Daniel Pham

Gray matter prefrontal changes in type 2 diabetes detected using MRI

To examine the volumes of the gray and white matter both globally and regionally in patients diagnosed with type 2 diabetes and controls.

Executive function and MRI prefrontal volumes among healthy older adults.

Brain atrophy and decline in executive functioning have been reported during late life, but the relationship between the 2 phenomena is not clear. To examine associations between executive tasks and morphometry, MRIs of the prefrontal cortex from 23 healthy elders were manually masked and automatically segmented. Total brain matter of the bilateral orbitofrontal, anterior cingulate, gyrus rectus, precentral gyrus, and middle frontal gyrus were computed as ratios of intracranial volume. A neuropsychological battery of five clinical tests of executive function was administered. Better performance on a response inhibition task was associated with larger volume in anterior cingulate, and performance on a nonverbal inductive reasoning task was associated with larger gyrus rectus volumes. In contrast, larger orbitofrontal volumes were associated with lower verbal and nonverbal generative output. An aggregated error index from 4 executive tests correlated negatively with a regional composite brain index. In conclusion, some executive abilities correlate with volumes of specific prefrontal subregions despite a robust neural interconnectedness between the subregions.

Prefrontal brain morphology and executive function in healthy and depressed elderly

Late‐life depression is known to correlate independently with decreased brain volumes in anterior cingulate, gyrus rectus and orbitofrontal cortex and with executive dysfunction, but the relationship between morphometry of reduced volume regions and executive dysfunction has not been well defined.

Mapping Callosal Morphology in Early- and Late-Onset Elderly Depression: An Index of Distinct Changes in Cortical Connectivity

There is some evidence of corpus callosum abnormalities in elderly depression, but it is not known whether these deficits are region-specific or differ based on age at onset of depression. Twenty-four patients with early-onset depression (mean age=68.00, SD±5.83), 22 patients with late-onset depression (mean age=74.50, SD±8.09) and 34 elderly control subjects (mean age=72.38; SD±6.93) were studied. Using 3D MRI data, novel mesh-based geometrical modeling methods were applied to compare the midsagittal thickness of the corpus callosum at high spatial resolution between groups. Neuropsychological correlates of midsagittal callosal area differences were additionally investigated in a subsample of subjects. Depressed patients exhibited significant callosal thinning in the genu and splenium compared to controls. Significant callosal thinning was restricted to the genu in early-onset patients, but patients with late-onset depression exhibited significant callosal thinning in both the genu and splenium relative to controls. The splenium of the corpus callosum was also significantly thinner in subjects with late- vs early-onset depression. Genu and splenium midsagittal areas significantly correlated with memory and attention functioning among late-onset depressed patients, but not early-onset depressed patients or controls. Circumscribed structural alterations in callosal morphology may distinguish late- from early-onset depression in the elderly. These findings suggest distinct abnormalities of cortical connectivity in late- and early-onset elderly depression with possible influence on the course of illness. Patients with a late onset of depression may be at higher risk of illness progression and eventually dementia conversion than early-onset depression, with potentially important implications for research and therapy.

Regional cortical gray matter thickness differences associated with type 2 diabetes and major depression

The purpose of this study was to examine the effect of type 2 diabetes with major depression on cortical gray matter using magnetic resonance imaging and cortical pattern matching techniques. We hypothesized that diabetic subjects and depressed diabetic subjects would demonstrate decreased cortical gray matter thickness in prefrontal areas as compared to healthy control subjects. Patients with type 2 diabetes (n=26) and patients with diabetes and major depression (n=26) were compared with healthy controls (n=20). Gray matter thickness across the entire cortex was measured using cortical pattern matching methods. All subjects with diabetes demonstrated decreased cortical gray matter thickness in the left anterior cingulate region. Additionally, depressed diabetic subjects showed significant cortical gray matter decreases in bilateral prefrontal areas compared with healthy controls. Correlations between clinical variables and cortical gray matter thickness revealed a significant negative relationship with cerebrovascular risk factors across all three groups, most consistently in the left dorsomedial prefrontal cortex. A significant positive relationship between performance on attention and executive function tasks and cortical gray matter thickness predominantly in left hemisphere regions was also seen across all subjects. Depression and diabetes are associated with significant cortical gray matter thinning in medial prefrontal areas.

Neuroanatomical correlates of executive functioning in depressed adults with type 2 diabetes

Depression is often comorbid with type 2 diabetes. Depression may increase vulnerability to and/or exacerbate existing cognitive deficits. Little is known about the brain pathophysiology underlying depression and cognitive abnormalities in diabetes. The aim of this study was to examine the relationship of orbitofrontal and anterior cingulate volumes with executive functioning and attention/processing speed in type 2 diabetic participants with and without major depression. A total of 21 diabetic participants with major depression, 23 diabetic participants with no depression, and 22 healthy controls were compared. Using brain magnetic resonance imaging, volumetric measures of the prefrontal cortex were examined in relation to executive functioning and attention/processing speed. Partial correlations suggested a significant positive relationship between right orbitofrontal regions and executive functioning in the group with diabetes and depression only, indicating that neurobiological changes in the orbitofrontal region may contribute to observed cognitive dysfunction.

Daily Functioning and Prefrontal Brain Morphology in Healthy and Depressed Community-Dwelling Elderly

OBJECTIVE Self-perceived emotional vitality, intact mood, physical activity, and social engagement are recognized as important indicators for lowered rates of morbidity and increased longevity in late-life, but little is known about their underlying neural substrates. This study examined relationships between self-reported levels of general functioning and the combined volume of three integrated prefrontal structures associated with self-perception and emotion. DESIGN Cross-sectional. SETTING UCLA Semel Institute for Neuroscience, Los Angeles. PARTICIPANTS Depressed (N = 43) and comparison (N = 41) elderly subjects. MEASUREMENTS Magnetic resonance images of orbitofrontal, gyrus rectus, and anterior cingulate gray and white matter volumes were corrected for intracranial volume and combined across structures to form white matter and gray matter scales. Subjects completed the RAND Short-Form 36 Questionnaire, a self-report evaluation of daily functioning. Subscales used for analysis were physical function, energy, and general health, which were not correlated with depression. RESULTS White matter volumes were associated with self-perceptions of Energy for healthy as well as depressed individuals, and gray matter volume was associated with General Health. This latter association was strongest among patients with late-onset of depression, i.e., onset > age 50, although it appeared in all diagnostic groups. CONCLUSIONS Although mild to moderate atrophy is expected in late-life, prefrontal atrophy may represent changes to neuroanatomic substrates that qualitatively modulate self-perceptions of energy and general health for both depressed and nondepressed persons.

Cortical thinning in patients with late-life minor depression.

OBJECTIVES Clinically significant minor depression is among the most common mental disorders in the elderly individuals and is associated with considerable medical and psychosocial morbidity. Despite its clinical impact, the biological basis of minor depression in the elderly individuals remains poorly understood. The purpose of our current study was to examine cortical thickness in a sample of patients with late-life minor depression and non-depressed comparison subjects using magnetic resonance imaging (MRI). DESIGN Cross-sectional analysis. SETTING Community. PARTICIPANTS Patients (n = 16; mean age = 76.2 ± 7.5) met modified DSM (Diagnostic and Statistical Manual of Mental Disorders) criteria for minor depression and were free of other brain diseases. Healthy comparison subjects (HC; n = 16) were of comparable age and gender distribution. MEASUREMENTS All subjects were scanned on a 1.5-Tesla GE scanner and brain regions were outlined using Freesurfer Image Analysis. RESULTS Results show that patients with minor depression have cortical thinning in the right cingulate cortex compared to HC. CONCLUSIONS These findings indicate that abnormalities in specific structures and associated neural circuitry may underlie minor and major depression in the elderly individuals and the pathophysiological abnormalities are comparable in major and less severe forms of the disorder.