatic brain injury (TBI) in childhood and adolescence can interrupt expected development, compromise the integrity of the social brain network (SBN) and impact social skills. Yet, no study has investigated functional alterations of the SBN following pediatric TBI. This study explored functional connectivity within the SBN following TBI in two independent adolescent samples. First, 14 adolescents with mild complex, moderate or severe TBI and 16 typically developing controls (TDC) underwent resting‐state functional magnetic resonance imaging 12–24 months post‐injury. Region of interest analyses were conducted to compare the groups' functional connectivity using selected SBN seeds. Then, replicative analysis was performed in an independent sample of adolescents with similar characteristics (9 TBI, 9 TDC). Results were adjusted for age, sex, socioeconomic status and total gray matter volume, and corrected for multiple comparisons. Significant between‐group differences were detected for functional connectivity in the dorsomedial prefrontal cortex and left fusiform gyrus, and between the left fusiform gyrus and left superior frontal gyrus, indicating positive functional connectivity for the TBI group (negative for TDC). The replication study revealed group differences in the same direction between the left superior frontal gyrus and right fusiform gyrus. This study indicates that pediatric TBI may alter functional connectivity of the social brain. Frontal‐fusiform connectivity has previously been shown to support affect recognition and changes in the function of this network could relate to more effortful processing and broad social impairments.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The Neuropsychology of Traumatic Brain Injury: Looking Back, Peering Ahead

The past 50 years have been a period of exciting progress in neuropsychological research on traumatic brain injury (TBI). Neuropsychologists and neuropsychological testing have played a critical role in these advances. This study looks back at three major scientific advances in research on TBI that have been critical in pushing the field forward over the past several decades: The advent of modern neuroimaging; the recognition of the importance of non-injury factors in determining recovery from TBI; and the growth of cognitive rehabilitation. Thanks to these advances, we now have a better understanding of the pathophysiology of TBI and how recovery from the injury is also shaped by pre-injury, comorbid, and contextual factors, and we also have increasing evidence that active interventions, including cognitive rehabilitation, can help to promote better outcomes. The study also peers ahead to discern two important directions that seem destined to influence research on TBI over the next 50 years: the development of large, multi-site observational studies and randomized controlled trials, bolstered by international research consortia and the adoption of common data elements; and attempts to translate research into health care and health policy by the application of rigorous methods drawn from implementation science. Future research shaped by these trends should provide critical evidence regarding the outcomes of TBI and its treatment, and should help to disseminate and implement the knowledge gained from research to the betterment of the quality of life of persons with TBI. (JINS, 2017, 23, 806-817).

Neural substrates of inhibitory and emotional processing in adolescents with traumatic brain injury

PURPOSE

Disturbances of emotional regulation and social difficulties are common in children and adolescents with traumatic brain injury (TBI). Recent research suggests that developments within ``socio-emotional'' brain systems during early adolescence and more protracted development of "cognitive control'' systems have implications for emotional and behavioral regulation during adolescence. However, few functional neuroimaging studies have directly examined the interaction of these neuropsychological processes in adolescents with TBI. The current study examined how affective processing might modulate inhibitory processing in an Emotional Go/NoGo paradigm.

METHOD

The study uses a cross-sectional, age, gender, and maternal education matched design.A response inhibition paradigm (i.e., the Go/NoGo task with emotional faces) was used to examine emotional-cognition interaction in 11 adolescents with complicated mild to moderate TBI, at least 12 months post injury, and 14 typically-developing (TD) adolescents using functional magnetic resonance imaging (fMRI). Participants saw adult facial expressions of emotions (happy, sad, fearful, and angry) and were instructed to respond (``go'') on all expressions other than angry (``no-go'').

RESULTS

Preliminary results (p= 0.001 uncorrected, cluster size = 50) showed higher levels of inhibition-related activation in TD adolescents than in adolescents with TBI in several brain regions including anterior cingulate and motor/premotor regions.

CONCLUSION

These results suggest that TBI in adolescence might alter brain activation patterns and interrupt the development of brain networks governing emotion-cognition interactions.

Alterations in brain activation during cognitive empathy are related to social functioning in schizophrenia

Impaired cognitive empathy (ie, understanding the emotional experiences of others) is associated with poor social functioning in schizophrenia. However, it is unclear whether the neural activity underlying cognitive empathy relates to social functioning. This study examined the neural activation supporting cognitive empathy performance and whether empathy-related activation during correctly performed trials was associated with self-reported cognitive empathy and measures of social functioning. Thirty schizophrenia outpatients and 24 controls completed a cognitive empathy paradigm during functional magnetic resonance imaging. Neural activity corresponding to correct judgments about the expected emotional expression in a social interaction was compared in schizophrenia subjects relative to control subjects. Participants also completed a self-report measure of empathy and 2 social functioning measures (social competence and social attainment). Schizophrenia subjects demonstrated significantly lower accuracy in task performance and were characterized by hypoactivation in empathy-related frontal, temporal, and parietal regions as well as hyperactivation in occipital regions compared with control subjects during accurate cognitive empathy trials. A cluster with peak activation in the supplementary motor area (SMA) extending to the anterior midcingulate cortex (aMCC) correlated with social competence and social attainment in schizophrenia subjects but not controls. These results suggest that neural correlates of cognitive empathy may be promising targets for interventions aiming to improve social functioning and that brain activation in the SMA/aMCC region could be used as a biomarker for monitoring treatment response.

Oxidative stress in schizophrenia: a case-control study on the effects on social cognition and neurocognition

BACKGROUND

Schizophrenia is a debilitating mental disorder that presents impairments in neurocognition and social cognition. Several studies have suggested that the etiology of schizophrenia can be partly explained by oxidative stress. However, our knowledge about the implications of oxidative stress on illness-related cognitive deficits is still far from being clear. The aim of this work was to study the role of oxidative stress molecules on social cognition and neurocognition in patients with schizophrenia.

METHODS

We assessed the peripheral levels of several molecules associated with oxidative stress, namely nitric oxide (NO), malondialdehyde (MDA), glutathione (GSH), homocysteine, superoxide dismutase (SOD) and neurotrophin 4/5 (NT4/5), in forty-one patients with schizophrenia and forty-three healthy participants. A battery of tests to measure neurocognition and social cognition was also administered to the schizophrenia group.

RESULTS

We found that the schizophrenia group presented substantially higher levels of oxidative stress than the control group, as revealed by elevated quantities of the pro-oxidants NO and MDA, and decreased levels of the antioxidants GSH, SOD and NT4/5. Interestingly, the levels of NT4/5, which have been shown to have antioxidant effects, correlated with executive functioning, as measured by two distinct tests (WCST and TMT). However, social cognition and symptom severity were not found to be associated with oxidative stress.

CONCLUSIONS

We propose a protective role of NT4/5 against oxidative stress, which appears to have a potentially beneficial impact on neurocognition in schizophrenia.

Hippocampal adaptive response following extensive neuronal loss in an inducible transgenic mouse model

Neuronal loss is a common component of a variety of neurodegenerative disorders (including Alzheimer's, Parkinson's, and Huntington's disease) and brain traumas (stroke, epilepsy, and traumatic brain injury). One brain region that commonly exhibits neuronal loss in several neurodegenerative disorders is the hippocampus, an area of the brain critical for the formation and retrieval of memories. Long-lasting and sometimes unrecoverable deficits caused by neuronal loss present a unique challenge for clinicians and for researchers who attempt to model these traumas in animals. Can these deficits be recovered, and if so, is the brain capable of regeneration following neuronal loss? To address this significant question, we utilized the innovative CaM/Tet-DT(A) mouse model that selectively induces neuronal ablation. We found that we are able to inflict a consistent and significant lesion to the hippocampus, resulting in hippocampally-dependent behavioral deficits and a long-lasting upregulation in neurogenesis, suggesting that this process might be a critical part of hippocampal recovery. In addition, we provide novel evidence of angiogenic and vasculature changes following hippocampal neuronal loss in CaM/Tet-DTA mice. We posit that angiogenesis may be an important factor that promotes neurogenic upregulation following hippocampal neuronal loss, and both factors, angiogenesis and neurogenesis, can contribute to the adaptive response of the brain for behavioral recovery.

Functional MRI and outcome in traumatic coma

Advances in task-based functional MRI (fMRI), resting-state fMRI (rs-fMRI), and arterial spin labeling (ASL) perfusion MRI have occurred at a rapid pace in recent years. These techniques for measuring brain function have great potential to improve the accuracy of prognostication for civilian and military patients with traumatic coma. In addition, fMRI, rs-fMRI, and ASL perfusion MRI have provided novel insights into the pathophysiology of traumatic disorders of consciousness, as well as the mechanisms of recovery from coma. However, functional neuroimaging techniques have yet to achieve widespread clinical use as prognostic tests for patients with traumatic coma. Rather, a broad spectrum of methodological hurdles currently limits the feasibility of clinical implementation. In this review, we discuss the basic principles of fMRI, rs-fMRI, and ASL perfusion MRI and their potential applications as prognostic tools for patients with traumatic coma. We also discuss future strategies for overcoming the current barriers to clinical implementation.

How functional connectivity between emotion regulation structures can be disrupted: preliminary evidence from adolescents with moderate to severe traumatic brain injury

Outcome of moderate to severe traumatic brain injury (TBI) includes impaired emotion regulation. Emotion regulation has been associated with amygdala and rostral anterior cingulate (rACC). However, functional connectivity between the two structures after injury has not been reported. A preliminary examination of functional connectivity of rACC and right amygdala was conducted in adolescents 2 to 3 years after moderate to severe TBI and in typically developing (TD)control adolescents, with the hypothesis that the TBI adolescents would demonstrate altered functional connectivity in the two regions. Functional connectivity was determined by correlating fluctuations in the blood oxygen level dependent(BOLD) signal of the rACC and right amygdala with that of other brain regions. In the TBI adolescents, the rACC was found to be significantly less functionally connected to medial prefrontal cortices and to right temporal regions near the amygdala (height threshold T = 2.5, cluster level p < .05, FDR corrected), while the right amygdala showed a trend in reduced functional connectivity with the rACC (height threshold T = 2.5, cluster level p = .06, FDR corrected). Data suggest disrupted functional connectivity in emotion regulation regions. Limitations include small sample sizes. Studies with larger sample sizes are necessary to characterize the persistent neural damage resulting from moderate to severe TBI during development.

What do I want and when do I want it: brain correlates of decisions made for self and other

A number of recent functional Magnetic Resonance Imaging (fMRI) studies on intertemporal choice behavior have demonstrated that so-called emotion- and reward-related brain areas are preferentially activated by decisions involving immediately available (but smaller) rewards as compared to (larger) delayed rewards. This pattern of activation was not seen, however, when intertemporal choices were made for another (unknown) individual, which speaks to that activation having been triggered by self-relatedness. In the present fMRI study, we investigated the brain correlates of individuals who passively observed intertemporal choices being made either for themselves or for an unknown person. We found higher activation within the ventral striatum, medial prefrontal and orbitofrontal cortex, pregenual anterior cingulate cortex, and posterior cingulate cortex when an immediate reward was possible for the observer herself, which is in line with findings from studies in which individuals actively chose immediately available rewards. Additionally, activation in the dorsal anterior cingulate cortex, posterior cingulate cortex, and precuneus was higher for choices that included immediate options than for choices that offered only delayed options, irrespective of who was to be the beneficiary. These results indicate that (1) the activations found in active intertemporal decision making are also present when the same decisions are merely observed, thus supporting the assumption that a robust brain network is engaged in immediate gratification; and (2) with immediate rewards, certain brain areas are activated irrespective of whether the observer or another person is the beneficiary of a decision, suggesting that immediacy plays a more general role for neural activation. An explorative analysis of participants’ brain activation corresponding to chosen rewards, further indicates that activation in the aforementioned brain areas depends on the mere presence, availability, or actual reception of immediate rewards.

How an Occupational Therapist Should Conceptualise Self-Awareness following Traumatic Brain Injury in Childhood — A Literature Review

Introduction:

The development of self-awareness across childhood is a complex and protracted phenomenon. Little is known about the consequences of an interruption to development as a result of a traumatic brain injury in childhood. The aim of this paper was to review the available literature on self-awareness in children following a traumatic brain injury and relate the findings to occupational therapy practice with this group of children and young people.

Method:

A comprehensive search of the current literature relating to self-awareness following a traumatic brain injury.

Findings:

A small amount of theoretical and qualitative literature was sourced and critically appraised using appropriate tools. Although only nine relevant papers were identified, those that were evaluated were found to be of a high quality. The findings were supplemented with additional material from developmental psychology and adult brain injury literature.

Conclusion:

Occupational therapists are encouraged to conceptualise self-awareness in childhood traumatic brain injury within a developmental context. A fuller understanding of self-awareness in childhood and the consequences of an interruption to its development will help to establish age-appropriate interventions.

Impairments in social cognition following severe traumatic brain injury

Severe traumatic brain injury (TBI) leads to physical, neuropsychological, and emotional deficits that interfere with the individual’s capacity to return to his or her former lifestyle. This review focuses on social cognition, that is, the capacity to attend to, recognize and interpret interpersonal cues that guide social behavior. Social cognition entails ‘‘hot’’ processes, that is, emotion perception and emotional empathy and ‘‘cold’’ processes, that is, the ability to infer the beliefs, feelings, and intentions of others (theory of mind: ToM) to see their point of view (cognitive empathy) and what they mean when communicating (pragmatic inference). This review critically examines research attesting to deficits in each of these domains and also examines evidence for theorized mechanisms including specific neural networks, the role of simulation, and non-social cognition. Current research is hampered by small, heterogeneous samples and the inherent complexity of TBI pathology. Nevertheless, there is evidence that facets of social cognition are impaired in this population. New assessment tools to measure social cognition following TBI are required that predict everyday social functioning. In addition, research into remediation needs to be guided by the growing empirical base for understanding social cognition that may yet reveal how deficits dissociate following TBI.

Advanced neuroimaging in traumatic brain injury

Advances in structural and functional neuroimaging have occurred at a rapid pace over the past two decades. Novel techniques for measuring cerebral blood flow, metabolism, white matter connectivity, and neural network activation have great potential to improve the accuracy of diagnosis and prognosis for patients with traumatic brain injury (TBI), while also providing biomarkers to guide the development of new therapies. Several of these advanced imaging modalities are currently being implemented into clinical practice, whereas others require further development and validation. Ultimately, for advanced neuroimaging techniques to reach their full potential and improve clinical care for the many civilians and military personnel affected by TBI, it is critical for clinicians to understand the applications and methodological limitations of each technique. In this review, we examine recent advances in structural and functional neuroimaging and the potential applications of these techniques to the clinical care of patients with TBI. We also discuss pitfalls and confounders that should be considered when interpreting data from each technique. Finally, given the vast amounts of advanced imaging data that will soon be available to clinicians, we discuss strategies for optimizing data integration, visualization, and interpretation.

Social function in children and adolescents after traumatic brain injury: a systematic review 1989-2011

Clinical reports and case studies suggest that traumatic brain injury (TBI) can have significant social consequences, with social dysfunction reported to be the most debilitating problem for child and adolescent survivors. From a social neuroscience perspective, evidence suggests that social skills are not localized to a specific brain region, but are mediated by an integrated neural network. Many components of this network are susceptible to disruption in the context of TBI. In early development, a brain injury can disrupt this neural network while it is in the process of being established, resulting in social dysfunction. In order to clarify the prevalence and nature of social dysfunction after child TBI, studies of social outcomes in children and adolescents after TBI over the last 23 years have been reviewed. Despite casting a wide net initially, only 28 articles met review criteria. These studies were characterized by methodological weaknesses, including variations in definitions of TBI, limited assessment tools, reliance on parent reports, small sample sizes, and absent control groups. Despite these limitations, the weight of evidence confirmed an elevated risk of social impairment in the context of moderate and severe injury. While rarely examined, younger age at insult, pathology to frontal regions and the corpus callosum, and social disadvantage and family dysfunction may also increase the likelihood of social difficulties. More research is needed to obtain an accurate picture of social outcomes post-brain injury.

The relationship of resting cerebral blood flow and brain activation during a social cognition task in adolescents with chronic moderate to severe traumatic brain injury: a preliminary investigation

Alterations in cerebrovascular function are evident acutely in moderate to severe traumatic brain injury (TBI), although less is known about their chronic effects. Adolescent and adult patients with moderate to severe TBI have been reported to demonstrate diffuse activation throughout the brain during functional magnetic resonance imaging (fMRI). Because fMRI is a measure related to blood flow, it is possible that any deficits in blood flow may alter activation. An arterial spin labeling (ASL) perfusion sequence was performed on seven adolescents with chronic moderate to severe TBI and seven typically developing (TD) adolescents during the same session in which they had performed a social cognition task during fMRI. In the TD group, prefrontal CBF was positively related to prefrontal activation and negatively related to non-prefrontal, posterior, brain activation. This relationship was not seen in the TBI group, who demonstrated a greater positive relationship between prefrontal CBF and non-prefrontal activation than the TD group. An analysis of CBF data independent of fMRI showed reduced CBF in the right non-prefrontal region (p<.055) in the TBI group. To understand any role reduced CBF may play in diffuse extra-activation, we then related the right non-prefrontal CBF to activation. CBF in the right non-prefrontal region in the TD group was positively associated with prefrontal activation, suggesting an interactive role of non-prefrontal and prefrontal blood flow throughout the right hemisphere in healthy brains. However, the TBI group demonstrated a positive association with activation constrained to the right non-prefrontal region. These data suggest a relationship between impaired non-prefrontal CBF and the presence of non-prefrontal extra-activation, where the region with more limited blood flow is associated with activation limited to that region. In a secondary analysis, pathology associated with hyperintensities on T2-weighted FLAIR imaging over the whole brain was related to whole brain activation, revealing a negative relationship between lesion volume and frontal activation, and a positive relationship between lesion volume and posterior activation. These preliminary data, albeit collected with small sample sizes, suggest that reduced non-prefrontal CBF, and possibly pathological tissue associated with T2-hyperintensities, may provide contributions to the diffuse, primarily posterior extra-activation observed in adolescents following moderate to severe TBI.

Brain activation during a social attribution task in adolescents with moderate to severe traumatic brain injury

The ability to make accurate judgments about the mental states of others, sometimes referred to as theory of mind (ToM), is often impaired following traumatic brain injury (TBI), and this deficit may contribute to problems with interpersonal relationships. The present study used an animated social attribution task (SAT) with functional magnetic resonance imaging (fMRI) to examine structures mediating ToM in adolescents with moderate to severe TBI. The study design also included a comparison group of matched, typically developing (TD) adolescents. The TD group exhibited activation within a number of areas that are thought to be relevant to ToM, including the medial prefrontal and anterior cingulate cortex, fusiform gyrus, and posterior temporal and parietal areas. The TBI subjects had significant activation within many of these same areas, but their activation was generally more intense and excluded the medial prefrontal cortex. Exploratory regression analyses indicated a negative relation between ToM-related activation and measures of white matter integrity derived from diffusion tensor imaging, while there was also a positive relation between activation and lesion volume. These findings are consistent with alterations in the level and pattern of brain activation that may be due to the combined influence of diffuse axonal injury and focal lesions.

Voxel-based morphometry studies of personality: issue of statistical model specification--effect of nuisance covariates

There are an increasing number of studies on the localization of personality using voxel-based morphometry. Due to the complex analytic challenge in volumetric studies, the specification and treatment of the nuisance covariate (such as age, gender, and global measures) is currently not consistent. Here, we present a study in which we conducted voxel-based morphometry with Five-Factor Model (FFM) of personality traits (extraversion, neuroticism, openness to experience, agreeableness, and conscientiousness) that aimed to test the influence of NC specification in the determination of the results. In this study, 62 healthy subjects underwent MRI investigation and completed a German version of the FFM personality questionnaire. Voxel-based morphometry was used to investigate the correlation between the FFM personality traits and subtle brain structure. Different NC combinations were used during the model specification. Significant clusters were found only under the condition of some of the NC combinations but not under the others. In addition, we use the structure equation modeling (automated specification search from AMOS) to narrow down the possible choices of NC combinations according to a set of goodness-of-fit indices to identify well-fitted statistic models. As a final step, theoretical implications of the results are discussed, before accepting the selected model.