The midpoint of cortical thinning between late childhood and early adulthood differs between individuals and brain regions: Evidence from longitudinal modelling in a 12-wave neuroimaging sample.

Charting human brain maturation between childhood and adulthood is a fundamental prerequisite for understanding the rapid biological and psychological changes during human development. Two barriers have precluded the quantification of maturational trajectories: demands on data and demands on estimation. Using high-temporal resolution neuroimaging data of up to 12-waves in the HUBU cohort (N = 90, aged 7-21 years) we investigate changes in apparent cortical thickness across childhood and adolescence. Fitting a four-parameter logistic nonlinear random effects mixed model, we quantified the characteristic, s-shaped, trajectory of cortical thinning in adolescence. This approach yields biologically meaningful parameters, including the midpoint of cortical thinning (MCT), which corresponds to the age at which the cortex shows most rapid thinning - in our sample occurring, on average, at 14 years of age. These results show that, given suitable data and models, cortical maturation can be quantified with precision for each individual and brain region.

Healthy minds from 0-100 years: Optimising the use of European brain imaging cohorts ("Lifebrain").

The main objective of "Lifebrain" is to identify the determinants of brain, cognitive and mental (BCM) health at different stages of life. By integrating, harmonising and enriching major European neuroimaging studies across the life span, we will merge fine-grained BCM health measures of more than 5,000 individuals. Longitudinal brain imaging, genetic and health data are available for a major part, as well as cognitive and mental health measures for the broader cohorts, exceeding 27,000 examinations in total. By linking these data to other databases and biobanks, including birth registries, national and regional archives, and by enriching them with a new online data collection and novel measures, we will address the risk factors and protective factors of BCM health. We will identify pathways through which risk and protective factors work and their moderators. Exploiting existing European infrastructures and initiatives, we hope to make major conceptual, methodological and analytical contributions towards large integrative cohorts and their efficient exploitation. We will thus provide novel information on BCM health maintenance, as well as the onset and course of BCM disorders. This will lay a foundation for earlier diagnosis of brain disorders, aberrant development and decline of BCM health, and translate into future preventive and therapeutic strategies. Aiming to improve clinical practice and public health we will work with stakeholders and health authorities, and thus provide the evidence base for prevention and intervention.

BDNF val66met association with serotonin transporter binding in healthy humans.

The serotonin transporter (5-HTT) is a key feature of the serotonin system, which is involved in behavior, cognition and personality and implicated in neuropsychiatric illnesses including depression. The brain-derived neurotrophic factor (BDNF) val66met and 5-HTTLPR polymorphisms have predicted differences in 5-HTT levels in humans but with equivocal results, possibly due to limited sample sizes. Within the current study we evaluated these genetic predictors of 5-HTT binding with [11C]DASB positron emission tomography (PET) in a comparatively large cohort of 144 healthy individuals. We used a latent variable model to determine genetic effects on a latent variable (5-HTTLV), reflecting shared correlation across regional 5-HTT binding (amygdala, caudate, hippocampus, midbrain, neocortex, putamen and thalamus). Our data supported a significant BDNF val66met effect on 5-HTTLV such that met-carriers showed 2-7% higher subcortical 5-HTT binding compared with val/val individuals (P=0.042). Our data did not support a BDNF val66met effect in neocortex and 5-HTTLPR did not significantly predict 5-HTTLV. We did not observe evidence for an interaction between genotypes. Our findings indicate that met-carriers have increased subcortical 5-HTT binding. The small difference suggests limited statistical power may explain previously reported null effects. Our finding adds to emerging evidence that BDNF val66met contributes to differences in the human brain serotonin system, informing how variability in the 5-HTT level emerges and may represent an important molecular mediator of BDNF val66met effects on behavior and related risk for neuropsychiatric illness.

Associations between social cognition, skills, and function and subclinical negative and positive symptoms in 22q11.2 deletion syndrome.

BACKGROUND: Identification of the early signs of schizophrenia would be a major achievement for the early intervention and prevention strategies in psychiatry. Social impairments are defining features of schizophrenia. Impairments of individual layers of social competencies are frequently described in individuals with 22q11.2 deletion syndrome (22q11.2DS), who have high risk of schizophrenia. It is unclear whether and to what extent social impairments associate with subclinical negative and positive symptoms in 22q11.2DS, and which layer of social impairments are more correlated with schizophrenia-related symptoms. The aims of this study were to conduct a comprehensive investigation of social impairments at three different levels (function, skill, and cognition) and their interrelationship and to determine to what degree the social impairments correlate to subclinical levels of negative and positive symptoms, respectively, in a young cohort of 22q11.2DS not diagnosed with schizophrenia. METHODS: The level of social impairment was addressed using questionnaires and objective measures of social functioning (The Adaptive Behavior Assessment System), skills (Social Responsiveness Scale), and cognition (The Awareness of Social Inference Test and CANTAB Emotional Recognition Task), and the presence of subclinical symptoms of schizophrenia were evaluated using the Structured Interview for Prodromal Syndromes in a cross-sectional case-control study of 29 cases and 29 controls, aged 12 to 25 years. Association between social impairment and negative and positive symptoms levels was examined in cases only. RESULTS: Subjects with 22q11.2DS were highly impaired in social function, social skills, and social cognition (p ≤ 6.2 × 10-9) relative to control peers and presented with more negative (p = 5.8 × 10-11) and positive (p = 7.5 × 10-4) symptoms. In particular, social functional and skill levels were highly associated with notably subclinical negative symptoms levels. CONCLUSIONS: This study shows strong correlations between levels of social impairments and subclinical negative and positive symptoms. However, longitudinal studies are required to show if social impairments represent early disease manifestations. If parental or self-reporting suggests severe social impairment, it should advocate for clinical awareness not only to social deficits per se but also of potential subclinical psychosis symptoms.

Unaffected twins discordant for affective disorders show changes in anterior callosal white matter microstructure.

OBJECTIVE: The neurobiological mechanisms mediating an increased risk to develop affective disorders remain poorly understood. In a group of individuals with a family history of major depressive (MDD) or bipolar disorder (BD), we investigated the microstructural properties of white matter fiber tracts, that is, cingulum bundle, uncinate fasciculus, anterior limb of the internal capsule, and corpus callosum, that facilitate the communication between brain regions implicated in affective disorders. METHOD: Eighty-nine healthy mono- or dizygotic twins with a co-twin diagnosed with MDD or BD (high-risk) and 57 healthy twins with a co-twin with no familial history of affective disorders (low-risk) were included in a diffusion tensor imaging study. RESULT: The high-risk group showed decreased fractional anisotropy (FA), a measure of water diffusion directionality, and increased radial diffusivity in the anterior region of corpus callosum compared to the low-risk group. This abnormality was not associated with zygosity or type of depressive disorder of co-twin. CONCLUSION: The observed decreased anterior callosal fiber FA in the high-risk group may be indicative of a compromised interhemispheric communication between left and right frontal regions critically involved in mood regulation. Reduced anterior callosal FA may act as a vulnerability marker for affective disorders in individuals at familial risk.

Central 5-HT neurotransmission modulates weight loss following gastric bypass surgery in obese individuals.

The cerebral serotonin (5-HT) system shows distinct differences in obesity compared with the lean state. Here, it was investigated whether serotonergic neurotransmission in obesity is a stable trait or changes in association with weight loss induced by Roux-in-Y gastric bypass (RYGB) surgery. In vivo cerebral 5-HT2A receptor and 5-HT transporter binding was determined by positron emission tomography in 21 obese [four men; body mass index (BMI), 40.1 ± 4.1 kg/m(2)] and 10 lean (three men; BMI, 24.6 ± 1.5 kg/m(2)) individuals. Fourteen obese individuals were re-examined after RYGB surgery. First, it was confirmed that obese individuals have higher cerebral 5-HT2A receptor binding than lean individuals. Importantly, we found that higher presurgical 5-HT2A receptor binding predicted greater weight loss after RYGB and that the change in 5-HT2A receptor and 5-HT transporter binding correlated with weight loss after RYGB. The changes in the 5-HT neurotransmission before and after RYGB are in accordance with a model wherein the cerebral extracellular 5-HT level modulates the regulation of body weight. Our findings support that the cerebral 5-HT system contributes both to establish the obese condition and to regulate the body weight in response to RYGB.

Central 5-HT4 receptor binding as biomarker of serotonergic tonus in humans: a [11C]SB207145 PET study.

Identification of a biomarker that can inform on extracellular serotonin (5-HT) levels in the brains of living humans would enable greater understanding of the way brain circuits are modulated by serotonergic neurotransmission. Substantial evidence from studies in animals and humans indicates an inverse relationship between central 5-HT tonus and 5-HT type 4 receptor (5-HT4R) density, suggesting that 5-HT4R receptor density may be a biomarker marker for 5-HT tonus. Here, we investigated whether a 3-week administration of a selective serotonin reuptake inhibitor, expected to increase brain 5-HT levels, is associated with a decline in brain 5-HT4R binding. A total of 35 healthy men were studied in a placebo-controlled, randomized, double-blind study. Participants were assigned to receive 3 weeks of oral dosing with placebo or fluoxetine, 40 mg per day. Brain 5-HT4R binding was quantified at baseline and at follow-up with [(11)C]SB207145 positron emission tomography (PET). Three weeks of intervention with fluoxetine was associated with a 5.2% reduction in brain 5-HT4R binding (P=0.017), whereas placebo intervention did not change 5-HT4R binding (P=0.52). Our findings are consistent with a model, wherein the 5-HT4R density adjusts to changes in the extracellular 5-HT tonus. Our data demonstrate for the first time in humans that the imaging of central 5-HT4R binding may be used as an in vivo biomarker of the central 5-HT tonus.

Obesity is associated with high serotonin 4 receptor availability in the brain reward circuitry.

The neurobiology underlying obesity is not fully understood. The neurotransmitter serotonin (5-HT) is established as a satiety-generating signal, but its rewarding role in feeding is less well elucidated. From animal experiments there is now evidence that the 5-HT(4) receptor (5-HT(4)R) is involved in food intake, and that pharmacological or genetic manipulation of the receptor in reward-related brain areas alters food intake. Here, we used positron emission tomography in humans to examine the association between cerebral 5-HT(4)Rs and common obesity. We found in humans a strong positive association between body mass index and the 5-HT(4)R density bilaterally in the two reward 'hot spots' nucleus accumbens and ventral pallidum, and additionally in the left hippocampal region and orbitofrontal cortex. These findings suggest that the 5-HT(4)R is critically involved in reward circuits that regulate people's food intake. They also suggest that pharmacological stimulation of the cerebral 5-HT(4)R may reduce reward-related overeating in humans.

Brain serotonin 2A receptor binding: relations to body mass index, tobacco and alcohol use.

Manipulations of the serotonin levels in the brain can affect impulsive behavior and influence our reactivity to conditioned reinforcers. Eating, tobacco smoking, and alcohol consumption are reinforcers that are influenced by serotonergic neurotransmission; serotonergic hypofunction leads to increased food and alcohol intake, and conversely, stimulation of the serotonergic system induces weight reduction and decreased food/alcohol intake as well as tobacco smoking. To investigate whether body weight, alcohol intake and tobacco smoking were related to the regulation of the cerebral serotonin 2A receptor (5-HT(2A)) in humans, we tested in 136 healthy human subjects if body mass index (BMI), degree of alcohol consumption and tobacco smoking was associated to the cerebral in vivo 5-HT(2A) receptor binding as measured with (18)F-altanserin PET. The subjects' BMI's ranged from 18.4 to 42.8 (25.2+/-4.3) kg/m(2). Cerebral cortex 5-HT(2A) binding was significantly positively correlated to BMI, whereas no association between cortical 5-HT(2A) receptor binding and alcohol or tobacco use was detected. We suggest that our observation is driven by a lower central 5-HT level in overweight people, leading both to increased food intake and to a compensatory upregulation of cerebral 5-HT(2A) receptor density.

Structural brain abnormalities in early onset first-episode psychosis.

BACKGROUND: Brain morphometry in children and adolescents with first-episode psychosis offer a unique opportunity for pathogenetic investigations. METHODS: We compared high-resolution 3D T1-weighted magnetic resonance images of the brain in 29 patients (schizophrenia, schizotypal disorder, delusional disorder or other non-organic psychosis), aged 10-18 to those of 29 matched controls, using optimized voxel-based morphometry. RESULTS: Psychotic patients had frontal white matter abnormalities, but expected (regional) gray matter reductions were not observed. Post hoc analyses revealed that schizophrenia patients (n = 15) had significantly larger lateral ventricles as compared to controls. Duration and dose of antipsychotics correlated negatively with global gray matter volume in minimally medicated patients (n = 18). CONCLUSION: Findings of white matter changes and enlarged lateral ventricles already at illness onset in young schizophrenia spectrum patients, suggests aberrant neurodevelopmental processes in the pathogenesis of these disorders. Gray matter volume changes, however, appear not to be a key feature in early onset first-episode psychosis.

Differentiating between low and high susceptibility to schizophrenia in twins: the significance of dermatoglyphic indices in relation to other determinants of brain development.

Both the skin and the brain develop from the same ectoderm and it is thought, therefore, that dermatoglyphics are informative for early disturbances in brain development in schizophrenia. This study was aimed at investigating the differences in both digital and palmar dermatoglyphic indices between twins discordant for schizophrenia and control twins. Furthermore, the significance of dermatoglyphic indices in relation to other determinants of brain development with regard to the susceptibility to schizophrenia was investigated. Data on dermatoglyphic indices of the hand and the palm were obtained from 21 same-sex discordant and 37 same-sex control twins. For 19 discordant and 25 control twins, there was also data available on brain volumes. Non-genetic intra-uterine circumstances early in pregnancy (10-13 weeks of gestation) are associated with a susceptibility to schizophrenia, since both the twins with schizophrenia and the unaffected co-twins showed more fluctuating asymmetry of the finger ridges (P<0.01), and marginally higher absolute finger ridge counts (P=0.06) than control twin pairs. Fluctuating asymmetry of the finger ridges was as important as whole brain and left hippocampal volumes in differentiating twins with a high susceptibility to schizophrenia from those with a low susceptibility.

Quantitative genetic modeling of variation in human brain morphology.

The degree to which individual variation in brain structure in humans is genetically or environmentally determined is as yet not well understood. We studied the brains of 54 monozygotic (33 male, 21 female) and 58 dizygotic (17 male, 20 female, 21 opposite sex) pairs of twins and 34 of their full siblings (19 male, 15 female) by means of high resolution magnetic resonance imaging scans. Structural equation modeling was used to quantify the genetic and environmental contributions to phenotypic (co)variance in whole brain, gray and white matter volume of the cerebrum, lateral ventricle volume and associated variables such as intracranial volume and height. Because the cerebral cortex makes up more that two-thirds of the brain mass and almost three-quarters of its synapses, our data predominantly concerns the telencephalon. Genetic factors accounted for most of the individual differences in whole brain (90%), gray (82%) and white (88%) matter volume. Individual differences in lateral ventricle volume were best explained by a model containing common (58%) and unique (42%) environmental factors, indicating genes to be of no or minor influence. In our sample, genetic or environmental influences were not different for males and females. The same genes influenced brain volumes and intracranial volume and almost completely explained their high phenotypic correlation. Genes influencing gray and white matter overlapped to a large extent and completely determined their phenotypic correlation. The high heritability estimates that were found indicate that brain volumes may be useful as intermediate phenotypes in behavioral genetic research.

Automatic segmentation of the ventricular system from MR images of the human brain.

An algorithm was developed that automatically segments the lateral and third ventricles from T1-weighted 3-D-FFE MR images of the human brain. The algorithm is based upon region-growing and mathematical morphology operators and starts from a coarse binary total brain segmentation, which is obtained from the 3-D-FFE image. Anatomical knowledge of the ventricular system has been incorporated into the method in order to find all constituting parts of the system, even if they are disconnected, and to avoid inclusion of nonventricle cerebrospinal fluid (CSF) regions. A test of the method on a synthetic MR brain image produced a segmentation overlap of 0.98 between the simulated ventricles ("model") and those defined by the algorithm. Further tests were performed on a large data set of 227 1.5 T MR brain images. The algorithm yielded useful results for 98% of the images. The automatic segmentations had intra-class correlation coefficients of 0.996 for the lateral ventricles and 0.86 for the third ventricle, with manually edited segmentations. Comparison of ventricular volumes of schizophrenia patients compared with those of healthy control subjects showed results in agreement with the literature.

Volumes of brain structures in twins discordant for schizophrenia.

BACKGROUND: The study was designed to examine the relative contributions of genetic and nongenetic factors to structural brain abnormalities in schizophrenia and subjects at risk to develop the disorder. METHODS: The brains of 15 monozygotic and 14 same-sex dizygotic twins discordant for schizophrenia (patients) and 29 healthy twins pair-wise matched for zygosity, sex, age, and birth order were studied using high-resolution magnetic resonance imaging scans. RESULTS: Intracranial and whole-brain corrected frontal lobe volumes were smaller (4.6% and 2.7%, respectively) in discordant monozygotic twins as compared with healthy monozygotic twins. Irrespective of zygosity, discordant twins had smaller whole-brain (2%), parahippocampal (9%), and hippocampal (8%) volumes than healthy twins. Moreover, patients had smaller whole-brain volumes (2. 2%) than their nonschizophrenic cotwins, who in turn had smaller brains (1%) than healthy twins. Lateral and third-ventricle volumes were increased in discordant dizygotic twins as compared with healthy dizygotic twins (60.6% and 56.6%, respectively). Finally, within discordant twins, lateral ventricles were larger (14.4%) in patients than in their nonschizophrenic cotwins. CONCLUSIONS: Smaller intracranial volumes in the monozygotic patients and their cotwins suggest that increased genetic risk to develop schizophrenia is related to reduced brain growth early in life. The additional reduction in whole-brain volume found in the patients suggests that the manifestation of the disorder is related to (neurodegenerative) processes that are most likely nongenetic in origin.

Automated separation of gray and white matter from MR images of the human brain.

A simple automatic procedure for segmentation of gray and white matter in high resolution 1.5T T1-weighted MR human brain images was developed and validated. The algorithm is based on histogram shape analysis of MR images that were corrected for scanner nonuniformity. Calibration and validation was done on a set of 80 MR images of human brains. The automatic method's values for the gray and white matter volumes were compared with the values from thresholds set twice by the best three of six raters. The automatic procedure was shown to perform as good as the best rater, where the average result of the best three raters was taken as reference. The method was also compared with two other histogram-based threshold methods, which yielded comparable results. The conclusion of the study thus is that automated threshold based methods can separate gray and white matter from MR brain images as reliably as human raters using a thresholding procedure.

Odor discrimination and task duration in young and older adults.

The effect of task duration on odor discrimination in aging was studied. Twenty-seven young male adults and 24 young female adults between 18 and 30 years of age, and 17 older male adults between 45 and 65 years of age completed an odor discrimination task. The odor discrimination task consisted of two parts of 16 trials each in which, from three bottles consisting of two identical and one aberrant odor, the aberrant odor had to be identified. The two parts were identical except that the aberrant odor was interchanged with the identical odors in the second as compared with the first part. Results revealed a decrease in odor discrimination with age. Moreover, with increased task duration odor discrimination performance decreased considerably in older male adults while it remained unchanged in young male adults. In addition, in young adults a small advantage in females as compared with males was found in the first part of the odor discrimination task, but this effect disappeared with increased task duration. In conclusion, task duration should be taken into consideration as a factor influencing odor discrimination in aging.

Statistical sulcal shape comparisons: application to the detection of genetic encoding of the central sulcus shape.

Principal Component Analysis allows a quantitative description of shape variability with a restricted number of parameters (or modes) which can be used to quantify the difference between two shapes through the computation of a modal distance. A statistical test can then be applied to this set of measurements in order to detect a statistically significant difference between two groups. We have applied this methodology to highlight evidence of genetic encoding of the shape of neuroanatomical structures. To investigate genetic constraint, we studied if shapes were more similar within 10 pairs of monozygotic twins than within interpairs and compared the results with those obtained from 10 pairs of dizygotic twins. The statistical analysis was performed using a Mantel permutation test. We show, using simulations, that this statistical test applied on modal distances can detect a possible genetic encoding. When applied to real data, this study highlighted genetic constraints on the shape of the central sulcus. We found from 10 pairs of monozygotic twins that the intrapair modal distance of the central sulcus was significantly smaller than the interpair modal distance, for both the left central sulcus (Z = -2.66; P < 0.005) and the right central sulcus (Z = -2.26; P < 0.05). Genetic constraints on the definition of the central sulcus shape were confirmed by applying the same experiment to 10 pairs of normal young individuals (Z = -1.39; Z = -0.63, i.e., values not significant at the P < 0.05 level) and 10 pairs of dizygotic twins (Z = 0.47; Z = 0.03, i.e., values not significant at the P < 0.05 level).

Volumetric analysis of frontal lobe regions in schizophrenia: relation to cognitive function and symptomatology.

BACKGROUND: The purpose of this study was to examine the structure of dorsolateral, medial, and orbital regions of the frontal lobe in schizophrenia, and to determine whether their volumetric measurements were related to cognitive function and symptomatology. METHODS: High resolution magnetic resonance imaging scans of the brains of 14 schizophrenic patients and 14 closely matched healthy controls were acquired. Volumes of gray and white matter of the left and right dorsolateral, medial, and orbital prefrontal brain regions were measured. Tests of verbal and visual memory and executive functions were used to assess cognitive function. The SANS and SAPS were used to obtain symptom ratings in patients. RESULTS: Data of 13 schizophrenic patients were analyzed. Patients showed a general, though not significant, decrease in volumes of frontal regions as compared to controls. In patients, but not in controls, smaller left and right prefrontal gray matter volumes were significantly correlated with impaired performance on immediate recall in verbal and visual memory and semantic fluency. Furthermore, in patients, smaller total orbitofrontal gray matter volume was significantly correlated with more severe negative symptomatology (rs = -.76, p = .006). CONCLUSIONS: These findings suggest that in schizophrenia, deficits in verbal and visual memory and semantic fluency and negative symptoms may be related to (subtle) abnormalities in frontal lobe structure.

Effects of context on judgements of odor intensities in humans.

This study evaluated whether the intensity of previously smelled odors could unintentionally influence the subsequent judgement of odor intensity. The predicted context effect was based on the adaptation-level theory. Before and 25 min after either WEAK or STRONG biasing odor concentrations, 51 subjects were required to rate the intensity of 10 different odor concentrations of California Orange Oil. After the WEAK bias, subjects judged the odor intensity as being stronger than they did after the STRONG bias. Thus the intensity of odors smelled 25 min earlier can unintentionally influence subsequent odor intensity judgement. The findings are discussed in the light of two alternative explanations, namely, a central implicit memory process and a stimulus-level-based change at the peripheral level.