A causal role for right temporo-parietal junction in signaling moral conflict

International audienceThe right temporo-parietal junction (rTPJ) has been proposed to play a key role in guiding human altruistic behavior, but its precise functional contribution to altruism remains unclear. We aimed to disentangle three possible functions of the rTPJ for human altruism, namely: implementing the motivation to help, signaling conflicts between moral and material values, or representing social reputation concerns. Our novel donation-decision task consisted of decisions requiring trade-offs of either positive moral values and monetary cost when donating to a good cause, or negative moral values and monetary benefits when sending money to a bad cause. Disrupting the rTPJ using transcranial magnetic stimulation did not change the general motivation to give or to react to social reputation cues, but specifically reduced the behavioral impact of moral-material conflicts. These findings reveal that signaling moral-material conflict is a core rTPJ mechanism that may contribute to a variety of human moral behaviors

Occipital transcranial direct current stimulation in episodic migraine patients: effect on cerebral perfusion

Cerebral blood flow differs between migraine patients and healthy controls during attack and the interictal period. This study compares the brain perfusion of episodic migraine patients and healthy controls and investigates the influence of anodal transcranial direct current stimulation (tDCS) over the occipital cortex. We included healthy adult controls and episodic migraineurs. After a 28-day baseline period and the baseline visit, migraine patients received daily active or sham anodal tDCS over the occipital lobe for 28 days. All participants underwent a MRI scan at baseline; migraineurs were also scanned shortly after the stimulation period and about five months later. At baseline, brain perfusion of migraine patients and controls differed in several areas; among the stimulated areas, perfusion was increased in the cuneus of healthy controls. At the first visit, the active tDCS group had an increased blood flow in regions processing visual stimuli and a decreased perfusion in other areas. Perfusion did not differ at the second follow-up visit. The lower perfusion level in migraineurs in the cuneus indicates a lower preactivation level. Anodal tDCS over the occipital cortex increases perfusion of several areas shortly after the stimulation period, but not 5 months later. An increase in the cortical preactivation level could mediate the transient reduction of the migraine frequency.Trial registration: NCT03237754 (registered at clincicaltrials.gov; full date of first trial registration: 03/08/2017)

Long-Term Effects of Self-Administered Transcranial Direct Current Stimulation in Episodic Migraine Prevention: Results of a Randomized Controlled Trial.

peer reviewed[en] BACKGROUND: Migraine is a multifactorial neurovascular disorder, which affects about 12% of the general population. In episodic migraine, the visual cortex revealed abnormal processing, most likely due to decreased preactivation level. Transcranial direct current stimulation (tDCS) is able to modify cortical excitability and might result in an alleviation of migraine occurrence if used repetitively. OBJECTIVE: To test the hypothesis that self-administered anodal tDCS over the visual cortex significantly decreases the number of monthly migraine days in episodic migraine. MATERIALS AND METHODS: The study was single-blind, randomized, and sham-controlled. Inclusion criteria were age 18-80 years and an ICHD-3 diagnosis of episodic migraine. Exclusion criteria were pregnancy, presence of a neurodegenerative disorder, a contraindication against MRI examinations, and less than two migraine days during the 28-day baseline period. Patients in whom the baseline period suggested chronic migraine were excluded. After baseline, participants applied daily either verum (anodal-1 mA to 20 min) or sham tDCS (anodal-1 mA to 30 sec) at Oz (reference Cz electrode) for 28 days. Headache diaries were used to record the number of migraine days at baseline, during the stimulation period, and during four subsequent 28-day periods. RESULTS: Twenty-eight patients were included; two were excluded after the baseline period because less than two migraine days occurred; three were excluded because their headache diaries suggested the diagnosis of chronic migraine. Twenty-three datasets were taken for further analysis. Compared to sham tDCS (n = 12), verum tDCS (n = 11) resulted in a lower number of migraine days (p = 0.010) across all follow-up periods. We found no significant change in total headache days (p = 0.165), anxiety (p = 0.884), or depression scores (p = 0.535). No serious adverse events occurred; minor side effects were similar in both groups. CONCLUSIONS: This study provides Class II evidence that self-administered anodal tDCS over the visual cortex in episodic migraine results in a significantly lower number of monthly migraine days. However, it has neither an immediate nor a long-term effect

A causal account of the brain network computations underlying strategic social behavior

During competitive interactions, humans have to estimate the impact of their own actions on their opponent's strategy. Here we provide evidence that neural computations in the right temporoparietal junction (rTPJ) and interconnected structures are causally involved in this process. By combining inhibitory continuous theta-burst transcranial magnetic stimulation with model-based functional MRI, we show that disrupting neural excitability in the rTPJ reduces behavioral and neural indices of mentalizing-related computations, as well as functional connectivity of the rTPJ with ventral and dorsal parts of the medial prefrontal cortex. These results provide a causal demonstration that neural computations instantiated in the rTPJ are neurobiological prerequisites for the ability to integrate opponent beliefs into strategic choice, through system-level interaction within the valuation and mentalizing networks

A checklist for assessing the methodological quality of concurrent tES-fMRI studies (ContES checklist): a consensus study and statement

Background: Low intensity transcranial electrical stimulation (tES), including alternating or direct current stimulation (tACS or tDCS), applies weak electrical stimulation to modulate the activity of brain circuits. Integration of tES with concurrent functional magnetic resonance imaging (fMRI) allows for the mapping of neural activity during neuromodulation, supporting causal studies of both brain function and tES effects. Methodological aspects of tES-fMRI studies underpin the results, and reporting them in appropriate detail is required for reproducibility and interpretability. Despite the growing number of published reports, there are no consensus-based checklists for disclosing methodological details of concurrent tES-fMRI studies. Objective: To develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency, and reproducibility (ContES Checklist). Methods: A two-phase Delphi consensus process was conducted by a steering committee (SC) of 13 members and 49 expert panelists (EP) through the International Network of the tES-fMRI (INTF) Consortium. The process began with a circulation of a preliminary checklist of essential items and additional recommendations, developed by the SC based on a systematic review of 57 concurrent tES-fMRI studies. Contributors were then invited to suggest revisions or additions to the initial checklist. After the revision phase, contributors rated the importance of the 17 essential items and 42 additional recommendations in the final checklist. The state of methodological transparency within the 57 reviewed concurrent tES-fMRI studies was then assessed using the checklist. Results: Experts refined the checklist through the revision and rating phases, leading to a checklist with three categories of essential items and additional recommendations: (1) technological factors, (2) safety and noise tests, and (3) methodological factors. The level of reporting of checklist items varied among the 57 concurrent tES-fMRI papers, ranging from 24% to 76%. On average, 53% of checklist items were reported in a given article. Conclusions: Use of the ContES checklist is expected to enhance the methodological reporting quality of future concurrent tES-fMRI studies, and increase methodological transparency and reproducibility

Methodologische Optimierung für kombinierte TMS und fMRT Anwendungen

Since 1997, when Bohning and colleagues demonstrated for the first time the feasibility of interleaving transcranial magnetic stimulation (TMS) with blood oxygenation level dependency functional magnetic resonance imaging (BOLD fMRI), this combination became a very promising techniques to study brain connectivity. However, the implementation of a reliable setup for interleaved TMS/fMRI is still technically challenging. In this thesis, I intended to further explore and develop methodological improvements in combining TMS and fMRI and to apply them in order to better understand the neural underpinnings of the behavioral TMS effects and to study brain connectivity. First, I developed and validated a new hardware/software coil positioning method for interleaved TMS/fMRI and demonstrated the feasibility of our overall setup. Second, a setup for combining TMS with continuous arterial spin labeling (CASL) was implemented and I tested the feasibility of this novel combination. Third, I demonstrated that this combination is sensitive enough to reliably measure rCBF changes induced by TMS, and that interleaved TMS/CASL can detect differences between the effects on regional cerebral flow (rCBF) of two different stimulation protocols. Fourth, it was shown that interleaved TMS/CASL is suitable to target questions from cognitive neuroscience. It was demonstrated that TMS applied over left dorsal premotor cortex (PMd) has different effects on the remote rCBF activation depending on the motor task. Overall, the results presented in this thesis suggest that interleaved TMS/CASL can become an interesting complement to interleaving TMS with normal BOLD fMRI, and that this combination can be considered for studying the impact of fully-fledged repetitive TMS protocols.Seit 1997, als Bohning und Kollegen zum ersten Mal die Möglichkeit einer Integration von TMS (Transkranieller Magnetstimulation) mit BOLD-fMRT (Blood Oxygenation Level Dependency Magnetresonanztomographie) demonstrierten, wurde diese Kombination rasch eine verheissungsvolle Methode, um die Konnektivität des Gehirns zu untersuchen. Die Implementierung eines zuverlässigen Setups für die Kombination von TMS/fMRT ist technisch nach wie vor eine grosse Herausforderung. Diese Dissertation beabsichtigt methodologische Verbesserungen für die Kombination von TMS mit fMRT weiter zu entwickeln und anzuwenden. Zuerst wird eine neue Hardware/Software TMS Spulenpositionierungsmethode für TMS kombiniert mit fMRT entwickelt, validiert sowohl die Realisierbarkeit des entwickelten, allgemeinen Setups untersucht. Zweitens wurde ein Setup für die Kombination von TMS mit CASL (Continuous Arterial Spin Labeling) eingeführt und ebenso die Realisierbarkeit dieser neuartigen Kombination geprüft. Drittens wird gezeigt, dass diese Kombination sensitiv genug ist für eine zuverlässige Messung der rCBF (Regional Cerebral Flow) Änderungen, verursacht durch TMS. Es wird ebenso demonstriert, dass die Kombination von TMS mit CASL Unterschiede in den Effekten auf den regionalen rCBF messen kann, hervorgerufen durch zwei verschieden Anregungsprotokolle. Viertens wird nachgewiesen, dass die Kombination von TMS mit CASL geeignet ist, Fragen der kognitiven Neurowissenschaft experimentell zu untersuchen. Es wird zum Beispiel gezeigt, dass TMS Stimulation über den linken dorsalen Premotor Cortex (PMd) verschiedene Effekte auf die rCBF Aktivierung hat, in Abhängigkeit von unterschiedlichen Bewegungszuständen. In Summe schlagen die Ergebnisse, die in dieser Dissertation dargestellt werden, vor, dass die Kombination von TMS mit CASL eine vielversprechende Ergänzung zur herkömmlichen Kombination von TMS mit BOLD-fMRT ist und dass diese Kombination als Auswirkung zur Erforschung neuer TMS Protokolle betrachtet werden kann

Brain network mechanisms underlying motor enhancement by transcranial entrainment of gamma oscillations

Gamma and beta oscillations are routinely observed in motor-related brain circuits during movement preparation and execution. Entrainment of gamma or beta oscillations via transcranial alternating current stimulation (tACS) over primary motor cortex (M1) has opposite effects on motor performance, suggesting a causal role of these brain rhythms for motor control. However, it is largely unknown which brain mechanisms characterize these changes in motor performance brought about by tACS. In particular, it is unclear whether these effects result from brain activity changes only in the targeted areas or within functionally connected brain circuits. Here we investigated this issue by applying gamma-band and beta-band tACS over M1 in healthy humans during a visuomotor task and concurrent functional magnetic resonance imaging (fMRI). Gamma tACS indeed improved both the velocity and acceleration of visually triggered movements, compared with both beta tACS and sham stimulation. Beta tACS induced a numerical decrease in velocity compared with sham stimulation, but this was not statistically significant. Crucially, gamma tACS induced motor performance enhancements correlated with changed BOLD activity in the stimulated M1. Moreover, we found frequency- and task-specific neural compensatory activity modulations in the dorsomedial prefrontal cortex (dmPFC), suggesting a key regulatory role of this region in motor performance. Connectivity analyses revealed that the dmPFC interacted functionally with M1 and with regions within the executive motor system. These results suggest a role of the dmPFC for motor control and show that tACS-induced behavioral changes not only result from activity modulations underneath the stimulation electrode but also reflect compensatory modulation within connected and functionally related brain networks. More generally, our results illustrate how combined tACS-fMRI can be used to resolve the causal link between cortical rhythms, brain systems, and behavior

Combined neuroimaging methods

This chapter presents an overview of methodological developments that attempt to deal with the fundamental problem as to what common 'true' brain state may underlie the method-specific observations. All of these developments focus on combinations of existing methods from the present armory of cognitive neuroscientists, an approach often referred to as multimodal imaging. The chapter discusses three such combinations: functional magnetic resonance imaging (fMRI)–electroencephalography (EEG)/magnetoencephalography (MEG), noninvasive brain stimulation (NIBS)-EEG, and NIBS-fMRI. The chapter begins with a brief description of the basic mechanisms of action for EEG/MEG, fMRI, and NIBS. It outlines only the strengths and shortcomings of each technique to motivate their multimodal combination. The chapter also describes the three multimodal combinations in detail. It presents the general rationale of each approach, gives a brief outline of technical considerations, and discusses the unique insights that can be gained with the particular methodical combination by means of illustrative studies

The right temporoparietal junction enables delay of gratification by allowing decision makers to focus on future events

Studies of neural processes underlying delay of gratification usually focus on prefrontal networks related to curbing affective impulses. Here, we provide evidence for an alternative mechanism that facilitates delaying gratification by mental orientation towards the future. Combining continuous theta-burst stimulation (cTBS) with functional neuroimaging, we tested how the right temporoparietal junction (rTPJ) facilitates processing of future events and thereby promotes delay of gratification. Participants performed an intertemporal decision task and a mental time-travel task in the MRI scanner before and after receiving cTBS over the rTPJ or the vertex (control site). rTPJ cTBS led to both stronger temporal discounting for longer delays and reduced processing of future relative to past events in the mental time-travel task. This finding suggests that the rTPJ contributes to the ability to delay gratification by facilitating mental representation of outcomes in the future. On the neural level, rTPJ cTBS led to a reduction in the extent to which connectivity of rTPJ with striatum reflected the value of delayed rewards, indicating a role of rTPJ–striatum connectivity in constructing neural representations of future rewards. Together, our findings provide evidence that the rTPJ is an integral part of a brain network that promotes delay of gratification by facilitating mental orientation to future rewards