Three-dimensional maximum probability atlas of the human brain, with particular reference to the temporal lobe

[18F]AV-1451 PET in behavioral variant frontotemporal dementia due to MAPT mutation

The validation of tau radioligands could improve the diagnosis of frontotemporal lobar degeneration and the assessment of disease‐modifying therapies. Here, we demonstrate that binding of the tau radioligand [¹⁸F]AV‐1451 was significantly abnormal in both magnitude and distribution in a patient with familial frontotemporal dementia due to a MAPT 10 + 16C>T gene mutation, recapitulating the pattern of neuropathology seen in her father. Given the genetic diagnosis and the non‐Alzheimer's pathology, these findings suggest that [¹⁸F]AV‐1451 might be a useful biomarker in primary tauopathies. Largerscale in vivo and post‐mortem studies will be needed to assess the technique's specificity.

Evaluation of early-phase [18F]-florbetaben PET acquisition in clinical routine cases

Objectives

In recent years several [¹⁸F]-labelled amyloid PET tracers have been developed and have obtained clinical approval. There is accumulating evidence that early (post injection) acquisitions with these tracers are equally informative as conventional blood flow and metabolism studies for diagnosis of Alzheimer's disease, but there have been few side-by-side studies. Therefore, we investigated the performance of early acquisitions of [¹⁸F]-florbetaben (FBB) PET compared to [¹⁸F]-fluorodeoxyglucose (FDG) PET in a clinical setting.

Methods

All subjects were recruited with clinical suspicion of dementia due to neurodegenerative disease. FDG PET was undertaken by conventional methods, and amyloid PET was performed with FBB, with early recordings for the initial 10 min (early-phase FBB), and late recordings at 90–110 min p.i. (late-phase FBB). Regional SUVR with cerebellar and global mean normalization were calculated for early-phase FBB and FDG PET. Pearson correlation coefficients between FDG and early-phase FBB were calculated for predefined cortical brain regions. Furthermore, a visual interpretation of disease pattern using 3-dimensional stereotactic surface projections (3D-SSP) was performed, with assessment of intra-reader agreement.

Results

Among a total of 33 patients (mean age 67.5 ± 11.0 years) included in the study, 18 were visually rated amyloid-positive, and 15 amyloid-negative based on late-phase FBB scans. Correlation coefficients for early-phase FBB vs. FDG scans displayed excellent agreement in all target brain regions for global mean normalization. Cerebellar normalization gave strong, but significantly lower correlations. 3D representations of early-phase FBB visually resembled the corresponding FDG PET images, irrespective of the amyloid-status of the late FBB scans.

Conclusions

Early-phase FBB acquisitions correlate on a relative quantitative and visual level with FDG PET scans, irrespective of the amyloid plaque density assessed in late FBB imaging. Thus, early-phase FBB uptake depicts a metabolism-like image, suggesting it as a valid surrogate marker for synaptic dysfunction, which could ultimately circumvent the need for additional FDG PET investigation in diagnosis of dementia.

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Early-phase [¹⁸F]-florbetaben uptake depicts a metabolism-like image

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Strong relative quantitative and visual correlations of early-phase [¹⁸F]-florbetaben uptake with FDG images

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A two-phase [¹⁸F]-florbetaben protocol might give combined neurodegeneration and amyloid pathology biomarker information

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Early-phase [¹⁸F]-florbetaben PET could ultimately circumvent the need for an additional FDG-PET in the dementia work-up.

Predicting Regional Pattern of Longitudinal β-Amyloid Accumulation by Baseline PET

Knowledge about spatial and temporal patterns of β-amyloid (Aβ) accumulation is essential for understanding Alzheimer disease (AD) and for design of antiamyloid drug trials. Here, we tested whether the regional pattern of longitudinal Aβ accumulation can be predicted by baseline amyloid PET. Methods: Baseline and 2-y follow-up ¹⁸F-florbetapir PET data from 58 patients with incipient and manifest dementia due to AD were analyzed. With the determination of how fast amyloid deposits in a given region relative to the whole-brain gray matter, a pseudotemporal accumulation rate for each region was calculated. The actual accumulation rate of ¹⁸F-florbetapir was calculated from follow-up data. Results: Pseudotemporal measurements from baseline PET data explained 87% (P < 0.001) of the variance in longitudinal accumulation rate across 62 regions. The method accurately predicted the top 10 fast and slow accumulating regions. Conclusion: Pseudotemporal analysis of baseline PET images is capable of predicting the regional pattern of longitudinal Aβ accumulation in AD at a group level. This approach may be useful in exploring spatial patterns of Aβ accumulation in other amyloid-associated disorders such as Lewy body disease and atypical forms of AD. In addition, the method allows identification of brain regions with a high accumulation rate of Aβ, which are of particular interest for antiamyloid clinical trials.

Adversity in childhood linked to elevated striatal dopamine function in adulthood

Childhood adversity increases the risk of psychosis in adulthood. Theoretical and animal models suggest that this effect may be mediated by increased striatal dopamine neurotransmission. The primary objective of this study was to examine the relationship between adversity in childhood and striatal dopamine function in early adulthood. Secondary objectives were to compare exposure to childhood adversity and striatal dopamine function in young people at ultra high risk (UHR) of psychosis and healthy volunteers. Sixty-seven young adults, comprising 47 individuals at UHR for psychosis and 20 healthy volunteers were recruited from the same geographic area and were matched for age, gender and substance use. Presynaptic dopamine function in the associative striatum was assessed using 18F-DOPA positron emission tomography. Childhood adversity was assessed using the Childhood Experience of Care and Abuse questionnaire. Within the sample as a whole, both severe physical or sexual abuse (T63=2.92; P=0.005), and unstable family arrangements (T57=2.80; P=0.007) in childhood were associated with elevated dopamine function in the associative striatum in adulthood. Comparison of the UHR and volunteer subgroups revealed similar incidence of childhood adverse experiences, and there was no significant group difference in dopamine function. This study provides evidence that childhood adversity is linked to elevated striatal dopamine function in adulthood.

Word Imageability Enhances Association-memory by Increasing Hippocampal Engagement

The hippocampus is thought to support association-memory, particularly when tested with cued recall. One of the most well-known and studied factors that influences accuracy of verbal association-memory is imageability; participants remember pairs of high-imageability words better than pairs of low-imageability words. High-imageability words are also remembered better in tests of item-memory. However, we previously found that item-memory effects could not explain the enhancement in cued recall, suggesting that imageability enhances association-memory strength. Here we report an fMRI study designed to ask, what is the role of the hippocampus in the memory advantage for associations due to imageability? We tested two alternative hypotheses: (1) Recruitment Hypothesis: High-imageability pairs are remembered better because they recruit the underlying hippocampal association-memory function more effectively. Alternatively, (2) Bypassing Hypothesis: Imageability functions by making the association-forming process easier, enhancing memory in a way that bypasses the hippocampus, as has been found, for example, with explicit unitization imagery strategies. Results found, first, hippocampal BOLD signal was greater during study and recall of high- than low-imageability word pairs. Second, the difference in activity between recalled and forgotten pairs showed a main effect, but no significant interaction with imageability, challenging the bypassing hypothesis, but consistent with the predictions derived from the recruitment hypothesis. Our findings suggest that certain stimulus properties, like imageability, may leverage, rather than avoid, the associative function of the hippocampus to support superior association-memory.

Relationship of recent stress to amygdala volume in depressed and healthy adults

BACKGROUND

The amygdala is an integral part of the extrahypothalamic stress-response system, and its volume related to childhood trauma has been studied, but less is known of associations with recent stressful life events. Amygdala volume differences also have been studied in depression, with conflicting results. We hypothesized that effects of stress may be a confound for amygdala volumetric differences in the context of depression.

METHODS

Right-handed participants (n=61) experiencing a major depressive episode during major depressive disorder (n=40) or bipolar depression (n=21) and healthy volunteers (n=60) underwent 1.5T magnetic resonance imaging (MRI). The amygdala perimeter was manually traced with an electronic mouse, based on anatomical landmarks on consecutive coronal slices, by raters blind to diagnosis. The effects of stress on amygdala volume were examined in linear regression models with self-reported physical/sexual abuse or highest category score on the St. Paul-Ramsey scale of stressful life events within the past 6 months as predictors, testing separately for age, sex, race, and depression status as covariates.

RESULTS

Diagnostic groups did not differ significantly with respect to mean age (depressed, 37.8±11.8yrs; healthy, 34.9±13.8yrs) or proportion of males (depressed, 39%, healthy, 50%). We found no association between physical and/or sexual abuse history and amygdala volume. Life stress within the last six months, however, was associated with smaller left amygdala volume. The association between stress and amygdala volume did not differ by diagnostic group.

LIMITATIONS

Most depressed patients were off medications for at least 2 weeks; however, this may not have been long enough to reverse effects of medications on amygdala structure.

CONCLUSIONS

That life stress of relatively short duration was associated with amygdala size in the entire sample, while temporally distant life stress was not, suggests that amygdala volume changes may occur rapidly and reversibly, and independent of depression status.

Rawlsian maximin rule operates as a common cognitive anchor in distributive justice and risky decisions

Distributive justice concerns the moral principles by which we seek to allocate resources fairly among diverse members of a society. Although the concept of fair allocation is one of the fundamental building blocks for societies, there is no clear consensus on how to achieve "socially just" allocations. Here, we examine neurocognitive commonalities of distributive judgments and risky decisions. We explore the hypothesis that people's allocation decisions for others are closely related to economic decisions for oneself at behavioral, cognitive, and neural levels, via a concern about the minimum, worst-off position. In a series of experiments using attention-monitoring and brain-imaging techniques, we investigated this "maximin" concern (maximizing the minimum possible payoff) via responses in two seemingly disparate tasks: third-party distribution of rewards for others, and choosing gambles for self. The experiments revealed three robust results: (i) participants' distributive choices closely matched their risk preferences-"Rawlsians," who maximized the worst-off position in distributions for others, avoided riskier gambles for themselves, whereas "utilitarians," who favored the largest-total distributions, preferred riskier but more profitable gambles; (ii) across such individual choice preferences, however, participants generally showed the greatest spontaneous attention to information about the worst possible outcomes in both tasks; and (iii) this robust concern about the minimum outcomes was correlated with activation of the right temporoparietal junction (RTPJ), the region associated with perspective taking. The results provide convergent evidence that social distribution for others is psychologically linked to risky decision making for self, drawing on common cognitive-neural processes with spontaneous perspective taking of the worst-off position.

Repetition Enhancement of Amygdala and Visual Cortex Functional Connectivity Reflects Nonconscious Memory for Negative Visual Stimuli

Most studies using a recognition memory paradigm examine the neural processes that support the ability to consciously recognize past events. However, there can also be nonconscious influences from the prior study episode that reflect repetition suppression effects-a reduction in the magnitude of activity for repeated presentations of stimuli-that are revealed by comparing neural activity associated with forgotten items to correctly rejected novel items. The present fMRI study examined the effect of emotional valence (positive vs. negative) on repetition suppression effects. Using a standard recognition memory task, 24 participants viewed line drawings of previously studied negative, positive, and neutral photos intermixed with novel line drawings. For each item, participants made an old-new recognition judgment and a sure-unsure confidence rating. Collapsed across valence, repetition suppression effects were found in ventral occipital-temporal cortex and frontal regions. Activity levels in the majority of these regions were not modulated by valence. However, repetition enhancement of the amygdala and ventral occipital-temporal cortex functional connectivity reflected nonconscious memory for negative items. In this study, valence had little effect on activation patterns but had a larger effect on functional connectivity patterns that were markers of nonconscious memory. Beyond memory and emotion, these findings are relevant to other cognitive and social neuroscientists that utilize fMRI repetition effects to investigate perception, attention, social cognition, and other forms of learning and memory.

Hippocampal shape alterations are associated with regional Aβ load in cognitively normal elderly individuals

Aβ deposition is a driving force of Alzheimer's disease pathology and can be detected early by amyloid positron emission tomography. Identifying presymptomatic structural brain changes associated with Aβ deposition might lead to a better understanding of its consequences and provide early diagnostic information. In this respect we analyzed measures of cortical thickness and subcortical volumes along with hippocampal, thalamic and striatal shape and surface area by applying novel analysis strategies for structural magnetic resonance imaging. We included 69 cognitively normal elderly subjects after careful clinical and neuropsychological workup. Standardized uptake value ratios (cerebellar reference) for uptake of 11-C-Pittsburgh Compound B (PiB) were calculated from positron emission tomographic data for a cortical measurement and for bilateral hippocampus, thalamus and striatum. Associations to shape, surface area, volume and cortical thickness were tested using regression models that included significant predictors as covariates. Left anterior hippocampal shape was associated with regional PiB uptake (P < 0.05, FDR corrected), whereas volumes of the hippocampi and their subregions were not associated with cortical or regional PiB uptake (all P > 0.05, FDR corrected). Within the entorhinal cortical region of both hemispheres, thickness was negatively associated with cortical PiB uptake (P < 0.05, FDR corrected). Hence, localized shape measures and cortical thickness may be potential biomarkers of presymptomatic Alzheimer's disease.

Volumetric and shape analysis of the thalamus and striatum in amnestic mild cognitive impairment

Alterations in brain structures, including progressive neurodegeneration, are a hallmark in patients with Alzheimer's disease (AD). However, pathological mechanisms, such as the accumulation of amyloid and the proliferation of tau, are thought to begin years, even decades, before the initial clinical manifestations of AD. In this study, we compare the brain anatomy of amnestic mild cognitive impairment patients (aMCI, n = 16) to healthy subjects (CS, n = 22) using cortical thickness, subcortical volume, and shape analysis, which we believe to be complimentary to volumetric measures. We were able to replicate "classical" cortical thickness alterations in aMCI in the hippocampus, amygdala, putamen, insula, and inferior temporal regions. Additionally, aMCI showed significant thalamic and striatal shape differences. We observed higher global amyloid deposition in aMCI, a significant correlation between striatal displacement and global amyloid, and an inverse correlation between executive function and right-hemispheric thalamic displacement. In contrast, no volumetric differences were detected in thalamic, striatal, and hippocampal regions. Our results provide new evidence for early subcortical neuroanatomical changes in patients with aMCI, which are linked to cognitive abilities and amyloid deposition. Hence, shape analysis may aid in the identification of structural biomarkers for identifying individuals at highest risk of conversion to AD.

Detection of Lesions Underlying Intractable Epilepsy on T1-Weighted MRI as an Outlier Detection Problem

Pattern recognition methods, such as computer aided diagnosis (CAD) systems, can help clinicians in their diagnosis by marking abnormal regions in an image. We propose a machine learning system based on a one-class support vector machine (OC-SVM) classifier for the detection of abnormalities in magnetic resonance images (MRI) applied to patients with intractable epilepsy. The system learns the features associated with healthy control subjects, allowing a voxelwise assessment of the deviation of a test subject pattern from the learned patterns. While any number of various features can be chosen and learned, here we focus on two texture parameters capturing image patterns associated with epileptogenic lesions on T1-weighted brain MRI e.g. heterotopia and blurred junction between the grey and white matter. The CAD output consists of patient specific 3D maps locating clusters of suspicious voxels ranked by size and degree of deviation from control patterns. System performance was evaluated using realistic simulations of challenging detection tasks as well as clinical data of 77 healthy control subjects and of eleven patients (13 lesions). It was compared to that of a mass univariate statistical parametric mapping (SPM) single subject analysis based on the same set of features. For all simulations, OC-SVM yielded significantly higher values of the area under the ROC curve (AUC) and higher sensitivity at low false positive rate. For the clinical data, both OC-SVM and SPM successfully detected 100% of the lesions in the MRI positive cases (3/13). For the MRI negative cases (10/13), OC-SVM detected 7/10 lesions and SPM analysis detected 5/10 lesions. In all experiments, OC-SVM produced fewer false positive detections than SPM. OC-SVM may be a versatile system for unbiased lesion detection.

Fine-mapping the effects of Alzheimer's disease risk loci on brain morphology

The neural substrate of genetic risk variants for Alzheimer's disease (AD) remains unknown. We studied their effect on healthy brain morphology to provide insight into disease etiology in the preclinical phase. We included 4071 nondemented, elderly participants of the population-based Rotterdam Study who underwent brain magnetic resonance imaging and genotyping. We performed voxel-based morphometry (VBM) on all gray-matter voxels for 19 previously identified, common AD risk variants. Whole-brain expression data from the Allen Human Brain Atlas was used to examine spatial overlap between VBM association results and expression of genes in AD risk loci regions. Brain regions most significantly associated with AD risk variants were the left postcentral gyrus with ABCA7 (rs4147929, p = 4.45 × 10^-6), right superior frontal gyrus by ZCWPW1 (rs1476679, p = 5.12 × 10^-6), and right postcentral gyrus by APOE (p = 6.91 × 10^-6). Although no individual voxel passed multiple-testing correction, we found significant spatial overlap between the effects of AD risk loci on VBM and the expression of genes (MEF2C, CLU, and SLC24A4) in the Allen Brain Atlas. Results are available online on www.imagene.nl/ADSNPs/. In this single largest imaging genetics data set worldwide, we found that AD risk loci affect cortical gray matter in several brain regions known to be involved in AD, as well as regions that have not been implicated before.

Deep brain stimulation of the periaqueductal gray releases endogenous opioids in humans

Deep brain stimulation (DBS) of the periaqueductal gray (PAG) is used in the treatment of severe refractory neuropathic pain. We tested the hypothesis that DBS releases endogenous opioids to exert its analgesic effect using [¹¹C]diprenorphine (DPN) positron emission tomography (PET). Patients with de-afferentation pain (phantom limb pain or Anaesthesia Dolorosa (n=5)) who obtained long-lasting analgesic benefit from DBS were recruited. [¹¹C]DPN and [¹⁵O]water PET scanning was performed in consecutive sessions; first without, and then with PAG stimulation. The regional cerebral tracer distribution and kinetics were quantified for the whole brain and brainstem. Analysis was performed on a voxel-wise basis using statistical parametric mapping (SPM) and also within brainstem regions of interest and correlated to the DBS-induced improvement in pain score and mood. Brain-wide analysis identified a single cluster of reduced [¹¹C]DPN binding (15.5% reduction) in the caudal, dorsal PAG following DBS from effective electrodes located in rostral dorsal/lateral PAG. There was no evidence for an accompanying focal change in blood flow within the PAG. No correlation was found between the change in PAG [¹¹C]DPN binding and the analgesic effect or the effect on mood (POMS_SV) of DBS. The analgesic effect of DBS in these subjects was not altered by systemic administration of the opioid antagonist naloxone (400 ug). These findings indicate that DBS of the PAG does indeed release endogenous opioid peptides focally within the midbrain of these neuropathic pain patients but we are unable to further resolve the question of whether this release is responsible for the observed analgesic benefit.

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Sequential opioid-PET imaging study of deafferentation pain patients.

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All obtained analgesic benefit from deep brain stimulators (DBS) in periaqueductal grey (PAG).

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PET imaging with diprenorphine showed DBS reduced binding of the radioligand in the PAG.

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Change in binding consistent with DBS-evoked release of endogenous opioids.

Automated Detection of Lupus White Matter Lesions in MRI

Brain magnetic resonance imaging provides detailed information which can be used to detect and segment white matter lesions (WML). In this work we propose an approach to automatically segment WML in Lupus patients by using T1w and fluid-attenuated inversion recovery (FLAIR) images. Lupus WML appear as small focal abnormal tissue observed as hyperintensities in the FLAIR images. The quantification of these WML is a key factor for the stratification of lupus patients and therefore both lesion detection and segmentation play an important role. In our approach, the T1w image is first used to classify the three main tissues of the brain, white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF), while the FLAIR image is then used to detect focal WML as outliers of its GM intensity distribution. A set of post-processing steps based on lesion size, tissue neighborhood, and location are used to refine the lesion candidates. The proposal is evaluated on 20 patients, presenting qualitative, and quantitative results in terms of precision and sensitivity of lesion detection [True Positive Rate (62%) and Positive Prediction Value (80%), respectively] as well as segmentation accuracy [Dice Similarity Coefficient (72%)]. Obtained results illustrate the validity of the approach to automatically detect and segment lupus lesions. Besides, our approach is publicly available as a SPM8/12 toolbox extension with a simple parameter configuration.

Brain structural anomalies in borderline and avoidant personality disorder patients and their associations with disorder-specific symptoms

BACKGROUND

Borderline personality disorder (BPD) and avoidant personality disorder (AvPD) are characterized by hyper-reactivity to negatively-perceived interpersonal cues, yet they differ in degree of affective instability. Recent work has begun to elucidate the neural (structural and functional) and cognitive-behavioral underpinnings of BPD, although some initial studies of brain structure have reached divergent conclusions. AvPD, however, has been almost unexamined in the cognitive neuroscience literature.

METHODS

In the present study we investigated group differences among 29 BPD patients, 27 AvPD patients, and 29 healthy controls (HC) in structural brain volumes using voxel-based morphometry (VBM) in five anatomically-defined regions of interest: amygdala, hippocampus, medial prefrontal cortex (MPFC), dorsolateral prefrontal cortex (DLPFC), and anterior cingulate cortex (ACC). We also examined the relationship between individual differences in brain structure and self-reported anxiety and affective instability in each group.

RESULTS

We observed reductions in MPFC and ACC volume in BPD relative to HC, with no significant difference among patient groups. No group differences in amygdala volume were found. However, BPD and AvPD patients each showed a positive relationship between right amygdala volume and state-related anxiety. By contrast, in HC there was an inverse relationship between MPFC volume and state and trait-related anxiety as well as between bilateral DLPFC volume and affective instability.

LIMITATIONS

Current sample sizes did not permit examination of gender effects upon structure-symptom correlations.

CONCLUSIONS

These results shed light on potentially protective, or compensatory, aspects of brain structure in these populations-namely, relatively reduced amygdala volume or relatively enhanced MPFC and DLPFC volume.

Pilot PET Study to Assess the Functional Interplay Between ABCB1 and ABCG2 at the Human Blood-Brain Barrier

ABCB1 and ABCG2 work together at the blood-brain barrier (BBB) to limit brain distribution of dual ABCB1/ABCG2 substrates. In this pilot study we used positron emission tomography (PET) to assess brain distribution of two model ABCB1/ABCG2 substrates ([(11) C]elacridar and [(11) C]tariquidar) in healthy subjects without (c.421CC) or with (c.421CA) the ABCG2 single-nucleotide polymorphism (SNP) c.421C>A. Subjects underwent PET scans under conditions when ABCB1 and ABCG2 were functional and during ABCB1 inhibition with high-dose tariquidar. In contrast to the ABCB1-selective substrate (R)-[(11) C]verapamil, [(11) C]elacridar and [(11) C]tariquidar showed only moderate increases in brain distribution during ABCB1 inhibition. This provides evidence for a functional interplay between ABCB1 and ABCG2 at the human BBB and suggests that both ABCB1 and ABCG2 need to be inhibited to achieve substantial increases in brain distribution of dual ABCB1/ABCG2 substrates. During ABCB1 inhibition c.421CA subjects had significantly higher increases in [(11) C]tariquidar brain distribution than c.421CC subjects, pointing to impaired cerebral ABCG2 function.

Striatal opioid receptor availability is related to acute and chronic pain perception in arthritis: does opioid adaptation increase resilience to chronic pain?

The experience of pain in humans is modulated by endogenous opioids, but it is largely unknown how the opioid system adapts to chronic pain states. Animal models of chronic pain point to upregulation of opioid receptors (OpR) in the brain, with unknown functional significance. We sought evidence for a similar relationship between chronic pain and OpR availability in humans. Using positron emission tomography and the radiotracer (11)C-diprenorphine, patients with arthritis pain (n = 17) and healthy controls (n = 9) underwent whole-brain positron emission tomography scanning to calculate parametric maps of OpR availability. Consistent with the upregulation hypothesis, within the arthritis group, greater OpR availability was found in the striatum (including the caudate) of patients reporting higher levels of recent chronic pain, as well as regions of interest in the descending opioidergic pathway including the anterior cingulate cortex, thalamus, and periaqueductal gray. The functional significance of striatal changes were clarified with respect to acute pain thresholds: data across patients and controls revealed that striatal OpR availability was related to reduced pain perception. These findings are consistent with the view that chronic pain may upregulate OpR availability to dampen pain. Finally, patients with arthritis pain, compared with healthy controls, had overall less OpR availability within the striatum specifically, consistent with the greater endogenous opioid binding that would be expected in chronic pain states. Our observational evidence points to the need for further studies to establish the causal relationship between chronic pain states and OpR adaptation.

Positive Association Between Limbic Metabotropic Glutamate Receptor 5 Availability and Novelty-Seeking Temperament in Humans: An 18F-FPEB PET Study

Heritable temperament traits have been linked to several neuropsychiatric illnesses, including disorders associated with metabotropic glutamate receptor 5 (mGluR5) and dopaminergic dysfunctions. Considering its modulating effect on neurotransmission, we hypothesized that cerebral mGluR5 availability is associated with temperament traits in healthy humans.

METHODS

Forty-four nonsmoking healthy volunteers (mean age ± SD, 40 ± 14 y; age range, 22-66 y; 22 women) were included in this cross-sectional investigation. Brain mGluR5 availability was quantified on both a voxel-by-voxel and a volume-of-interest basis using the total distribution volume of the radioligand ¹⁸F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (¹⁸F-FPEB) with 90-min dynamic PET and arterial input function. Moreover, glutamate-glutamine concentrations in the anterior cingulate cortex were measured using MR spectroscopy. These measures were related to the temperament traits of the 240-item Cloninger temperament and character inventory using a regression analysis with age and sex as nuisance variables.

RESULTS

High novelty-seeking temperament was robustly associated with increased mGluR5 availability in various regions including the thalamus (r = 0.71; the strongest association), amygdala, parahippocampus, insula, anterior and posterior cingulate cortex, and several primary sensory areas (all r > 0.58; P < 0.05, corrected for familywise error). These associations were specific because no correlations were found with other temperament scales or with spectroscopic measures of glutamatergic transmission.

CONCLUSION

Overall, these data posit mGluR5 in key paralimbic areas as a strong determinant of the temperament trait novelty seeking. These data add to our understanding of how brain neurochemistry accounts for the variation in human behavior and strongly support further research on mGluR5 as a potential therapeutic target in neuropsychiatric disorders associated with abnormal novelty-seeking behaviors.

Parametric Binding Images of the TSPO Ligand 18F-DPA-714

¹⁸F-labeled N,N-diethyl-2-(2-[4-(2-fluoroethoxy)phenyl]-5,7-dimethylpyrazolo[1,5-α]pyrimidine-3-yl)acetamide (DPA-714) is a radioligand for the 18-kDa translocator protein. The purpose of the present study was to identify the best method for generating quantitative parametric images of ¹⁸F-DPA-714 binding.

METHODS

Ninety-minute dynamic ¹⁸F-DPA-714 PET scans with full arterial sampling from 6 healthy subjects and 9 Alzheimer disease (AD) patients were used. Plasma-input-based Logan graphical analysis and spectral analysis were used to generate parametric volume of distribution (V_T) images. Five versions of Ichise, reference Logan, and 2 basis function implementations (receptor parametric mapping and simplified reference tissue model 2 [SRTM2]) of SRTM, all using gray matter cerebellum as the reference region, were applied to generate nondisplaceable binding potential (BP_ND) images.

RESULTS

Plasma-input Logan analysis (r² = 0.99; slope, 0.88) and spectral analysis (r² = 0.99, slope, 0.93) generated estimates of V_T that correlated well with values obtained using nonlinear regression. BP_ND values generated using SRTM2 (r² = 0.83; slope, 0.95) and reference Logan analysis (r² = 0.88; slope, 1.01) correlated well with nonlinear regression-based estimates.

CONCLUSION

Both Logan analysis and spectral analysis can be used to obtain quantitatively accurate V_T images of ¹⁸F-DPA-714. In addition, SRTM2 and reference Logan analysis can provide accurate BP_ND images. These parametric images could be used for voxel-based comparisons.

Normal gray matter volumes in women recovered from anorexia nervosa: a voxel-based morphometry study

BACKGROUND

Anorexia nervosa (AN) has consistently been associated with reduced gray (GM) and white matter (WM) brain volumes. It is unclear whether GM alterations are present following recovery from AN, as previous findings are inconsistent. The aim of the present study was to determine if women recovered from AN exhibit reduced global or regional GM volumes.

METHODS

Global GM and WM, as well as regional GM volumes, were investigated in 22 women recovered from AN and 22 age-matched healthy controls using magnetic resonance imaging. Women were considered recovered if they had maintained a body mass index above 18.0 and had not engaged in binge eating, purging, or restrictive eating behaviors during the past year.

RESULTS

There were no significant differences between recovered AN women and healthy controls in terms of GM and WM volumes. There were also no significant differences between restricting and binging-purging AN subtypes. Lowest lifetime weight was positively correlated with regional GM volumes in the precuneus and insula.

CONCLUSIONS

The present study showed that regional GM and global GM and WM volumes were similar for women long-term recovered from AN and age-matched healthy controls. Further research is needed to determine the extent to which illness severity affect regional GM volumes.

In vivo imaging of neuromelanin in Parkinson's disease using 18F-AV-1451 PET

The tau tangle ligand (18)F-AV-1451 ((18)F-T807) binds to neuromelanin in the midbrain, and may therefore be a measure of the pigmented dopaminergic neuronal count in the substantia nigra. Parkinson's disease is characterized by progressive loss of dopaminergic neurons. Extrapolation of post-mortem data predicts that a ∼30% decline of nigral dopamine neurons is necessary to cause motor symptoms in Parkinson's disease. Putamen dopamine terminal loss at disease onset most likely exceeds that of the nigral cell bodies and has been estimated to be of the order of 50-70%. We investigated the utility of (18)F-AV-1451 positron emission tomography to visualize the concentration of nigral neuromelanin in Parkinson's disease and correlated the findings to dopamine transporter density, measured by (123)I-FP-CIT single photon emission computed tomography. A total of 17 patients with idiopathic Parkinson's disease and 16 age- and sex-matched control subjects had (18)F-AV-1451 positron emission tomography using a Siemens high-resolution research tomograph. Twelve patients with Parkinson's disease also received a standardized (123)I-FP-CIT single photon emission computed tomography scan at our imaging facility. Many of the patients with Parkinson's disease displayed visually apparent decreased (18)F-AV-1451 signal in the midbrain. On quantitation, patients showed a 30% mean decrease in total nigral (18)F-AV-1451 volume of distribution compared with controls (P = 0.004), but there was an overlap of the individual ranges. We saw no significant correlation between symptom dominant side and contralateral nigral volume of distribution. There was no correlation between nigral (18)F-AV-1451 volume of distribution and age or time since diagnosis. In the subset of 12 patients, who also had a (123)I-FP-CIT scan, the mean total striatal dopamine transporter signal was decreased by 45% and the mean total (18)F-AV-1451 substantia nigra volume of distribution was decreased by 33% after median disease duration of 4.7 years (0.5-12.4 years). (18)F-AV-1451 positron emission tomography may be the first radiotracer to reflect the loss of pigmented neurons in the substantia nigra of parkinsonian patients. The magnitude of the nigral signal loss was smaller than the decrease in striatal dopamine transporter signal measured by dopamine transporter single photon emission computed tomography. These findings suggest a more severe loss of striatal nerve terminal function compared with neuronal cell bodies, in accordance with the post-mortem literature.

Probing neuronal activation by functional quantitative susceptibility mapping under a visual paradigm: A group level comparison with BOLD fMRI and PET

Dynamic changes of brain-tissue magnetic susceptibility provide the basis for functional MR imaging (fMRI) via T2*-weighted signal-intensity modulations. Promising initial work on a detection of neuronal activity via quantitative susceptibility mapping (fQSM) has been published but consistently reported on ill-understood positive and negative activation patterns (Balla et al., 2014; Chen and Calhoun, 2015a). We set out to (i) demonstrate that fQSM can exploit established fMRI data acquisition and processing methods and to (ii) better describe aspects of the apparent activation patterns using fMRI and PET as standards of reference. Under a standardized visual-stimulation paradigm PET and 3-T gradient-echo EPI-based fQSM, fMRI data from 9 healthy volunteers were acquired and analyzed by means of Independent Component Analysis (ICA) at subject level and, for the first time, at group level. Numbers of activated (z-score>2.0) voxels were counted and their mean z-scores calculated in volumes of interest (occipital lobe (Nocc_lobe), segmented occipital gray-matter (NGM_occ_lobe), large veins (Nveins)), and in occipital-lobe voxels commonly activated in fQSM and fMRI component maps. Common but not entirely congruent regions of apparent activation were found in the occipital lobe in z-score maps from all modalities, fQSM, fMRI and PET, with distinct BOLD-negatively correlated regions in fQSM data. At subject-level, Nocc_lobe, NGM_occ_lobe and their mean z-scores were significantly smaller in fQSM than in fMRI, but their ratio, NGM_occ_lobe/Nocc_lobe, was comparable. Nveins did not statistically differ and the ratio Nveins/NGM_occ_lobe as well as the mean z-scores were higher for fQSM than for fMRI. In veins and immediate vicinity, z-score maps derived from both phase and fQSM-data showed positive and negative lobes resembling dipole shapes in simulated field and phase maps with no correlate in fMRI or PET data. Our results show that standard fMRI tools can directly be used for fQSM processing, and suggest that fQSM may have the potential to detect gray-matter activation distant from large veins, to improve detection of veins with stimulus-induced venous oxygen saturation (SvO2) variations, and to better localize areas of activation. However, our results seem to clearly expose issues that phenomenologically resemble an incomplete dipolar inversion and that need to be subject to further investigation.

Radionecrosis versus disease progression in brain metastasis. Value of (18)F-DOPA PET/CT/MRI

The use of (18)F-DOPA PET/CT with magnetic resonance imaging fusion and the use of visual methods and quantitative analysis helps to differentiate between changes post-radiosurgery vs. suspicion of disease progression in a patient with brain metastases from melanoma, thus facilitating taking early surgical action.

Structural and functional brain abnormalities place phenocopy frontotemporal dementia (FTD) in the FTD spectrum

Purpose

‘Phenocopy’ frontotemporal dementia (phFTD) patients may clinically mimic the behavioral variant of FTD (bvFTD), but do not show functional decline or abnormalities upon visual inspection of routine neuroimaging. We aimed to identify abnormalities in gray matter (GM) volume and perfusion in phFTD and to assess whether phFTD belongs to the FTD spectrum. We compared phFTD patients with both healthy controls and bvFTD patients.

Materials & methods

Seven phFTD and 11 bvFTD patients, and 20 age-matched controls underwent structural T1-weighted magnetic resonance imaging (MRI) and 3D pseudo-continuous arterial spin labeling (pCASL) at 3T. Normalized GM (nGM) volumes and perfusion, corrected for partial volume effects, were quantified regionally as well as in the entire supratentorial cortex, and compared between groups taking into account potential confounding effects of gender and scanner.

Results

PhFTD patients showed cortical atrophy, most prominently in the right temporal lobe. Apart from this regional atrophy, GM volume was generally not different from either controls or from bvFTD. BvFTD however showed extensive frontotemporal atrophy. Perfusion was increased in the left prefrontal cortex compared to bvFTD and to a lesser extent to controls.

Conclusion

PhFTD and bvFTD show overlapping cortical structural abnormalities indicating a continuum of changes especially in the frontotemporal regions. Together with functional changes suggestive of a compensatory response to incipient pathology in the left prefrontal regions, these findings are the first to support a possible neuropathological etiology of phFTD and suggest that phFTD may be a neurodegenerative disease on the FTD spectrum.

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Both phFTD and bvFTD show frontotemporal cortical structural abnormalities.

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PhFTD shows left frontal hyperperfusion, suggestive of functional compensation.

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Overlapping findings in phFTD and bvFTD findings suggest a common disease spectrum.

Concurrent white and gray matter degeneration of disease-specific networks in early-stage Alzheimer's disease and behavioral variant frontotemporal dementia

This study investigates regional coherence between white matter (WM) microstructure and gray matter (GM) volume and perfusion measures in Alzheimer's disease (AD) and behavioral variant frontotemporal dementia (bvFTD) using a correlational approach. WM-GM coherence, compared with controls, was stronger between cingulum WM and frontotemporal GM in AD, and temporoparietal GM in bvFTD. In addition, in AD compared with controls, coherence was stronger between inferior fronto-occipital fasciculus WM microstructure and occipital GM perfusion. In this first study assessing regional WM-GM coherence in AD and bvFTD, we show that WM microstructure and GM volume and perfusion measures are coherent, particularly in regions implicated in AD and bvFTD pathology. This indicates concurrent degeneration in disease-specific networks. Our methodology allows for the detection of incipient abnormalities that go undetected in conventional between-group analyses.

Imaging in-vivo tau pathology in Alzheimer's disease with THK5317 PET in a multimodal paradigm

Purpose

The aim of this study was to explore the cerebral distribution of the tau-specific PET tracer [¹⁸F]THK5317 (also known as (S)-[¹⁸F]THK5117) retention in different stages of Alzheimer’s disease; and study any associations with markers of hypometabolism and amyloid-beta deposition.

Methods

Thirty-three individuals were enrolled, including nine patients with Alzheimer’s disease dementia, thirteen with mild cognitive impairment (MCI), two with non-Alzheimer’s disease dementia, and nine healthy controls (five young and four elderly). In a multi-tracer PET design [¹⁸F]THK5317, [¹¹C] Pittsburgh compound B ([¹¹C]PIB), and [¹⁸F]FDG were used to assess tau pathology, amyloid-beta deposition and cerebral glucose metabolism, respectively. The MCI patients were further divided into MCI [¹¹C]PIB-positive (n = 11) and MCI [¹¹C]PIB-negative (n = 2) groups.

Results

Test-retest variability for [¹⁸F]THK5317-PET was very low (1.17–3.81 %), as shown by retesting five patients. The patients with prodromal (MCI [¹¹C]PIB-positive) and dementia-stage Alzheimer’s disease had significantly higher [¹⁸F]THK5317 retention than healthy controls (p = 0.002 and p = 0.001, respectively) in areas exceeding limbic regions, and their discrimination from this control group (using the area under the curve) was >98 %. Focal negative correlations between [¹⁸F]THK5317 retention and [¹⁸F]FDG uptake were observed mainly in the frontal cortex, and focal positive correlations were found between [¹⁸F]THK5317 and [¹¹C]PIB retentions isocortically. One patient with corticobasal degeneration syndrome and one with progressive supranuclear palsy showed no [¹¹C]PIB but high [¹⁸F]THK5317 retentions with a different regional distribution from that in Alzheimer’s disease patients.

Conclusions

The tau-specific PET tracer [¹⁸F]THK5317 images in vivo the expected regional distribution of tau pathology. This distribution contrasts with the different patterns of hypometabolism and amyloid-beta deposition.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-016-3363-z) contains supplementary material, which is available to authorized users.

Does posterior cingulate hypometabolism result from disconnection or local pathology across preclinical and clinical stages of Alzheimer's disease?

PURPOSE

Posterior cingulate cortex (PCC) hypometabolism as measured by FDG PET is an indicator of Alzheimer's disease (AD) in prodromal stages, such as in mild cognitive impairment (MCI), and has been found to be closely associated with hippocampus atrophy in AD dementia. We studied the effects of local and remote atrophy and of local amyloid load on the PCC metabolic signal in patients with different preclinical and clinical stages of AD.

METHODS

We determined the volume of the hippocampus and PCC grey matter based on volumetric MRI scans, PCC amyloid load based on AV45 PET, and PCC metabolism based on FDG PET in 667 subjects participating in the Alzheimer's Disease Neuroimaging Initiative spanning the range from cognitively normal ageing through prodromal AD to AD dementia.

RESULTS

In cognitively normal individuals and those with early MCI, PCC hypometabolism was exclusively associated with hippocampus atrophy, whereas in subjects with late MCI it was associated with both local and remote effects of atrophy as well as local amyloid load. In subjects with AD dementia, PCC hypometabolism was exclusively related to local atrophy.

CONCLUSION

Our findings suggest that the effects of remote pathology on PCC hypometabolism decrease and the effects of local pathology increase from preclinical to clinical stages of AD, consistent with a progressive disconnection of the PCC from downstream cortical and subcortical brain regions.

Amygdala alterations during an emotional conflict task in women recovered from anorexia nervosa

The pathophysiology of anorexia nervosa (AN) is not completely understood, but research suggests that alterations in brain circuits related to cognitive control and emotion are central. The aim of this study was to explore neural responses to an emotional conflict task in women recovered from AN. Functional magnetic resonance imaging was used to measure neural responses to an emotional conflict task in 22 women recovered from AN and 21 age-matched healthy controls. The task involved categorizing affective faces while ignoring affective words. Face and word stimuli were either congruent (non-conflict) or incongruent (conflict). Brain responses to emotional conflict did not differ between groups. However, in response to emotional non-conflict, women recovered from AN relative to healthy controls showed significantly less activation in the bilateral amygdala. Specifically, while emotional non-conflict evoked significant activations of the amygdala in healthy controls, recovered AN women did not show such activations. Similar significant group differences were also observed in the hippocampus and basal ganglia. These results suggest that women recovered from AN are characterized by alterations within emotion-related brain circuits. Recovered women's absence of amygdala and hippocampus activation during non-conflict trials possibly reflects an impaired ability to process emotional significant stimuli.

Comparison of Early-Phase 11C-Deuterium-l-Deprenyl and 11C-Pittsburgh Compound B PET for Assessing Brain Perfusion in Alzheimer Disease

The PET tracer (11)C-deuterium-L-deprenyl ((11)C-DED) has been used to visualize activated astrocytes in vivo in patients with Alzheimer disease (AD). In this multitracer PET study, early-phase (11)C-DED and (11)C-Pittsburgh compound B ((11)C-PiB) (eDED and ePiB, respectively) were compared as surrogate markers of brain perfusion, and the extent to which (11)C-DED binding is influenced by brain perfusion was investigated.

METHODS

(11)C-DED, (11)C-PiB, and (18)F-FDG dynamic PET scans were obtained in age-matched groups comprising AD patients (n = 8), patients with mild cognitive impairment (n = 17), and healthy controls (n = 16). A modified reference Patlak model was used to quantify (11)C-DED binding. A simplified reference tissue model was applied to both (11)C-DED and (11)C-PiB to measure brain perfusion relative to the cerebellar gray matter (R1) and binding potentials. (11)C-PiB retention and (18)F-FDG uptake were also quantified as target-to-pons SUV ratios in 12 regions of interest (ROIs).

RESULTS

The strongest within-subject correlations with the corresponding R1 values (R1,DED and R1,PiB, respectively) and with (18)F-FDG uptake were obtained when the eDED and ePiB PET data were measured 1-4 min after injection. The optimum eDED/ePiB intervals also showed strong, significant ROI-based intersubject Pearson correlations with R1,DED/R1,PiB and with (18)F-FDG uptake, whereas (11)C-DED binding was largely independent of brain perfusion, as measured by eDED. Corresponding voxelwise correlations confirmed the ROI-based results. Temporoparietal eDED or ePiB brain perfusion measurements were highly discriminative between patient and control groups, with discriminative ability statistically comparable to that of temporoparietal (18)F-FDG glucose metabolism. Hypometabolism extended over wider regions than hypoperfusion in patient groups compared with controls.

CONCLUSION

The 1- to 4-min early-frame intervals of (11)C-DED or (11)C-PiB are suitable surrogate measures for brain perfusion. (11)C-DED binding is independent of brain perfusion, and thus (11)C-DED PET can provide information on both functional (brain perfusion) and pathologic (astrocytosis) aspects from a single PET scan. In comparison with glucose metabolism, early-phase (11)C-DED and (11)C-PiB perfusion appear to provide complementary rather than redundant information.

Using [(11)C]Ro15 4513 PET to characterise GABA-benzodiazepine receptors in opiate addiction: Similarities and differences with alcoholism

The importance of the GABA-benzodiazepine receptor complex and its subtypes are increasingly recognised in addiction. Using the α1/α5 benzodiazepine receptor PET radioligand [¹¹C]Ro15 4513, we previously showed reduced binding in the nucleus accumbens and hippocampus in abstinent alcohol dependence. We proposed that reduced [¹¹C]Ro15 4513 binding in the nucleus accumbens was a marker of addiction whilst the reduction in hippocampus and positive relationship with memory was a consequence of chronic alcohol abuse. To examine this further we assessed [¹¹C]Ro15 4513 binding in another addiction, opiate dependence, and used spectral analysis to estimate contributions of α1 and α5 subtypes to [¹¹C]Ro15 4513 binding in opiate and previously acquired alcohol-dependent groups. Opiate substitute maintained opiate-dependent men (n = 12) underwent an [¹¹C]Ro15 4513 PET scan and compared with matched healthy controls (n = 13). We found a significant reduction in [¹¹C]Ro15 4513 binding in the nucleus accumbens in the opiate-dependent compared with the healthy control group. There was no relationship between [¹¹C]Ro15 4513 binding in the hippocampus with memory. We found that reduced [¹¹C]Ro15 4513 binding was associated with reduced α5 but not α1 subtypes in the opiate-dependent group. This was also seen in an alcohol-dependent group where an association between memory performance and [¹¹C]Ro15 4513 binding was primarily driven by α5 and not α1 subtype. We suggest that reduced α5 levels in the nucleus accumbens are associated with addiction since we have now shown this in dependence to two pharmacologically different substances, alcohol and opiates.

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Lower [¹¹C]Ro15 4513 binding is evident in the nucleus accumbens of opiate addicts.

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This appears primarily due to lower levels of α5 subtype of the GABA-A receptor.

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Lower [¹¹C]Ro15 4513 binding is similarly found in alcoholism.

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Lower levels of α5 GABA-A receptor in nucleus accumbens may underpin addiction.

Fast Automatic Step Size Estimation for Gradient Descent Optimization of Image Registration

Fast automatic image registration is an important prerequisite for image-guided clinical procedures. However, due to the large number of voxels in an image and the complexity of registration algorithms, this process is often very slow. Stochastic gradient descent is a powerful method to iteratively solve the registration problem, but relies for convergence on a proper selection of the optimization step size. This selection is difficult to perform manually, since it depends on the input data, similarity measure and transformation model. The Adaptive Stochastic Gradient Descent (ASGD) method is an automatic approach, but it comes at a high computational cost. In this paper, we propose a new computationally efficient method (fast ASGD) to automatically determine the step size for gradient descent methods, by considering the observed distribution of the voxel displacements between iterations. A relation between the step size and the expectation and variance of the observed distribution is derived. While ASGD has quadratic complexity with respect to the transformation parameters, fast ASGD only has linear complexity. Extensive validation has been performed on different datasets with different modalities, inter/intra subjects, different similarity measures and transformation models. For all experiments, we obtained similar accuracy as ASGD. Moreover, the estimation time of fast ASGD is reduced to a very small value, from 40 s to less than 1 s when the number of parameters is 105, almost 40 times faster. Depending on the registration settings, the total registration time is reduced by a factor of 2.5-7 × for the experiments in this paper.

Confidence Estimation for Medical Image Registration Based On Stereo Confidences

In this paper, we propose a novel method to estimate the confidence of a registration that does not require any ground truth, is independent from the registration algorithm and the resulting confidence is correlated with the amount of registration error. We first apply a local search to match patterns between the registered image pairs. Local search induces a cost space per voxel which we explore further to estimate the confidence of the registration similar to confidence estimation algorithms for stereo matching. We test our method on both synthetically generated registration errors and on real registrations with ground truth. The experimental results show that our confidence measure can estimate registration errors and it is correlated with local errors.

Diverging longitudinal changes in astrocytosis and amyloid PET in autosomal dominant Alzheimer's disease

See Schott and Fox (doi: 10.1093/brain/awv405 ) for a scientific commentary on this article.

Alzheimer’s disease is a multifactorial dementia disorder characterized by early amyloid-β, tau deposition, glial activation and neurodegeneration, where the interrelationships between the different pathophysiological events are not yet well characterized. In this study, longitudinal multitracer positron emission tomography imaging of individuals with autosomal dominant or sporadic Alzheimer’s disease was used to quantify the changes in regional distribution of brain astrocytosis (tracer ¹¹ C-deuterium-L-deprenyl), fibrillar amyloid-β plaque deposition ( ¹¹ C-Pittsburgh compound B), and glucose metabolism ( ¹⁸ F-fluorodeoxyglucose) from early presymptomatic stages over an extended period to clinical symptoms. The 52 baseline participants comprised autosomal dominant Alzheimer’s disease mutation carriers ( n = 11; 49.6 ± 10.3 years old) and non-carriers ( n = 16; 51.1 ± 14.2 years old; 10 male), and patients with sporadic mild cognitive impairment ( n = 17; 61.9 ± 6.4 years old; nine male) and sporadic Alzheimer’s disease ( n = 8; 63.0 ± 6.5 years old; five male); for confidentiality reasons, the gender of mutation carriers is not revealed. The autosomal dominant Alzheimer’s disease participants belonged to families with known mutations in either presenilin 1 ( PSEN1 ) or amyloid precursor protein ( APPswe or APParc ) genes. Sporadic mild cognitive impairment patients were further divided into ¹¹ C-Pittsburgh compound B-positive ( n = 13; 62.0 ± 6.4; seven male) and ¹¹ C-Pittsburgh compound B-negative ( n = 4; 61.8 ± 7.5 years old; two male) groups using a neocortical standardized uptake value ratio cut-off value of 1.41, which was calculated with respect to the cerebellar grey matter. All baseline participants underwent multitracer positron emission tomography scans, cerebrospinal fluid biomarker analysis and neuropsychological assessment. Twenty-six of the participants underwent clinical and imaging follow-up examinations after 2.8 ± 0.6 years. By using linear mixed-effects models, fibrillar amyloid-β plaque deposition was first observed in the striatum of presymptomatic autosomal dominant Alzheimer’s disease carriers from 17 years before expected symptom onset; at about the same time, astrocytosis was significantly elevated and then steadily declined. Diverging from the astrocytosis pattern, amyloid-β plaque deposition increased with disease progression. Glucose metabolism steadily declined from 10 years after initial amyloid-β plaque deposition. Patients with sporadic mild cognitive impairment who were ¹¹ C-Pittsburgh compound B-positive at baseline showed increasing amyloid-β plaque deposition and decreasing glucose metabolism but, in contrast to autosomal dominant Alzheimer’s disease carriers, there was no significant longitudinal decline in astrocytosis over time. The prominent initially high and then declining astrocytosis in autosomal dominant Alzheimer’s disease carriers, contrasting with the increasing amyloid-β plaque load during disease progression, suggests astrocyte activation is implicated in the early stages of Alzheimer’s disease pathology.

Improved segmentation of cerebellar structures in children

BACKGROUND

Consistent localization of cerebellar cortex in a standard coordinate system is important for functional studies and detection of anatomical alterations in studies of morphometry. To date, no pediatric cerebellar atlas is available.

NEW METHOD

The probabilistic Cape Town Pediatric Cerebellar Atlas (CAPCA18) was constructed in the age-appropriate National Institute of Health Pediatric Database asymmetric template space using manual tracings of 16 cerebellar compartments in 18 healthy children (9-13 years) from Cape Town, South Africa. The individual atlases of the training subjects were also used to implement multi atlas label fusion using multi atlas majority voting (MAMV) and multi atlas generative model (MAGM) approaches. Segmentation accuracy in 14 test subjects was compared for each method to 'gold standard' manual tracings.

RESULTS

Spatial overlap between manual tracings and CAPCA18 automated segmentation was 73% or higher for all lobules in both hemispheres, except VIIb and X. Automated segmentation using MAGM yielded the best segmentation accuracy over all lobules (mean Dice Similarity Coefficient 0.76; range 0.55-0.91; mean Hausdorff distance 0.9 mm; range 0.8-2.7 mm).

COMPARISON WITH EXISTING METHODS

In all lobules, spatial overlap of CAPCA18 segmentations with manual tracings was similar or higher than those obtained with SUIT (spatially unbiased infra-tentorial template), providing additional evidence of the benefits of an age appropriate atlas. MAGM segmentation accuracy was comparable to values reported recently by Park et al. (Neuroimage 2014;95(1):217) in adults (across all lobules mean DSC=0.73, range 0.40-0.89).

CONCLUSIONS

CAPCA18 and the associated multi-subject atlases of the training subjects yield improved segmentation of cerebellar structures in children.

Effects of norepinephrine transporter gene variants on NET binding in ADHD and healthy controls investigated by PET

Attention deficit hyperactivity disorder (ADHD) is a heterogeneous disorder with a strong genetic component. The norepinephrine transporter (NET) is a key target for ADHD treatment and the NET gene has been of high interest as a possible modulator of ADHD pathophysiology. Therefore, we conducted an imaging genetics study to examine possible effects of single nucleotide polymorphisms (SNPs) within the NET gene on NET nondisplaceable binding potential (BPND ) in patients with ADHD and healthy controls (HCs). Twenty adult patients with ADHD and 20 HCs underwent (S,S)-[18F]FMeNER-D2 positron emission tomography (PET) and were genotyped on a MassARRAY MALDI-TOF platform using the Sequenom iPLEX assay. Linear mixed models analyses revealed a genotype-dependent difference in NET BPND between groups in the thalamus and cerebellum. In the thalamus, a functional promoter SNP (-3081 A/T) and a 5'-untranslated region (5'UTR) SNP (-182 T/C), showed higher binding in ADHD patients compared to HCs depending on the major allele. Furthermore, we detected an effect of genotype in HCs, with major allele carriers having lower binding. In contrast, for two 3'UTR SNPs (*269 T/C, *417 A/T), ADHD subjects had lower binding in the cerebellum compared to HCs depending on the major allele. Additionally, symptoms of hyperactivity and impulsivity correlated with NET BPND in the cerebellum depending on genotype. Symptoms correlated positively with cerebellar NET BPND for the major allele, while symptoms correlated negatively to NET BPND in minor allele carriers. Our findings support the role of genetic influence of the NE system on NET binding to be pertubated in ADHD.

Neuroanatomical Correlates of Recognizing Face Expressions in Mild Stages of Alzheimer's Disease

Early Alzheimer's disease can involve social disinvestment, possibly as a consequence of impairment of nonverbal communication skills. This study explores whether patients with Alzheimer's disease at the mild cognitive impairment or mild dementia stage have impaired recognition of emotions in facial expressions, and describes neuroanatomical correlates of emotion processing impairment. As part of the ongoing PACO study (personality, Alzheimer's disease and behaviour), 39 patients with Alzheimer's disease at the mild cognitive impairment or mild dementia stage and 39 matched controls completed tests involving discrimination of four basic emotions-happiness, fear, anger, and disgust-on photographs of faces. In patients, automatic volumetry of 83 brain regions was performed on structural magnetic resonance images using MAPER (multi-atlas propagation with enhanced registration). From the literature, we identified for each of the four basic emotions one brain region thought to be primarily associated with the function of recognizing that emotion. We hypothesized that the volume of each of these regions would be correlated with subjects' performance in recognizing the associated emotion. Patients showed deficits of basic emotion recognition, and these impairments were correlated with the volumes of the expected regions of interest. Unexpectedly, most of these correlations were negative: better emotional facial recognition was associated with lower brain volume. In particular, recognition of fear was negatively correlated with the volume of amygdala, disgust with pallidum, and happiness with fusiform gyrus. Recognition impairment in mild stages of Alzheimer's disease for a given emotion was thus associated with less visible atrophy of functionally responsible brain structures within the patient group. Possible explanations for this counterintuitive result include neuroinflammation, regional β-amyloid deposition, or transient overcompensation during early stages of Alzheimer's disease.

Voxelwise atlas rating for computer assisted diagnosis: Application to congenital heart diseases of the great arteries

Atlas-based analysis methods rely on the morphological similarity between the atlas and target images, and on the availability of labelled images. Problems can arise when the deformations introduced by pathologies affect the similarity between the atlas and a patient's image. The aim of this work is to exploit the morphological dissimilarities between atlas databases and pathological images to diagnose the underlying clinical condition, while avoiding the dependence on labelled images. We propose a voxelwise atlas rating approach (VoxAR) relying on multiple atlas databases, each representing a particular condition. Using a local image similarity measure to assess the morphological similarity between the atlas and target images, a rating map displaying for each voxel the condition of the atlases most similar to the target is defined. The final diagnosis is established by assigning the condition of the database the most represented in the rating map. We applied the method to diagnose three different conditions associated with dextro-transposition of the great arteries, a congenital heart disease. The proposed approach outperforms other state-of-the-art methods using annotated images, with an accuracy of 97.3% when evaluated on a set of 60 whole heart MR images containing healthy and pathological subjects using cross validation.

Does stroke location predict walk speed response to gait rehabilitation?

OBJECTIVES

Recovery of independent ambulation after stroke is a major goal. However, which rehabilitation regimen best benefits each individual is unknown and decisions are currently made on a subjective basis. Predictors of response to specific therapies would guide the type of therapy most appropriate for each patient. Although lesion topography is a strong predictor of upper limb response, walking involves more distributed functions. Earlier studies that assessed the cortico-spinal tract (CST) were negative, suggesting other structures may be important.

EXPERIMENTAL DESIGN

The relationship between lesion topography and response of walking speed to standard rehabilitation was assessed in 50 adult-onset patients using both volumetric measurement of CST lesion load and voxel-based lesion-symptom mapping (VLSM) to assess non-CST structures. Two functional mobility scales, the functional ambulation category (FAC) and the modified rivermead mobility index (MRMI) were also administered. Performance measures were obtained both at entry into the study (3-42 days post-stroke) and at the end of a 6-week course of therapy. Baseline score, age, time since stroke onset and white matter hyperintensities score were included as nuisance covariates in regression models.

PRINCIPAL OBSERVATIONS

CST damage independently predicted response to therapy for FAC and MRMI, but not for walk speed. However, using VLSM the latter was predicted by damage to the putamen, insula, external capsule and neighbouring white matter.

CONCLUSIONS

Walk speed response to rehabilitation was affected by damage involving the putamen and neighbouring structures but not the CST, while the latter had modest but significant impact on everyday functions of general mobility and gait. Hum Brain Mapp 37:689-703, 2016. © 2015 Wiley Periodicals, Inc.