Striatal size, glucose metabolic rate, and verbal learning in normal aging

Age-Related Changes in Caudate Glucose Metabolism: Insights from Normative Modeling Study in Healthy Subjects

BACKGROUND

As the global population ages, the prevalence of neurodegenerative conditions, such as Alzheimer's disease (AD), Parkinson's disease (PD), dementia with Lewy bodies, and frontotemporal dementia, continues to rise. Understanding the impact of aging on striatal glucose metabolism is pivotal in identifying potential biomarkers for the early detection of these disorders.

METHODS

We investigated age-related changes in striatal glucose metabolism using both region of interest (ROI)-based and voxel-wise correlation analyses. Additionally, we employed a normative modeling approach to establish age-related metabolic trajectories and assess individual deviations from these normative patterns. In vivo cerebral glucose metabolism was quantified using a molecular neuroimaging technique, 18F-FDG PET.

RESULTS

Our results revealed significant negative correlations between age and glucose metabolism in the bilateral caudate. Furthermore, the normative modeling demonstrated a clear, progressive decline in caudate metabolism with advancing age, and the most pronounced reductions were observed in older individuals.

CONCLUSIONS

These findings suggest that metabolic reductions in the caudate may serve as a sensitive biomarker for normal aging and offer valuable insights into the early stages of neurodegenerative diseases. Moreover, by establishing age-specific reference values for caudate glucose metabolism, the normative model provides a framework for detecting deviations from expected metabolic patterns, which may facilitate the early identification of metabolic alterations that could precede clinical symptoms of neurodegenerative processes.

Long-term trends in total administered radiation dose from brain [18F]FDG-PET in children with drug-resistant epilepsy

PURPOSE

To assess the trends in administered 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) doses, computed tomography (CT) radiation doses, and image quality over the last 15 years in children with drug-resistant epilepsy (DRE) undergoing hybrid positron emission tomography (PET) brain scans.

METHODS

We retrospectively analyzed data from children with DRE who had [18F]FDG-PET/CT or magnetic resonance scans for presurgical evaluation between 2005 and 2021. We evaluated changes in injected [18F]FDG doses, administered activity per body weight, CT dose index volume (CTDIvol), and dose length product (DLP). PET image quality was assessed visually by four trained raters. Conversely, CT image quality was measured using region-of-interest analysis, normalized by signal-to-noise (SNR) and contrast-to-noise ratio (CNR).

RESULTS

We included 55 children (30 male, mean age: 9 ± 6 years) who underwent 61 [18F]FDG-PET scans (71% as PET/CT). Annually, the injected [18F]FDG dose decreased by ~ 1% (95% CI: 0.92%-0.98%, p < 0.001), with no significant changes in administered activity per body weight (p = 0.51). CTDIvol and DLP decreased annually by 16% (95% CI: 9%-23%) and 15% (95% CI: 8%-21%, both p < 0.001), respectively. PET image quality improved by 9% year-over-year (95% CI: 6%-13%, p < 0.001), while CT-associated SNR and CNR decreased annually by 7% (95% CI: 3%-11%, p = 0.001) and 6% (95% CI: 2%-10%, p = 0.008), respectively.

CONCLUSION

Our findings indicate stability in [18F]FDG administered activity per body weight alongside improvements in PET image quality. Conversely, CT-associated radiation doses reduced. These results reaffirm [18F]FDG-PET as an increasingly safer and higher-resolution auxiliary imaging modality for children with DRE. These improvements, driven by technological advancements, may enhance the diagnostic precision and patient outcomes in pediatric epilepsy surgery.

Neuroimaging of autobiographical memory in dementia with Lewy bodies: a story of insula

Although deficits in learning and retrieving new information are well characterized in dementia with Lewy bodies, autobiographical memory has never been explored in this disease. Yet, autobiographical memory impairments are a pervasive feature of dementia, well characterized in other neurodegenerative diseases. Moreover, autobiographical memory corresponds to an extension over time of the self, which we hypothesize is altered in dementia with Lewy bodies and impairment of which could be linked to the insular atrophy occurring from an early stage of the disease. In this study, we sought to characterize autobiographical memory impairments and explore their neural correlates in dementia with Lewy bodies, on the assumption that insular damage could impact the self, including its most elaborate components, such as autobiographical memory. Twenty patients with prodromal to mild dementia with Lewy bodies were selected to participate in this exploratory study along with 20 healthy control subjects. The Autobiographical Interview was used to assess autobiographical memory. Performances were compared between patients and control subjects, and an analysis across life periods and recall conditions was performed. 3D magnetic resonance images were acquired for all participants, and correlational analyses were performed in the patient group using voxel-based morphometry. The behavioural results of the Autobiographical Interview showed that autobiographical memory performances were significantly impaired in dementia with Lewy body patients compared to control subjects in a temporally ungraded manner, for both the free recall and the specific probe conditions (P < 0.0001), though with greater improvement after probing in the patient group. Furthermore, autobiographical memory impairments were correlated with grey matter volume within right insular cortex, temporoparietal junction, precuneus, putamen, left temporal cortex, bilateral parahippocampus and cerebellum, using a threshold of P = 0.005 uncorrected. The behavioural results confirm the existence of temporally ungraded autobiographical memory impairments in dementia with Lewy bodies, from the early stage of the disease. As we expected, neuroimaging analysis revealed a role for the insula and the precuneus in autobiographical memory retrieval, two regions associated with elementary aspects of the self, among other brain regions classically associated with autobiographical memory, such as medial temporal lobe and temporoparietal junction. Our findings provide important insights regarding the involvement of the insula in the self and suggest that insular damage could lead to a global collapse of the self, including its more elaborated components, such as autobiographical memory.

Distinct neuroanatomical correlates of interference-related verbal episodic memory test in healthy older adults

Verbal learning test can include a trial of interference process that intrude initial learning and impose additional cognitive stress. However, it has been unclear whether the multiple memory processes underly different brain structural bases. We measured performances of word retrieval that represents distinct memory processes (initial learning, interference, and retention) and regional gray matter morphology from 230 cognitively unimpaired older adults. We identified three distinct multivariate pattern modes using canonical correlation analysis that map correspondence between memory and brain morphometry. The first mode comprised weights highly loaded on temporal lobe and overall performances. The second mode reflected subcortical volumes and initial learning performances. The third mode comprised thickness in the lateral prefrontal and parietal cortex and captured an ability to resist retroactive interference effect. While overall test performance reflected the temporal lobe and whole-gray matter volume, the interim trial of interference signifies neural correlates extending to subcortical and frontoparietal regions.

Gender-Related Differences in Regional Cerebral Glucose Metabolism in Normal Aging Brain

Objectives: This study was aimed to investigate the gender-related differences of regional cerebral glucose metabolism in healthy people along the age using 18F-FDG PET/CT.

Methods: We recruited 344 healthy volunteers, including 217 males and 127 females (age range: 40–89 years old). All subjects underwent fluorine-18 fluorodeoxyglucose(18F-FDG) positron emission tomography (PET). All the data were divided into four groups for every 10 years old. Each participant was carefully screened from PET, MR, and other examinations in order to exclude the abnormalities, such as neurodegenerative or psychiatric disorders, alcohol/abuse, cerebral vascular disorders, metabolic diseases like diabetes mellitus and hyperthyroidism, and other systemic malignancies. The 40–50 years old group was set as the baseline group. Statistical parametric mapping (SPM) analysis was employed to illustrate the differences among groups.

Results: Compared to the baseline group, whether in a cohort or different gender groups, the decrease of brain glucose metabolism was shown in the bilateral frontal lobe, anterior cingulate gyrus, and the bilateral temporal lobe. In males, the regions of decreased metabolism were bilateral frontal lobe, caudate nucleus, and cingulate gyrus, whereas that of females were left occipital lobe, cerebellum, and the thalamus. However, the overall decrease of brain metabolism in men and women began from the age of 60s, an aggravated decrease from 70s was only observed in males.

Conclusion: (1) An obviously decreased brain metabolism was found from 60 years old, especially in the bilateral frontal lobe, bilateral temporal lobe, and inferior cingulate gyrus; (2) We found specific brain metabolic differences between genders, including the caudate nucleus region in males and the occipital lobe region in females; and (3) The aging trend is different between genders.

Brain Network Segregation and Glucose Energy Utilization: Relevance for Age-Related Differences in Cognitive Function

The human brain is organized into segregated networks with strong within-network connections and relatively weaker between-network connections. This "small-world" organization may be essential for maintaining an energetically efficient system, crucial to the brain which consumes 20% of the body's energy. Brain network segregation and glucose energy utilization both change throughout the lifespan. However, it remains unclear whether these processes interact to contribute to differences in cognitive performance with age. To address this, we examined fluorodeoxyglucose-positron emission tomography and resting-state functional magnetic resonance imaging from 88 participants aged 18-73 years old. Consistent with prior work, brain network segregation showed a negative association with age across both sensorimotor and association networks. However, relative glucose metabolism demonstrated an interaction with age, showing a negative slope in association networks but a positive slope in sensorimotor networks. Overall, brain networks with lower segregation showed significantly steeper age-related differences in glucose metabolism, compared with highly segregated networks. Sensorimotor network segregation mediated the association between age and poorer spatial cognition performance, and sensorimotor network metabolism mediated the association between age and slower response time. These data provide evidence that sensorimotor segregation and glucose metabolism underlie some age-related changes in cognition. Interventions that stimulate somatosensory networks could be important for treatment of age-related cognitive decline.

D2/D3 dopamine receptor binding with [F-18]fallypride correlates of executive function in medication-naïve patients with schizophrenia

Converging evidence indicates that the prefrontal cortex is critically involved in executive control and that executive dysfunction is implicated in schizophrenia. Reduced dopamine D2/D3 receptor binding potential has been reported in schizophrenia, and the correlations with neuropsychological test scores have been positive and negative for different tasks. The aim of this study was to examine the relation between dopamine D2/D3 receptor levels with frontal and temporal neurocognitive performance in schizophrenia. Resting-state ¹⁸F-fallypride positron emission tomography was performed on 20 medication-naïve and 5 previously medicated for brief earlier periods patients with schizophrenia and 19 age- and sex-matched healthy volunteers. Striatal and extra-striatal dopamine D2/D3 receptor levels were quantified as binding potential using fallypride imaging. Magnetic resonance images in standard Talairach position and segmented into gray and white matter were co-registered to the fallypride images, and the AFNI stereotaxic atlas was applied. Two neuropsychological tasks known to activate frontal and temporal lobe function were chosen, specifically the Wisconsin Card Sorting Test (WCST) and the California Verbal Learning Test (CVLT). Images of the correlation coefficient between fallypride binding and WCST and CVLT performance showed a negative correlation in contrast to positive correlations in healthy volunteers. The results of this study demonstrate that lower fallypride binding potential in patients with schizophrenia may be associated with better performance. Our findings are consistent with previous studies that failed to find cognitive improvements with typical dopamine-blocking medications.

Study of normal volumetric variation in the putamen with age and sex using magnetic resonance imaging

Putamen volume is seen to alter in neurological and psychiatric disorders like Parkinson's disease, depression, schizophrenia, Alzheimer's disease, and in individuals treated with antipsychotics. To establish a trend in volume changes in pathologic states, studies on factors influencing normal variation in a given population become essential. This study aimed to evaluate the normal variations in putamen volume in the Indian population and correlate them with the effects of age and sex. Bilateral symmetry was also evaluated. The study included MR images of 98 individuals aged 10-87 years. Axial sections of T2-weighted spin echo sequences were used to estimate putamen volume. The putamen was delineated manually and its volume was estimated using Cavalieri's principle. Linear regression and paired t-test were used to analyze data. Bilateral putamen volume reduced with age in both sexes. This was statistically significant (P < 0.05) except for the left putamen volume in males. There was no significant age-adjusted effect of sex on putamen volume in both hemispheres (P > 0.05). Age and sex interaction was not found to be statistically significant. Hemispherical asymmetry was not established as the difference between the right and left putamen volume did not reach statistical significance in both males and females (P > 0.05). In conclusion, this study demonstrated an age related decline in the volumes of both putamen in males and females. The rate of volume reduction was not affected by sex. The study failed to establish a significant sex difference and hemispherical asymmetry in putamen volume. Clin. Anat. 30:461-466, 2017. © 2017 Wiley Periodicals, Inc.

FDG-PET scans in patients with Kraepelinian and non-Kraepelinian schizophrenia

We recruited 14 unmedicated patients with Kraepelinian schizophrenia (12 men and 2 women; mean age = 47 years old), 27 non-Kraepelinian patients (21 men and 6 women; mean age = 36.4 years old) and a group of 56 age- and sex-matched healthy volunteers. FDG positron emission tomography and MRI scans were coregistered for both voxel-by-voxel statistical mapping and stereotaxic regions of interest analysis. While both Kraepelinian and non-Kraepelinian patients showed equally lower uptake than healthy volunteers in the frontal lobe, the temporal lobes (Brodmann areas 20 and 21) showed significantly greater decreases in Kraepelinian than in non-Kraepelinian patients. Kraepelinian patients had lower FDG uptake in parietal regions 39 and 40, especially in the right hemisphere, while non-Kraepelinian patients had similar reductions in the left. Only non-Kraepelinian patients had lower caudate FDG uptake than healthy volunteers. While both patient groups had lower uptake than healthy volunteers in the medial dorsal nucleus of the thalamus, Kraepelinian patients alone had higher uptake in the ventral nuclei of the thalamus. Kraepelinian patients also showed higher metabolic rates in white matter. Our results are consistent with other studies indicating that Kraepelinian schizophrenia is a subgroup of schizophrenia, characterized by temporal and right parietal deficits and normal rather than reduced caudate uptake. It suggests that Kraepelinian schizophrenia may be more primarily characterized by FDG uptake decreased in both the frontal and temporal lobes, while non-Kraepelinian schizophrenia may have deficits more limited to the frontal lobe. This is consistent with some neuropsychological and prognosis reports of disordered sensory information processing in Kraepelinian schizophrenia in addition to deficits in frontal lobe executive functions shared with the non-Kraepelinian subtype.

Brain: normal variations and benign findings in fluorodeoxyglucose-PET/computed tomography imaging

Brain 18F-fluorodeoxyglucose (18F-FDG) PET allows the in vivo study of cerebral glucose metabolism, reflecting neuronal and synaptic activity. 18F-FDG-PET has been extensively used to detect metabolic alterations in several neurologic diseases compared with normal aging. However, healthy subjects have variants of 18F-FDG distribution, especially as associated with aging. This article focuses on 18F-FDG-PET findings in so-called normal brain aging, and in particular on metabolic differences occurring with aging and as a function of people’s gender. The effect of different substances, medications, and therapy procedures are discussed, as well as common artifacts.

Larger putamen size in antipsychotic-naïve individuals with schizotypal personality disorder

OBJECTIVE

To (a) compare the size of the dorsal and ventral striatum (caudate and putamen) in a large sample of antipsychotic-naïve individuals with schizotypal personality disorder (SPD) and healthy control participants; (b) examine symptom correlates of striatal size in SPD.

METHODS

The left and right caudate and putamen were hand-traced on structural MRI at five dorsal to ventral slice levels in 76 SPD and 148 healthy control participants. A Group×Region (caudate, putamen)×Slice (1-5: ventral, 2, 3, 4, dorsal)×Hemisphere (left, right) mixed-model MANOVA was conducted on size relative to whole brain.

RESULTS

Primary results showed that compared with the controls, the SPD group showed (a) larger bilateral putamen size overall and this enlargement was more pronounced at the most ventral and dorsal levels; in contrast, there were no between-group differences in caudate volume; (b) larger bilateral size of the striatum ventrally, averaged across the caudate and putamen. Among the SPD group, larger striatal size ventrally, particularly in the left hemisphere was associated with less severe paranoid symptoms.

CONCLUSIONS

Striatal size is abnormal in SPD and resembles that of patients with schizophrenia who respond well to antipsychotic treatment. The results suggest that striatal size may be an important endophenotype to consider when developing new pharmacological treatments and when studying factors mitigating psychosis.

Striatal activity in borderline personality disorder with comorbid intermittent explosive disorder: sex differences

Borderline Personality Disorder (BPD) is associated with behavioral and emotional dysregulation, particularly in social contexts; however, the underlying pathophysiology at the level of brain function is not well understood. Previous studies found abnormalities in frontal cortical and limbic areas suggestive of poor frontal regulation of downstream brain regions. However, the striatum, which is closely connected with the medial frontal cortices and plays an important role in motivated behaviors and processing of rewarding stimuli, has been understudied in BPD. Here we hypothesized that, in addition to frontal dysfunction, BPD patients may show abnormal striatal function. In this study, 38 BPD patients with intermittent explosive disorder (BPD-IED) and 36 healthy controls (HC) participated in the Point Subtraction Aggression Paradigm (PSAP), a computer game played with a fictitious other player. (18)Fluoro-deoxyglucose positron emission tomography (FDG-PET) measured relative glucose metabolism (rGMR) within caudate and putamen in response to aggression-provoking and non-provoking versions of the PSAP. Male BPD-IED patients had significantly lower striatal rGMR than all other groups during both conditions, although male and female BPD-IED patients did not differ in clinical or behavioral measures. These sex differences suggest differential involvement of frontal-striatal circuits in BPD-IED, and are discussed in relation to striatal involvement in affective learning and social decision-making.

18F-FDG PET uptake in the pre-Huntington disease caudate affects the time-to-onset independently of CAG expansion size

PURPOSE

To test in a longitudinal follow-up study whether basal glucose metabolism in subjects with a genetic risk of Huntington disease (HD) may influence the onset of manifest symptoms.

METHODS

The study group comprised 43 presymptomatic (preHD) subjects carrying the HD mutation. They underwent a (18)F-FDG PET scan and were prospectively followed-up for at least 5 years using the unified HD rating scale to detect clinical changes. Multiple regression analysis included subject's age, CAG mutation size and glucose uptake as variables in a model to predict age at onset.

RESULTS

Of the 43 preHD subjects who manifested motor symptoms, suggestive of HD, after 5 years from the PET scan, 26 showed a mean brain glucose uptake below the cut-off of 1.0493 in the caudate, significantly lower than the 17 preHD subjects who remained symptom-free (P < 0.0001). This difference was independent of mutation size. Measurement of brain glucose uptake improved the CAG repeat number and age-based model for predicting age at onset by 37 %.

CONCLUSION

A reduced level of glucose metabolism in the brain caudate may represent a predisposing factor that contributes to the age at onset of HD in preHD subjects, in addition to the mutation size.

Correlations between ventricular enlargement and gray and white matter volumes of cortex, thalamus, striatum, and internal capsule in schizophrenia

Ventricular enlargement is one of the most consistent abnormal structural brain findings in schizophrenia and has been used to infer brain shrinkage. However, whether ventricular enlargement is related to local overlying cortex and/or adjacent subcortical structures or whether it is related to brain volume change globally has not been assessed. We systematically assessed interrelations of ventricular volumes with gray and white matter volumes of 40 Brodmann areas (BAs), the thalamus and its medial dorsal nucleus and pulvinar, the internal capsule, caudate and putamen. We acquired structural MRI ( patients with schizophrenia (n = 64) and healthy controls (n = 56)) and diffusion tensor fractional anisotropy (FA) (untreated schizophrenia n = 19, controls n = 32). Volumes were assessed by manual tracing of central structures and a semi-automated parcellation of BAs. Patients with schizophrenia had increased ventricular size associated with decreased cortical gray matter volumes widely across the brain; a similar but less pronounced pattern was seen in normal controls; local correlations (e.g. temporal horn with temporal lobe volume) were not appreciably higher than non-local correlations (e.g. temporal horn with prefrontal volume). White matter regions adjacent to the ventricles similarly did not reveal strong regional relationships. FA and center of mass of the anterior limb of the internal capsule also appeared differentially influenced by ventricular volume but findings were similarly not regional. Taken together, these findings indicate that ventricular enlargement is globally interrelated with gray matter volume diminution but not directly correlated with volume loss in the immediately adjacent caudate, putamen, or internal capsule.

Effects of sex and normal aging on regional brain activation during verbal memory performance

This study examined the main and interactive effects of age and sex on relative glucose metabolic rate (rGMR) within gray matter of 39 cortical Brodmann areas (BAs) and the cingulate gyrus using (18)FDG-PET during a verbal memory task in 70 healthy normal adults, aged 20-87 years. Women showed significantly greater age-related rGMR decline in left cingulate gyrus than men (BAs 25, 24, 23, 31, 29). Both groups showed a decline in the anterior cingulate--a neuroanatomical structure that mediates effective cognitive-emotional interactions (BAs 32, 24, 25), while the other frontal regions did not show substantial decline. No sex differences in rGMR were identified within temporal, parietal and occipital lobes. Sex differences were observed for rGMR within subcomponents of the cingulate gyrus with men higher in BA25 and BA29, but lower in BA24 and BA 23 compared to women. For men, better memory performance was associated with greater rGMR in BA24, whereas in women better performance was associated with orbitofrontal-BA12. These results suggest that both age-related metabolic decline and sex differences within frontal regions are more marked in medial frontal and cingulate areas, consistent with some age-related patterns of affective and cognitive change.

Changes in glucose metabolism due to aging and gender-related differences in the healthy human brain

Using [(18)F]fluoro-deoxy-glucose-PET, we studied relative metabolic changes due to age- and gender-related differences in the brain of 126 healthy subjects from their twenties to seventies. We used a data-extraction technique, the three-dimensional stereotactic surface projections (3D-SSP) method, to measure metabolic changes with fewer effects of regional anatomic variances. Simple regression analysis revealed significant age-related increases in relative metabolic values in the parahippocampal and amygdala regions in both sexes in their twenties to forties, and significant age-related decreases in both sexes in their fifties to seventies. Relative values in the frontal lobe showed significant age-related decreases in both sexes in their twenties to forties, but these effects were not seen in subjects in their fifties to seventies. Significant gender differences in correlation coefficients of relative values with age were shown in the parahippocampal, primary sensorimotor, temporal, thalamus and vermis regions in subjects in their 20s to 40s, but disappeared in subjects in their twenties to forties, but were not apparent in subjects in their fifties to seventies except in the vermis. Males in their twenties to sixties and females in their fifties showed significant laterality in relative values in the temporal lobes. Our study demonstrated age- and gender-related differences in glucose metabolism in healthy subjects.

Frontal-striatal-thalamic mediodorsal nucleus dysfunction in schizophrenia-spectrum patients during sensorimotor gating

Prepulse inhibition (PPI) refers to a reduction in the amplitude of the startle eyeblink reflex to a strong sensory stimulus, the pulse, when it is preceded shortly by a weak stimulus, the prepulse. PPI is a measure of sensorimotor gating which serves to prevent the interruption of early attentional processing and it is impaired in schizophrenia-spectrum patients. In healthy individuals, PPI is more robust when attending to than ignoring a prepulse. Animal and human work demonstrates that frontal-striatal-thalamic (FST) circuitry modulates PPI. This study used functional magnetic resonance imaging (fMRI) to investigate FST circuitry during an attention-to-prepulse paradigm in 26 unmedicated schizophrenia-spectrum patients (13 schizotypal personality disorder (SPD), 13 schizophrenia) and 13 healthy controls. During 3T-fMRI acquisition and separately measured psychophysiological assessment of PPI, participants heard an intermixed series of high- and low-pitched tones serving as prepulses to an acoustic-startle stimulus. Event-related BOLD response amplitude curves in FST regions traced on co-registered anatomical MRI were examined. Controls showed greater activation during attended than ignored PPI conditions in all FST regions-dorsolateral prefrontal cortex (Brodmann areas 46, 9), striatum (caudate, putamen), and the thalamic mediodorsal nucleus. In contrast, schizophrenia patients failed to show differential BOLD responses in FST circuitry during attended and ignored prepulses, whereas SPD patients showed greater-than-normal activation during ignored prepulses. Among the three diagnostic groups, lower left caudate BOLD activation during the attended PPI condition was associated with more deficient sensorimotor gating as measured by PPI. Schizophrenia-spectrum patients exhibit inefficient utilization of FST circuitry during attentional modulation of PPI. Schizophrenia patients have reduced recruitment of FST circuitry during task-relevant stimuli, whereas SPD patients allocate excessive resources during task-irrelevant stimuli. Dysfunctional FST activation, particularly in the caudate may underlie PPI abnormalities in schizophrenia-spectrum patients.

Relative sensitivity of magnetic resonance spectroscopy and quantitative magnetic resonance imaging to cognitive function among nondemented individuals infected with HIV

In the present study, we examined the relationships among cognitive function, magnetic resonance spectroscopy (MRS) brain metabolite indices measured in the basal ganglia, and quantitative magnetic resonance imaging (MRI) of the caudate nucleus and the putamen in the earliest stages of HIV-related cognitive involvement. Participants included 22 HIV-positive individuals and 20 HIV-negative individuals. HIV-positive individuals performed significantly more poorly than the HIV-negative individuals on several cognitive measures. In addition, the choline/creatine ratio was significantly higher and the N-acetyl aspartate/choline ratio was significantly lower among HIV patients. The caudate and putamen sizes were smaller among HIV-positive patients compared with controls; however, the differences did not reach statistical significance. Correlation analyses revealed associations between cognitive function and select MRS indices. In addition, caudate size was significantly correlated with performances on higher-order thinking tests whereas putamen size was significantly correlated with performances on motor tests. The results suggest that MRS differences are more pronounced than area size differences between seropositive and seronegative individuals in mild stages of HIV-related cognitive impairment. However, basal ganglia size remains an important contributor to cognitive status in this population. Longitudinal studies are needed to determine the evolution of these imaging correlates of HIV-cognitive impairment in HIV.

Modelling human drug abuse and addiction with dedicated small animal positron emission tomography

Drug addiction is a chronically relapsing brain disorder, which causes substantial harm to the addicted individual and society as a whole. Despite considerable research we still do not understand why some people appear particularly disposed to drug abuse and addiction, nor do we understand how frequently co-morbid brain disorders such as depression and attention-deficit hyperactivity disorder (ADHD) contribute causally to the emergence of addiction-like behaviour. In recent years positron emission tomography (PET) has come of age as a translational neuroimaging technique in the study of drug addiction, ADHD and other psychopathological states in humans. PET provides unparalleled quantitative assessment of the spatial distribution of radiolabelled molecules in the brain and because it is non-invasive permits longitudinal assessment of physiological parameters such as binding potential in the same subject over extended periods of time. However, whilst there are a burgeoning number of human PET experiments in ADHD and drug addiction there is presently a paucity of PET imaging studies in animals despite enormous advances in our understanding of the neurobiology of these disorders based on sophisticated animal models. This article highlights recent examples of successful cross-species convergence of findings from PET studies in the context of drug addiction and ADHD and identifies how small animal PET can more effectively be used to model complex psychiatric disorders involving at their core impaired behavioural self-control.

Accelerated aging of the putamen in men but not in women

Age-related structural brain changes have been demonstrated repeatedly but data on the effect of gender on age-related structural brain changes are conflicting. Using high-resolution T1-weighted magnetic resonance imaging and voxel-based morphometry, we examined a population of 133 healthy adults (women, 73; men, 60; age range, 29-80 years) focusing on differential aging between men and women (i.e., interaction of age and gender). Compared to women, men showed accelerated age-related gray matter (GM) loss in the posterior putamen. Our data may constitute the structural substrate for age-related differences in motor function between men and women such as the higher incidence and earlier onset of Parkinson's disease in men.

Shape variability of the human striatum—Effects of age and gender

Human striatum is involved in the regulation of movement, reinforcement, learning, reward, cognitive functioning, and addiction. Previous classical volumetric MRI studies have implicated age-, disease- and medication-related changes in striatal structures. Yet, no studies to date have addressed the effects of these factors on the shape variability and local structural alterations in the striatum. The local alterations may provide meaningful additional information in the context of functional neuroanatomy and brain connectivity. We developed image analysis methodology for the measurement of the volume and local shape variability of the human striatum. The method was applied in a group of 43 healthy controls to study the effects of age and gender on striatal shape variability. In the volume analysis, the volume of the striatum was normalized using the volume of the whole brain. In the local shape analysis, the deviations from a mean surface were studied for each surface point using high-dimensional mapping. Also, discriminant functions were constructed from a statistical shape model. The accuracy and reproducibility of the methods used were evaluated. The results confirmed that the volume of the striatum decreases as a function of age. However, the volume decrease was not uniform and age-related shape differences were observed in several subregions of the human striatum whereas no local gender differences were seen. Examination of the variability of striatal shape in the healthy population will pave the way for applying this method in clinical settings. This method will be particularly useful for investigating neuropsychiatric disorders that are associated with subtle morphological alterations of the brain, such as schizophrenia.

Age-related water diffusion changes in human brain: a voxel-based approach

The aim of the present study is to investigate age-related changes in water self-diffusion in cerebral white matter by analysing diffusion-weighted MRI from a sample of 54 healthy volunteers. A voxel-based analysis of the relative anisotropy and the apparent diffusion coefficients was performed by applying an optimized normalization protocol. Linear regression analysis revealed significant correlations with age in the corpus callosum, prefrontal regions, the internal capsule, the hippocampal complex, and the putamen. However, in other regions, such as those surrounding the ventricles, the insula, or the inferior frontal plane, significant correlations between age and ADC were observed, presumably as a result of morphological age-related variations. A mask procedure was carried out in order to distinguish between morphological involvement and real age-related white matter changes. Our results indicate that in interpreting the changes in each significant region it is necessary to proceed with precaution because the voxel-based statistical analysis might yield a mixture of two effects: (i) morphological changes that remain after the normalization procedure and (ii) actual diffusivity parameter changes. Anatomically defined regions of interest may help us to minimize morphologic involvement and draw comparisons with findings previously published.

The relationship between frontal gray matter volume and cognition varies across the healthy adult lifespan

OBJECTIVE

Age-associated decline in gray matter brain volume and cognitive function in healthy adults has been reported in the literature. The goal of the current study is to examine the relationship between age-related changes in regional gray matter volumes and cognitive function in a large, cross-sectional sample of healthy adults across the lifespan.

METHODS

Magnetic resonance imaging and cognitive assessment were conducted on 148 adults aged 21-76 years. Multiple regression analyses examining the effect of age were performed on magnetic resonance image-derived gray matter brain volumes and standardized cognitive summary scores of attention and executive function. Regression was also performed to test the effect of age, gray matter volumes, and their interaction on the prediction of cognitive performance.

RESULTS

Age significantly predicted performance on tests of attention (F [1, 146]=50.97, p <0.01, R2=0.26) and executive function (F [1, 146]=126.19, p <0.01, R2=0.46) and gray matter volumes for frontal subregions (lateral, medial, orbital), hippocampus, amygdala, and putamen (F [2, 145]=45.34-23.96, p <0.01-0.02). Lateral frontal (beta=-1.53, t=-2.16, df=131, p <0.03) and orbital frontal (beta=1.24, t=2.08, df=131, p <0.04) regions significantly predicted performance on tests of attention. Lateral frontal (beta=-1.69, t=-2.83, df=131, p <0.01) and the interaction between age and lateral frontal volume (beta=3.76, t=2.49, df=131, p <0.02) significantly predicted executive function.

CONCLUSIONS

The findings confirm age-associated decline in cognitive function and gray matter volumes, particularly in anterior cortical brain regions. Furthermore, the association between lateral frontal gray matter volume and the ability to successfully plan, organize, and execute strategies varies as a function of age across the healthy adult lifespan.

Regional white matter and neuropsychological functioning across the adult lifespan

BACKGROUND

The current study utilized magnetic resonance imaging (MRI) to more fully elucidate the relationship among age, regional white matter, and neuropsychological functioning.

METHODS

One hundred ninety-nine neurologically healthy adults received MRI and standardized neuropsychological assessment. MR images were spatially normalized and segmented by tissue type; relative white matter values in each of the four cerebral lobes in each hemisphere were computed. Subjects were divided into Younger (ages 21-30), Middle (ages 31-54), and Older (ages 55-79) age groups.

RESULTS

The Older group had significantly less overall relative white matter than the Middle group, who had significantly less overall relative white matter than the Younger participants (F (2, 193) = 5.42, p = 0.005). Differences in frontal lobe white matter were of largest magnitude, followed by temporal lobe (F (6, 579) = 3.32, p = 0.003). Age and frontal and temporal lobe white matter were primarily associated with performance on neuropsychological tests of executive functioning and memory. Mediational analysis suggested that frontal lobe white matter mediated the relationship between age and performance on tasks of executive functioning and memory.

CONCLUSIONS

The results confirm age-associated decline in frontal and temporal white matter, and age-related cognitive decline in several domains. Decline in neuropsychological functioning is, in part, mediated by a relative age-related reduction in frontal white matter.

Category and letter verbal fluency across the adult lifespan: relationship to EEG theta power

The purpose of this study was to examine the impact of age, sex, and education on category and letter verbal fluency task performance. A secondary goal was to examine whether resting EEG theta power in bilateral frontal and temporal lobes impacts age-associated decline in verbal fluency task performance. A large sample (N = 471) of healthy, normal participants, age 21-82, was assessed for letter fluency (i.e., FAS), and for category fluency (i.e., Animal Naming), and with a 32-channel EEG system for 'eyes-open' resting theta power. The effects of age, sex, and education were examined using analyses of variance. Correlation analyses were used to test the impact of theta power on age and fluency performance by controlling for the effects of theta when examining the relationship between the other two variables. The results indicated that performance on both fluency tests declined linearly with age, but that the rate of decline was greater for category fluency. These age changes were not associated with education level, and there were no sex differences. While theta power was negatively associated with age and positively associated with Animal Naming performance, it did not moderate the relationship between the two. The differential age-associated decline between category and letter fluency suggests separate neurobiological substrates underlying the two domains of performance, which is not related to theta activity.

Correlations between MRI-assessed volumes of the thalamus and cortical Brodmann's areas in schizophrenia

BACKGROUND

We compared the thalamic-cortical volumetric correlational patterns in patients with schizophrenia and normal comparison subjects, and evaluated their relations to outcome.

METHODS

High-resolution MR images were acquired in patients with schizophrenia (n=106) and normal comparison subjects (n=42). Patients were divided into good-outcome (n=52) and poor-outcome (Kraepelinian, n=54) subtypes based on their ability for self-care. Correlations between the relative gray and white matter volumes of the individual cortical Brodmann's areas and five dorsoventral levels of the thalamus were assessed.

RESULTS

Compared to normal subjects, schizophrenia patients lacked significant thalamic gray matter volume correlations with the prefrontal and medial temporal cortical regions in the right hemisphere, and with frontal, cingulate, posterior parietal and occipital regions in the left hemisphere, while normal white matter volume cortical-thalamic correlations along the cingulate gyrus and in the temporal lobe were not found in schizophrenia patients in both hemispheres. In contrast to both normal comparison subjects and good-outcome group, schizophrenia patients with poor outcomes showed significant bilateral gray matter volume correlations between the dorsal thalamus and ventral prefrontal cortex, while the group differences in the white matter volume correlations were mostly restricted to the cingulate arch.

CONCLUSIONS

Whereas patients with schizophrenia exhibit deficiencies in cortical-thalamic correlational patterns, poor outcome is associated with abnormal interregional correlations not observed in either normal subjects or patients with good outcomes. This latter finding may be explained by a core neurodevelopmental disturbance that results in aberrant cortical-thalamic connectivity in poor-outcome schizophrenia.

Thalamus size and outcome in schizophrenia

The size of the thalamus was assessed in 106 patients with schizophrenia and 42 normal controls using high-resolution magnetic resonance imaging. The thalamus was traced at five axial levels proportionately spaced from dorsal to ventral directions. Patients with schizophrenia had significantly smaller thalamic areas at more ventral levels. Thalamic size was positively associated with frontal lobe and temporal lobe size. The effects were most marked in the patients with poorer clinical outcome (i.e., "Kraepelinian" patients). These findings are consistent with post-mortem and MRI measurement suggesting reduction in volume of the pulvinar, which occupies a large proportion of the ventral thalamus and which has prominent connections to the temporal lobe.

Neuropsychological functioning in first-break, never-medicated adolescents with psychosis

The purpose of the current study was to examine neuropsychological functioning in a group of never-medicated first-break adolescents with psychosis. It is the first report of cognition in a sample of adolescents with psychosis in which all patients were drug-naive. Twenty-nine adolescent patients (mean age = 16.07; SD = 2.00; 15 male and 14 female patients) experiencing their first psychotic episode and 17 age-matched and sex-matched normal volunteers (mean age = 16.88; SD = 2.39; 9 male and 8 female subjects) were recruited and assessed with a neuropsychological battery. Measures of attention, memory, language, executive functioning, perceptual motor processing, and motor speed were obtained. Psychiatric symptomatology, estimated verbal IQ, and parental socioeconomic status were also determined. Patients with psychosis were significantly more impaired than normal volunteers; effect sizes were greatest in the areas of executive functioning, attention, and memory, and significantly smaller in areas of language, perceptual motor processing, and motor speed. The pattern was not altered when differences in verbal IQ and parental socioeconomic status were controlled. Sex and age interactions indicated that younger male patients were particularly impaired. The findings demonstrate neuropsychological deficits in adolescents with psychosis and suggest that cognitive deficits are core symptoms in psychotic disorders.