The influence of season on glutamate and GABA levels in the healthy human brain investigated by magnetic resonance spectroscopy imaging

Seasonal changes in neurotransmitter systems have been demonstrated in imaging studies and are especially noticeable in diseased states such as seasonal affective disorder (SAD). These modulatory neurotransmitters, such as serotonin, are influencing glutamatergic and GABAergic neurotransmission. Furthermore, central components of the circadian pacemaker are regulated by GABA (the suprachiasmatic nucleus) or glutamate (e.g., the retinohypothalamic tract). Therefore, we explored seasonal differences in the GABAergic and glutamatergic system in 159 healthy individuals using magnetic resonance spectroscopy imaging with a GABA-edited 3D-MEGA-LASER sequence at 3T. We quantified GABA+/tCr, GABA+/Glx, and Glx/tCr ratios (GABA+, GABA+ macromolecules; Glx, glutamate + glutamine; tCr, total creatine) in five different subcortical brain regions. Differences between time periods throughout the year, seasonal patterns, and stationarity were tested using ANCOVA models, curve fitting approaches, and unit root and stationarity tests, respectively. Finally, Spearman correlation analyses between neurotransmitter ratios within each brain region and cumulated daylight and global radiation were performed. No seasonal or monthly differences, seasonal patterns, nor significant correlations could be shown in any region or ratio. Unit root and stationarity tests showed stable patterns of GABA+/tCr, GABA+/Glx, and Glx/tCr levels throughout the year, except for hippocampal Glx/tCr. Our results indicate that neurotransmitter levels of glutamate and GABA in healthy individuals are stable throughout the year. Hence, despite the important correction for age and gender in the analyses of MRS derived GABA and glutamate, a correction for seasonality in future studies does not seem necessary. Future investigations in SAD and other psychiatric patients will be of high interest.

Effects of sex hormones on brain GABA and glutamate levels in a cis- and transgender cohort

Sex hormones affect the GABAergic and glutamatergic neurotransmitter system as demonstrated in animal studies. However, human research has mostly been correlational in nature. Here, we aimed at substantiating causal interpretations of the interaction between sex hormones and neurotransmitter function by using magnetic resonance spectroscopy imaging (MRSI) to study the effect of gender-affirming hormone treatment (GHT) in transgender individuals. Fifteen trans men (TM) with a DSM-5 diagnosis of gender dysphoria, undergoing GHT, and 15 age-matched cisgender women (CW), receiving no therapy, underwent MRSI before and after at least 12 weeks. Additionally, sex differences in neurotransmitter levels were evaluated in an independent sample of 80 cisgender men and 79 cisgender women. Mean GABA+ (combination of GABA and macromolecules) and Glx (combination of glutamate and glutamine) ratios to total creatine (GABA+/tCr, Glx/tCr) were calculated in five predefined regions-of-interest (hippocampus, insula, pallidum, putamen and thalamus). Linear mixed models analysis revealed a significant measurement by gender identity effect (p_corr. = 0.048) for GABA+/tCr ratios in the hippocampus, with the TM cohort showing decreased GABA+/tCr levels after GHT compared to CW. Moreover, analysis of covariance showed a significant sex difference in insula GABA+/tCr ratios (p_corr. = 0.049), indicating elevated GABA levels in cisgender women compared to cisgender men. Our study demonstrates GHT treatment-induced GABA+/tCr reductions in the hippocampus, indicating hormone receptor activation on GABAergic cells and testosterone-induced neuroplastic processes within the hippocampus. Moreover, elevated GABA levels in the female compared to the male insula highlight the importance of including sex as factor in future MRS studies. DATA AVAILABILITY STATEMENT: Due to data protection laws processed data is available from the authors upon reasonable request. Please contact rupert.lanzenberger@meduniwien.ac.at with any questions or requests.

Escitalopram administration, relearning, and neuroplastic effects: A diffusion tensor imaging study in healthy individuals

BACKGROUND

Neuroplastic processes are influenced by serotonergic agents, which reportedly alter white matter microstructure in humans in conjunction with learning. The goal of this double-blind, placebo-controlled imaging study was to investigate the neuroplastic properties of escitalopram and cognitive training on white matter plasticity during (re)learning as a model for antidepressant treatment and environmental factors.

METHODS

Seventy-one healthy individuals (age=25.6 ± 5.0, 43 females) underwent three diffusion magnetic resonance imaging scans: at baseline, after 3 weeks of associative learning (emotional/non-emotional content), and after relearning shuffled associations for an additional 3 weeks. During the relearning phase, participants received a daily dose of 10 mg escitalopram or placebo orally. Fractional anisotropy (FA), and mean (MD), axial (AD), and radial diffusivity (RD) were calculated within the FMRIB software library and analyzed using tract-based spatial statistics.

RESULTS

In a three-way repeated-measures marginal model with sandwich estimator standard errors, we found no significant effects of escitalopram and content on AD, FA, MD, and RD during both learning and relearning periods (p_FDR>0.05). When testing for escitalopram or content effects separately, we also demonstrated no significant findings (p_FDR>0.05) for any of the diffusion tensor imaging metrics.

LIMITATIONS

The intensity of the study interventions might have been too brief to induce detectable white matter changes.

DISCUSSION

Previous studies examining the effects of SSRIs on white matter tracts in humans have yielded inconclusive outcomes. Our results indicate that relearning under escitalopram does not affect the white matter microstructures in healthy individuals when administered for 3 weeks.

Coexpression of Gene Transcripts with Monoamine Oxidase A Quantified by Human In Vivo Positron Emission Tomography

The monoamine oxidase A (MAO-A) is integral to monoamine metabolism and is thus relevant to the pathophysiology of various neuropsychiatric disorders; however, associated gene-enzyme relations are not well understood. This study aimed to unveil genes coexpressed with MAO-A. Therefore, 18 179 mRNA expression maps (based on the Allen Human Brain Atlas) were correlated with the cerebral distribution volume (VT) of MAO-A assessed in 36 healthy subjects (mean age ± standard deviation: 32.9 ± 8.8 years, 18 female) using [11C]harmine positron emission tomography scans. Coexpression analysis was based on Spearman's ρ, over-representation tests on Fisher's exact test with false discovery rate (FDR) correction. The analysis revealed 35 genes in cortex (including B-cell translocation gene family, member 3, implicated in neuroinflammation) and 247 genes in subcortex (including kallikrein-related peptidase 10, implicated in Alzheimer's disease). Significantly over-represented Gene Ontology terms included "neuron development", "neuron differentiation", and "cell-cell signaling" as well as "axon" and "neuron projection". In vivo MAO-A enzyme distribution and MAOA expression did not correlate in cortical areas (ρ = 0.08) while correlation was found in subcortical areas (ρ = 0.52), suggesting influences of region-specific post-transcriptional and -translational modifications. The herein reported information could contribute to guide future genetic studies, deepen the understanding of associated pathomechanisms and assist in the pursuit of novel therapeutic targets.

Tools for optimising pharmacotherapy in psychiatry (therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests): focus on antidepressants

Objectives: More than 40 drugs are available to treat affective disorders. Individual selection of the optimal drug and dose is required to attain the highest possible efficacy and acceptable tolerability for every patient.Methods: This review, which includes more than 500 articles selected by 30 experts, combines relevant knowledge on studies investigating the pharmacokinetics, pharmacodynamics and pharmacogenetics of 33 antidepressant drugs and of 4 drugs approved for augmentation in cases of insufficient response to antidepressant monotherapy. Such studies typically measure drug concentrations in blood (i.e. therapeutic drug monitoring) and genotype relevant genetic polymorphisms of enzymes, transporters or receptors involved in drug metabolism or mechanism of action. Imaging studies, primarily positron emission tomography that relates drug concentrations in blood and radioligand binding, are considered to quantify target structure occupancy by the antidepressant drugs in vivo. Results: Evidence is given that in vivo imaging, therapeutic drug monitoring and genotyping and/or phenotyping of drug metabolising enzymes should be an integral part in the development of any new antidepressant drug.Conclusions: To guide antidepressant drug therapy in everyday practice, there are multiple indications such as uncertain adherence, polypharmacy, nonresponse and/or adverse reactions under therapeutically recommended doses, where therapeutic drug monitoring and cytochrome P450 genotyping and/or phenotyping should be applied as valid tools of precision medicine.

Disrupted relationship between blood glucose and brain dopamine D2/3 receptor binding in patients with first-episode schizophrenia

An elemental function of brain dopamine is to coordinate cognitive and motor resources for successful exploitation of environmental energy sources. Dopamine transmission, goal-directed behavior, and glucose homeostasis are altered in schizophrenia patients prior to and after initiation of pharmacological treatment. Thus, we investigated the relationship between blood glucose levels and brain dopamine signaling in drug-naïve patients with first-episode psychosis. We quantified blood glucose levels and binding of the dopamine D_2/3 receptor agonist radioligand (+)-[¹¹C]-PHNO in 15 medication-naïve patients and 27 healthy volunteers employing positron emission tomography. Whole-brain voxel-wise linear model analysis identified two clusters of significant interaction between blood glucose levels and diagnosis on (+)-[¹¹C]-PHNO binding-potential values. We observed positive relationships between blood glucose levels and binding-potential values in healthy volunteers but negative ones in patients with first episode psychosis in a cluster surviving rigorous multiple testing correction located in the in the right ventral tegmental area. Another cluster of homologous behavior, however at a lower level of statistical significance, comprised the ventral striatum and pallidum. Extracellular dopamine levels are a major determinant of (+)-[¹¹C]-PHNO binding in the brain. In line with the concept that increased dopamine signaling occurs when goal-directed behavior is needed for restoring energy supply, our data indicate that in healthy volunteers, extracellular dopamine levels are high when blood glucose levels are low and vice-versa. This relationship is reversed in patients with first-episode psychosis, possibly reflecting an underlying pathogenic alteration that links two seemingly unrelated aspects of the illness: altered dopamine signaling and dysfunctional glucose homeostasis.

Neuroplastic effects of a selective serotonin reuptake inhibitor in relearning and retrieval

Animal studies using selective serotonin reuptake inhibitors (SSRIs) and learning paradigms have demonstrated that serotonin is important for flexibility in executive functions and learning. SSRIs might facilitate relearning through neuroplastic processes and thus exert their clinical effects in psychiatric diseases where cognitive functioning is affected. However, translation of these mechanisms to humans is missing. In this randomized placebo-controlled trial, we assessed functional brain activation during learning and memory retrieval in healthy volunteers performing associative learning tasks aiming to translate facilitated relearning by SSRIs.

To this extent, seventy-six participants underwent three MRI scanning sessions: (1) at baseline, (2) after three weeks of daily associative learning and subsequent retrieval (face-matching or Chinese character–noun matching) and (3) after three weeks of relearning under escitalopram (10 mg/day) or placebo. Associative learning and retrieval tasks were performed during each functional MRI (fMRI) session. Statistical modeling was done using a repeated-measures ANOVA, to test for content-by-treatment-by-time interaction effects.

During the learning task, a significant substance-by-time interaction was found in the right insula showing a greater deactivation in the SSRI cohort after 21 days of relearning compared to the learning phase. In the retrieval task, there was a significant content-by-time interaction in the left angular gyrus (AG) with an increased activation in face-matching compared to Chinese-character matching for both learning and relearning phases. A further substance-by-time interaction was found in task performance after 21 days of relearning, indicating a greater decrease of performance in the placebo group.

Our findings that escitalopram modulate insula activation demonstrates successful translation of relearning as a mechanism of SSRIs in human. Furthermore, we show that the left AG is an active component of correct memory retrieval, which coincides with previous literature. We extend the function of this region by demonstrating its activation is not only stimulus dependent but also time constrained. Finally, we were able to show that escitalopram aids in relearning, irrespective of content.

The Influence of Acute SSRI Administration on White Matter Microstructure in Patients Suffering From Major Depressive Disorder and Healthy Controls

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are predominantly prescribed for people suffering from major depressive disorder. These antidepressants exert their effects by blocking the serotonin transporter (SERT), leading to increased levels of serotonin in the synaptic cleft and subsequently to an attenuation of depressive symptoms and elevation in mood. Although long-term studies investigating white matter (WM) alterations after exposure to antidepressant treatment exist, results on the acute effects on the brain's WM microstructure are lacking.

METHODS

In this interventional longitudinal study, 81 participants were included (33 patients and 48 healthy controls). All participants underwent diffusion weighted imaging on 2 separate days, receiving either citalopram or placebo using a randomized, double-blind, cross-over design. Fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were calculated within the FMRIB software library and analyzed using tract-based spatial statistics.

RESULTS

The repeated-measures ANOVA model revealed significant decreases after SSRI administration in mean diffusivity, axial diffusivity, and radial diffusivity regardless of the group (P < .05, family-wise error [FWE] corrected). Results were predominantly evident in frontal WM regions comprising the anterior corona radiata, corpus callosum, and external capsule and in distinct areas of the frontal blade. No increases in diffusivity were found, and no changes in fractional anisotropy were present.

CONCLUSIONS

Our investigation provides the first evidence, to our knowledge, that fast WM microstructure adaptations within 1 hour after i.v. SSRI administration precede elevations in mood due to SSRI treatment. These results add a new facet to the complex mode of action of antidepressant therapy. This study was registered at clinicaltrials.gov with the identifier NCT02711215.

Volitional modification of brain activity in adolescents with Autism Spectrum Disorder: A Bayesian analysis of Slow Cortical Potential neurofeedback

Autism spectrum disorder is (ASD) characterized by a persisting triad of impairments of social interaction, language as well as inflexible, stereotyped and ritualistic behaviors. Increasingly, scientific evidence suggests a neurobiological basis of these emotional, social and cognitive deficits in individuals with ASD. The aim of this randomized controlled brain self-regulation intervention study was to investigate whether the core symptomatology of ASD could be reduced via an electroencephalography (EEG) based brain self-regulation training of Slow Cortical Potentials (SCP). 41 male adolescents with ASD were recruited and allocated to a) an experimental group undergoing 24 sessions of EEG-based brain training (n1 = 21), or to b) an active control group undergoing conventional treatment (n2 = 20), that is, clinical counseling during a 3-months intervention period. We employed real-time neurofeedback training recorded from a fronto-central electrode intended to enable participants to volitionally regulate their brain activity. Core autistic symptomatology was measured at six time points during the intervention and analyzed with Bayesian multilevel approach to characterize changes in core symptomatology. Additional Bayesian models were formulated to describe the neural dynamics of the training process as indexed by SCP (time-domain) and power density (PSD, frequency-domain) measures. The analysis revealed a substantial improvement in the core symptomatology of ASD in the experimental group (reduction of 21.38 points on the Social Responsiveness Scale, SD = 5.29), which was slightly superior to that observed in the control group (evidence Ratio = 5.79). Changes in SCP manifested themselves as different trajectories depending on the different feedback conditions and tasks. Further, the model of PSD revealed a continuous decrease in delta power, parallel to an increase in alpha power. Most notably, a non-linear (quadratic) model turned out to be better at predicting the data than a linear model across all analyses. Taken together, our analyses suggest that behavioral and neural processes of change related to neurofeedback training are complex and non-linear. Moreover, they have implications for the design of future trials and training protocols.

Voxel-Based Morphometry-from Hype to Hope. A Study on Hippocampal Atrophy in Mesial Temporal Lobe Epilepsy

BACKGROUND AND PURPOSE

Automated volumetry of the hippocampus is considered useful to assist the diagnosis of hippocampal sclerosis in temporal lobe epilepsy. However, voxel-based morphometry is rarely used for individual subjects because of high rates of false-positives. We investigated whether an approach with high dimensional warping to the template and nonparametric statistics would be useful to detect hippocampal atrophy in patients with hippocampal sclerosis.

MATERIALS AND METHODS

We performed single-subject voxel-based morphometry with nonparametric statistics within the framework of Statistical Parametric Mapping to compare MRI from 26 well-characterized patients with temporal lobe epilepsy individually against a group of 110 healthy controls. The following statistical threshold was used: P < .05 corrected for multiple comparisons with family-wise error over the region of interest right and left hippocampus.

RESULTS

The sensitivity for the detection of atrophy related to hippocampal sclerosis was 0.92 (95% CI, 0.67-0.99) for the right hippocampus and 0.60 (0.31-0.83) for the left, and the specificity for volume changes was 0.98 (0.93-0.99). All clusters of decreased hippocampal volumes were correctly lateralized to the seizure focus. Hippocampal volume decrease was in accordance with neuronal cell loss on histology reports.

CONCLUSIONS

Nonparametric voxel-based morphometry is sensitive and specific for hippocampal atrophy in patients with mesial temporal lobe epilepsy and may be useful in clinical practice.

The "sugar dilemma"

Type 2 diabetes mellitus is characterized by insulin resistance and elevated blood glucose levels. Treatment protocols generally include dietary restriction of sugar, as well as drugs aiming at a reduction of blood glucose, mainly by activating the insulin system or supplementing insulin. This established approach does not take into account the outstanding physiological role of glucose as a key molecule in metabolism. Glucose is crucial to meet the high energy demand of the brain, which depends on it as an exclusive nutrient. Insulin independent glucose transporters GLUT1 import glucose into the brain. Reduction of blood glucose, as in current treatment concepts, may lead to energy deficiency in the brain and consecutively to worsening of - possibly already impaired - neurocognitive function. Reduced cell membrane fluidity of the vascular endothelium of the bloodbrain-barrier (BBB) - due to malnutrition and/or aging - is considered a major factor in pathogenesis of the cerebral metabolic syndrome, which is a key step in neurodegeneration. Under this aspect we suggest a novel approach to prophylaxis and treatment focusing on a sufficient supply of glucose to the brain.

Acute stress alters neural patterns of value representation for others

Acute stress is often evoked during social interactions, by feelings of threat or negative evaluation by other people. We also constantly interact with others while under stress - in the workplace or in private alike. However, it is not clear how stress affects social interactions. For one, individuals could become more selfish and focused on their own goals. On the other hand, individuals might also become more focused on affiliating with potential social partners, in order to secure their support. There is, indeed, accumulating behavioral evidence that prosocial behaviors increase rather than decrease under stress. Here, we tested the underlying brain processes of such findings, by assessing the effects of stress on the neural representations of (monetary) value for self and other. Participants (N ​= ​30; male, 18-40 years) played a gambling task for themselves and for another participant while undergoing functional magnetic resonance imaging (fMRI). Each participant played the gambling task twice: once immediately following acute stress induction, and once in a control session. We compared neural patterns of value representation in the dorsomedial prefrontal cortex (dmPFC), ventromedial prefrontal cortex (vmPFC) and striatum using representational similarity analysis (RSA). We found that under stress, dmPFC and striatum showed higher dissimilarity between neural patterns underlying high and low value for the other. Dissimilarity of neural patterns underlying high and low value for the self was unaffected by stress. These findings suggest that participants track the magnitude of possible rewards for others more under stress, suggesting increased prosocial orientation.

Repetitive enhancement of serum BDNF subsequent to continuation ECT

INTRODUCTION

Continuation electroconvulsive therapy (c-ECT) is highly effective for the prevention of depressive symptom relapse. There is a lack of understanding, about how c-ECT works in humans, particularly with regard to its effects on brain derived neurotrophic factor (BDNF) concentrations. Here, we aimed to close a gap in the literature by evaluating BDNF levels in patients receiving c-ECT.

METHODS

We included 13 patients with either unipolar or bipolar depression (mean age ± SD: 55.5 ± 17.1; f/m: 10/3; unipolar/bipolar: 10/3) who received between one and four c-ECT (average per patient: 2.8). Serum BDNF (sBDNF) levels were assessed before and after each c-ECT sessions. Clinical assessments were also administered both before and after treatment.

RESULTS

Our analysis revealed a significant increase in sBDNF after each treatment (c-ECT 1-3: P < 0.001, c-ECT 4: P = 0.018). The application of multiple c-ECT treatments was not, however, associated with further sBDNF enhancements. Psychometric scores were not significantly altered following c-ECT.

DISCUSSION

An increase in sBDNF concentrations subsequent to c-ECT parallel data from the animal literature, which has linked regularly applied electrical stimulation to neuroplastic processes. This finding suggests a relationship between ECT-induced sBDNF concentrations and (sustained) remission status, considering a stable clinical condition across c-ECT.

Clinical factors predicting treatment resistant depression: affirmative results from the European multicenter study

OBJECTIVES

Clinical variables were investigated in the 'treatment resistant depression (TRD)- III' sample to replicate earlier findings by the European research consortium 'Group for the Study of Resistant Depression' (GSRD) and enable cross-sample prediction of treatment outcome in TRD.

EXPERIMENTAL PROCEDURES

TRD was defined by a Montgomery and Åsberg Depression Rating Scale (MADRS) score ≥22 after at least two antidepressive trials. Response was defined by a decline in MADRS score by ≥50% and below a threshold of 22. Logistic regression was applied to replicate predictors for TRD among 16 clinical variables in 916 patients. Elastic net regression was applied for prediction of treatment outcome.

RESULTS

Symptom severity (odds ratio (OR) = 3.31), psychotic symptoms (OR = 2.52), suicidal risk (OR = 1.74), generalized anxiety disorder (OR = 1.68), inpatient status (OR = 1.65), higher number of antidepressants administered previously (OR = 1.23), and lifetime depressive episodes (OR = 1.15) as well as longer duration of the current episode (OR = 1.022) increased the risk of TRD. Prediction of TRD reached an accuracy of 0.86 in the independent validation set, TRD-I.

CONCLUSION

Symptom severity, suicidal risk, higher number of lifetime depressive episodes, and comorbid anxiety disorder were replicated as the most prominent risk factors for TRD. Significant predictors in TRD-III enabled robust prediction of treatment outcome in TRD-I.

Association of Protein Distribution and Gene Expression Revealed by PET and Post-Mortem Quantification in the Serotonergic System of the Human Brain

Regional differences in posttranscriptional mechanisms may influence in vivo protein densities. The association of positron emission tomography (PET) imaging data from 112 healthy controls and gene expression values from the Allen Human Brain Atlas, based on post-mortem brains, was investigated for key serotonergic proteins. PET binding values and gene expression intensities were correlated for the main inhibitory (5-HT1A) and excitatory (5-HT2A) serotonin receptor, the serotonin transporter (SERT) as well as monoamine oxidase-A (MAO-A), using Spearman's correlation coefficients (rs) in a voxel-wise and region-wise analysis. Correlations indicated a strong linear relationship between gene and protein expression for both the 5-HT1A (voxel-wise rs = 0.71; region-wise rs = 0.93) and the 5-HT2A receptor (rs = 0.66; 0.75), but only a weak association for MAO-A (rs = 0.26; 0.66) and no clear correlation for SERT (rs = 0.17; 0.29). Additionally, region-wise correlations were performed using mRNA expression from the HBT, yielding comparable results (5-HT1Ars = 0.82; 5-HT2Ars = 0.88; MAO-A rs = 0.50; SERT rs = -0.01). The SERT and MAO-A appear to be regulated in a region-specific manner across the whole brain. In contrast, the serotonin-1A and -2A receptors are presumably targeted by common posttranscriptional processes similar in all brain areas suggesting the applicability of mRNA expression as surrogate parameter for density of these proteins.

The influence of the rs6295 gene polymorphism on serotonin-1A receptor distribution investigated with PET in patients with major depression applying machine learning

Major depressive disorder (MDD) is the most common neuropsychiatric disease and despite extensive research, its genetic substrate is still not sufficiently understood. The common polymorphism rs6295 of the serotonin-1A receptor gene (HTR1A) is affecting the transcriptional regulation of the 5-HT_1A receptor and has been closely linked to MDD. Here, we used positron emission tomography (PET) exploiting advances in data mining and statistics by using machine learning in 62 healthy subjects and 19 patients with MDD, which were scanned with PET using the radioligand [carbonyl-¹¹C]WAY-100635. All the subjects were genotyped for rs6295 and genotype was grouped in GG vs C allele carriers. Mixed model was applied in a ROI-based (region of interest) approach. ROI binding potential (BP_ND) was divided by dorsal raphe BP_ND as a specific measure to highlight rs6295 effects (BP_Div). Mixed model produced an interaction effect of ROI and genotype in the patients' group but no effects in healthy controls. Differences of BP_Div was demonstrated in seven ROIs; parahippocampus, hippocampus, fusiform gyrus, gyrus rectus, supplementary motor area, inferior frontal occipital gyrus and lingual gyrus. For classification of genotype, 'RandomForest' and Support Vector Machines were used, however, no model with sufficient predictive capability could be computed. Our results are in line with preclinical data, mouse model knockout studies as well as previous clinical analyses, demonstrating the two-pronged effect of the G allele on 5-HT_1A BP_ND for, we believe, the first time. Future endeavors should address epigenetic effects and allosteric heteroreceptor complexes. Replication in larger samples of MDD patients is necessary to substantiate our findings.

Systematic evaluation of dose-escalation strategies after initial non-response to standard-dose pharmacotherapy in schizophrenia

Objectives

This meta-analysis investigates if dose increase of an antipsychotic drug (high-dose treatment, dose escalation) is advantageous for schizophrenic patients who failed to respond adequately to standard-dose treatment with the same antipsychotic.

Methods

Within a systematic literature survey, we identified all randomized controlled trials (RCTs) comparing a dose increase directly to standard-dose continuation treatment in schizophrenic subjects with initial non-response to prospective standard-dose pharmacotherapy with the same antipsychotic. The primary outcome was mean change in the Positive and Negative Syndrome Scale (PANSS) total score. Secondary outcomes were dichotomous response and attrition rates. Study selection and data extraction were conducted independently by two authors. We calculated effect sizes (Hedges's g and risks ratios) using the Mante–Haenszel random-effects model. Meta-regression analyses were performed to explore the influence of the degree of the dose increase on effect sizes.

Results

Five trials (n = 348) examining quetiapine (n = 2, n = 191), ziprasidone (n = 1, n = 75), haloperidol (n = 1, n = 48), and fluphenazine (n = 1, n = 34) were included. We found no significant between-group differences for the mean PANSS/BPRS total score change, even not when itemized according to the individual antipsychotic agents. There were no between-group differences for response and dropout rates. The non-significant meta-regressions indicate no impact of the different amounts of dose increments on effect sizes.

Conclusions

We found no evidence for the efficacy of a dose escalation after initial non-response to standard-dose pharmacotherapy as general advisable treatment strategy. As the high-dose treatment was not accompanied by significant increased attrition rates, appropriate tolerability and acceptability of this pharmacological option can be assumed.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Default mode network deactivation during emotion processing predicts early antidepressant response

Several previous functional magnetic resonance imaging (fMRI) studies have demonstrated the predictive value of brain activity during emotion processing for antidepressant response, with a focus on clinical outcome after 6-8 weeks. However, longitudinal studies emphasize the paramount importance of early symptom improvement for the course of disease in major depressive disorder (MDD). We therefore aimed to assess whether neural activity during the emotion discrimination task (EDT) predicts early antidepressant effects, and how these predictive measures relate to more sustained response. Twenty-three MDD patients were investigated once with ultrahigh-field 7T fMRI and the EDT. Following fMRI, patients received Escitalopram in a flexible dose schema and were assessed with the Hamilton Depression Rating Scale (HAMD) before, and after 2 and 4 weeks of treatment. Deactivation of the precuneus and posterior cingulate cortex (PCC) during the EDT predicted change in HAMD scores after 2 weeks of treatment. Baseline EDT activity was not predictive of HAMD change after 4 weeks of treatment. The precuneus and PCC are integral components of the default mode network (DMN). We show that patients who exhibit stronger DMN suppression during emotion processing are more likely to show antidepressant response after 2 weeks. This is, to our knowledge, the first study to show that DMN activity predicts early antidepressant effects. However, DMN deactivation did not predict response at 4 weeks, suggesting that our finding is representative of early, likely treatment-related, yet unspecific symptom improvement. Regardless, early effects may be harnessed for optimization of treatment regimens and patient care.

Combined PET/MRI: from Status Quo to Status Go. Summary Report of the Fifth International Workshop on PET/MR Imaging; February 15-19, 2016; Tübingen, Germany

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited presentations from active researchers in the field of PET/MRI and associated fields augmented by round table discussions and dialogue boards with specific topics. This year, this included practical advice as to possible approaches to moving PET/MRI into clinical routine, the use of PET/MRI in brain receptor imaging, in assessing cardiovascular diseases, cancer, infection, and inflammatory diseases. To address perceived challenges still remaining to innovatively integrate PET and MRI system technologies, a dedicated round table session brought together key representatives from industry and academia who were engaged with either the conceptualisation or early adoption of hybrid PET/MRI systems. Discussions during the workshop highlighted that emerging unique applications of PET/MRI such as the ability to provide multi-parametric quantitative and visual information which will enable not only overall disease detection but also disease characterisation would eventually be regarded as compelling arguments for the adoption of PET/MR. However, as indicated by previous workshops, evidence in favour of this observation is only growing slowly, mainly due to the ongoing inability to pool data cohorts from independent trials as well as different systems and sites. The participants emphasised that moving from status quo to status go entails the need to adopt standardised imaging procedures and the readiness to act together prospectively across multiple PET/MRI sites and vendors.

Parameter evaluation and fully-automated radiosynthesis of [(11)C]harmine for imaging of MAO-A for clinical trials

The aim of the present study was the evaluation and automation of the radiosynthesis of [¹¹C]harmine for clinical trials. The following parameters have been investigated: amount of base, precursor concentration, solvent, reaction temperature and time. The optimum reaction conditions were determined to be 2–3 mg/mL precursor activated with 1 eq. 5 M NaOH in DMSO, 80 °C reaction temperature and 2 min reaction time. Under these conditions 6.1±1 GBq (51.0±11% based on [¹¹C]CH₃I, corrected for decay) of [¹¹C]harmine (n=72) were obtained. The specific activity was 101.32±28.2 GBq/µmol (at EOS). All quality control parameters were in accordance with the standards for parenteral human application. Due to its reliability and high yields, this fully-automated synthesis method can be used as routine set-up.

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Preparation of [¹¹C]harmine on a commercially available synthesizer for the routine application.

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High reliability: only 4 out of 72 failed syntheses; 5% due to technical problems.

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High yields: 6.1±1 GBq overall yield (EOS).

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High specific activities: 101.32±28.2 GBq/µmol.

[The effects of hormone replacement therapy on mind and brain]

Hormonal fluctuations during the perimenopausal transition lead to physical discomfort but are also frequently accompanied by mood swings, depressive symptoms, anxiety and sleeping disorders. The important role of the neurotransmitter serotonin in the pathogenesis of anxiety disorders and major depression is unquestioned, but only little is known about the influence of sex hormones on the serotonergic system. This review provides an overview of potential risk factors for the occurrence of affective disorders in the menopausal transition and discusses possible therapeutic options. Current research findings from longitudinal studies testing the efficacy of hormone replacement therapy and antidepressants with effects on the serotonergic neurotransmission on physical and mental discomforts during menopause are presented. Furthermore, studies using positron emission tomography and genetic methods that explore the effects of sex steroids on different components of the serotonergic system are shown. The interactions between estrogen, progesterone and the serotonergic system are described, and possible neurobiological and endocrinological mechanisms underlying depressive symptoms in the perimenopause are elucidated.

Global decrease of serotonin-1A receptor binding after electroconvulsive therapy in major depression measured by PET

Electroconvulsive therapy (ECT) is a potent therapy in severe treatment-refractory depression. Although commonly applied in psychiatric clinical routine since decades, the exact neurobiological mechanism regarding its efficacy remains unclear. Results from preclinical and clinical studies emphasize a crucial involvement of the serotonin-1A receptor (5-HT(1A)) in the mode of action of antidepressant treatment. This includes associations between treatment response and changes in 5-HT(1A) function and density by antidepressants. Further, alterations of the 5-HT(1A) receptor are consistently reported in depression. To elucidate the effect of ECT on 5-HT(1A) receptor binding, 12 subjects with severe treatment-resistant major depression underwent three positron emission tomography (PET) measurements using the highly selective radioligand [carbonyl-(11)C]WAY100635, twice before (test-retest variability) and once after 10.08±2.35 ECT sessions. Ten patients (~83%) were responders to ECT. The voxel-wise comparison of the 5-HT(1A) receptor binding (BP(ND)) before and after ECT revealed a widespread reduction in cortical and subcortical regions (P<0.05 corrected), except for the occipital cortex and the cerebellum. Strongest reductions were found in regions consistently reported to be altered in major depression and involved in emotion regulation, such as the subgenual part of the anterior cingulate cortex (-27.5%), the orbitofrontal cortex (-30.1%), the amygdala (-31.8%), the hippocampus (-30.6%) and the insula (-28.9%). No significant change was found in the raphe nuclei. There was no significant difference in receptor binding in any region comparing the first two PET scans conducted before ECT. This PET study proposes a global involvement of the postsynaptic 5-HT(1A) receptor binding in the effect of ECT.

P02 - 369 - Neuroimaging of the various symptom dimensions in obsessive - compulsive disorder - a systematic review

Introduction

Several neuroimaging studies in obsessive-compulsive disorders (OCD) have shown a dysfunction in the orbito-fronto-striato-thalamamic neural circuitry as the fundamental neuropathological correlate, consistent across all symptom subtypes.

Therefore, the neurobiological differentiation of the various obsessive-compulsive symptoms is attracting increasing interest in neuroimaging as this clinical picture becomes increasingly subclassified.

Method

A systematic literature survey was used to search for original papers that studied the neurobiological correlates of the various symptom dimensions of OCD (symmetry, forbidden thoughts, washing, hoarding).

Results

It was possible to include a total of 15 original papers in the assessment. The “forbidden thoughts” factor, which also includes compulsion to control, is associated mainly with activations in brain structures of the cognitive control system, i.e. the basal ganglia and parts of the anterior cingulate cortex (ACC). Therefore, the neural representation pattern of “forbidden thoughts” differs clearly from that of “washing”, in which cerebral regions of emotional control seem to be particularly involved, i.e. the orbito-frontal cortex (OFC), ACC, the amygdala and insula. On the other hand, the “hoarding and collecting” dimension is primarily associated with brain areas involved in decision-making, i.e. the ventro-medial OFC, the dorsal ACC and the dorso-lateral prefrontal cortex (DLPC).

Discussion

The results confirm the hypothesis that all dimensions of OCD are based on different neuronal networks, which underlines the neurobiological heterogeneity of the clinical picture of OCD, thus pointing the way for future research strategies.

Serotonin - 1A binding in the subgenual anterior cingulate cortex is associated with regional grey matter volume in striatum and temporal areas

Introduction

The subgenual part of the anterior cingulate cortex (sgACC) has been frequently reported to be structurally and cytoarchitectually changed in major depressive disorder (MDD) and is also a promising target in deep brain stimulation in treatment-resistant MDD. Furthermore, substantial evidence demonstrates a high density of serotonin-1A (5-HT1A) receptors in the sgACC, a key area involved in emotional processing.

Objectives

Here, we investigated the relationship between the 5-HT1A receptor in the sgACC and changes in regional grey matter volume with voxel-based morphometry.

Methods

PET ([carbonyl-11C]WAY-100635) was used to quantify 5-HT1A receptor binding (BPND) together with structural magnetic resonance images from 32 healthy subjects (mean 26.68 ± 5.1 years; 17 women). Regression analysis was performed in SPM8 (p < .001 uncorr.) using sgACC 5-HT1A BPND as regressor, controlling for sex, age and total grey matter volume (GMV).

Results

5-HT1A BPND in the sgACC was positively associated with regional GMV in the medial temporal gyri (T=4.37) and nucleus accumbens bilaterally (T = 4.19). Furthermore, sgACC 5-HT1A binding was negatively correlated with GMV within the inferior temporal gyri (T = 5.22) and putamen bilaterally (T = 5.12).

Conclusions

Our findings demonstrate structural relationships between sgACC 5-HT1A receptor binding and grey matter volume in the ventral striatum as well as in temporal regions, which both exhibit close neuronal connections with the sgACC. Moreover, the GMV of the ventral striatum has been reported to be decreased in patients with MDD. Conclusively, our results underpin the role of serotonergic neuronal transmission in cytoarchitectural processes within regions involved in the modulation of mood.

CS02-01 - Imaging the serotonergic system

Biological markers are an important objective in psychiatric research. Molecular and functional neuroimaging techniques are promising tools to provide these biomarkers that may be used for early detection, indication of presence and severity of psychiatric disorders, prediction of treatment response and clinical prognosis. In this lecture, recent results from molecular imaging with positron emission tomography (PET) will be presented, including cerebral quantification of several major players in serotonergic neurotransmission, i.e. the serotonin transporter, the serotonin 1A, 2A, and 1B receptor subtypes, and the degrading enzyme MAOA. Differences between psychiatric disorders will be discussed. Furthermore, pharmacological effects on these targets and brain activation will be shown using PET and functional magnetic resonance imaging (fMRI).

Are there structural brain changes following 10 days of SSRI administration investigated by voxel-based morphometry?

Introduction

There is evidence that psychiatric diseases are accompanied by structural alterations in the human brain, partly reversible by pharmacological treatments. Several studies including Tost et al. (Nat.Neurosci.2010;13(8):920-2) investigated the effect of psychotropic drugs on neuronal plasticity pointing towards rapid pharmacologically induced brain grey matter variations, apart from already presumed slow structural changes within weeks. Here, we investigated the short-term (days) structural effects of SSRIs.

Objective

To identify structural changes of grey and white matter following 10d of oral administration (citalopram/escitalopram vs. placebo) in 18 healthy subjects investigated by magnetic resonance imaging (MRI) using voxel-based morphometry (VBM).

Methods

Study design: Randomized, cross-over, placebo-controlled, double-blind study.

Subjects: 18 healthy caucasian subjects (6 female 24.8 ± 2.5 years, 12 males 28.9 ± 6.7 years) MRI: 3 MRI scans/subject (3 Tesla scanner)

Treatment: 10d of oral medication intake of either 20 mg citalopram/d, 10 mg escitalopram/d or placebo in alternating order of administration

Data analysis: VBM, as implemented in SPM8.

Statistical analysis: analysis of variance (ANOVA, FWE corrected), post-hoc pair-wise comparisons.

Results

ANOVA (grey matter: F(2,48) = 18.85, p < 0.05; white matter: F(2,48) = 17.79, p < 0.05) did not reveal suprathreshold clusters in grey or white matter.

Conclusion

This VBM-study does not support previous short-time (days) MR findings of pharmacologically-induced structural alterations in the brain, considering the lack of significant changes in grey and white matter volumes following 10d of SSRI administration. This divergence may be caused by dissent pharmacological effects of SSRIs compared to other psychotropic drugs.

Reduced connectivity in the uncinate fiber tract between the frontal cortex and limbic subcortical areas in social phobia

Introduction

Several fMRI and resting-state connectivity studies have demonstrated alterations in the limbic system and frontal areas in social anxiety disorder (SAD).

Aims

Here we used high-resolution whole-brain diffusion tensor imaging (DTI) to examine differences in anatomical connectivity between patients and controls in the white matter.

Methods

We examined 14 SAD patients (age 26.3 ± 9.0y) and 15 healthy controls (age 25.6 ± 3.3y) using DTI on a 3T Trio MRI scanner (Siemens, Germany). DTI acquisition with 1.6 mm isotropic resolution was performed in 30 directions and a maximum b-value of 800. Fractional anisotropy (FA) maps were obtained using FSL. Group analysis was performed in SPM8 (two sample t-test).

Results

The figure shows a coronal slice through the uncinate fasciculus. Arrows point to areas where SAD patients show decreased FA-values compared to controls (p < 0.05). Note that these areas are limited to the uncinate fasciculus and are found bilaterally.

Conclusion

Reduced FA-values indicate a reduction in anatomical connectivity strength. Our study thus clearly shows reduced connectivity strength in the uncinate fasciculus connecting frontal regions with limbic areas as the amygdalae and hippocampus. This reduced structural connectivity supports functional data demonstrating alterations of brain activation in the amygdala and prefrontal regions in social phobia.

Cortisol plasma levels are associated with serotonin - 1A receptor binding in postmenopausal women

Introduction

Alterations of the serotonin-1A receptor (5-HT1A) and the hypothalamic-pituitary-adrenal (HPA) axis have been reported in depression and anxiety disorders. We previously showed a strong negative correlation between cortisol plasma levels and 5-HT1A receptor binding potential (BP) in patients with social anxiety disorder but not in healthy controls using PET [1].

Objectives

To investigate the relationship of cortisol and the 5-HT1A BP in postmenopausal women, a population that is at increased risk of suffering from depressive symptoms.

Methods

Subjects: 19 postmenopausal women, aged 55.26 ± 4.98, medication free, no current substance abuse or hormone replacement therapy.

PET

Dynamic measurements (50 frames, 90 min) were performed using the radioligand [carbonyl-11C]WAY100635 and a GE-Advance scanner. PET data were normalized to a ligand-specific template [2]. Regions-of-interest (ROI) were defined as given in [3]. TACs within ROIs were averaged and the 5-HT1A receptor BP was quantified using Logan-plot and PMOD 3.1. Measurement of total cortisol plasma levels was done using electrochemoluminescence.

Results

We found negative correlations between cortisol and 5-HT1A BP in the midbrain (Spearman's rs = −0.54, p = 0.02), the median raphe nucleus (rs = −0.47, p = 0.04) and the nucleus accumbens (rs = −0.505, p = 0.03).

Conclusions

In line with our previous findings [1], the observed negative association between cortisol plasma levels and 5-HT1A BP might reflect an increased vulnerability for mood disorders in postmenopausal women.

In vivo molecular imaging reveals distinct distributions of the serotonin transporter, the major inhibitory and excitatory serotonin receptors

Introduction

Based on evidences in molecular neuroimaging, postmortem and genetic studies, impaired serotonergic neurotransmission has been implicated with affective disorders. Moreover, a growing number of evidences showed strong interrelations within the serotonergic system suggesting a common mechanism in the modulation of receptor and transporter densities.

Objective

Here we directly investigated the regional expression of the 5-HT1A, 5-HT2A and 5-HTT using PET and the three highly selective and specific radioligands [carbonyl-11C]WAY-100635, [18F]Altanserin and [11C]DASB in healthy subjects.

Methods

A total of 55 healthy subjects (5-HT1A: 36 subjects, 18 males, age = 26.0 ± 4.9; 5-HT2A: 19 subjects, 11 males, age = 28.2 ± 5.9; 5-HTT: 8 males, age = 28.12 ± 3.6) were included in this study. Binding potential (BPND) values were quantified according to the AAL parcellation scheme.

Results

BPND values averaged over both hemispheres ranged from 0.40–6.35 for the 5-HT1A receptor; 0.01–2.01 for the 5-HT2A receptor and 0.09–2.05 for the 5-HTT, respectively. There was a specific topological pattern according to the ratio between the 5-HT1A, 5-HT2A receptors and 5-HTT (“fingerprints”).

Conclusions

Such information can be essential for detecting potential local alterations in the ratio between different binding proteins on a network level in pathological conditions.

Moreover, these data might provide further insight in area-specific effects of frequently prescribed selective serotonin re-uptake inhibitors (SSRI): 1)

Antipsychotics in obsessive-compulsive disorder - an auspicious approach for treatment-resistant patients?

Introduction

Because only 40 – 60% of all patients with obsessive-compulsive disorder (OCD) respond to selective serotonin reuptake inhibitors (SSRIs), the evaluation of alternative therapy methods in the presence of treatment resistance has high clinical relevance. In this context, many studies have examined additive medication with antipsychotics.

Method

All double-blind randomised controlled trials (DBRCTs) that evaluated the efficacy of a combination therapy of antipsychotics and SSRIs in treatment-resistant OCD were covered by systematic literature searches.

Results

A total of ten DBRCTs were identified (four for quetiapine, three for risperidone, two for olanzapine and one for haloperidol) with a participant collective comprising in total 316 treatment-resistant OCD patients. After the augmentation therapy, significantly more subjects in the intervention group (antipsychotic + SSRI), 32% of the patients, fulfilled the response criterion (reduction in the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) ≥ 35%) than in the control group (placebo + SSRI) (relative risk (RR) = 2.08; 95% CI: 1.3 – 3.32). The standardised mean difference (SMD) of the Y-BOCS reduction between the pooled two study-groups revealed an effect size of 0,62. The sub-group analyses showed significant efficacy only for haloperidol and risperidone. Further significant differences existed regarding the duration of SSRI medication before the augmentation phase.

Conclusion / Discussion

Based on the favourable benefit-risk-ratio, risperidone can be regarded as the agent of first choice for augmentation treatment with an SSRI. Overall, about one third of patients benefit from this therapy option. However, further scientific studies are needed before sufficiently empirically secured pharmacological treatment recommendations can be expressed.

Multimodal imaging of an astrocytoma affecting the amygdalar region

Introduction

Regional alterations of serotonergic neurotransmission and functional activation in the amygdalar region of patients with major depression are underpinning its important role in affective disorders. In this study we used fMRI and PET to describe functional and molecular alterations associtated with an astrocytoma in the left amygdalar region in a patient with organic depressive disorder compared to control subjects.

Methods

The serotonin-1A (5-HT1A) receptor binding (BPND) was quantified with PET (30 frames, 90 min, 4.4 mm FWHM) in 36 subjects using the radioligand [carbonyl-11C]WAY-100635, and a reference tissue model (MRTM2). In fMRI (3T, EPI inplane resolution 1.6*2.7 mm, 10 AC-PC orientated slices, ST = 3 mm, TE/TR = 31/1000 ms), 32 participants performed emotion discrimination and sensorimotor control tasks. Statistical analysis with SPM5 and unpaired t-tests were performed on molecular and functional data separately.

Results

The astrocytoma was delineated in the serotonin-1A receptor distribution showing (p < 0.01, uncorrected) regional BPND decrease. The ipsilateral thalamus and bilateral habenula regions displayed (p < 0.001; uncorrected) BPND increase. The fMRI data showed significantly (p < 0.05; uncorrected) reduced activation in the affected amygdalar region, ipsilateral fusiform gyrus, bilateral orbitofrontal cortex and temporal regions and increased activation in the contralateral temporal pole.

Conclusions

Lower serotonin-1A receptor binding in the left amydala region reflects the glial provenance of the tumor. The increased receptor binding in the habenulae might be associated with altered monoaminergic neurotransmission and depressive symptoms according to the influence of the habenulae on monoaminergic nuclei. The functional data demonstrate neuroplastic changes beyond affected areas and might indicate compensatory mechanisms.

FC10-05 - Attenuated serotonin transporter association between midbrain and nucleus accumbens in major depression

Introduction

Patients suffering from major depressive disorder (MDD) exhibit alterations in serotonin transporter (5-HTT) binding clinically reflected by lack of hedonic experience. We recently demonstrated the importance to evaluate interregional relationships of neurotransmitter systems, providing important complementary information on a network level.

Objective

To identify interregional 5-HTT relationships between the midbrain raphe region and projection areas in MDD patients compared to controls.

Methods

Eighteen medication-free patients with MDD and 16 healthy subjects underwent PET using [11C] DASB. 5-HTT binding potential (BPND) maps were computed with the multilinear-reference-tissue-model-2 in PMOD3.1. Voxel-wise linear regression was calculated in SPM8 using midbrain 5-HTT BPND as regressor; group comparisons were assessed by ANOVA (p < 0.001).

Results

Healthy subjects showed positive associations between serotonin transporters located in the midbrain and transporters expressed in the nucleus accumbens bilaterally. Importantly, this relationship was significantly decreased in MDD patients as compared to controls (t = 5.41/4.84, right/left hemisphere; see figure).

Conclusions

This study demonstrates for the first time 5-HTT alterations on a network level in MDD patients between the midbrain and a major projection area. Our results complement previous findings emphasizing the importance of the nucleus accumbens in MDD and indicate a disturbed serotonergic regulation in this key area of reward processing.

Prediction of steady-state occupancy of the serotonin transporter based on single-dose occupancy: A [11C]DASB pet study

Introduction

Clinical studies point toward a potential role of the serotonin transporter (SERT) binding as a predictor of clinical outcome in the treatment of depression. After long-term treatment with clinical doses of SSRIs the expected SERT occupancy is about 80%. Here, we were interested to investigate the relationship of SERT occupancy values between short- and longterm treatment.

Objectives

To test if the SERT occupancy at steady-state can be predicted based on the single dose occupancy by escitalopram (S-citalopram) or citalopram (racemate of S-citalopram and R-citalopram).

Methods

18 patients with major depressive disorder received either escitalpram (10 mg/d) or citalopram (20 mg/d) in a double-blind, randomized, longitudinal study. They underwent three PET scans using the radioligand [11C]DASB: PET1 baseline, PET2 6 hours after first drug intake and PET3 after three weeks of daily oral treatment. Occupancy of SERT was quantified in six subcortical regions: thalamus, N. caudatus, putamen, mibrain, dorsal raphe and median raphe nuclei. Data was analyzed by means of multiple linear regression models corrected for baseline SERT availability values using SPSS 15.0.

Results

Single dose occupancy of the SERT significantly predicted steady-state occupancy after three weeks in three regions: thalamus (r2 = 0.45, p = 0.009), N. caudatus (r2 = 0.4, p = 0.006) and putamen (r2 = 0.43, p = 0.005). Other regions did not show significant relationships.

Conclusions

In this study we demonstrated that single-dose occupancy in SERT rich regions such as thalamus, N. caudatus and the putamen could serve as reliable predictors for steady-state occupancy. However, a linear model failed to explain the relationship in regions known for serotonergic cell origin.

Model-free fMRI group analysis using FENICA

Exploratory analysis of functional MRI data allows activation to be detected even if the time course differs from that which is expected. Independent Component Analysis (ICA) has emerged as a powerful approach, but current extensions to the analysis of group studies suffer from a number of drawbacks: they can be computationally demanding, results are dominated by technical and motion artefacts, and some methods require that time courses be the same for all subjects or that templates be defined to identify common components. We have developed a group ICA (gICA) method which is based on single-subject ICA decompositions and the assumption that the spatial distribution of signal changes in components which reflect activation is similar between subjects. This approach, which we have called Fully Exploratory Network Independent Component Analysis (FENICA), identifies group activation in two stages. ICA is performed on the single-subject level, then consistent components are identified via spatial correlation. Group activation maps are generated in a second-level GLM analysis. FENICA is applied to data from three studies employing a wide range of stimulus and presentation designs. These are an event-related motor task, a block-design cognition task and an event-related chemosensory experiment. In all cases, the group maps identified by FENICA as being the most consistent over subjects correspond to task activation. There is good agreement between FENICA results and regions identified in prior GLM-based studies. In the chemosensory task, additional regions are identified by FENICA and temporal concatenation ICA that we show is related to the stimulus, but exhibit a delayed response. FENICA is a fully exploratory method that allows activation to be identified without assumptions about temporal evolution, and isolates activation from other sources of signal fluctuation in fMRI. It has the advantage over other gICA methods that it is computationally undemanding, spotlights components relating to activation rather than artefacts, allows the use of familiar statistical thresholding through deployment of a higher level GLM analysis and can be applied to studies where the paradigm is different for all subjects.

Reward and the serotonergic system

Anhedonia, as a failure to experience rewarding stimuli, is a key characteristic of many psychiatric disorders including depression and schizophrenia. Investigations on the neurobiological correlates of reward and hedonia/anhedonia have been a growing subject of research demonstrating several neuromodulators to mediate different aspects of reward processing. Whereas the majority of research on reward mainly focused on the dopamine and opioid systems, a serotonergic mechanism has been neglected. However, recent promising results strengthen the pivotal role of serotonin in reward processing. Evidence includes electrophysical and pharmacological as well as genetic and imaging studies. Primate research using single-unit recording of neurons within the dorsal raphe nucleus argues for a serotonergic mediation of reward value, whereas studies using intracranial self-stimulation point to an important contribution of serotonin in modulating motivational aspects of rewarding brain stimulation. Pharmacological studies using agonists and antagonists of serotonergic receptor subtypes and approaches investigating an increase or decrease of the extracellular level of serotonin offer strong evidence for a serotonergic mediation, ranging from aversion to pleasure. This review provides an argument for serotonin as a fundamental mediator of emotional, motivational and cognitive aspects of reward representation, which makes it possibly as important as dopamine for reward processing.

Network atrophy in temporal lobe epilepsy: a voxel-based morphometry study

BACKGROUND

Recent evidence suggests that temporal lobe epilepsy affects a neuronal network rather than a single circumscribed structure within the temporal lobe. Thus, in mesial temporal lobe epilepsy (mTLE) with hippocampal sclerosis gray matter abnormalities have been found beyond the hippocampus in extrahippocampal regions by means of voxel-based morphometry (VBM). On the contrary, in cryptogenic or MRI-negative TLE (cTLE) no consistent gray matter abnormalities in VBM studies have been reported.

METHODS

We used optimized VBM with modulation to detect gray matter abnormalities compared to healthy controls in patients with mTLE and cTLE. Twenty-two patients with mTLE (right/left TLE 13:9), 17 patients with cTLE (right/left TLE 7:10), and 12 healthy controls were enrolled in the study.

RESULTS

In mTLE we found decreased gray matter volume (GMV) beyond the hippocampus in the ipsilateral thalamus. GMV decrease was more widespread in patients with left-sided seizure focus including the left parahippocampal and superior temporal gyrus, frontal regions, cerebellum, and the right cingulum. In cTLE, decreased GMV was observed in the frontal and orbitofrontal cortex, the cerebellum, neocortical temporal regions, and in the right parahippocampal cortex. Again, patients with left-sided seizure focus had a more widespread and extensive GMV decrease including regions such as the right and left cingulum.

CONCLUSION

We found evidence for distinct neuronal network damage in mesial temporal lobe epilepsy (mTLE) and cryptogenic TLE (cTLE) which is more widespread in patients with left-sided seizure focus. Atrophy of the cingulum was a common feature in left- but not in right-sided mTLE and cTLE.

In vivo imaging of serotonin transporter occupancy by means of SPECT and [123I]ADAM in healthy subjects administered different doses of escitalopram or citalopram

BACKGROUND

Escitalopram is a dual serotonin reuptake inhibitor (SSRI) approved for the treatment of depression and anxiety disorders. It is the S-enantiomer of citalopram, and is responsible for the serotonin reuptake activity, and thus for its pharmacological effects. Previous studies pointed out that clinically efficacious doses of other SSRIs produce an occupancy of the serotonin reuptake transporter (SERT) of about 80% or more. The novel radioligand [123I]ADAM and single photon emission computer tomography (SPECT) were used to measure midbrain SERT occupancies for different doses of escitalopram and citalopram.

METHODS

Twenty-five healthy subjects received a single dose of escitalopram [5 mg (n=5), 10 mg (n=5), and 20 mg (n=5)] or citalopram [(10 mg (n=5) and 20 mg (n=5)]. Midbrain SERT binding was measured with [(123)I]ADAM and SPECT on two study days, once without study drug and once 6 h after single dose administration of the study drug. The ratio of midbrain-cerebellum/cerebellum was the outcome measure (V3") for specific binding to SERT in midbrain. Subsequently, SERT occupancy levels were calculated using the untreated baseline level for each subject. An Emax model was used to describe the relationship between S-citalopram concentrations and SERT occupancy values. Additionally, four subjects received placebo to determine test-retest variability.

RESULTS

Single doses of 5, 10, or 20 mg escitalopram led to a mean SERT occupancy of 60+/-6, 64+/-6, and 75+/-5%, respectively. SERT occupancies for subjects treated with single doses of 10 and 20 mg citalopram were 65+/-10 and 70+/-6%, respectively. A statistically significant difference was found between SERT occupancies after application of 10 and 20 mg escitalopram, but not for 10 and 20 mg citalopram. There was no statistically significant difference between the SERT occupancies of either 10 mg citalopram or 10 mg escitalopram, or between 20 mg citalopram and 20 mg escitalopram. Emax was slightly higher after administration of citalopram (84%) than escitalopram (79%). In the test-retest study, a mean SERT "occupancy" of 4% was found after administration of placebo, the intraclass correlation coefficient was 0.92, and the repeatability coefficient was 0.25.

CONCLUSION

SPECT and [123I]ADAM were used to investigate SERT occupancies after single doses of escitalopram or citalopram. The test-retest study revealed good reproducibility of SERT quantification. Similar SERT occupancies were found after administration of equal doses (in respect to mg) of escitalopram and citalopram, giving indirect evidence for a fractional blockade of SERT by the inactive R-citalopram.

NeuroImaging bei schizophrenen Erkrankungen

This overview is focused on functional neuroimaging including functional magnetic resonance imaging (fMRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT). Recent evidence for the "dopamine hypothesis of schizophrenia" is summarized including alterations of presynaptic dopamine metabolism and postsynaptic receptor binding potential. Emphasis is given to dopaminergic challenge studies using amphetamine and AMPT. Several PET and SPECT studies have shown a pronounced increase of amphetamine-induced dopamine release as well as decrease of AMPT-induced dopamine depletion in drug-naive schizophrenic patients, indicating a dysregulation of dopaminergic neurotransmission. Results of studies combining amphetamine challenge and the NMDA receptor antagonist ketamine are related to glutaminergic dysfunction and neurotransmitter interactions. FMRI and PET results demonstrating alterations in task-specific functional connectivity between brain areas are discussed with a focus on the prefrontal cortex and temporal structures. Increase of serotonin-1A receptor binding potential in prefrontal and mesotemporal cortex is related to the serotonin-dopamine interaction. Genetic neuroimaging techniques, including voxel-based morphometry (VBM) and fMRI, revealing significant effects of the dopamine metabolizing enzyme COMT on functional activation in prefrontal areas are also discussed. Functional neuroimaging based on challenge-paradigms in PET as well as task-specific state- or trait-dependent alterations of activation patterns in fMRI, seems to be a promising candidate for the development of biological marker tests for schizophrenia.

Evaluation of preoperative high magnetic field motor functional MRI (3 Tesla) in glioma patients by navigated electrocortical stimulation and postoperative outcome

OBJECTIVES

The validity of 3 Tesla motor functional magnetic resonance imaging (fMRI) in patients with gliomas involving the primary motor cortex was investigated by intraoperative navigated motor cortex stimulation (MCS).

METHODS

Twenty two patients (10 males, 12 females, mean age 39 years, range 10-65 years) underwent preoperative fMRI studies, performing motor tasks including hand, foot, and mouth movements. A recently developed high field clinical fMRI technique was used to generate pre-surgical maps of functional high risk areas defining a motor focus. Motor foci were tested for validity by intraoperative motor cortex stimulation (MCS) employing image fusion and neuronavigation. Clinical outcome was assessed using the Modified Rankin Scale.

RESULTS

FMRI motor foci were successfully detected in all patients preoperatively. In 17 of 22 patients (77.3%), a successful stimulation of the primary motor cortex was possible. All 17 correlated patients showed 100% agreement on MCS and fMRI motor focus within 10 mm. Technical problems during stimulation occurred in three patients (13.6%), no motor response was elicited in two (9.1%), and MCS induced seizures occurred in three (13.6%). Combined fMRI and MCS mapping results allowed large resections in 20 patients (91%) (gross total in nine (41%), subtotal in 11 (50%)) and biopsy in two patients (9%). Pathology revealed seven low grade and 15 high grade gliomas. Mild to moderate transient neurological deterioration occurred in six patients, and a severe hemiparesis in one. All patients recovered within 3 months (31.8% transient, 0% permanent morbidity).

CONCLUSIONS

The validation of clinically optimised high magnetic field motor fMRI confirms high reliability as a preoperative and intraoperative adjunct in glioma patients selected for surgery within or adjacent to the motor cortex.