It has previously been possible to measure regional glucose use in the cerebral cortex in animals only with autoradiographic techniques. With the advent of position emission tomography (PET) using (I8F-2DG) 18F-2-deoxyglucose, it is now possible to assess local glucose uptake in pmolil00 g tissueimin in normal volunteers or patients. The PET technique is complex and costly and cannot be repeated frequently because of the radiation dosage. However, local glucose use is closely tied to cerebral blood flow, and studies have related blood flow to EEG frequency measures. In this study, we have simultaneously investigated local glucose metabolism using 18F-2DG with PET and EEG frequency with 16-lead topographic mapping in six normal controls. Subjects sat in an acoustically treated darkened room with eyes closed for 10 min prior to, and 30 min following injection of 3-5 mCi I8F-2DG. Following uptake, seven to eight horizontal scans parallel to the canthomeatal line were made. EEG recordings are made beginning 1 min after injection of the isotope and continuing for 30 min with 12 standard 1Oi20 system points on the left hemisphere and midline, and 4 additional points between existing posterior leads. Ten-second EEG epochs are edited for artifacts and then analyzed by fast Fourier transform techniques. Using a cross-sectional whole-head atlas, a standardized, approximately equal-area two-dimensional representation of a lateral view of the brain was developed and 10120 system scalp coordinates were projected onto it. EEG power estimates are interpolated for all points on this brain map. Using digital techniques, a 1 -cm-thick cortical strip is peeled off each PET,
The authors aimed to examine central glucocorticoids effects by measuring relative glucose metabolic rate (rGMR) in the hippocampus, amygdala, and anterior cingulate cortex (ACC) and the relationship between amygdala and ACC activity. The participants were male combat veterans with and without PTSD, 52 to 81 years old. The authors utilized randomized, double-blind, placebo-controlled examinations of the rGMR response to 17.5 mg hydrocortisone (HCORT) using 2-Deoxy-2-[(18)F]fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) neuroimaging. Group differences in hemispheric laterality of rGMR were observed following placebo administration, reflecting lower rGMR in the right hippocampus and ventral amygdala, and higher rGMR in the left ventral amygdala in the PTSD+ group compared to the PTSD- group. HCORT reduced these group differences in laterality. The net effect of HCORT was to restore a normal inverse association between the ACC and amygdala in the PTSD+ group, but disrupt this neural network in the PTSD- group. The magnitude of improvement in working memory correlated with greater hemispheric laterality in the dorsal amygdala following HCORT in both groups. The restorative effects of HCORT on metabolism and working memory provide a rationale for examining the therapeutic benefits of glucocorticoid manipulation in aging PTSD patients.
Converging lines of research suggest that white matter abnormalities may be central to the pathophysiology of schizophrenia. The purpose of this study was to examine regional white matter in the anterior limb of the internal capsules in patients with schizophrenia. The authors obtained high-resolution magnetic resonance imaging in 106 patients with schizophrenia and 42 age and sex-matched healthy comparison subjects. The area of the anterior limb of the internal capsule was measured at five proportionately spaced dorsal-to-ventral levels. Schizophrenia patients were divided into good-outcome and poor-outcome groups, based on longitudinal analysis of self-care deficits. Patients with poor-outcome had significantly smaller dorsal areas than healthy comparison subjects, but good-outcome patients did not differ from healthy comparison subjects. Larger relative volumes of the caudate, putamen, and thalamus tended to be associated with relatively larger volumes of the internal capsule in healthy comparison subjects and good-outcome patients, consistent with the known frontal-striatal-thalamic pathways. Larger ventricles were associated with smaller internal capsules, particularly in healthy comparison subjects. The findings suggest disruption of internal capsule fibers in poor-outcome patients with schizophrenia. These abnormalities may be independent of other structural changes in schizophrenia.
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