Biomedical subjects

Vince Schmithorst

Publications and source records attributed to Vince Schmithorst.

4 recordsLinked to original sources

PubMed2006

Evidence of white matter pathology in bipolar disorder adolescents experiencing their first episode of mania: a diffusion tensor imaging study.

OBJECTIVE: Previous diffusion tensor imaging findings have supported suggestions that bipolar disorder is characterized by subtle white matter changes. The chronic nature of the study population, however, has limited interpretation of these findings. In this study the authors utilized diffusion tensor imaging to study white matter tracts of adolescents in their first episode of mania to address whether abnormalities are present in early bipolar disorder. METHOD: Eleven medication-naive adolescents in their first episode of mania and 17 healthy subjects underwent diffusion tensor imaging scans. Fractional anisotropy and trace apparent diffusion coefficients of prefrontal and posterior regions of interest were compared between groups. RESULTS: Bipolar adolescents showed significantly decreased fractional anisotropy only in superior-frontal white matter tracts. Trace apparent diffusion coefficients did not significantly differ in any regions examined. CONCLUSIONS: These findings suggest that prefrontal white matter abnormalities are present early in bipolar disorder and may consist largely of axonal disorganization. The presence of changes in young first-episode patients also suggests that white matter pathology may represent an early marker of bipolar disorder.

Adolescent↗

PubMed2005

Comorbid ADHD is associated with altered patterns of neuronal activation in adolescents with bipolar disorder performing a simple attention task.

OBJECTIVES: Bipolar disorder is increasingly recognized as a significant source of psychiatric morbidity in children and adolescents. Younger bipolar patients symptomatically differ from adults, and frequently present with comorbid disorders, particularly attention-deficit hyperactivity disorder (ADHD). The neurophysiological relationship between these two disorders, however, remains unclear. In this study we utilized functional magnetic resonance imaging (fMRI) to compare activation patterns during performance of a simple attention task between bipolar adolescents with and without ADHD. METHODS: Eleven bipolar adolescents with comorbid ADHD and 15 bipolar adolescents without comorbidity were recruited to participate in fMRI scans. A single-digit continuous performance task alternated with a control task in a block-design paradigm. between-group comparisons were made using voxel-by-voxel analysis. Follow-up correlations were made between performance and activation. RESULTS: Group performance did not significantly differ in percentage correct (p = 0.36) or discriminability (p = 0.11). ADHD comorbidity was associated with less activation in the ventrolateral prefrontal cortex (Brodmann 10) and anterior cingulate, and greater activation in posterior parietal cortex and middle temporal gyrus. Comorbid ADHD was associated with substantial differences in patterns of correlation between performance and voxel-by-voxel activation. CONCLUSIONS: Our findings suggest that comorbid ADHD in bipolar adolescents is associated with activation of alternative pathways during performance of a simple attention task. The pattern of differences suggests that bipolar adolescents with comorbid ADHD demonstrate decreased activation of prefrontal regions, compared with bipolar adolescents without ADHD, and preferentially recruit portions of posterior parietal and temporal cortex.

Adolescent↗

PubMed2004

Abnormal frontal white matter tracts in bipolar disorder: a diffusion tensor imaging study.

OBJECTIVES: Prefrontal white matter has been hypothesized to be integral to the pathophysiology of bipolar disorder. Recent morphometric studies however, have not observed changes in white matter in bipolar patients. We hypothesized that changes in prefrontal function in bipolar disorder, widely reported in the literature, may be related to a loss of white matter tract integrity with a resultant dysconnectivity syndrome. In this study we utilized diffusion tensor imaging (DTI) to examine prefrontal white matter in patients with bipolar disorder. METHODS: Nine patients with bipolar disorder and nine healthy controls were recruited. DTI and localizing anatomic data were acquired, and regions of interest (ROIs) identified in the prefrontal white matter at 15, 20, 25, and 30 mm superior to the anterior commissure (AC). Fractional anisotropy (FA) and trace apparent diffusion coefficient (TADC) were compared by ROI between study groups. RESULTS: The FA of ROIs 25 and 30 mm above the AC was significantly reduced in patients with bipolar disorder; FA of all ROIs showed high-medium to large effect sizes. No significant group differences were identified in TADC. CONCLUSIONS: Our findings suggest that a loss of bundle coherence is present in prefrontal white matter. This loss of coherence may contribute to prefrontal cortical pathology in patients with bipolar disorder.

Adult↗

PubMed2004

Changes in neuronal activation in patients with bipolar disorder during performance of a working memory task.

OBJECTIVES: Several lines of evidence suggest that deficits in cognition persist in bipolar patients during periods of euthymia. Working memory impairment has been observed in euthymic bipolar patients and noted to be a significant source of functional deficits in psychiatric disorders. Functional changes associated with these cognitive deficits however, remain poorly understood. We hypothesized that patients with bipolar disorder would demonstrate changes in neuronal activation in specific regions forming part of the working memory network. METHODS: Fifteen euthymic bipolar patients and fifteen age- and gender-matched healthy controls were recruited. Subjects participated in fMRI scans during which a two-back working memory task alternated with a zero-back control/attention task using a block-design paradigm. Groups were analyzed separately, and intergroup comparisons were made using an exploratory, voxel-by-voxel analysis. RESULTS: Bipolar patients performed more poorly on the cognitive tasks than did healthy controls (F = 3.77, p = 0.04). After covarying for task performance and reaction time, bipolar patients demonstrated significantly greater activation than healthy subjects in several regions including the fronto-polar prefrontal cortex, temporal cortex, basal ganglia, thalamus, and posterior parietal cortex. No areas showed a significant decrease in activation, compared with healthy controls. CONCLUSIONS: Our findings suggest that decreased working memory performance in bipolar patients reflects specific neurofunctional deficits. These deficits may represent primary areas of neuropathology or be secondary to neuropathology elsewhere in the working memory network. Continued research utilizing other imaging modalities may further clarify the underlying neuropathology involved in these cognitive deficits.

Adult↗