Expectation and dopamine release: mechanism of the placebo effect in Parkinson's disease

Short-Term Cannabidiol with Δ-9-Tetrahydrocannabinol in Parkinson's Disease: A Randomized Trial

BACKGROUND

Cannabis use is frequent in Parkinson's disease (PD), despite inadequate evidence of benefits and risks.

OBJECTIVE

The aim is to study short-term efficacy and tolerability of relatively high cannabidiol (CBD)/low Δ-9-tetrahydrocannabinol (THC) to provide preliminary data for a longer trial.

METHODS

Persons with PD with ≥20 on motor Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) who had negative cannabis testing took cannabis extract (National Institute of Drug Abuse) oral sesame oil solution for 2 weeks, increasing to final dose of 2.5 mg/kg/day. Primary outcome was change in motor MDS-UPDRS from baseline to final dose.

RESULTS

Participants were randomized to CBD/THC (n = 31) or placebo (n = 30). Mean final dose (CBD/THC group) was 191.8 ± 48.9 mg CBD and 6.4 ± 1.6 mg THC daily. Motor MDS-UPDRS was reduced by 4.57 (95% CI, -8.11 to -1.03; P = 0.013) in CBD/THC group, and 2.77 (-4.92 to -0.61; P = 0.014) in placebo; the difference between groups was non-significant: -1.80 (-5.88 to 2.27; P = 0.379). Several assessments had a strong placebo response. Sleep, cognition, and activities of daily living showed a treatment effect, favoring placebo. Overall adverse events were mild and reported more in CBD/THC than placebo group. On 2.5 mg/kg/day CBD plasma level was 54.0 ± 33.8 ng/mL; THC 1.06 ± 0.91 ng/mL.

CONCLUSIONS

The brief duration and strong placebo response limits interpretation of effects, but there was no benefit, perhaps worsened cognition and sleep, and there was many mild adverse events. Longer duration high quality trials that monitor cannabinoid concentrations are essential and would require improved availability of research cannabinoid products in the United States. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Placebo Effects Are Small on Average in the 7.5% CO2 Inhalational Model of Generalized Anxiety

BACKGROUND

Anxiety disorders are highly prevalent and socio-economically costly. Novel pharmacological treatments for these disorders are needed because many patients do not respond to current agents or experience unwanted side effects. However, a barrier to treatment development is the variable and large placebo response rate seen in trials of novel anxiolytics. Despite this, the mechanisms that drive placebo responses in anxiety disorders have been little investigated, possibly due to low availability of convenient experimental paradigms. We aimed to develop and test a novel protocol for inducing placebo anxiolysis in the 7.5% CO2 inhalational model of generalized anxiety in healthy volunteers.

METHODS

Following a baseline 20-minute CO2 challenge, 32 healthy volunteers were administered a placebo intranasal spray labelled as either the anxiolytic "lorazepam" or "saline." Following this, participants surreptitiously underwent a 20-minute inhalation of normal air. Post-conditioning, a second dose of the placebo was administered, after which participants completed another CO2 challenge.

RESULTS

Participants administered sham "lorazepam" reported significant positive expectations of reduced anxiety (P = .001), but there was no group-level placebo effect on anxiety following CO2 challenge post-conditioning (Ps > .350). Surprisingly, we found many participants exhibited unexpected worsening of anxiety, despite positive expectations.

CONCLUSIONS

Contrary to our hypothesis, our novel paradigm did not induce a placebo response, on average. It is possible that effects of 7.5% CO2 inhalation on prefrontal cortex function or behavior in line with a Bayesian predictive coding framework attenuated the effect of expectations on subsequent placebo response. Future studies are needed to explore these possibilities.

Novel ultrasound neuromodulation therapy with transcranial pulse stimulation (TPS) in Parkinson's disease: a first retrospective analysis

BACKGROUND

Transcranial Pulse Stimulation (TPS) has been recently introduced as a novel ultrasound neuromodulation therapy with the potential to stimulate the human brain in a focal and targeted manner. Here, we present a first retrospective analysis of TPS as an add-on therapy for Parkinson's disease (PD), focusing on feasibility, safety, and clinical effects. We also discuss the placebo response in non-invasive brain stimulation studies as an important context.

METHODS

This retrospective clinical data analysis included 20 PD patients who received ten sessions of TPS intervention focused on the individual motor network. Safety evaluations were conducted throughout the intervention period. We analyzed changes in motor symptoms before and after TPS treatment using Unified Parkinson's Disease Rating Scale part III (UPDRS-III).

RESULTS

We found significant improvement in UPDRS-III scores after treatment compared to baseline (pre-TPS: 16.70 ± 8.85, post-TPS: 12.95 ± 8.55; p < 0.001; Cohen's d = 1.38). Adverse events monitoring revealed no major side effects.

CONCLUSION

These preliminary findings suggest that TPS can further improve motor symptoms in PD patients already on optimized standard therapy. Findings have to be evaluated in context with the current literature on placebo effects.

Sham surgery for the trialing of cell-based therapies to the CNS may not be necessary

Sham surgery is often required for cell therapies adopting a randomized placebo-controlled double-blinded trial design. Using the case of dopamine neuron therapy for Parkinson's disease, we argue that alternative trial designs should be considered instead, for several reasons relating to ethics, patient burden, ease of unblinding, and cost.

How brain structure-function decoupling supports individual cognition and its molecular mechanism

Functional signals emerge from the structural network, supporting multiple cognitive processes through underlying molecular mechanism. The link between human brain structure and function is region-specific and hierarchical across the neocortex. However, the relationship between hierarchical structure-function decoupling and the manifestation of individual behavior and cognition, along with the significance of the functional systems involved, and the specific molecular mechanism underlying structure-function decoupling remain incompletely characterized. Here, we used the structural-decoupling index (SDI) to quantify the dependency of functional signals on the structural connectome using a significantly larger cohort of healthy subjects. Canonical correlation analysis (CCA) was utilized to assess the general multivariate correlation pattern between region-specific SDIs across the whole brain and multiple cognitive traits. Then, we predicted five composite cognitive scores resulting from multivariate analysis using SDIs in primary networks, association networks, and all networks, respectively. Finally, we explored the molecular mechanism related to SDI by investigating its genetic factors and relationship with neurotransmitter receptors/transporters. We demonstrated that structure-function decoupling is hierarchical across the neocortex, spanning from primary networks to association networks. We revealed better performance in cognition prediction is achieved by using high-level hierarchical SDIs, with varying significance of different brain regions in predicting cognitive processes. We found that the SDIs were associated with the gene expression level of several receptor-related terms, and we also found the spatial distributions of four receptors/transporters significantly correlated with SDIs, namely D2, NET, MOR, and mGluR5, which play an important role in the flexibility of neuronal function. Collectively, our findings corroborate the association between hierarchical macroscale structure-function decoupling and individual cognition and provide implications for comprehending the molecular mechanism of structure-function decoupling. PRACTITIONER POINTS: Structure-function decoupling is hierarchical across the neocortex, spanning from primary networks to association networks. High-level hierarchical structure-function decoupling contributes much more than low-level decoupling to individual cognition. Structure-function decoupling could be regulated by genes associated with pivotal receptors that are crucial for neuronal function flexibility.

Placebo effects in mental health disorders: protocol for an umbrella review

INTRODUCTION

Given the high prevalence of mental health disorders and their significant socioeconomic burden, there is a need to develop improved treatments, and to evaluate them through placebo-controlled trials. However, the magnitude of the placebo response in randomised controlled trials to test medications may be substantial, affecting their interpretation. Therefore, improved understanding of the patient, trial and mental disorder factors that influence placebo responses would inform clinical trial design to better detect active treatment effects. There is a growing literature exploring the placebo response within specific mental health disorders, but no overarching synthesis of this research has been produced to date. We present a protocol for an umbrella review of systematic reviews and/or meta-analyses in which we aim to understand the effect size and potential predictors of placebo response within, and across, mental health disorders.

METHODS AND ANALYSIS

We will systematically search databases (Medline, PsycINFO, EMBASE+EMBASE Classic, Web of Knowledge) for systematic reviews and/or meta-analyses that report placebo effect size in clinical trials in patients with mental health disorders (initial search date 23 October 2022). Screening of abstracts and full texts will be done in pairs. We will extract data to qualitatively examine how placebo effect size varies across mental health disorders. We also plan to qualitatively summarise predictors of increased placebo response identified either quantitatively (eg, through meta-regression) or qualitatively. Risk of bias will be assessed using the AMSTAR-2 tool. We aim to not only summarise the current literature but also to identify gaps in knowledge and generate further hypotheses.

ETHICS AND DISSEMINATION

We do not believe there are any specific ethical considerations relevant to this study. We will publish the results in a peer-reviewed journal.

Role of expectations in clinical outcomes after deep brain stimulation in patients with Parkinson's disease: a systematic review

Deep brain stimulation (DBS) is a well-established treatment that significantly improves the motor symptoms of patients with Parkinson's disease (PD); however, patients may experience post-operative psychological distress and social maladjustments. This phenomenon has been shown to be related to patients' pre-operative cognitive representations, such as expectations. In this systematic review, we discuss the findings on the role of the expectations of patients with PD regarding the clinical outcomes of DBS to identify areas of intervention to improve pre-operative patient education and promote successful post-operative psychosocial adjustment. PubMed was searched for relevant articles published up to 16 January 2023. Of the 84 identified records, 10 articles focusing on the treatment expectations of patients with PD undergoing DBS were included in this review. The selected studies were conducted among cohorts of patients with different DBS targets, among which the most common was the bilateral subthalamic nucleus. Overall, the data showed that patients' expectations contribute to treatment efficacy. Experiments investigating the placebo effect itself have shown clinical improvement after the induction of positive therapeutic expectations; conversely, unrealistic treatment expectations can affect patient satisfaction after surgery, clinical outcomes, and subjective well-being. This review highlights the need for routine clinical practice to better investigate and manage patients' pre-operative expectations, as well as multidisciplinary education to improve patient satisfaction and psychosocial adjustment after DBS.

Placebo Effect and Its Determinants in Ocular Hypotensive Therapy: Meta-analysis and Multiple Meta-regression Analysis

TOPIC

The placebo effect and its potential determinants in ocular hypotensive therapy.

CLINICAL RELEVANCE

The placebo effect has been studied and documented within a wide clinical context. It remains unclear whether placebo is effective in glaucoma treatment or, if so, which factors are determinative of effect size (ES).

METHODS

Randomized controlled trials (RCTs) of topical ocular hypotensive therapy for patients with open-angle glaucoma or ocular hypertension, conducted through June 2, 2022, were included. First, a perceived placebo effect was measured as the overall intraocular pressure (IOP) change from the baseline. It was evaluated in terms of the ES (mean difference between the baseline and the end point) and then was compared with the ES, as obtained from the untreated control participant to obtain a true placebo effect. The primary outcome was ES based on 4 weeks of treatment. Meta-analysis-based statistical pooling was performed where appropriate, and 95% confidence intervals (CIs) were used for comparison. Potential placebo effect determinants were scrutinized using a multiple meta-regression model (PROSPERO identifier, CRD42022348098).

RESULTS

A total of 40 RCTs (7829 eyes) with 33 placebo groups (2055 eyes) along with 7 untreated groups (1184 eyes) were included. Among placebo-controlled trials, placebo was determined to be effective in lowering IOP (ES, -1.30 mmHg; 95% CI, -1.75 to -0.84 mmHg). Using NMA, the ES for placebo was -2.27 mmHg (95% CI, -3.52 to -1.01 mmHg) greater than ES for untreated control participants.. According to the multiple meta-regression model, the active treatment ES was a significant factor to predict the amount of placebo effect. Placebo additionally lowered IOP by -0.45 mmHg per -1 mmHg of active treatment effect. Add-on study design and larger sample size also were associated with greater amount of placebo effect. No publication bias was evident in either a funnel plot or the Begg and Mazumdar adjusted rank correlation test results (P = 0.24).

DISCUSSION

This meta-analysis indicated that placebo is effective in lowering IOP and is superior to the effect observed for the untreated control participants. However, caution is required in interpreting the results because of the small number of untreated controlled trials and potential bias from the lack of direct comparison between the placebo and untreated arms.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

How Do Expectations Modulate Pain? A Motivational Perspective

Expectations can profoundly modulate pain experience, during which the periaqueductal gray (PAG) plays a pivotal role. In this article, we focus on motivationally evoked neural activations in cortical and brainstem regions both before and during stimulus administration, as has been demonstrated by experimental studies on pain-modulatory effects of expectations, in the hope of unraveling how the PAG is involved in descending and ascending nociceptive processes. This motivational perspective on expectancy effects on the perception of noxious stimuli sheds new light on psychological and neuronal substrates of pain and its modulation, thus having important research and clinical implications.

Functional Brain Networks to Evaluate Treatment Responses in Parkinson's Disease

Network analysis of functional brain scans acquired with [18F]-fluorodeoxyglucose positron emission tomography (FDG PET, to map cerebral glucose metabolism), or resting-state functional magnetic resonance imaging (rs-fMRI, to map blood oxygen level-dependent brain activity) has increasingly been used to identify and validate reproducible circuit abnormalities associated with neurodegenerative disorders such as Parkinson's disease (PD). In addition to serving as imaging markers of the underlying disease process, these networks can be used singly or in combination as an adjunct to clinical diagnosis and as a screening tool for therapeutics trials. Disease networks can also be used to measure rates of progression in natural history studies and to assess treatment responses in individual subjects. Recent imaging studies in PD subjects scanned before and after treatment have revealed therapeutic effects beyond the modulation of established disease networks. Rather, other mechanisms of action may be at play, such as the induction of novel functional brain networks directly by treatment. To date, specific treatment-induced networks have been described in association with novel interventions for PD such as subthalamic adeno-associated virus glutamic acid decarboxylase (AAV2-GAD) gene therapy, as well as sham surgery or oral placebo under blinded conditions. Indeed, changes in the expression of these networks with treatment have been found to correlate consistently with clinical outcome. In aggregate, these attributes suggest a role for functional brain networks as biomarkers in future clinical trials.

Longitudinal Meta-Analysis of Historical Parkinson's Disease Trials to Inform Future Trial Design

BACKGROUND

The outcome of clinical trials in neurodegeneration can be highly uncertain due to the presence of a strong placebo effect.

OBJECTIVES

To develop a longitudinal model that can enhance the success of future Parkinson's disease trials by quantifying trial-to-trial variations in placebo and active treatment response.

METHODS

A longitudinal model-based meta-analysis was conducted on the total score of Unified Parkinson's Disease Rating Scale (UPDRS) Parts 1, 2, and 3. The analysis included aggregate data from 66 arms (observational [4], placebo [28], or investigational-drug-treated [34]) from 4 observational studies and 17 interventional trials. Inter-study variabilities in key parameters were estimated. Residual variability was weighted by the size of study arms.

RESULTS

The baseline total UPDRS was estimated to average at 24.5 points. Disease score was estimated to worsen by 3.90 points/year for the duration of the treatments; whilst notably, arms with a lower baseline progressed faster. The model captured the transient nature of the placebo response and sustained symptomatic drug effect. Both placebo and drug effects peaked within 2 months; although, 1 year was needed to observe the full treatment difference. Across these studies, the progression rate varied by 59.4%, the half-life for offset of placebo response varied by 79.4%, and the amplitude for drug effect varied by 105.3%.

CONCLUSION

The longitudinal model-based meta-analysis describes UPDRS progression rate, captures the dynamics of the placebo response, quantifies the effect size of the available therapies, and sets the expectation of uncertainty for future trials. The findings provide informative priors to enhance the rigor and success of future trials of promising agents, including potential disease modifiers. © 2023 GSK. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Safety and efficacy of venglustat in GBA1-associated Parkinson's disease: an international, multicentre, double-blind, randomised, placebo-controlled, phase 2 trial

BACKGROUND

Variants in the GBA1 gene, which encodes lysosomal acid glucocerebrosidase, are among the most common genetic risk factors for Parkinson's disease and are associated with faster disease progression. The mechanisms involved are unresolved but might include accumulation of glucosylceramide. Venglustat is a brain-penetrant glucosylceramide synthase inhibitor that, in previous studies, reduced amounts of the glycosphingolipid. We aimed to assess the safety, efficacy, and target engagement of venglustat in people with early-stage Parkinson's disease carrying pathogenic GBA1 variants.

METHODS

MOVES-PD part 2 was a randomised, double-blinded, placebo-controlled phase 2 study done at 52 centres (academic sites, specialty clinics, and general neurology centres) in 16 countries. Eligible adults aged 18-80 years with Parkinson's disease (Hoehn and Yahr stage ≤2) and one or more GBA1 variants were randomly assigned using an interactive voice-response system (1:1) to 52 weeks of treatment with oral venglustat (15 mg/day) or matching placebo. Investigators, site personnel, participants, and their caregivers were masked to treatment allocation. The primary outcome measure was the change from baseline to 52 weeks in the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) parts II and III combined score (a higher score indicates greater impairment), and it was analysed in a modified intention-to-treat population (ie, all randomly assigned participants with a baseline and at least one post-baseline measurement during the treatment period). This study was registered with ClinicalTrials.gov (NCT02906020) and is closed to recruitment.

FINDINGS

Between Dec 15, 2016, and May 27, 2021, 221 participants were randomly assigned to venglustat (n=110) or placebo (n=111). The least squares mean change in MDS-UPDRS parts II and III combined score was 7·29 (SE 1·36) for venglustat (n=96) and 4·71 (SE 1·27) for placebo (n=105); the absolute difference between groups was 2·58 (95% CI -1·10 to 6·27; p=0·17). The most common treatment-emergent adverse events (TEAEs) were constipation and nausea (both were reported by 23 [21%] of 110 participants in the venglustat group and eight [7%] of 111 participants in the placebo group). Serious TEAEs were reported for 12 (11%) participants in each group. There was one death in the venglustat group owing to an unrelated cardiopulmonary arrest and there were no deaths in the placebo group.

INTERPRETATION

In people with GBA1-associated Parkinson's disease in our study, venglustat had a satisfactory safety profile but showed no beneficial treatment effect compared with placebo. These findings indicate that glucosylceramide synthase inhibition with venglustat might not be a viable therapeutic approach for GBA1-associated Parkinson's disease.

FUNDING

Sanofi.

Restless Legs Syndrome and Other Common Sleep-Related Movement Disorders

OBJECTIVE

This article reviews common sleep-related movement disorders, including their clinical description, epidemiology, pathophysiology (if known), and evaluation and management strategies. This article will provide the reader with a good foundation for approaching concerns that are suggestive of sleep-related movement disorders to properly evaluate and manage these conditions.

LATEST DEVELOPMENTS

α2δ Ligands, such as gabapentin enacarbil, can be used for the initial treatment of restless legs syndrome (RLS) or in those who cannot tolerate, or have developed augmentation to, dopamine agonists. Another option is the rotigotine patch, which has a 24-hour treatment window and may be beneficial for those who have developed augmentation with short-acting dopamine agonists. IV iron can improve RLS symptoms even in those whose serum ferritin level is between 75 ng/mL and 100 ng/mL. At serum ferritin levels greater than 75 ng/mL, oral iron will likely have minimal absorption or little effect on the improvement of RLS. Research has found an association between RLS and cardiovascular disease, particularly in people who have periodic limb movements of sleep.

ESSENTIAL POINTS

RLS is the most common sleep-related movement disorder. Its pathophysiology is likely a combination of central iron deficiency, dopamine overproduction, and possibly cortical excitation. Treatment includes oral or IV iron. Dopaminergic medications can be very effective but often lead to augmentation, which limits their long-term use. Other sleep-related movement disorders to be aware of are sleep-related rhythmic movement disorder, nocturnal muscle cramps, sleep-related propriospinal myoclonus, sleep bruxism, and benign myoclonus of infancy.

The Effect of Positive Therapeutic Communication on Pain (POPAIN) and Anxiety During Arterial Blood Gas Standardized Procedures in the Emergency Department Compared to Traditional Communication: Protocol for a Monocentric Randomized Controlled Trial

BACKGROUND

In the emergency department (ED), medical procedures, such as arterial blood gas (ABG) testing, can cause pain and high stress levels. However, ABG testing is a routine procedure assessing the severity of the patient's condition. To reduce the pain of ABG, several methods have been investigated without significant difference in pain perception. Communication, a key element of care, has shown a significant effect on pain perception. A positive communication strategy, including positive, kind, or reassuring words, can reduce pain perception, while negative words can raise this perception, causing discomfort, known as the "nocebo effect." Although some studies have compared the impact of verbal attitudes, particularly in anesthesia and mainly with staff already trained in hypnosis, to the best of our knowledge, none have investigated the effect of communication in the emergency setting, where patients may be more suggestible to the words used.

OBJECTIVE

In this study, we will investigate the effect of positive therapeutic communication on pain, anxiety, discomfort, and global satisfaction in patients requiring ABG compared to nocebo and neutral communication.

METHODS

A single-center, double-blind randomized controlled trial (RCT) with 3 parallel arms will be conducted with 249 patients requiring ABG during their ED visit. Patients will be randomly assigned to 1 of 3 groups before receiving ABG: positive communication group, negative communication (nocebo) group, or neutral communication (neutral) group. The communication and the words used by the physicians during hygiene preparation, artery location, and puncture will be imposed in each group. The study will be proposed to each patient corresponding to the inclusion criteria. The physicians will not be trained in hypnosis or in positive therapeutic communication. The procedure will be recorded with audio recorders to test its quality. Intention-to-treat analysis will be performed. The primary endpoint is the onset of pain. The secondary outcomes are patient comfort, patient anxiety, and global satisfaction of the patient with the communication strategy used.

RESULTS

On average, 2000 ABG procedures are performed each year in the EDs of hospitals. In this study, 249 patients are expected to be included. With a projected positive response rate of 80%, we intend to include 25 (10%) patients per month. The inclusion period began in April 2023 and will run until July 2024. We hope to publish the results of the study during the fall of 2024.

CONCLUSIONS

To the best of our knowledge, this study is the first RCT assessing the use of positive communication on pain and anxiety in patients undergoing the ABG procedure in the ED. A reduction in pain, discomfort, and anxiety is expected when using positive communication. If the results are positive, this could be useful to the medical community and encourage clinicians to monitor their communication during care.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05434169; https://clinicaltrials.gov/ct2/show/NCT05434169.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/42043.

Are there placebo or nocebo effects in balancing performance?

Placebo and nocebo effects could influence the perceived, actual, or both postural stabilities. Therefore, this experiment examined whether postural stability is susceptible to placebo and nocebo effects. Driven by expectations, these cognitions could influence the motor stability of people in physical rehabilitation and those with motion instability. We randomly assigned 78 participants to a placebo, nocebo, or control group. Then, we applied a sham sports cream with positive, negative, or neutral instructions about its impact on balance. Next, we tested postural stability with a modified version of the Modified Clinical Test of Sensory Interaction in Balance, including standard, proprioceptive, visual, and vestibular tests before and after the intervention. Further, we measured expected and perceived performance with visual analog scales and assessed trait anxiety, change in state anxiety, optimism, holistic thinking, persistence, and cooperation with questionnaires. The intervention did not affect actual test performances; similarly, trait and state variables and expectations did not have an impact. Furthermore, the experimental manipulation and trait and state variables did not significantly affect perceived performance. However, the association between expectation and perceived performance was strong (ϱ = 0.627, p < 0.001). These findings suggest that postural stability is not susceptible to placebo and nocebo influences. Still, there is a dissociation between objective and subjective performance, showing that expectations impact perceived but not actual performance, which could fuel motivation in rehabilitation settings.

Placebo effect on gait: a way to reduce the dual-task cost in older adults

The ability to perform two tasks simultaneously is essential for daily activities. In older adults, this ability is markedly reduced, as evidenced by the dual-task cost on gait. Preliminary evidences indicate that the dual-task cost can be influenced by different types of manipulations. Here, we explored the effectiveness of a new approach to reduce the dual-task cost, based on the placebo effect, a psychobiological phenomenon whereby a positive outcome follows the administration of an inert device thought to be effective. Thirty-five healthy older adults were asked to walk on a sensorized carpet (single-task condition) and to walk while counting backward (dual-task condition) in two sessions (pre-test and post-test). A placebo group, randomly selected, underwent sham transcranial direct current stimulation over the supraorbital areas between sessions, along with information about its positive effects on concentration and attention. A control group did not receive any intervention between sessions. The dual-task cost was significantly reduced in the placebo group at the post-test session compared to the pre-test for several gait parameters (Cohen's d > 1.43). At the post-test session, the dual-task cost was also lower in the placebo group than in the control group (d > 0.73). Cognitive (number of subtractions and number of errors) and subjective (perceived mental fatigability) variables remained stable across sessions. The reduced dual-task cost in the placebo group could indicate the ability to re-establish the allocation of attentional resources between tasks. These findings could contribute to the development of cognitive strategies that leverage positive expectations to boost motor control in older adults.

From Neurotransmitters to Networks: Transcending Organisational Hierarchies with Molecular-informed Functional Imaging

The human brain exhibits complex interactions across micro, meso-, and macro-scale organisational principles. Recent synergistic multi-modal approaches have begun to link micro-scale information to systems level dynamics, transcending organisational hierarchies and offering novel perspectives into the brain's function and dysfunction. Specifically, the distribution of micro-scale properties (such as receptor density or gene expression) can be mapped onto macro-scale measures from functional MRI to provide novel neurobiological insights. Methodological approaches to enrich functional imaging analyses with molecular information are rapidly evolving, with several streams of research having developed relatively independently, each offering unique potential to explore the trans-hierarchical functioning of the brain. Here, we address the three principal streams of research - spatial correlation, molecular-enriched network, and in-silico whole brain modelling analyses - to provide a critical overview of the different sources of molecular information, how this information can be utilised within analyses of fMRI data, the merits and pitfalls of each methodology, and, through the use of key examples, highlight their promise to shed new light on key domains of neuroscientific inquiry.

Effects of monotherapy with a monoamine oxidase B inhibitor on motor symptoms in Parkinson's disease are dependent on frontal function

BACKGROUND

Monotherapy with monoamine oxidase B (MAO-B) inhibitors enhances the level of endogenous dopamine in treatment for Parkinson's disease (PD) and provides some benefits. Certain neuropsychiatric functions are also regulated by central dopaminergic activity.

AIM

To investigate the relationship of the efficacy of monotherapy with MAO-B inhibitors on motor symptoms in PD with baseline cognitive function.

PATIENTS AND METHODS

Outcomes were examined for 27 consecutive drug-naïve PD patients who received initial treatment with a MAO-B inhibitor (selegiline: 11, rasagiline: 16). Selegiline was titrated to an optimal dose. The dose of rasagiline was fixed at 1 mg/day. Motor symptoms were assessed using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale part III before treatment and after the efficacy reached a plateau within 19 weeks after drug initiation, and the % improvement in motor symptoms was calculated. Pre-treatment cognitive function was assessed using the Montreal Cognitive Assessment (MoCA) and Frontal Assessment Battery (FAB). Correlations of % improvement in motor symptoms and baseline cognitive assessments were examined using Spearman correlation coefficients and multiple regression analysis.

RESULTS

In all patients, the mean % improvement in motor symptoms was 46.5% (range 0-83.3%). Spearman correlation coefficients showed the % improvement in motor symptoms was correlated with FAB (r = 0.631, p < 0.001). In multiple regression analysis with patient background factors as independent variables, only FAB was associated with improvement in motor symptoms in the MAO-B group.

CONCLUSION

Better FAB scores predict a significant improvement in motor symptoms with treatment with MAO-B inhibitors, suggesting high activity of endogenous dopamine.

Association between personality traits and placebo effects: a preregistered systematic review and meta-analysis

ABSTRACT

Placebo effects are ubiquitous yet highly variable between individuals and therefore strongly affect clinical trial outcomes such as pain relief. It is unclear whether dispositional psychological traits influence responsiveness to placebo. This preregistered meta-analysis and systematic review synthesized the literature investigating the association between personality traits and placebo effects. Based on 21 studies with 798 participants, we performed formal meta-analyses for 10 different personality traits, including behavioral inhibition, fun seeking, goal-drive persistence, reward responsiveness, empathic concern, empathic fantasy, perspective-taking, personal distress, optimism, and anxiety. We did not find evidence of associations between any of these traits and magnitude of placebo effects, which was supported by equivalence tests. Furthermore, we did not find evidence for moderating factors such as placebo manipulation type (conditioning or nonconditioning) or condition (pain or nonpain). These findings challenge the notion that personality influences responsiveness to placebos and contradict its utility for identifying placebo "responders" and "nonresponders."

Combined metabolic activators improve cognitive functions in Alzheimer's disease patients: a randomised, double-blinded, placebo-controlled phase-II trial

BACKGROUND

Alzheimer's disease (AD) is associated with metabolic abnormalities linked to critical elements of neurodegeneration. We recently administered combined metabolic activators (CMA) to the AD rat model and observed that CMA improves the AD-associated histological parameters in the animals. CMA promotes mitochondrial fatty acid uptake from the cytosol, facilitates fatty acid oxidation in the mitochondria, and alleviates oxidative stress.

METHODS

Here, we designed a randomised, double-blinded, placebo-controlled phase-II clinical trial and studied the effect of CMA administration on the global metabolism of AD patients. One-dose CMA included 12.35 g L-serine (61.75%), 1 g nicotinamide riboside (5%), 2.55 g N-acetyl-L-cysteine (12.75%), and 3.73 g L-carnitine tartrate (18.65%). AD patients received one dose of CMA or placebo daily during the first 28 days and twice daily between day 28 and day 84. The primary endpoint was the difference in the cognitive function and daily living activity scores between the placebo and the treatment arms. The secondary aim of this study was to evaluate the safety and tolerability of CMA. A comprehensive plasma metabolome and proteome analysis was also performed to evaluate the efficacy of the CMA in AD patients.

RESULTS

We showed a significant decrease of AD Assessment Scale-cognitive subscale (ADAS-Cog) score on day 84 vs day 0 (P = 0.00001, 29% improvement) in the CMA group. Moreover, there was a significant decline (P = 0.0073) in ADAS-Cog scores (improvement of cognitive functions) in the CMA compared to the placebo group in patients with higher ADAS-Cog scores. Improved cognitive functions in AD patients were supported by the relevant alterations in the hippocampal volumes and cortical thickness based on imaging analysis. Moreover, the plasma levels of proteins and metabolites associated with NAD + and glutathione metabolism were significantly improved after CMA treatment.

CONCLUSION

Our results indicate that treatment of AD patients with CMA can lead to enhanced cognitive functions and improved clinical parameters associated with phenomics, metabolomics, proteomics and imaging analysis. Trial registration ClinicalTrials.gov NCT04044131 Registered 17 July 2019, https://clinicaltrials.gov/ct2/show/NCT04044131.

The effect of whole body vibration on gait stability in individuals with Parkinson's disease: a preliminary study

Background/Aims

Whole body vibration could benefit functional mobility in people with Parkinson's disease. A preliminary study was undertaken to analyse the acute effect of whole body vibration on unobstructed walking and obstacle circumvention in people with Parkinson's disease.

Methods

People with Parkinson's disease and typically healthy individuals as matched controls were divided into four groups with nine individuals in each: experimental or placebo for people with Parkinson's disease and experimental or placebo for the control group. The participants were evaluated in two different gait conditions: unobstructed walking and obstacle circumvention. Then the participants undertook a session of whole body vibration on a KIKOS P201 lateral vibratory platform in two positions: feet shoulder-width apart, and feet shoulder-width apart with slightly flexed knees. The participants were re-evaluated after this session.

Results

After whole body vibration, those in the experimental Parkinson's disease group had a reduced co-contraction of the tibialis anterior and the gastrocnemius lateralis muscles during unobstructed walking, whereas the co-contraction of the tibialis anterior and the gastrocnemius lateralis muscles increased in the experimental control group. In addition, those in the experimental control group had reduced stride duration in unobstructed walking and in obstacle circumvention. After the placebo intervention, the co-contraction of the tibialis anterior and the gastrocnemius lateralis muscles increased in all conditions and stride duration was reduced in unobstructed walking.

Conclusions

Although whole body vibration had no acute efficiency on gait (unobstructed walking and obstacle circumvention), it can improve other components, such as strength, which could be important for people with Parkinson's disease.

Placebo and nocebo effects: from observation to harnessing and clinical application

Placebo and nocebo effects are salubrious benefits and negative outcomes attributable to non-specific symbolic components. Leveraging advanced experimental and analytical approaches, recent studies have elucidated complicated neural mechanisms that may serve as a solid basis for harnessing the powerful self-healing and self-harming capacities and applying these findings to improve medical practice and minimize the unintended exacerbation of symptoms in medical practice. We review advances in employing psychosocial, pharmacological, and neuromodulation approaches to modulate/harness placebo and nocebo effects. While these approaches show promising potential, translating these research findings into clinical settings still requires careful methodological, technical, and ethical considerations.

High throughput 3D gel-based neural organotypic model for cellular assays using fluorescence biosensors

Three-dimensional (3D) organotypic models that capture native-like physiological features of tissues are being pursued as clinically predictive assays for therapeutics development. A range of these models are being developed to mimic brain morphology, physiology, and pathology of neurological diseases. Biofabrication of 3D gel-based cellular systems is emerging as a versatile technology to produce spatially and cell-type tailored, physiologically complex and native-like tissue models. Here we produce 3D fibrin gel-based functional neural co-culture models with human-iPSC differentiated dopaminergic or glutamatergic neurons and astrocytes. We further introduce genetically encoded fluorescence biosensors and optogenetics activation for real time functional measurements of intracellular calcium and levels of dopamine and glutamate neurotransmitters, in a high-throughput compatible plate format. We use pharmacological perturbations to demonstrate that the drug responses of 3D gel-based neural models are like those expected from in-vivo data, and in some cases, in contrast to those observed in the equivalent 2D neural models.

Fibrin gel-based 3D co-culture models with human-iPSC differentiated dopaminergic or glutamatergic neurons and astrocytes are shown to be functional using biosensors and can be scaled up for high-throughput assays.

The reward for placebos: mechanisms underpinning placebo-induced effects on motor performance

Different from the most popular thinking, the placebo effect is not a purely psychological phenomenon. A body of knowledge from multidisciplinary fields has shown that the expectation of a potential benefit when receiving a treatment induces a cascade of neurochemical-electrophysiological alterations in brain reward areas, including motor-related ones. Alterations in the dopamine, opioid, and glutamate metabolism are the neural representation converting reward-derived declarative forms into an attractive and wanted behavior, thereby changing the activation in reward subcortical and cortical structures involved in motor planning, motor execution, and emotional-cognitive attributes of decision-making. We propose that the expectation of receiving a treatment that is beneficial to motor performance triggers a cascade of activations in brain reward areas that travels from motor planning and motor command areas, passing through corticospinal pathways until driving the skeletal muscles, therefore facilitating the motor performance. Although alternative explanations cannot be totally ruled out, this mechanistic route is robust in explaining the results of placebo-induced effects on motor performance and could lead to novel insights and applications in the exercise sciences. Factors such as sex differences in reward-related mechanisms and aversion-induced nocebo effects should also be addressed.

Imaging Dopaminergic Neurotransmission in Neurodegenerative Disorders

Imaging of dopaminergic transmission in neurodegenerative disorders such as Parkinson disease (PD) or dementia with Lewy bodies plays a major role in clinical practice and in clinical research. We here review the role of imaging of the nigrostriatal pathway, as well as of striatal receptors and dopamine release, in common neurodegenerative disorders in clinical practice and research. Imaging of the nigrostriatal pathway has a high diagnostic accuracy to detect nigrostriatal degeneration in disorders characterized by nigrostriatal degeneration, such as PD and dementia with Lewy bodies, and disorders of more clinical importance, namely in patients with clinically uncertain parkinsonism. Imaging of striatal dopamine D2/3 receptors is not recommended for the differential diagnosis of parkinsonian disorders in clinical practice anymore. Regarding research, recently the European Medicines Agency has qualified dopamine transporter imaging as an enrichment biomarker for clinical trials in early PD, which underlines the high diagnostic accuracy of this imaging tool and will be implemented in future trials. Also, imaging of the presynaptic dopaminergic system plays a major role in, for example, examining the extent of nigrostriatal degeneration in preclinical and premotor phases of neurodegenerative disorders and to examine subtypes of PD. Also, imaging of postsynaptic dopamine D2/3 receptors plays a role in studying, for example, the neuronal substrate of impulse control disorders in PD, as well as in measuring endogenous dopamine release to examine, for example, motor complications in the treatment of PD. Finally, novel MRI sequences as neuromelanin-sensitive MRI are promising new tools to study nigrostriatal degeneration in vivo.

Oxytocin and the social facilitation of placebo effects

Significant clinical improvement is often observed in patients who receive placebo treatment in randomized double-blind placebo-controlled trials. While a proportion of this "improvement" reflects experimental design limitations (e.g., reliance on subjective outcomes, unbalanced groups, reporting biases), some of it reflects genuine improvement corroborated by physiological change. Converging evidence across diverse medical conditions suggests that clinically-relevant benefits from placebo treatment are associated with the activation of brain reward circuits. In parallel, evidence has accumulated showing that such benefits are facilitated by clinicians that demonstrate warmth and proficiency during interactions with patients. Here, we integrate research on these neural and social aspects of placebo effects with evidence linking oxytocin and social reward to advance a neurobiological account for the social facilitation of placebo effects. This account frames oxytocin as a key mediator of treatment success across a wide-spectrum of interventions that increase social connectedness, thereby providing a biological basis for assessing this fundamental non-specific element of medical care.

Vinyl as Fine Wine: The Role of Expectation on the Perception of Music Format

While vinyl, compact discs, and even eight-track tapes were traditionally promoted to consumers as producing superior sound, the introduction of compressed digital music, such as mp3s, was markedly different. Initially, one of the primary selling features of digital music was convenience and portability rather than sound quality. Recently, vinyl music sales have experienced a substantial resurgence. Waveforms from vinyl represent recorded music more accurately than compressed digital formats and have the potential to produce better sound. Even so, most music listeners do not reliably listen to music on audiophile quality high-end equipment. For this reason, we believe one aspect of vinyl sales is the expectation that vinyl quality is superior. In this study, we sought to isolate the contribution of expectation to perceived sound quality. Participants were asked to listen to a selection of music on either vinyl or mp3. Some participants were told that they were listening to vinyl when the musical selection was an mp3, while others were told they were listening to an mp3 while actually listening to vinyl. A multivariate analysis through a Canonical Correlation Analysis established that expectation of music format quality drove post-listening evaluations.

Non-invasive brain stimulation and neuroenhancement

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The available data frame with a wide parameter space of tES does not allow an overarching protocol recommendation.

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Established engineering risk-management procedures with regard to manufacturing should be followed.

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Consensus among experts is that tES for neuroenhancement is safe as long as tested protocols are followed.

Attempts to enhance human memory and learning ability have a long tradition in science. This topic has recently gained substantial attention because of the increasing percentage of older individuals worldwide and the predicted rise of age-associated cognitive decline in brain functions. Transcranial brain stimulation methods, such as transcranial magnetic (TMS) and transcranial electric (tES) stimulation, have been extensively used in an effort to improve cognitive functions in humans.

Here we summarize the available data on low-intensity tES for this purpose, in comparison to repetitive TMS and some pharmacological agents, such as caffeine and nicotine. There is no single area in the brain stimulation field in which only positive outcomes have been reported. For self-directed tES devices, how to restrict variability with regard to efficacy is an essential aspect of device design and function. As with any technique, reproducible outcomes depend on the equipment and how well this is matched to the experience and skill of the operator. For self-administered non-invasive brain stimulation, this requires device designs that rigorously incorporate human operator factors. The wide parameter space of non-invasive brain stimulation, including dose (e.g., duration, intensity (current density), number of repetitions), inclusion/exclusion (e.g., subject’s age), and homeostatic effects, administration of tasks before and during stimulation, and, most importantly, placebo or nocebo effects, have to be taken into account. The outcomes of stimulation are expected to depend on these parameters and should be strictly controlled. The consensus among experts is that low-intensity tES is safe as long as tested and accepted protocols (including, for example, dose, inclusion/exclusion) are followed and devices are used which follow established engineering risk-management procedures. Devices and protocols that allow stimulation outside these parameters cannot claim to be “safe” where they are applying stimulation beyond that examined in published studies that also investigated potential side effects.

Brain stimulation devices marketed for consumer use are distinct from medical devices because they do not make medical claims and are therefore not necessarily subject to the same level of regulation as medical devices (i.e., by government agencies tasked with regulating medical devices). Manufacturers must follow ethical and best practices in marketing tES stimulators, including not misleading users by referencing effects from human trials using devices and protocols not similar to theirs.

Effects of Immediate Aversive Stimulation on Haloperidol-Induced Catalepsy in Rats

In animal models, the administration of the dopaminergic D2 antagonist haloperidol affects the nigrostriatal pathway, inducing catalepsy, a state of immobility similar to Parkinson’s disease (PD) bradykinesia and akinesia. In PD, the motor impairments are due to difficulties in selecting and executing motor actions, associated with dopamine loss in basal ganglia and cortical targets. Motor and affective limbic networks seem to be integrated via a striato-nigro-striatal network, therefore, it is not surprising that the motor impairments in PD can be influenced by the patient’s emotional state. Indeed, when exposed to aversive stimuli or life-threatening events, immobile patients are capable of performing sudden movements, a phenomenon known as paradoxical kinesia. Thus, the present study investigated the effects of unconditioned and conditioned aversive stimulation on haloperidol-induced catalepsy in rats. First, male Wistar rats received intraperitoneal administration of saline or haloperidol (1 or 2 mg/kg) and were evaluated in the catalepsy bar test to assess the cataleptic state induced by the different doses of haloperidol over time. Next, we evaluated the effects of two types of unconditioned aversive stimuli–100 lux light (1 and 20 s) or 0.6 mA footshock (1 s)–on the catalepsy. Finally, we evaluated the effects of light conditioned stimuli (Light-CS), previously paired with footshocks, on the cataleptic state. Catalepsy was observed following haloperidol 1 and 2 mg/kg administration. Exposure to footshocks, but not to light, significantly reduced step-down latency during the catalepsy test. Although unconditioned light did not affect catalepsy, paired Light-CS did reduce step-down latency. Here, we have provided evidence of face validity for the study of paradoxical kinesia. In addition to demonstrating that immediate exposure to an aversive stimulus is capable of disrupting the cataleptic state, our findings show that haloperidol-induced catalepsy seems to be differently influenced depending on the modality of aversive stimulation. Our data suggest that the selective recruitment of threat response systems may bypass the dysfunctional motor circuit leading to the activation of alternative routes to drive movement.

Psycho-Neuro-Endocrine-Immunological Basis of the Placebo Effect: Potential Applications beyond Pain Therapy

The placebo effect can be defined as the improvement of symptoms in a patient after the administration of an innocuous substance in a context that induces expectations regarding its effects. During recent years, it has been discovered that the placebo response not only has neurobiological functions on analgesia, but that it is also capable of generating effects on the immune and endocrine systems. The possible integration of changes in different systems of the organism could favor the well-being of the individuals and go hand in hand with conventional treatment for multiple diseases. In this sense, classic conditioning and setting expectations stand out as psychological mechanisms implicated in the placebo effect. Recent advances in neuroimaging studies suggest a relationship between the placebo response and the opioid, cannabinoid, and monoaminergic systems. Likewise, a possible immune response conditioned by the placebo effect has been reported. There is evidence of immune suppression conditioned through the insular cortex and the amygdala, with noradrenalin as the responsible neurotransmitter. Finally, a conditioned response in the secretion of different hormones has been determined in different studies; however, the molecular mechanisms involved are not entirely known. Beyond studies about its mechanism of action, the placebo effect has proved to be useful in the clinical setting with promising results in the management of neurological, psychiatric, and immunologic disorders. However, more research is needed to better characterize its potential use. This review integrates current knowledge about the psycho-neuro-endocrine-immune basis of the placebo effect and its possible clinical applications.

Assessing preoperative hope and expectations related to functional neurosurgery: a new questionnaire

BACKGROUND

Despite successful functional neurosurgery, patients suffering from epilepsy or Parkinson's disease may experience postoperative psychological distress and social maladjustments. Difficulties in coping with postoperative changes, even positive ones, have shown to be related to patients' presurgery cognitive representations (i.e., expectations, hope). The aim of this study was to develop an instrument assessing various key features of surgery outcomes' representations, namely the Preoperative Hope and Expectations Questionnaire (PHEQ).

METHODS

Participants were patients (n = 50) diagnosed with Parkinson's disease (n = 25) or epilepsy (n = 25), candidates for functional neurosurgery (i.e., Deep brain stimulation, anterior temporal lobectomy). Two to three weeks before the planned surgery, they were administrated items assessing their actual state, preoperative expectations, and hope regarding surgery outcomes. They also completed measures assessing optimism, quality of life and mood.

RESULTS

Exploratory analysis resulted in a 14-item version of the PHEQ composed of two factors (abstract representations, including psychological well-being and concrete representations, such as direct surgery outcomes). The PHEQ demonstrated high internal consistency and good convergent validity. Patients were more prone to express postoperative improvements in terms of hope rather than expectations. They generally focused on concrete rather than abstract features, although patients with Parkinson's disease had higher abstract future-oriented representations.

CONCLUSIONS

The PHEQ presents satisfactory psychometric properties and may be considered as a reliable instrument for research and clinical practice.

Insight Into the Effects of Clinical Repetitive Transcranial Magnetic Stimulation on the Brain From Positron Emission Tomography and Magnetic Resonance Imaging Studies: A Narrative Review

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a therapeutic tool to alleviate symptoms for neurological and psychiatric diseases such as chronic pain, stroke, Parkinson’s disease, major depressive disorder, and others. Although the therapeutic potential of rTMS has been widely explored, the neurological basis of its effects is still not fully understood. Fortunately, the continuous development of imaging techniques has advanced our understanding of rTMS neurobiological underpinnings on the healthy and diseased brain. The objective of the current work is to summarize relevant findings from positron emission tomography (PET) and magnetic resonance imaging (MRI) techniques evaluating rTMS effects. We included studies that investigated the modulation of neurotransmission (evaluated with PET and magnetic resonance spectroscopy), brain activity (evaluated with PET), resting-state connectivity (evaluated with resting-state functional MRI), and microstructure (diffusion tensor imaging). Overall, results from imaging studies suggest that the effects of rTMS are complex and involve multiple neurotransmission systems, regions, and networks. The effects of stimulation seem to not only be dependent in the frequency used, but also in the participants characteristics such as disease progression. In patient populations, pre-stimulation evaluation was reported to predict responsiveness to stimulation, while post-stimulation neuroimaging measurements showed to be correlated with symptomatic improvement. These studies demonstrate the complexity of rTMS effects and highlight the relevance of imaging techniques.

Methodological Considerations for Setting Up Deep Brain Stimulation Studies for New Indications

Deep brain stimulation (DBS) is a neurosurgical treatment with a growing range of indications. The number of clinical studies is expanding because of DBS for new indications and efforts to improve DBS for existing indications. To date, various methods have been used to perform DBS studies. Designing a clinical intervention study with active implantable medical devices has specific challenges while expanding patient treatment. This paper provides an overview of the key aspects that are essential for setting up a DBS study.

Phasic firing of dopaminergic neurons in the ventral tegmental area triggers peripheral immune responses

Dopaminergic neurons in the ventral tegmental area (VTA) play a crucial role in the processing of reward-related information. Recent studies with pharmacological manipulations of VTA neuronal activity demonstrated a VTA-induced immunoenhancement in peripheral organs. Here, to examine the detailed physiological dynamics, we took an optogenetic approach in which VTA dopaminergic neurons were selectively activated with millisecond precision. Optogenetic phasic, rather than tonic, stimulation of VTA dopaminergic neurons increased serum cytokine levels, such as IL-2, IL-4 and TNF-α. These results provide direct evidence to link dopaminergic neuronal phasic firing to peripheral immunity. Next, we tested whether cytokine induction in male mice was boosted by female encounters, a natural condition that induces increased active VTA neurons and gamma power. Female encounters increased serum IL-2 levels, which were abolished by pharmacological inhibition of VTA neuronal activity. Taken together, our results highlight the importance of the brain reward system in the treatment and management of immune-related disorders.

Functional Neuroimaging Correlates of Placebo Response in Patients With Depressive or Anxiety Disorders: A Systematic Review

BACKGROUND

The mechanisms underlying placebo effects of psychotropic drugs remain poorly understood. We carried out the first, to our knowledge, systematic review of functional neuroimaging correlates of placebo response in adults with anxiety/depressive disorders.

METHODS

We systematically searched a large set of databases up to February 2021 based on a pre-registered protocol (PROSPERO CRD42019156911). We extracted neuroimaging data related to clinical improvement following placebo or related to placebo mechanisms. We did not perform a meta-analysis due to the small number of included studies and significant heterogeneity in study design and outcome measures.

RESULTS

We found 12 relevant studies for depressive disorders and 4 for anxiety disorders. Activity in the ventral striatum, rostral anterior cingulate cortex and other default mode network regions, orbitofrontal cortex, and dorsolateral prefrontal cortex correlated with placebo antidepressant responses. Activity in regions of the default mode network, including posterior cingulate cortex, was associated with placebo anxiolysis. There was also evidence for possible involvement of the endogenous opioid, dopamine, and serotonin systems in placebo antidepressant and anxiolytic effects.

CONCLUSIONS

Several brain regions and molecular systems may be involved in these placebo effects. Further adequately powered studies exploring causality and controlling for confounders are required.

The placebo and nocebo effects in functional urology

A placebo is an inert substance normally used in clinical trials for comparison with an active substance. However, a placebo has been shown to have an effect on its own; commonly known as the placebo effect. A placebo is an essential component in the design of conclusive clinical trials but has itself become the focus of intense research. The placebo effect is partly the result of positive expectations of the recipient on the state of health. Conversely, a nocebo effect is when negative expectations from a substance lead to poor treatment outcomes and/or adverse events. Randomized controlled trials in functional urology have demonstrated the importance of the placebo and nocebo effects across different diseases such as overactive bladder, urinary incontinence, lower urinary tract symptoms and interstitial cystitis/painful bladder syndrome, as well as male and female sexual dysfunction. Understanding the true nature of the placebo-nocebo complex and the scope of its effect in functional urology could help urologists to maximize the positive effects of this phenomenon while minimizing its potentially negative effects.

A candidate neuroimaging biomarker for detection of neurotransmission-related functional alterations and prediction of pharmacological analgesic response in chronic pain

Chronic pain is a world-wide clinical challenge. Response to analgesic treatment is limited and difficult to predict. Functional MRI has been suggested as a potential solution. However, while most analgesics target specific neurotransmission pathways, functional MRI-based biomarkers are not specific for any neurotransmitter system, limiting our understanding of how they might contribute to predict treatment response. Here, we sought to bridge this gap by applying Receptor-Enriched Analysis of Functional Connectivity by Targets to investigate whether neurotransmission-enriched functional connectivity mapping can provide insights into the brain mechanisms underlying chronic pain and inter-individual differences in analgesic response after a placebo or duloxetine. We performed secondary analyses of two openly available resting-state functional MRI data sets of 56 patients with chronic knee osteoarthritis pain who underwent pre-treatment brain scans in two clinical trials. Study 1 (n = 17) was a 2-week single-blinded placebo pill trial. Study 2 (n = 39) was a 3-month double-blinded randomized trial comparing placebo to duloxetine, a dual serotonin–noradrenaline reuptake inhibitor. Across two independent studies, we found that patients with chronic pain present alterations in the functional circuit related to the serotonin transporter, when compared with age-matched healthy controls. Placebo responders in Study 1 presented with higher pre-treatment functional connectivity enriched by the dopamine transporter compared to non-responders. Duloxetine responders presented with higher pre-treatment functional connectivity enriched by the serotonin and noradrenaline transporters when compared with non-responders. Neurotransmission-enriched functional connectivity mapping might hold promise as a new mechanistic-informed biomarker for functional brain alterations and prediction of response to pharmacological analgesia in chronic pain.

What is the role of placebo in neurotherapeutics?

INTRODUCTION

The widespread use of the word 'placebo' in the medical literature emphasizes the importance of this phenomenon in modern biomedical sciences. Neuroscientific research over the past thirty years shows that placebo effects are genuine psychobiological events attributable to the overall therapeutic context, and can be robust in both laboratory and clinical settings.

AREAS COVERED

Here the authors describe the biological mechanisms and the clinical implications of placebo effects with particular emphasis on neurology and psychiatry, for example in pain, movement disorders, depression. In these conditions, a number of endogenous systems have been identified, such as endogenous opioids, endocannabinoids, and dopamine, which contribute to the placebo-induced benefit.

EXPERT OPINION

Every effort should be made to maximize the placebo effect and reduce its evil twin, the nocebo effect, in medical practice. This does not require the administration of a placebo, but rather the enhancement of the effects of pharmacological and nonpharmacological treatments through a good doctor-patient interaction.

Safety and Tolerability of a Wearable, Vibrotactile Stimulation Device for Parkinson's Disease

Background: Resting tremor is a cardinal symptom of Parkinson’s disease (PD) that contributes to the physical, emotional, and economic burden of the disease.

Objective: The goal of this study was to investigate the safety, tolerability, and preliminary effectiveness of a novel wearable vibrotactile stimulation device on resting tremor in individuals with PD.

Methods: Using a randomized cross-over design, subjects received two different vibrotactile stimulation paradigms (high amplitude patterned and low amplitude continuous) on two separate laboratory visits. On each visit, resting tremor was video recorded for 10 min at baseline and while the vibrotactile stimulation was applied. Tremor severity was scored by a blinded clinician.

Results: Both vibration paradigms were well safe and well tolerated and resulted in a reduction in resting tremor severity with a moderate effect size (n = 44, p < 0.001, r = 0.37–0.54). There was no significant difference between the two vibration paradigms (p = 0.14).

Conclusion: Short durations of vibrotactile stimulation delivered via wearable devices were safe and well tolerated and may attenuate resting tremor severity in individuals with PD. The sample size as well as the potential preliminary effectiveness revealed by two arms of the study could not eliminate the potential for a placebo effect.

SERS of Dopamine: Computational and experimental studies

Computational and experimental studies have been carried out on Dopamine. The calculated Raman spectra of Dopamine with and without Silver clusters (Ag_n (n = 1-4)) are compared with each other and it is shown that the intensity of the Raman activity increases with increasing number of silver atoms. The SERS effect shown by this system is further supported by calculating the Global electrophilicity index ω, the static mean polarizability α₀, and the anisotropy of the polarizabilities Δα. Stabilities of the complexes are analysed using the charge transfer, stabilization energies, and interaction energies. The reactive parameters for these complexes were further supported by looking at the molecular electrostatic potential (MESP) surfaces. SERS substrates were fabricated by sintering silver nanoparticle paste onto a fused silica substrate, using a femtosecond laser. Detection of Dopamine up to 1 μM is reported using the SERS substrates.

A digital SERS sensing platform using 3D nanolaminate plasmonic crystals coupled with Au nanoparticles for accurate quantitative detection of dopamine

We report a digital surface-enhanced Raman spectroscopy (SERS) sensing platform using the arrays of 3D nanolaminate plasmonic crystals (NLPC) coupled with Au nanoparticles and digital (on/off) SERS signal analysis for the accurate quantitative detection of dopamine (DA) at ultralow concentrations. 3D NLPC SERS substrates were fabricated to support the optically dense arrays of vertically-stacked multi-nanogap hotspots and combined with Raman tag-conjugated Au nanoparticles for NLPC-based dual-recognition structures. We demonstrate that the 3D NLPC-based dual-recognition structures including Au nanoparticle-induced additional hotspots can enable more effective SERS enhancement through the molecular recognition of DA. For the accurate quantification of DA at ultralow concentrations, we conducted digital SERS analysis to reduce stochastic signal variation due to various microscopic effects, including molecular orientation/position variation and the spatial distribution of nanoparticle-coupled hotspots. The digital SERS analysis allowed the SERS mapping results from the DA-specific dual-recognition structures to be converted into binary "On/Off" states; the number of "On" events was directly correlated with low-abundance DA molecules down to 1 pM. Therefore, the digital SERS platform using the 3D NLPC-based dual-recognition structures coupled with Au nanoparticles and digital SERS signal analysis can be used not only for the ultrasensitive, accurate, and quantitative determination of DA, but also for the practical and rapid analysis of various molecules on nanostructured surfaces.

COMT by DRD3 Epistatic Interaction in Modulating Behaviors in Children with ADHD: A Pharmaco-Dynamic Behavioral Approach

OBJECTIVE

Examining the joint effect of two functional variants in two dopamine-related genes (DRD3 and COMT) on ADHD-relevant behaviors under three experimental conditions (EC).

METHOD

362 children with ADHD were assessed by parents and teachers during a week of baseline evaluation, followed by 1 week of MPH and placebo, administered in a double-blind crossover design.

RESULTS

Statistically significant 3-way (DRD3-by-COMT-by-EC; p = .004) and 2-way interactions (COMT by EC; p = .002) were observed on Conners'-Teachers scores. Children with the COMT Met/Met genotype had lower scores at baseline and on placebo compared to the other genotype groups. Furthermore, stratifying the children according to their COMT genotypes helped to detect statistically significant and biologically meaningful effects of DRD3 genotype.

CONCLUSIONS

These findings suggest that COMT and DRD3 genetic variants may together play a role in ADHD symptomatology and response to treatment through gene-gene interaction.

Thirty Years of Neuroscientific Investigation of Placebo and Nocebo: The Interesting, the Good, and the Bad

Over the past 30 years there has been a surge of research on the placebo effect using a neuroscientific approach. The interesting aspects of this effort are related to the identification of several biological mechanisms of both the placebo and nocebo effects, the latter of which is defined as a negative placebo effect. Some important translational implications have emerged both in the setting of clinical trials and in routine medical practice. One of the principal contributions of neuroscience has been to draw the attention of the scientific and medical communities to the important role of psychobiological factors in therapeutic outcomes, be they drug related or not. Indeed, many biological mechanisms triggered by placebos and nocebos resemble those modulated by drugs, suggesting a possible interaction between psychological factors and drug action. Unfortunately, this new knowledge regarding placebos has the potential of being dangerously exploited by pseudoscience. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

On the learning of addictive behavior: Sensation-seeking propensity predicts dopamine turnover in dorsal striatum

We asked if sensation-seeking is linked to premorbid personality characteristics in patients with addictive disorders, or the characteristics follow the sensation-seeking activity. We interpreted the former as a state associated with normal rates of dopamine synthesis, and the latter as a trait of individuals with abnormally high rates of synthesis. We previously determined dopaminergic receptor density in striatum, and we now tested the hypothesis that an elevated dopaminergic condition with increased extracellular dopamine and receptor density follows increased dopamine synthesis capacity in highly sensation-seeking individuals, as measured by positron emission tomography of 18 men with tracer fluorodopa (FDOPA). We detected a site in left caudate nucleus where the volume of distribution of FDOPA-derived metabolites correlated negatively with FDOPA metabolite turnover, consistent with decreased metabolite breakdown in highly sensation-seeking subjects. High rates of sensation-seeking attenuated the dopamine turnover in association with a low rate of dopamine recycling, low dopamine oxidation, and elevated extracellular dopamine and receptors in caudate nucleus. In contrast, low rates of sensation-seeking were associated with rapid dopamine recycling, rapid dopamine oxidation, low extracellular dopamine, and low receptor density. We conclude that the modulation of dopaminergic neurotransmission associated with sensation-seeking is a state of sensation-seeking, rather than a trait of personality following abnormal regulation of dopaminergic neurotransmission.

The role of superstition in the placebo effect on memory performance

Superstitions and the placebo effect have each been found to influence human behaviour. The present study aimed to determine whether there is a relationship between superstition and the placebo effect, and whether this relationship affects human cognition and behaviour. We hypothesized that more superstitious people would be more prone to the placebo effect and that it would improve their performance on cognitive tasks. Results showed that in the placebo condition, more superstitious people memorized more words than less superstitious people. However, in the control condition, less superstitious people memorized more words than more superstitious people. Overall, the findings supported our hypothesis. The findings of the study are important, as they draw a link between the placebo effect and superstition, and further show that these two elements impact human performance in cognitive ability tasks.

Placebos and Movies: What Do They Have in Common?

Placebos are fake therapies that can induce real therapeutic effects, called placebo effects. It goes without saying that what matters for inducing a placebo effect is not so much the fake treatment itself, but rather the therapeutic ritual that is carried out, which is capable of triggering psychobiological mechanisms in the patient’s brain. Both laypersons and scientists often accept the phenomenon of the placebo effect with reluctance, as fiction-induced clinical improvements are at odds with common sense. However, it should be emphasized that placebo effects are not surprising after all if one considers that fiction-induced physiological effects occur in everyday life. Movies provide one of the best examples of how fictitious reality can induce psychological and physiological responses, such as fear, love, and tears. In the same way that a horror movie induces fear-related physiological responses, even though the viewer knows everything is fake, so the sight of a syringe may trigger the release of pain-relieving chemicals in the patient’s brain, even if the patient knows there is a fake painkiller inside. From this perspective, placebos can be better conceptualized as rituals, actions, and fictions within a more general framework that emphasizes the power of psychological factors in everyday life, including the healing context.

The placebo phenomenon and the underlying mechanisms

The clinical role of the placebo effect is a topic of increasing interest for the scientific community. Focus is shifting from the inert role of placebos in randomized controlled trials (RCTs) to potential effects in clinical applications, since the phenomenon is thought to be inherent in routine clinical practice, affecting therapy success rates. Mediation of the mind-brain-body relationship involves both psychosocial and neurobiological factors, the interaction of which comprises the placebo mechanisms. Psychosocial factors include environmentally induced expectations, reward expectations, and even conditioned responses to certain stimuli. Expectations also depend on previous experience of the patient with a similar procedure and can affect future responses. Moreover, the supportive bedside behavior of the clinician and the positive framing of information provided to the patient have proven to be of great importance, setting the foundations for reconsideration of standardized practices. Neurobiological mechanisms mediate these effects through neurotransmitter and neuromodulator pathways. The best understood mechanisms are those regulating non-opioid- and opioid-mediated analgesic responses that implicate specific brain regions of pain control and activation of endogenous opioids. Other responses concern, among others, hormonal control, motor performance, and antidepressant responses. Although mechanisms underlying placebo responses are not as yet completely elucidated, there is substantial evidence suggesting that placebo effects are indicative of healthy functioning of intact brain structures and occur through actual functional changes, and are not simply subjective symptom reports. These effects can be utilized in treatment optimization while maintaining an ethical and respectful manner toward the patient and the standardized disclosure procedures.