Effects of escitalopram on synaptic density in the healthy human brain: a randomized controlled trial

Selective serotonin reuptake inhibitors (SSRIs) are widely used for treating neuropsychiatric disorders. However, the exact mechanism of action and why effects can take several weeks to manifest is not clear. The hypothesis of neuroplasticity is supported by preclinical studies, but the evidence in humans is limited. Here, we investigate the effects of the SSRI escitalopram on presynaptic density as a proxy for synaptic plasticity. In a double-blind placebo-controlled study (NCT04239339), 32 healthy participants with no history of psychiatric or cognitive disorders were randomized to receive daily oral dosing of either 20 mg escitalopram (n = 17) or a placebo (n = 15). After an intervention period of 3-5 weeks, participants underwent a [11C]UCB-J PET scan (29 with full arterial input function) to quantify synaptic vesicle glycoprotein 2A (SV2A) density in the hippocampus and the neocortex. Whereas we find no statistically significant group difference in SV2A binding after an average of 29 (range: 24-38) days of intervention, our secondary analyses show a time-dependent effect of escitalopram on cerebral SV2A binding with positive associations between [11C]UCB-J binding and duration of escitalopram intervention. Our findings suggest that brain synaptic plasticity evolves over 3-5 weeks in healthy humans following daily intake of escitalopram. This is the first in vivo evidence to support the hypothesis of neuroplasticity as a mechanism of action for SSRIs in humans and it offers a plausible biological explanation for the delayed treatment response commonly observed in patients treated with SSRIs. While replication is warranted, these results have important implications for the design of future clinical studies investigating the neurobiological effects of SSRIs.

Serotonin 4 Receptor Brain Binding in Major Depressive Disorder and Association With Memory Dysfunction

Importance

The cerebral serotonin 4 (5-HT4) receptor is a promising novel target for treatment of major depressive disorder (MDD), and pharmacological stimulation of the 5-HT4 receptor has been associated with improved learning and memory in healthy individuals.

Objective

To map the neurobiological signatures of patients with untreated MDD compared with healthy controls and to examine the association between cerebral 5-HT4 receptor binding and cognitive functions in the depressed state.

Design, Setting, and Participants

This case-control study used baseline data from the NeuroPharm clinical depression trial in Denmark. Adult participants included antidepressant-free outpatients with a current moderate to severe depressive episode and healthy controls. All participants completed positron emission tomography (PET) scanning with [11C]SB207145 for quantification of brain 5-HT4 receptor binding, but only the patients underwent cognitive testing. Data analyses were performed from January 21, 2020, to April 22, 2022.

Main Outcomes and Measures

The main study outcome was the group difference in cerebral 5-HT4 receptor binding between patients with MDD and healthy controls. In addition, the association between 5-HT4 receptor binding and verbal memory performance in the patient group was tested. Other cognitive domains (working memory, reaction time, emotion recognition bias, and negative social emotions) were assessed as secondary outcomes.

Results

A total of 90 patients with untreated MDD (mean [SD] age, 27.1 [8.2] years; 64 women [71.1%]) and 91 healthy controls (mean [SD] age, 27.1 [8.0] years; 55 women [60.4%]) were included in the analysis. Patients with current MDD had significantly lower cerebral 5-HT4 receptor binding than healthy controls (-7.0%; 95% CI, -11.2 to -2.7; P = .002). In patients with MDD, there was a correlation between cerebral 5-HT4 receptor binding and verbal memory (r = 0.29; P = .02).

Conclusions and Relevance

Results of this study show that cerebral 5-HT4 receptor binding was lower in patients with MDD than in healthy controls and that the memory dysfunction in patients with MDD was associated with lower cerebral 5-HT4 receptor binding. The cerebral 5-HT4 receptor is a promising treatment target for memory dysfunction in patients with MDD.

Psilocybin modulation of time-varying functional connectivity is associated with plasma psilocin and subjective effects

BACKGROUND

Psilocin, the neuroactive metabolite of psilocybin, is a serotonergic psychedelic that induces an acute altered state of consciousness, evokes lasting changes in mood and personality in healthy individuals, and has potential as an antidepressant treatment. Examining the acute effects of psilocin on resting-state time-varying functional connectivity implicates network-level connectivity motifs that may underlie acute and lasting behavioral and clinical effects.

AIM

Evaluate the association between resting-state time-varying functional connectivity (tvFC) characteristics and plasma psilocin level (PPL) and subjective drug intensity (SDI) before and right after intake of a psychedelic dose of psilocybin in healthy humans.

METHODS

Fifteen healthy individuals completed the study. Before and at multiple time points after psilocybin intake, we acquired 10-minute resting-state blood-oxygen-level-dependent functional magnetic resonance imaging scans. Leading Eigenvector Dynamics Analysis (LEiDA) and diametrical clustering were applied to estimate discrete, sequentially active brain states. We evaluated associations between the fractional occurrence of brain states during a scan session and PPL and SDI using linear mixed-effects models. We examined associations between brain state dwell time and PPL and SDI using frailty Cox proportional hazards survival analysis.

RESULTS

Fractional occurrences for two brain states characterized by lateral frontoparietal and medial fronto-parietal-cingulate coherence were statistically significantly negatively associated with PPL and SDI. Dwell time for these brain states was negatively associated with SDI and, to a lesser extent, PPL. Conversely, fractional occurrence and dwell time of a fully connected brain state partly associated with motion was positively associated with PPL and SDI.

CONCLUSION

Our findings suggest that the acute perceptual psychedelic effects induced by psilocybin may stem from drug-level associated decreases in the occurrence and duration of lateral and medial frontoparietal connectivity motifs. We apply and argue for a modified approach to modeling eigenvectors produced by LEiDA that more fully acknowledges their underlying structure. Together these findings contribute to a more comprehensive neurobiological framework underlying acute effects of serotonergic psychedelics.

Acute Traumatic Stress Screening Can Identify Patients and Their Partners at Risk for Posttraumatic Stress Disorder Symptoms After a Cardiac Arrest: A Multicenter Prospective Cohort Study

BACKGROUND

Posttraumatic stress disorder (PTSD) is prevalent in patients who have had a cardiac arrest and their partners. Accordingly, acute traumatic stress screening is recommended, but its association with later PTSD symptoms has never been addressed in postresuscitation settings.

OBJECTIVE

The aim of this study was to examine whether acute traumatic stress is associated with PTSD symptoms in patients who have had a cardiac arrest and their partners.

METHODS

This multicenter longitudinal study of 141 patients and 97 partners measures acute traumatic stress at 3 weeks and PTSD symptoms at 3 months and 1 year after resuscitation, using the Impact of Event Scale. Linear regression models were used to evaluate the association between severity of acute traumatic stress and PTSD symptoms and post hoc to explore effects of group (patients/partners), age, and sex on acute traumatic stress severity. We categorized Impact of Event Scale scores higher than 26 at 3 months and 1 year as clinical severe PTSD symptoms .

RESULTS

Higher acute traumatic stress severity is significantly positively associated with higher PTSD symptom severity at 3 months (patients and partners: P < .001) and 1 year (patients and partners: P < .001) postresuscitation, with the strongest association for women compared with men ( P = .03). Acute traumatic stress was higher in women compared with men across groups ( P = .02). Clinical severe PTSD symptoms were present in 26% to 28% of patients and 45% to 48% of partners.

CONCLUSION

Experiencing a cardiac arrest may elicit clinical severe PTSD symptoms in patients, but particularly in their partners. Screening patients and partners for acute traumatic stress postresuscitation is warranted to identify those at increased risk of long-term PTSD symptoms.

Hot and Cold Cognitive Disturbances in Parkinson Patients Treated with DBS-STN: A Combined PET and Neuropsychological Study

Patients with Parkinson’s disease (PD) often suffer from non-motor symptoms, which may be caused by serotonergic dysfunction. Deep Brain Stimulation (DBS) in the subthalamic nucleus (STN) may also influence non-motor symptoms. The aim of this study is to investigate how the cerebral 5-HT system associates to disturbances in cognition and mood in PD patients with DBS-STN turned on and off. We used psychological tests and questionnaires to evaluate cognitive function and the effects on mood from turning DBS-STN off. We applied a novel PET neuroimaging methodology to evaluate the integrity of the cerebral serotonin system. We measured 5-HT1BR binding in 13 DBS-STN-treated PD patients, at baseline and after turning DBS off. Thirteen age-matched volunteers served as controls. The measures for cognition and mood were correlated to the 5-HT1BR availability in temporal limbic cortex. 5-HT1BR binding was proportional to working memory performance and inverse proportional to affective bias for face recognition. When DBS is turned off, patients feel less vigorous; the higher the limbic and temporal 5-HT1BR binding, the more they are affected by DBS being turned off. Our study suggests that cerebral 5-HTR binding is associated with non-motor symptoms, and that preservation of serotonergic functions may be predictive of DBS-STN effects.

Psilocybin-induced changes in brain network integrity and segregation correlate with plasma psilocin level and psychedelic experience

The emerging novel therapeutic psilocybin produces psychedelic effects via engagement of cerebral serotonergic targets by psilocin (active metabolite). The serotonin 2A receptor critically mediates these effects by altering distributed neural processes that manifest as increased entropy, reduced functional connectivity (FC) within discrete brain networks (i.e., reduced integrity) and increased FC between networks (i.e., reduced segregation). Reduced integrity of the default mode network (DMN) is proposed to play a particularly prominent role in psychedelic phenomenology, including perceived ego-dissolution. Here, we investigate the effects of a psychoactive peroral dose of psilocybin (0.2-0.3 mg/kg) on plasma psilocin level (PPL), subjective drug intensity (SDI) and their association in fifteen healthy individuals. We further evaluate associations between these measures and resting-state FC, measured with functional magnetic resonance imaging, acquired over the course of five hours after psilocybin administration. We show that PPL and SDI correlate negatively with measures of network integrity (including DMN) and segregation, both spatially constrained and unconstrained. We also find that the executive control network and dorsal attention network desegregate, increasing connectivity with other networks and throughout the brain as a function of PPL and SDI. These findings provide direct evidence that psilocin critically shapes the time course and magnitude of changes in the cerebral functional architecture and subjective experience following psilocybin administration. Our findings provide novel insight into the neurobiological mechanisms underlying profound perceptual experiences evoked by this emerging transnosological therapeutic and implicate the expression of network integrity and segregation in the psychedelic experience and consciousness.

Parkinson patients have a presynaptic serotonergic deficit: A dynamic deep brain stimulation PET study

Patients with Parkinson's disease (PD) often suffer from non-motor symptoms, which may be caused by serotonergic dysfunction. Apart from alleviating the motor symptoms, Deep Brain Stimulation (DBS) in the subthalamic nucleus (STN) may also influence non-motor symptoms. The aim of this study is to investigate how turning DBS off affects the serotonergic system. We here exploit a novel functional PET neuroimaging methodology to evaluate the preservation of serotonergic neurons and capacity to release serotonin. We measured cerebral 5-HT_1BR binding in 13 DBS-STN treated PD patients, at baseline and after turning DBS off. Ten age-matched volunteers served as controls. Clinical measures of motor symptoms were assessed under the two conditions and correlated to the PET measures of the static and dynamic integrity of the serotonergic system. PD patients exhibited a significant loss of frontal and parietal 5-HT_1BR, and the loss was significantly correlated to motor symptom severity. We saw a corresponding release of serotonin, but only in brain regions with preserved 5-HT_1BR, suggesting the presence of a presynaptic serotonergic deficit. Our study demonstrates that DBS-STN dynamically regulates the serotonin system in PD, and that preservation of serotonergic functions may be predictive of DBS-STN effects.

Default Mode Network Functional Connectivity Negatively Associated with Trait Openness to Experience

Evaluating associations between the five-factor personality domains and resting-state functional connectivity networks (e.g., default mode network, DMN) highlights distributed neurobiological systems linked to behaviorally relevant phenotypes. Establishing these associations can highlight a potential underlying role for these neural pathways in related clinical illness and treatment response. Here we examined associations between within- and between-network resting-state functional connectivity with functional magnetic resonance imaging (fMRI) and the five-factor personality domains: Openness to experience (Openness), Extraversion, Neuroticism, Agreeableness and Conscientiousness. We included data from 470 resting-state scan sessions and personality assessments in 295 healthy participants. Within- and between-network functional connectivity from 32 a priori defined regions was computed across seven resting-state networks. The association between functional connectivity and personality traits was assessed using generalized least squares. Within-network DMN functional connectivity was significantly negatively associated with trait Openness (regression coefficient= -0.0010; [95% CI] = [-0.0017, -0.0003]; pFWER = 0.033), seemingly driven by association with the Fantasy subfacet. Trait Extraversion was significantly negatively associated with functional connectivity between the visual and dorsal attention networks and positively associated with functional connectivity between the frontoparietal and language networks. Our findings provide evidence that resting-state DMN is associated with trait Openness and gives insight into personality neuroscience.

Psychometric Properties of the Verbal Affective Memory Test-26 and Evaluation of Affective Biases in Major Depressive Disorder

We developed the Verbal Affective Memory Test-26 (VAMT-26), a computerized test to assess verbal memory, as an improvement of the Verbal Affective Memory Test-24 (VAMT-24). Here, we psychometrically evaluate the VAMT-26 in 182 healthy controls, examine 1-month test–retest stability in 48 healthy controls, and examine whether 87 antidepressant-free patients diagnosed with Major Depressive Disorder (MDD) tested with VAMT-26 differed in affective memory biases from 335 healthy controls tested with VAMT24/26. We also examine whether affective memory biases are associated with depressive symptoms across the patients and healthy controls. VAMT-26 showed good psychometric properties. Age, sex, and IQ, but not education, influenced VAMT-26 scores. VAMT-26 scores converged satisfactorily with scores on a test associated with non-affective verbal memory. Test–retest analyses showed a learning effect and a r ≥ 0.0.8, corresponding to a typical variation of 10% in recalled words from first to second test. Patients tended to remember more negative words relative to positive words compared to healthy controls at borderline significance (p = 0.06), and affective memory biases were negatively associated with depressive symptoms across the two groups at borderline significance (p = 0.07), however, the effect sizes were small. Future studies are needed to address whether VAMT-26 can be used to distinguish between depression subtypes in patients with MDD. As a verbal memory test, VAMT-26 is a well validated neuropsychological test and we recommend it to be used in Danish and international studies on affective memory.

Psychometric Properties and Validation of the EMOTICOM Test Battery in a Healthy Danish Population

Disruptions in hot cognition, i.e., the processing of emotionally salient information, are prevalent in most neuropsychiatric disorders and constitute a potential treatment target. EMOTICOM is the first comprehensive neuropsychological test battery developed specifically to assess hot cognition. The aim of the study was to validate and establish a Danish language version and reference data for the EMOTICOM test battery. To evaluate the psychometric properties of 11 EMOTICOM tasks, we collected data from 100 healthy Danish participants (50 males, 50 females) including retest data from 49 participants. We assessed test-retest reliability, floor and ceiling effects, task-intercorrelations, and correlations between task performance and relevant demographic and descriptive factors. We found that test-retest reliability varied from poor to excellent while some tasks exhibited floor or ceiling effects. Intercorrelations among EMOTICOM task outcomes were low, indicating that the tasks capture different cognitive constructs. EMOTICOM task performance was largely independent of age, sex, education, and IQ as well as current mood, personality, and self-reported motivation and diligence during task completion. Overall, many of the EMOTICOM tasks were found to be useful and objective measures of hot cognition although select tasks may benefit from modifications to avoid floor and ceiling effects in healthy individuals.

Brain serotonin 4 receptor binding is inversely associated with verbal memory recall

BACKGROUND

We have previously identified an inverse relationship between cerebral serotonin 4 receptor (5-HT ₄R) binding and nonaffective episodic memory in healthy individuals. Here, we investigate in a novel sample if the association is related to affective components of memory, by examining the association between cerebral 5-HT ₄R binding and affective verbal memory recall.

METHODS

Twenty-four healthy volunteers were scanned with the 5-HT ₄R radioligand [¹¹C]SB207145 and positron emission tomography, and were tested with the Verbal Affective Memory Test-24. The association between 5-HT ₄R binding and affective verbal memory was evaluated using a linear latent variable structural equation model.

RESULTS

We observed a significant inverse association across all regions between 5-HT ₄R binding and affective verbal memory performances for positive (p = 5.5 × 10^-4) and neutral (p = .004) word recall, and an inverse but nonsignificant association for negative (p = .07) word recall. Differences in the associations with 5-HT ₄R binding between word categories (i.e., positive, negative, and neutral) did not reach statistical significance.

CONCLUSION

Our findings replicate our previous observation of a negative association between 5-HT ₄R binding and memory performance in an independent cohort and provide novel evidence linking 5-HT ₄R binding, as a biomarker for synaptic 5-HT levels, to the mnestic processing of positive and neutral word stimuli in healthy humans.

State-dependent alterations in inhibitory control and emotional face identification in seasonal affective disorder

BACKGROUND

Depressed individuals often exhibit impaired inhibition to negative input and identification of positive stimuli, but it is unclear whether this is a state or trait feature. We here exploited a naturalistic model, namely individuals with seasonal affective disorder (SAD), to study this feature longitudinally.

AIM

The goal of this study was to examine seasonal changes in inhibitory control and identification of emotional faces in individuals with SAD.

METHOD

Twenty-nine individuals diagnosed with winter-SAD and 30 demographically matched controls with no seasonality symptoms completed an emotional Go/NoGo task, requiring inhibition of prepotent responses to emotional facial expressions and an emotional face identification task twice, in winter and summer.

RESULTS

In winter, individuals with SAD showed impaired ability to inhibit responses to angry (p = .0006) and sad faces (p = .011), and decreased identification of happy faces (p = .032) compared with controls. In summer, individuals with SAD and controls performed similarly on these tasks (ps > .24).

CONCLUSION

We provide novel evidence that inhibition of angry and sad faces and identification of happy faces are impaired in SAD in the symptomatic phase, but not in the remitted phase. The affective biases in cognitive processing constitute state-dependent features of SAD. Our data show that reinstatement of a normal affective cognition should be possible and would constitute a major goal in psychiatric treatment to improve the quality of life for these patients. (PsycINFO Database Record

Sex hormone manipulation slows reaction time and increases labile mood in healthy women

BACKGROUND

Women show increased risk of depressive symptoms in life phases where ovarian steroid hormone levels fluctuate or decline rapidly. The risk mechanisms may include changes in mental state and affective cognition possibly mediated by serotonergic neurotransmission.

METHODS

In a randomized controlled double-blinded trial, 61 healthy women (mean age 24.3±4.9 years) were tested with measures of affective verbal memory, reaction time, mental distress, and serotonin transporter binding at baseline and at follow-up after receiving gonadotropin-releasing hormone agonist (GnRHa) or placebo intervention. Women also reported daily mood profiles during intervention. We tested direct effects of intervention and indirect effects through changes in serotonin transporter binding on verbal affective memory, simple reaction time and self-reported measures of mental distress, and further effects of GnRHa on daily mood.

RESULTS

GnRHa induced an increase in simple reaction time (p=0.03) and more pronounced fluctuations in daily self-reported mood in a manner dependent on baseline mood (p=0.003). Verbal affective memory recall, overall self-perceived mental distress, and serotonin transporter binding were not affected.

CONCLUSIONS

In healthy women transient sex-steroid hormone fluctuations decrease speed of information processing and further produce more labile mood only in women with elevated levels of mood disturbances at baseline.

Evaluation of acute tryptophan depletion and sham depletion with a gelatin-based collagen peptide protein mixture

Acute Tryptophan Depletion (ATD) is a dietary method used to modulate central 5-HT to study the effects of temporarily reduced 5-HT synthesis. The aim of this study is to evaluate a novel method of ATD using a gelatin-based collagen peptide (CP) mixture. We administered CP-Trp or CP+Trp mixtures to 29 healthy volunteers; 13 from a randomized, double-blinded crossover study and sixteen from a randomized, double-blinded study run in our laboratory. Plasma amino acids, mood, side effects, cortisol concentrations, mean arterial blood pressure and heart rate were measured at multiple time-points. Repeated measures analysis of variance and Wilcoxon or Mann-Whitney U non-parametric tests were used to analyze the effects of intervention. Intake of the CP-Trp mixture efficiently reduced plasma Trp; however, the CP+Trp mixture induced a large significant increase in plasma Trp. No other significant effects of CP-Trp compared to CP+Trp were observed. The transient increase in plasma Trp after CP+Trp may impair comparison to the CP-Trp and we therefore recommend in future studies to use a smaller dose of Trp supplement to the CP mixture.

The Center for Integrated Molecular Brain Imaging (Cimbi) database

We here describe a multimodality neuroimaging containing data from healthy volunteers and patients, acquired within the Lundbeck Foundation Center for Integrated Molecular Brain Imaging (Cimbi) in Copenhagen, Denmark. The data is of particular relevance for neurobiological research questions related to the serotonergic transmitter system with its normative data on the serotonergic subtype receptors 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT4 and the 5-HT transporter (5-HTT), but can easily serve other purposes. The Cimbi database and Cimbi biobank were formally established in 2008 with the purpose to store the wealth of Cimbi-acquired data in a highly structured and standardized manner in accordance with the regulations issued by the Danish Data Protection Agency as well as to provide a quality-controlled resource for future hypothesis-generating and hypothesis-driven studies. The Cimbi database currently comprises a total of 1100 PET and 1000 structural and functional MRI scans and it holds a multitude of additional data, such as genetic and biochemical data, and scores from 17 self-reported questionnaires and from 11 neuropsychological paper/computer tests. The database associated Cimbi biobank currently contains blood and in some instances saliva samples from about 500 healthy volunteers and 300 patients with e.g., major depression, dementia, substance abuse, obesity, and impulsive aggression. Data continue to be added to the Cimbi database and biobank.

Personality characteristics in surgery seeking and non-surgery seeking obese individuals compared to non-obese controls

It is currently unknown what makes some obese individuals opt for bariatric surgery whereas others choose not to. The aim of this study was to examine whether personality characteristics differed between obese individuals signed up for Roux-en-Y gastric bypass (RYGB) (N=30) and obese individuals not seeking RYGB (N=30) compared to non-obese controls (N=30). All participants completed the NEO Personality Inventory-Revised. The obese RYGB group displayed higher levels of Neuroticism and borderline lower levels of Extraversion compared to the obese non-RYGB and the non-obese group, while the two latter groups did not differ in terms of personality. The Neuroticism domain and possibly the Extraversion domain may therefore be worthwhile to consider in future studies investigating the outcome of bariatric surgery.