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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2021)

Rationale. Mild traumatic brain injury (mTBI), identified as the “signature” wound of U.S. veterans, is often associated with cognitive complaints, which have been inconsistently linked to working memory (WM) deficits. Moreover, the relationship between WM and brain function in mTBI veterans is understudied. The overarching aim of the study was to examine WM performance and underlying neural mechanisms via fMRI in mTBI veterans.Design. The study aimed to investigate: (1) whether veterans with mTBI demonstrated worse WM performance than veteran controls (VC); (2) whether brain activation in anterior cingulate cortex (ACC) and bilateral dorsolateral prefrontal cortex (DLPFC) during the WM task was higher in veterans with mTBI compared to VC; and (3) whether greater brain activation was associated with better WM performance in veterans with mTBI. Seventy-eight veterans (44 mTBI; 34 VC) completed neuroimaging, a WM task (modified Paced Auditory Serial Addition Test), and neuropsychiatric symptom measures. Hierarchical linear regression models including demographic and psychiatric variables were employed. Results. Veterans with and without mTBI did not differ in WM performance. However, groups differed in ACC activation during correct-incorrect trials (p=.003) after accounting for depression with lower activation in the mTBI group. Within veterans with mTBI, ACC correct-incorrect activation (p=.031) significantly predicted WM, controlling for education, such that higher activation was associated with higher false-alarm rate (worse performance). In VC, ACC activation (p=.030) during correct trials significantly predicted WM, such that higher ACC activation was associated with poorer performance; PTSD symptoms attenuated these associations, however. Conclusions & Implications. Despite similar WM performance, veterans with mTBI exhibited relatively higher ACC activation on incorrect trials than veterans without mTBI. Greater ACC activation was associated with worse WM performance in both groups. Elevated ACC activation was evident only during correct-incorrect trials; thus, the ACC may act as a salience detector signaling increased activation to errors in mTBI. This project enhances our knowledge of WM and brain activation in veterans with mTBI. Findings from this study contribute to our understanding of chronic sequelae following mTBI, which could ultimately be utilized in intervention studies to decrease distress and disability following mTBI in this vulnerable population.

    Cover page: Neural Correlates of Working Memory Performance in Veterans with Mild Traumatic Brain Injury
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2018)
    OBJECTIVE:Fatigue is a complex, multidimensional phenomenon that commonly occurs following traumatic brain injury (TBI). The thalamus-a structure vulnerable to both primary and secondary injuries in TBI-is thought to play a pivotal role in the manifestation of fatigue. We explored how neuroimaging markers of local and global thalamic morphometry relate to the subjective experience of fatigue post-TBI. METHODS:Sixty-three Veterans with a history of mild TBI underwent structural magnetic resonance imaging and completed questionnaires related to fatigue and psychiatric symptoms. FMRIB's Software (FSL) was utilized to obtain whole brain and thalamic volume estimates, as well as to perform regional thalamic morphometry analyses. RESULTS:Independent of age, sex, intracranial volume, posttraumatic stress disorder, and depressive symptoms, greater levels of self-reported fatigue were significantly associated with decreased right (P = .026) and left (P = .046) thalamic volumes. Regional morphometry analyses revealed that fatigue was significantly associated with reductions in the anterior and dorsomedial aspects of the right thalamic body (P < .05). Similar trends were observed for the left thalamic body (P < .10). CONCLUSIONS:Both global and regional thalamic morphometric changes are associated with the subjective experience of fatigue in Veterans with a history of mild TBI. These findings support a theory in which disruption of thalamocorticostriatal circuitry may result in the manifestation of fatigue in individuals with a history of neurotrauma.
      Cover page: Fatigue Is Associated With Global and Regional Thalamic Morphometry in Veterans With a History of Mild Traumatic Brain Injury.
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2021)

      Objective

      The evaluation of memory complaints in mild traumatic brain injury (mTBI) remains an important clinical consideration, especially in the context of comorbid psychiatric symptoms such as posttraumatic stress disorder (PTSD). We compared subjective memory complaints in veterans with and without a history of mTBI, examined ratings between those with single versus multiple mTBIs, and investigated associations between memory complaints and PTSD symptom severity.

      Methods

      117 outpatient veterans (mTBI: n = 79 [single mTBI: n = 22, multiple mTBI: n = 57], military controls [MCs]: n = 38) completed a TBI history assessment, the Prospective-Retrospective Memory Questionnaire (PRMQ), and the PTSD Checklist-Military Version (PCL-M).

      Results

      Hierarchical multiple regression showed that greater PCL-M scores significantly predicted elevated PRMQ-Total scores, accounting for 38% of the variance explained (P < .001). mTBI status predicted an additional 5% of variance in memory complaints (P < .01). The multiple-mTBI group endorsed more memory complaints than either MCs (P < .01) or the single-mTBI group (P < .05), who did not differ from MCs (P > .50).

      Conclusions

      Comorbid PTSD symptoms are an important factor when considering memory complaints in veterans with a reported history of mTBI. However, independent of comorbid PTSD symptoms, mTBI status-particularly in the context of repetitive neurotrauma-uniquely contributes to memory complaints. Findings suggest that veterans with a history of multiple mTBIs may be a particularly vulnerable group in need of specialized interventions and/or psychoeducation.
        Cover page: Research Letter: PTSD Symptom Severity and Multiple Traumatic Brain Injuries Are Associated With Elevated Memory Complaints in Veterans With Histories of Mild TBI
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2021)

        Objective

        The utility of informant-based measures of cognitive decline to accurately describe objective cognitive performance in Parkinson's disease (PD) without dementia is uncertain. Due to the clinical relevance of this information, the purpose of this study was to examine the relationship between informant-based reports of patient cognitive decline via the Informant Questionnaire of Cognitive Decline in the Elderly (IQCODE) and objective cognition in non-demented PD controlling for cognitive status (i.e., mild cognitive impairment; PD-MCI and normal cognition; PD-NC).

        Method

        One-hundred and thirty-nine non-demented PD participants (PD-MCI n = 38; PD-NC n = 101) were administered measures of language, executive function, attention, learning, delayed recall, visuospatial function, mood, and motor function. Each participant identified an informant to complete the IQCODE and a mood questionnaire.

        Results

        Greater levels of informant-based responses of patient cognitive decline on the IQCODE were significantly associated with worse objective performance on measures of global cognition, attention, learning, delayed recall, and executive function in the overall sample, above and beyond covariates and cognitive status. However, the IQCODE was not significantly associated with language or visuospatial function.

        Conclusions

        Results indicate that informant responses, as measured by the IQCODE, may provide adequate information on a wide range of cognitive abilities in non-demented PD, including those with MCI and normal cognition. Findings have important clinical implications for the utility of the IQCODE in the identification of PD patients in need of further evaluation, monitoring, and treatment.
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2021)

          Objective

          We examined whether intraindividual variability (IIV) across tests of executive functions (EF-IIV) is elevated in Veterans with a history of mild traumatic brain injury (mTBI) relative to military controls (MCs) without a history of mTBI. We also explored relationships among EF-IIV, white matter microstructure, and posttraumatic stress disorder (PTSD) symptoms.

          Method

          A total of 77 Veterans (mTBI = 43, MCs = 34) completed neuropsychological testing, diffusion tensor imaging (DTI), and PTSD symptom ratings. EF-IIV was calculated as the standard deviation across six tests of EF, along with an EF-Mean composite. DSI Studio connectometry analysis identified white matter tracts significantly associated with EF-IIV according to generalized fractional anisotropy (GFA).

          Results

          After adjusting for EF-Mean and PTSD symptoms, the mTBI group showed significantly higher EF-IIV than MCs. Groups did not differ on EF-Mean after adjusting for PTSD symptoms. Across groups, PTSD symptoms significantly negatively correlated with EF-Mean, but not with EF-IIV. EF-IIV significantly negatively correlated with GFA in multiple white matter pathways connecting frontal and more posterior regions.

          Conclusions

          Veterans with mTBI demonstrated significantly greater IIV across EF tests compared to MCs, even after adjusting for mean group differences on those measures as well as PTSD severity. Findings suggest that, in contrast to analyses that explore effects of mean performance across tests, discrepancy analyses may capture unique variance in neuropsychological performance and more sensitively capture cognitive disruption in Veterans with mTBI histories. Importantly, findings show that EF-IIV is negatively associated with the microstructure of white matter pathways interconnecting cortical regions that mediate executive function and attentional processes.
            Cover page: Elevated Intraindividual Variability in Executive Functions and Associations with White Matter Microstructure in Veterans with Mild Traumatic Brain Injury
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2017)

            Background

            Visual Hallucinations (VH) are a common symptom experienced by individuals with Parkinson's disease (PD); however, a validated measure of VH has yet to be established for this population. The North-East Visual Hallucinations Interview (NEVHI), a promising VH measure, has not been well validated in PD. The aim of this study was to evaluate the convergent and discriminant validity of the NEVHI as well as the proportional identification and characteristics of VH in PD.

            Methods

            One hundred seventeen individuals with PD completed the NEVHI as well as evaluations of psychological, cognitive, motor, and visual functioning as measures of convergent and divergent validity. The hallucination items from the Neuropsychiatric Inventory (NPI) and the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Scale (MDS-UPDRS) were used to assess convergent validity.

            Results

            The NEVHI identified 20.5% of PD patients with VH, which consisted of all individuals detected by the MDS-UPDRS and NPI and nine additional individuals not detected by the other measures. The NEVHI was strongly correlated with the MDS-UPDRS hallucinations item, and weakly correlated with the NPI VH item. Weak to non-significant correlations were found between the NEVHI and measures of psychological, cognitive, motor, visual, and demographic characteristics.

            Discussion

            The NEVHI identified a greater number of individuals with VH than either the MDS-UPDRS or NPI. Results demonstrated good convergent validity between the NEVHI and a clinician-administered-to-patient-report measure of VH and excellent divergent validity, supporting the NEVHI as a valid and preferable measure for assessing the presence of VH in PD.
              Cover page: Psychometric Properties and Characteristics of the North‐East Visual Hallucinations Interview in Parkinson's Disease
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