Higher C-peptide levels are associated with regional cortical thinning in 1093 cognitively normal subjects.

BACKGROUND AND PURPOSE: Recent studies have demonstrated an association between increased insulin secretion and cognitive impairment. However, there is no previous study that directly evaluates the association between increased insulin secretion and cortical thickness to our knowledge. Therefore, our aim was to evaluate the effect of hyperinsulinemia, as measured by C-peptide level, on cortical thickness in a large sample of cognitively normal individuals. METHODS: Cortical thickness was measured in 1093 patients who visited the Samsung Medical Health Promotion Center and underwent brain magnetic resonance imaging (MRI) and a blood test to measure C-peptide concentration. Automated surface-based analyses of the MRI data were used to measure cortical thickness. C-peptide levels were divided into quartiles for comparison. Patients in the first to third quartiles were used as the reference category. RESULTS: Patients in the highest quartile group (Q4) of C-peptide levels showed cortical thinning, predominantly in both medial temporal lobes, the right inferior temporal gyrus, both medial prefrontal lobes and the right superior parietal lobule, compared with the lower quartile groups (Q1-Q3) after controlling for age, gender, body mass index, history of hypertension, hyperlipidemia, previous stroke, cardiovascular disease and fasting glucose level. CONCLUSIONS: A higher C-peptide level is associated with regional cortical thinning, even in cognitively normal individuals.

Cortical thickness and hippocampal shape in pure vascular mild cognitive impairment and dementia of subcortical type.

BACKGROUND AND PURPOSE: The progression pattern of brain structural changes in patients with isolated cerebrovascular disease (CVD) remains unclear. To investigate the role of isolated CVD in cognitive impairment patients, patterns of cortical thinning and hippocampal atrophy in pure subcortical vascular mild cognitive impairment (svMCI) and pure subcortical vascular dementia (SVaD) patients were characterized. METHODS: Forty-five patients with svMCI and 46 patients with SVaD who were negative on Pittsburgh compound B (PiB) positron emission tomography imaging and 75 individuals with normal cognition (NC) were recruited. RESULTS: Compared with NC, patients with PiB(-) svMCI exhibited frontal, language and retrieval type memory dysfunctions, which in patients with PiB(-) SVaD were further impaired and accompanied by visuospatial and recognition memory dysfunctions. Compared with NC, patients with PiB(-) svMCI exhibited cortical thinning in the frontal, perisylvian, basal temporal and posterior cingulate regions. This atrophy was more prominent and extended further toward the lateral parietal and medial temporal regions in patients with PiB(-) SVaD. Compared with NC subjects, patients with PiB(-) svMCI exhibited hippocampal shape deformities in the lateral body, whilst patients with PiB(-) SVaD exhibited additional deformities within the lateral head and inferior body. CONCLUSIONS: Our findings suggest that patients with CVD in the absence of Alzheimer's disease pathology can be demented, showing cognitive impairment in multiple domains, which is consistent with the topography of cortical thinning and hippocampal shape deformity.

Comparison of cortical thickness in patients with early-stage versus late-stage amnestic mild cognitive impairment.

BACKGROUND AND PURPOSE: Disappointing outcomes from clinical trials involving amyloid-modifying therapies for Alzheimer's disease (AD) have prompted more focus on the concept of early-stage (E) amnestic mild cognitive impairment (E-aMCI). However, limited evidence suggests that E-aMCI may represent aMCI at a very early stage of AD. Furthermore, the nature of the progression of E-aMCI to late-stage aMCI (L-aMCI) remains unclear. Therefore, the aim of the present study was to characterize patterns of cortical thinning in both E-aMCI and L-aMCI patients. METHODS: Cortical thicknesses were measured in 190 patients with aMCI and 147 subjects with normal cognition. In accordance with memory test scores involving delayed recall items, aMCI patients were divided into two subgroups, containing 73 E-aMCI subjects with milder memory impairment [scores between -1.5 standard deviation (SD) and -1.0 SD compared with age- and education-matched norms] and 117 L-aMCI subjects with more severe memory impairment (scores lower than -1.5 SD). RESULTS: Compared with controls, the E-aMCI group exhibited cortical thinning in the left medial temporal and insular regions, whereas the L-aMCI group showed cortical thinning in widespread regions, including the bilateral dorsolateral prefrontal, anterior and medial temporal, and temporo-parietal association cortices, and the precuneus. When the two aMCI groups were directly compared, the L-aMCI group showed greater cortical thinning in the right superior prefrontal, medial temporal, posterior cingulate and lateral parietal cortices. CONCLUSION: Our findings suggest that E-aMCI might represent an early symptomatic stage of AD. Furthermore, L-aMCI might resemble AD more closely than E-aMCI, in terms of the topography of cortical thinning.

Photorealistic image generation of molecular structure on PC screen using the ray-tracing technique.

A PC version of three-dimensional molecular graphics package has been developed to run under MS-DOS environment on IBM PC-compatible computers equipped with a VGA graphics board. The program consists of two parts: a menu-driven interactive system module in EGA mode, and a ray-tracing module in VGA mode. In the 256-color VGA mode, ray-tracing images are represented with a 4-color map, with 64 levels for each color: 32 levels of illuminance and 32 levels of saturation. Molecular structure can be analyzed along various directions with various light sources. Ray-tracing images are also represented in a 16-color EGA mode with the half-toning method, which can display 76 gray levels for each color. To obtain good photo-realistic images in an efficient way, we have used two light sources, with an intensity ratio of 7:3, which are located in front of the top right and bottom left corners of the screen.