Asymmetry of Dopamine D2/3 Receptor Availability in Dorsal Putamen and Body Mass Index in Non-obese Healthy Males

The dopaminergic system is involved in the regulation of food intake, which is crucial for the maintenance of body weight. We examined the relationship between striatal dopamine (DA) D2/3 receptor availability and body mass index (BMI) in 25 non-obese healthy male subjects using [11C]raclopride and positron emission tomography. None of [11C]raclopride binding potential (BP) values (measures of DA D2/3 receptor availability) in striatal subregions (dorsal caudate, dorsal putamen, and ventral striatum) in the left and right hemispheres was significantly correlated with BMI. However, there was a positive correlation between the right-left asymmetry index of [11C]raclopride BP in the dorsal putamen and BMI (r=0.43, p<0.05), suggesting that greater BMI is linked with higher receptor availability in the right dorsal putamen relative to the left in non-obese individuals. The present results, combined with previous findings, may also suggest neurochemical mechanisms underlying the regulation of food intake in non-obese individuals.

Imaging of Dopamine Release Induced by Pharmacologic and Nonpharmacologic Stimulations / 핵의학분자영상

Technological advances in molecular imaging made it possible to image synaptic neurotransmitter concentration in living human brain. The dopaminergic system has been most intensively studied because of its importance in neurological as well as psychiatric disorders. This paper provides a brief overview of recent progress in imaging studies of dopamine release induced by pharmacologic and nonpharmacologic stimulations.

Metabolic Correlates of Temperament Factors of Personality / 핵의학분자영상

PURPOSE: Gender differences in personality are considered to have biological bases. In an attempt to understand the gender differences of personality on neurobiological bases, we conducted correlation analyses between regional brain glucose metabolism and temperament factors of personality in males and females. MATERIALS AND METHODS: Thirty-six healthy right-handed volunteers (18 males, 33.8+/-17.6 y; 18 females, 36.2+/-20.4 y) underwent FDG PET at resting state. Three temperament factors of personality (novelty seeking (NS), harm avoidance (HA), reward dependence (RD)) were assessed using Cloninger's 240-item Temperament and Character Inventory (TCI) within 10 days of FDG PET scan. Correlation between regional glucose metabolism and each temperament factor was tested using SPM2. RESULTS: In males, a significant negative correlation between NS score and glucose metabolism was observed in the bilateral superior temporal gyri, the hippocampus and the insula, while it was found in the bilateral middle frontal gyri, the right superior temporal gyrus and the left cingulate cortex and the putamen in females. A positive HA correlation was found in the right midbrain and the left cingulate gyrus in males, but in the bilateral basal ganglia in females. A negative RD correlation was observed in the right middle frontal and the left middle temporal gyri in males, while the correlation was found in the bilateral middle frontal gyri and the right basal ganglia and the superior temporal gyrus in females. CONCLUSION: These data demonstrate different cortical and subcortical metabolic correlates of temperament factors of personality between males and females. These results may help understand biological substrate of gender differences in personality and susceptibility to neuropsychiatric illnesses.

Metabolic Correlates of Temperament Factors of Personality / 핵의학분자영상

PURPOSE: Gender differences in personality are considered to have biological bases. In an attempt to understand the gender differences of personality on neurobiological bases, we conducted correlation analyses between regional brain glucose metabolism and temperament factors of personality in males and females. MATERIALS AND METHODS: Thirty-six healthy right-handed volunteers (18 males, 33.8+/-17.6 y; 18 females, 36.2+/-20.4 y) underwent FDG PET at resting state. Three temperament factors of personality (novelty seeking (NS), harm avoidance (HA), reward dependence (RD)) were assessed using Cloninger's 240-item Temperament and Character Inventory (TCI) within 10 days of FDG PET scan. Correlation between regional glucose metabolism and each temperament factor was tested using SPM2. RESULTS: In males, a significant negative correlation between NS score and glucose metabolism was observed in the bilateral superior temporal gyri, the hippocampus and the insula, while it was found in the bilateral middle frontal gyri, the right superior temporal gyrus and the left cingulate cortex and the putamen in females. A positive HA correlation was found in the right midbrain and the left cingulate gyrus in males, but in the bilateral basal ganglia in females. A negative RD correlation was observed in the right middle frontal and the left middle temporal gyri in males, while the correlation was found in the bilateral middle frontal gyri and the right basal ganglia and the superior temporal gyrus in females. CONCLUSION: These data demonstrate different cortical and subcortical metabolic correlates of temperament factors of personality between males and females. These results may help understand biological substrate of gender differences in personality and susceptibility to neuropsychiatric illnesses.

Effects of Motion Correction for Dynamic 11CRaclopride Brain PET Data on the Evaluation of Endogenous Dopamine Release in Striatum / 대한핵의학회잡지

PURPOSE: Neuroreceptor PET studies require 60-120 minutes to complete and head motion of the subject during the PET scan increases the uncertainty in measured activity. In this study, we investigated the effects of the data-driven head motion correction on the evaluation of endogenous dopamine release (DAR) in the striatum during the motor task which might have caused significant head motion artifact. MATERIALS AND METHODS: [11C]raclopride PET scans on 4 normal volunteers acquired with bolus plus constant infusion protocol were retrospectively analyzed. Following the 50 min resting period, the participants played a video game with a monetary reward for 40 min. Dynamic frames acquired during the equilibrium condition (pre-task: 30-50 min, task: 70-90 min, post-task: 110-120 min) were realigned to the first frame in pre-task condition. Intra-condition registrations between the frames were performed, and average image for each condition was created and registered to the pre-task image (inter-condition registration). Pre-task PET image was then co-registered to own MRI of each participant and transformation parameters were reapplied to the others. Volumes of interest (VOI) for dorsal putamen (PU) and caudate (CA), ventral striatum (VS), and cerebellum were defined on the MRI. Binding potential (BP) was measured and DAR was calculated as the percent change of BP during and after the task. SPM analyses on the BP parametric images were also performed to explore the regional difference in the effects of head motion on BP and DAR estimation. RESULTS: Changes in position and orientation of the striatum during the PET scans were observed before the head motion correction. BP values at pre-task condition were not changed significantly after the intra-condition registration. However, the BP values during and after the task and DAR were significantly changed after the correction. SPM analysis also showed that the extent and significance of the BP differences were significantly changed by the head motion correction and such changes were prominent in periphery of the striatum. CONCLUSION: The results suggest that misalignment of MRI-based VOI and the striatum in PET images and incorrect DAR estimation due to the head motion during the PET activation study were significant, but could be remedied by the data-driven head motion correction.

Smoking-Induced Dopamine Release Studied with 11CRaclopride PET / 대한핵의학회잡지

PURPOSE: It has been postulated that dopamine release in the striatum underlies the reinforcing properties of nicotine. Substantial evidence in the animal studies demonstrates that nicotine interacts with dopaminergic neuron and regulates the activation of the dopaminergic system. The aim of this study was to visualize the dopamine release by smoking in human brain using PET scan with [11C]raclopride. MATERIALS AND METHODS: Five male non-smokers or ex-smokers with an abstinence period longer than 1 year (mean age of 24.4+/-1.7 years) were enrolled in this study. [11C]raclopride, a dopamine D2 receptor radioligand, was administrated with bolus-plus- constant infusion. Dynamic PET was performed during 120 minutes (3x20s, 2x60s, 2x120s, 1x180s and 22x300s). Following the 50 minute-scanning, subjects smoked a cigarette containing 1 mg of nicotine while in the scanner. Blood samples for the measurement of plasma nicotine level were collected at 0, 5, 10, 15, 20, 25, 30, 45, 60, and 90 minute after smoking. Regions for striatal structures were drawn on the coronal summed PET images guided with co-registered MRI. Binding potential, calculated as (striatal-cerebellar) /cerebellar activity, was measured under equilibrium condition at baseline and smoking session. RESULTS: The mean decrease in binding potential of [11C]raclopride between the baseline and smoking in caudate head, anterior putamen and ventral striatum was 4.7 %, 4.0 % and 7.8 %, respectively. This indicated the striatal dopamine release by smoking. Of these, the reduction in binding potential in the ventral striatum was significantly correlated with the cumulated plasma level of the nicotine (Spearman's rho=0.9, p=0.04). CONCLUSION: These data demonstrate that in vivo imaging with [11C]raclopride PET could measure nicotine-induced dopamine release in the human brain, which has a significant positive correlation with the amount of nicotine administered by smoking.

Neuropsychological and Neuroimaging Findings of Frontal Variant of Alzheimer's Disease

BACKGROUND: Patients with Alzheimer's disease (AD) at an early stage present with memory decline and impairments of language and visuospatial functions. However, some AD patients occasionally show frontal lobe dysfunctions in the early stage those are known to emerge only at the advanced stage. This subtype of AD is called a frontal variant of AD (frontal AD). We report neuropsychological and FDG-PET findings of three cases of frontal AD. METHODS: Three patients met the diagnostic criteria of probable AD proposed by the NINCDS-ADRDA. However, they unusually showed clinical symptoms associated with frontal lobe dysfunctions even if they were relatively in the early stage of dementia. All the patients underwent neuropsychological tests and brain FDG-PET scans. Distribution of glucose hypometabolism was analyzed using statistical parametric mappings (SPM). RESULTS: Results of neuropsychological tests were consistent with findings of AD except that frontal lobe dysfunctions were prominent. FDG-PET scans and SPM analysis of these images showed hypometabolism in the frontal as well as temporo-parietal regions. Unlike the hypometabolism pattern found in frontotemporal dementia, frontal hypometabolism in our patients was not as severe as parietal hypometablism and hypometabolic regions within the temporal lobe were in the middle or posterior part of the middle and inferior temporal gyri rather than in the anterior part. CONCLUSIONS: Detailed neuropsycholgical tests and FDG-PET may help differentiate AD with frontal involvement in its early stage (frontal AD) from frontotemporal dementia. Future studies with FDG-PET in a larger series of frontal AD cases, especially with histologically proven cases, may be needed.

Application of False Discovery Rate Control in the Assessment of Decrease of FDG Uptake in Early Alzheimer Dementia / 대한핵의학회잡지

PURPOSE: Determining an appropriate thresholding is crucial for PDG PET analysis since strong control of Type I error could fail to find pathological differences between early Alzheimer' disease (AD) patients and healthy normal controls. We compared the SPM results on FDG PET imaging of early AD using uncorrected p-value, random-field based corrected p-value and false discovery rate (FDR) control. MATERIALS AND METHODS: Twenty-eight patients (66+/-7 years old) with early AD and 18 age-matched normal controls (68+/-6 years old) underwent FDG brain PET. To identify brain regions with hypo-metabolism in group or individual patient compared to normal controls, group images or each patient's image was compared with normal controls using the same fixed p-value of 0.001 on uncorrected thresholding, random-field based corrected thresholding and FDR control. RESULTS: The number of hypo-metabolic voxels was smallest in corrected p-value method, largest in uncorrected p-value method and intermediate in FDG thresholding in group analysis. Three types of result pattern were found. The first was that corrected p-value did not yield any voxel positive but FDR gave a few significantly hypometabolic voxels (8/28, 29%). The second was that both corrected p-value and FDR did not yield any positive region but numerous positive voxels were found with the threshold of uncorrected p-values (6/28, 21%). The last was that FDR was detected as many positive voxels as uncorrected p-value method (14/28, 50%). CONCLUSIONS: FDR control could identify hypo-metabolic areas in group or individual patients with early AD. We recommend FDR control instead of uncorrected or random-field corrected thresholding method to find the areas showing hypometabolism especially in small group or individual analysis of FDG PET.

Comparison of the Brain Activation Patterns during Focused Attention and Working Memory Using Positron Emission Tomography / 신경정신의학

OBJECTIVES: This study was undertaken to identify neural substrates for simple focused attention and more highly-focused working memory in normal people and investigate their characteristics and differences. METHOD: Fourteen normal subjects were studied with [15O]H 2O positron emission tomography during a visual processing baseline task, simple focused attention task and working memory task. Results were analyzed with the subtraction analysis to map the neural correlates of focused attention and working memory. RESULTS: Activated areas during focused attention tended to be lateralized to the left and scattered over various regions including the anterior cingulate, motor area, and primary and secondary visual cortices. While the areas activated during working memory also show the left lateralization and scattered distribution, activation prevailed more in the frontal lobe than in the visual cortex, and was particularly remarkable in the right anterior cingulate. CONCLULSION: Focused attention and working memory do not have only conceptually commonalities and differences but also have common and specific areas in their neural substrates. The anterior cingulate may commonly play an important role in both cognitive functions, whereas secondary visual cortex and prefrontal cortex seem to be predominantly implicated in each function, respectively.

Comparison of the Neural Substrates Mediating the Semantic Processing of Korean and English Words Using Positron Emission Tomography / 대한핵의학회잡지

No abstract available.