Translational application of neuromodulation of decision-making

Cathodal HD-tDCS above the left dorsolateral prefrontal cortex increases environmentally sustainable decision-making

Environmental sustainability is characterized by a conflict between short-term self-interest and longer-term collective interests. Self-control capacity has been proposed to be a crucial determinant of people's ability to overcome this conflict. Yet, causal evidence is lacking, and previous research is dominated by the use of self-report measures. Here, we modulated self-control capacity by applying inhibitory high-definition transcranial current stimulation (HD-tDCS) above the left dorsolateral prefrontal cortex (dlPFC) while participants engaged in an environmentally consequential decision-making task. The task includes conflicting and low conflicting trade-offs between short-term personal interests and long-term environmental benefits. Contrary to our preregistered expectation, inhibitory HD-tDCS above the left dlPFC, presumably by reducing self-control capacity, led to more, and not less, pro-environmental behavior in conflicting decisions. We speculate that in our exceptionally environmentally friendly sample, deviating from an environmentally sustainable default required self-control capacity, and that inhibiting the left dlPFC might have reduced participants' ability to do so.

Neuromodulation of inhibitory control using phase-lagged transcranial alternating current stimulation

BACKGROUND

Transcranial alternating current stimulation (tACS) is a prominent non-invasive brain stimulation method for modulating neural oscillations and enhancing human cognitive function. This study aimed to investigate the effects of individualized theta tACS delivered in-phase and out-of-phase between the dorsal anterior cingulate cortex (dACC) and left dorsolateral prefrontal cortex (lDLPFC) during inhibitory control performance.

METHODS

The participants engaged in a Stroop task with phase-lagged theta tACS over individually optimized high-density electrode montages targeting the dACC and lDLPFC. We analyzed task performance, event-related potentials, and prestimulus electroencephalographic theta and alpha power.

RESULTS

We observed significantly reduced reaction times following out-of-phase tACS, accompanied by reduced frontocentral N1 and N2 amplitudes, enhanced parieto-occipital P1 amplitudes, and pronounced frontocentral late sustained potentials. Out-of-phase stimulation also resulted in significantly higher prestimulus frontocentral theta and alpha activity.

CONCLUSIONS

These findings suggest that out-of-phase theta tACS potently modulates top-down inhibitory control, supporting the feasibility of phase-lagged tACS to enhance inhibitory control performance.

Out-of-phase transcranial alternating current stimulation modulates the neurodynamics of inhibitory control

Transcranial alternating current stimulation (tACS) is an efficient neuromodulation technique that enhances cognitive function in a non-invasive manner. Using functional magnetic resonance imaging, we investigated whether tACS with different phase lags (0° and 180°) between the dorsal anterior cingulate and left dorsolateral prefrontal cortices modulated inhibitory control performance during the Stroop task. We found out-of-phase tACS mediated improvements in task performance, which was neurodynamically reflected as putamen, dorsolateral prefrontal, and primary motor cortical activation as well as prefrontal-based top-down functional connectivity. Our observations uncover the neurophysiological bases of tACS-phase-dependent neuromodulation and provide a feasible non-invasive approach to effectively modulate inhibitory control.

Modulating risk-taking behavior with theta-band tACS

Although risk is prevalent in decision-making, the specific neural processes underlying risk-taking behavior remain unclear. Previous studies have suggested that frontal theta-band activity plays a crucial role in modulating risk-taking behavior. The functional relevance of theta in risk-taking behavior is yet to be clearly established and studies using noninvasive brain stimulation have yielded inconsistent findings. We aimed to investigate this relevance using transcranial alternating current stimulation (tACS) over right or left dorsolateral prefrontal cortex (DLPFC). We also studied the influence of stimulation intensity on risk-taking behavior and electrophysiological effects. We applied theta-band (6.5 Hz) tACS over the left (F3) and right (F4) DLPFC with lower (1.5 mA) and higher (3 mA) tACS intensities. We employed a single-blinded, sham-controlled, within-subject design and combined tACS with electroencephalography (EEG) measurements and the Maastricht Gambling Task (MGT) to elicit and evaluate risk-taking behavior. Our results show an increase in risk-taking behavior after left DLPFC stimulation at both intensities and a reduction of risk-taking behavior after 3 mA (and not 1.5 mA) right DLPFC stimulation compared to sham. Further analyses showed a negative correlation between resting-state frontal theta-power and risk-taking behavior. Overall, frontal theta-power was increased after left, but not right, theta-band tACS independent of stimulation intensity. Our findings confirm the functional relevance of frontal theta-band activity in decision-making under risk and the differential role of left and right DLPFC. We also were able to show that stimulation intensity did have an effect on behavioral responses, namely risk-taking behavior. Significant right hemisphere stimulation effects were observed only after high-intensity stimulation. Nevertheless, electrophysiological effects were only significant after left DLPFC stimulation, regardless of tACS intensity. Furthermore, the results indicate the role of the baseline frontal theta-power in the direction of behavioral effects after theta-band tACS.

Application of subject-specific helmets for the study of human visuomotor behavior using transcranial focused ultrasound: a pilot study

BACKGROUND AND OBJECTIVE

As a novel non-invasive human brain stimulation method, transcranial focused ultrasound (tFUS) is receiving growing attention due to its superior spatial specificity and depth penetrability. Since the focal point of tFUS needs to be fixated precisely to the target brain region during stimulation, a critical issue is to identify and maintain the accurate position and orientation of the tFUS transducer relative to the subject's head. This study aims to propose the entire framework of tFUS stimulation integrating the methods previously proposed by the authors for tFUS transducer configuration optimization and a subject-specific 3D-printed helmet, and to validate this complete setup in a human behavioral neuromodulation study.

METHODS

To find the optimal configuration of the tFUS transducer, a numerical method based on subject-specific tFUS beamlines simulation was used. Then, the subject-specific 3D-printed helmet has been applied to effectively secure the transducer at the estimated optimal configuration. To validate this tFUS framework, a common behavioral neuromodulation paradigm was chosen; the effect of the dorsolateral prefrontal cortex (DLPFC) stimulation on anti-saccade (AS) behavior. While human participants (n=2) were performing AS tasks, tFUS stimulations were randomly applied to the left DLPFC right after the fixation target disappeared.

RESULTS

The neuromodulation result strongly suggests that the cortical stimulation using the proposed tFUS setup is effective in significantly reducing the error rates of anti-saccades (about -10 %p for S1 and -16 %p for S2), whereas no significant effect was observed on their latencies. These observed behavioral effects are consistent with the previous results based on conventional brain stimulation or lesion studies.

CONCLUSIONS

The proposed subject-specific tFUS framework has been effectively used in human neuromodulation study. The result suggests that the tFUS stimulation targeted to the DLPFC can generate a neuromodulatory effect on AS behavior.

Non-invasive brain stimulation for smoking cessation: a systematic review and meta-analysis

BACKGROUND AND AIMS

Non-invasive brain stimulation (NIBS) methods have showed promising results for the treatment of tobacco use disorder, but little is known about the efficacy of NIBS on sustained tobacco abstinence. We aimed to assess its effectiveness for long-term smoking cessation.

METHODS

Systematic review and meta-analysis of randomized controlled trials (RCT). PubMed, Cochrane library, Embase, PsycINFO and clinical trials registries were systematically searched for relevant studies up to May 2021. Relevant studies included adult smokers seeking smoking cessation, included in an RCT using NIBS [specifically repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS)], and with follow-up of more than 4 weeks. There were no restrictions on location. Abstinence rates in the active NIBS groups were compared with abstinence rates in sham NIBS or in usual treatment groups, from 4 weeks to 12 months following the quit attempt. Smoking abstinence was measured on an intention-to-treat basis and we used risk ratios (RRs) as measures of effect size.

RESULTS

Seven studies were included (n = 699 patients). In all included studies, the control groups were receiving sham NIBS and only data from 3 to 6 months were analysable. By pooling the seven included studies, the RR of sustained abstinence of any form of NIBS relative to sham NIBS was 2.39 [95% confidence interval (CI) = 1.26-4.55; I²  = 40%]. Subgroup analyses found that the RR was even higher when excitatory rTMS was used on the left dorsolateral prefrontal cortex (RR = 4.34; 95% CI = 1.69-11.18; I²  = 0%) or when using deep rTMS targeting the lateral prefrontal cortex and insula bilaterally (RR = 4.64; 95% CI = 1.61-13.39; I²  = 0%). A high risk of bias was found in four included studies. We also determined, using grades of recommendation, assessment, development and evaluation, that overall there was a low level of confidence in the results.

CONCLUSION

Non-invasive brain stimulation (NIBS) may improve smoking abstinence rates from 3 to 6 months after quitting smoking, compared with sham NIBS or usual treatment.

Transcranial magnetic stimulation of the brain: What is stimulated? - A consensus and critical position paper

Transcranial (electro)magnetic stimulation (TMS) is currently the method of choice to non-invasively induce neural activity in the human brain. A single transcranial stimulus induces a time-varying electric field in the brain that may evoke action potentials in cortical neurons. The spatial relationship between the locally induced electric field and the stimulated neurons determines axonal depolarization. The induced electric field is influenced by the conductive properties of the tissue compartments and is strongest in the superficial parts of the targeted cortical gyri and underlying white matter. TMS likely targets axons of both excitatory and inhibitory neurons. The propensity of individual axons to fire an action potential in response to TMS depends on their geometry, myelination and spatial relation to the imposed electric field and the physiological state of the neuron. The latter is determined by its transsynaptic dendritic and somatic inputs, intrinsic membrane potential and firing rate. Modeling work suggests that the primary target of TMS is axonal terminals in the crown top and lip regions of cortical gyri. The induced electric field may additionally excite bends of myelinated axons in the juxtacortical white matter below the gyral crown. Neuronal excitation spreads ortho- and antidromically along the stimulated axons and causes secondary excitation of connected neuronal populations within local intracortical microcircuits in the target area. Axonal and transsynaptic spread of excitation also occurs along cortico-cortical and cortico-subcortical connections, impacting on neuronal activity in the targeted network. Both local and remote neural excitation depend critically on the functional state of the stimulated target area and network. TMS also causes substantial direct co-stimulation of the peripheral nervous system. Peripheral co-excitation propagates centrally in auditory and somatosensory networks, but also produces brain responses in other networks subserving multisensory integration, orienting or arousal. The complexity of the response to TMS warrants cautious interpretation of its physiological and behavioural consequences, and a deeper understanding of the mechanistic underpinnings of TMS will be critical for advancing it as a scientific and therapeutic tool.

Does non-invasive brain stimulation modulate emotional stress reactivity?

Excessive emotional responses to stressful events can detrimentally affect psychological functioning and mental health. Recent studies have provided evidence that non-invasive brain stimulation (NBS) targeting the prefrontal cortex (PFC) can affect the regulation of stress-related emotional responses. However, the reliability and effect sizes have not been systematically analyzed. In the present study, we reviewed and meta-analyzed the effects of repetitive transcranial magnetic (rTMS) and transcranial direct current stimulation (tDCS) over the PFC on acute emotional stress reactivity in healthy individuals. Forty sham-controlled single-session rTMS and tDCS studies were included. Separate random effects models were performed to estimate the mean effect sizes of emotional reactivity. Twelve rTMS studies together showed no evidence that rTMS over the PFC influenced emotional reactivity. Twenty-six anodal tDCS studies yielded a weak beneficial effect on stress-related emotional reactivity (Hedges’ g = −0.16, CI_95% = [−0.33, 0.00]). These findings suggest that a single session of NBS is insufficient to induce reliable, clinically significant effects but also provide preliminary evidence that specific NBS methods can affect emotional reactivity. This may motivate further research into augmenting the efficacy of NBS protocols on stress-related processes.

Framing and self-responsibility modulate brain activities in decision escalation

Background

Escalation of commitment is a common bias in human decision making. The present study examined (1) differences in neural recruitment for escalation and de-escalation decisions of prior investments, and (2) how the activations of these brain networks are affected by two factors that can arguably modulate escalation decisions: (i) self-responsibility, and (ii) framing of the success probabilities.

Results

Imaging data were obtained from functional magnetic resonance imaging (fMRI) applied to 29 participants. A whole-brain analysis was conducted to compare brain activations between conditions. ROI analysis, then, was used to examine if these significant activations were modulated by two contextual factors. Finally, mediation analysis was applied to explore how the contextual factors affect escalation decisions through brain activations. The findings showed that (1) escalation decisions are faster than de-escalation decisions, (2) the corresponding network of brain regions recruited for escalation (anterior cingulate cortex, insula and precuneus) decisions differs from this recruited for de-escalation decisions (inferior and superior frontal gyri), (3) the switch from escalation to de-escalation is primarily frontal gyri dependent, and (4) activation in the anterior cingulate cortex, insula and precuneus were further increased in escalation decisions, when the outcome probabilities of the follow-up investment were positively framed; and activation in the inferior and superior frontal gyri in de-escalation decisions were increased when the outcome probabilities were negatively framed.

Conclusions

Escalation and de-escalation decisions recruit different brain regions. Framing of possible outcomes as negative leads to escalation decisions through recruitment of the inferior frontal gyrus. Responsibility for decisions affects escalation decisions through recruitment of the superior (inferior) gyrus, when the decision is framed positively (negatively).

Reduced risk-taking behavior during frontal oscillatory theta band neurostimulation

BACKGROUND

Most of our decisions involve a certain degree of risk regarding the outcomes of our choices. People vary in the way they make decisions, resulting in different levels of risk-taking behavior. These differences have been linked to prefrontal theta band activity. However, a direct functional relationship between prefrontal theta band activity and risk-taking has not yet been demonstrated.

OBJECTIVE

We used noninvasive brain stimulation to test the functional relevance of prefrontal oscillatory theta activity for the regulatory control of risk-taking behavior.

METHODS

In a within-subject experiment, 31 healthy participants received theta (6.5 Hertz [Hz]), gamma (40 Hz), and sham transcranial alternating current stimulation (tACS) over the left prefrontal cortex (lPFC). During stimulation, participants completed a task assessing their risk-taking behavior as well as response times and sensitivity to value and outcome probabilities. Electroencephalography (EEG) was recorded before and immediately after stimulation to investigate possible long-lasting stimulation effects.

RESULTS

Theta band, but not gamma band or sham, tACS led to a significant reduction in risk-taking behavior, indicating a frequency-specific effect of prefrontal brain stimulation on the modulation of risk-taking behavior. Moreover, theta band stimulation led to increased response times and decreased sensitivity to reward values. EEG data analyses did not show an offline increase in power in the stimulated frequencies after the stimulation protocol.

CONCLUSION

These findings provide direct empirical evidence for the effects of prefrontal theta band stimulation on behavioral risk-taking regulation.

Better modulation for risk decision-making after optimized magnetic stimulation

Traditional repetitive transcranial magnetic stimulation can only produce a significant but weak effect on the cortex while theta burst stimulation (TBS), a patterned accelerated form of stimulation, can produce a stronger poststimulation effect, which may improve decision-making abilities. We designed a comparative assessment of the effect of intermittent TBS (iTBS), 20 Hz, in two risk decision-making tasks on healthy controls. Participants were randomized and assigned to the iTBS (n = 29), 20 Hz (n = 29), or sham (n = 29) groups. The effects of the different methods of left dorsolateral prefrontal cortex stimulation on risk decision-making functions were compared based on subjects' performance in the Game of Dice Task (GDT) and Risky Gains Task (RGT). The main indicators were positive and negative feedback utilization rates of GDT and RGT. Both iTBS and 20 Hz stimulation resulted in significant improvements upon negative feedback in the GDT, with increases in safe options and reductions in risky options; iTBS stimulation increased subjects' use of positive feedback in the GDT and RGT (all p < 0.05). Furthermore, the iTBS group had a stronger feedback risk reduction effect than the 20 Hz or sham group following RGT negative feedback (p < 0.05). Individuals would integrate positive and negative information more efficiently, leading to them making rational choices after excitatory transcranial magnetic stimulation. Moreover, iTBS has a stronger risk reduction effect following negative feedback than the 20Hz stimulation did. In summary, iTBS might have clinical value in decision promotion.

Associations Between Delay Discounting and Connectivity of the Valuation-control System in Healthy Young Adults

The process of valuation assists in determining if an object or course of action is rewarding. Delay discounting is the observed decay of a rewards' subjective value over time. Encoding the subjective value of rewards across a spectrum has been attributed to brain regions belonging to the valuation and executive control systems. The valuation system (VS) encodes reward value over short and long delays, influencing reinforcement learning and reward representation. The executive control system (ECS) becomes more active as choice difficulty increases, integrating contextual and mnemonic information with salience signals in the modulation of decision-making. Here, we aimed to identify resting-state functional connectivity-based patterns of the VS and ECS correlated with value-setting and delay discounting (outside-scanner paradigm) in a large (n = 992) cohort of healthy young adults from the Human Connectome Project (HCP). Results suggest the VS may be involved in value-setting of small, immediate rewards while the ECS may be involved in value-setting and delay discounting for large and small rewards over a range of delays. We observed magnitude sensitive connections involving the posterior cingulate cortex, time-sensitive connections with the ventromedial and lateral prefrontal cortex while connections involving the posterior parietal cortex appeared both magnitude- and time-sensitive. The ventromedial prefrontal cortex and posterior parietal cortex could act as "comparator" regions, weighing the value of small rewards against large rewards across various delay duration to aid in decision-making.

Effects of transcranial direct current stimulation of prefrontal cortex on risk-taking behavior

AIM

Recent cognitive neuroscience research shows that noninvasive brain stimulation can modify a wide range of behaviors in healthy people. Such regulation effects on human behaviors provide new insights into the neurobiology of cognitive processes and establish causal brain-behavior relations. Here, we aimed to examine the effects of transcranial electrical stimulation (TES) of the prefrontal cortex on risk-taking.

METHODS

We performed a systematic search on the PubMed, Web of Science, and Cochrane databases with appropriate keywords for original studies reporting the use of TES to modulate risk-taking behavior in healthy individuals. Then, in the meta-analysis phase, a random-effects model was used to measure the pooled effect size (ES).

RESULTS

Twenty articles were evaluated as eligible studies, including 16 articles on transcranial direct current stimulation (tDCS), two on transcranial alternating current stimulation, one on transcranial pulsed current stimulation, and one on high-definition tDCS. A meta-analysis showed a pooled estimated standardized ES of -0.20 (95% confidence interval [CI], -0.39 to -0.01), which indicates a small ES for active tDCS over the dorsolateral prefrontal cortex (DLPFC) in comparison to sham stimulation (z = 2.31, P = 0.03) in terms of less risky behaviors. Subgroup analysis showed that there is no significant ES for bilateral DLPFC stimulation (d = -0.01; 95%CI, -0.28 to 0.26), but a significant near-medium ES for unilateral DLPFC stimulation (d = -0.41; 95%CI, -0.71 to -0.10).

CONCLUSION

Our findings support a significant impact of neuroregulation of the DLPFC on risk-taking behavior in healthy individuals. Unilateral noninvasive electrical stimulation of the DLPFC can result in a conservative risk-averse response style, probably through modulating plasticity of the relevant brain networks, including cortical and subcortical structures, as well as increasing subcortical dopaminergic activity.

Change in core symptoms of borderline personality disorder by tDCS: A pilot study

Borderline personality disorder (BPD) recognizes several psychopathological dimensions related to prefrontal cortex impairments. Transcranial Direct Current Stimulation (tDCS) targeting the right prefrontal dorsolateral cortex (DLPFC) positively influence cognitive functions related to impulsivity in healthy subjects. A randomized double-blind study was designed to investigate whether tDCS could modulate core dimensions (impulsivity, aggression, affective dysregulation) of BPD. Also effects on decision making process and substances craving was assessed. Patients were randomized to receive active-tDCS at 2 mA versus sham-tDCS, once a day for 15 sessions. Anode was placed on the right DLPFC (F4), cathode on the left DLPFC (F3). Impulsivity and aggression measures were significantly reduced only in patients treated with active-tDCS. Decision-making process was marginally influenced by the active current. Craving intensity was reduced only in the active-tDCS sample. Both groups showed improvements in the affective dysregulation dimension and anxious and depressive symptoms. The application of bilateral tDCS targeting right DLPFC with anodal stimulation seems to improve core dimensions of BPD (mainly impulsivity and aggression) probably by restoring prefrontal activity. tDCS might be a potential tool for preventing self-harming behaviors.

Dosing parameters for the effects of high-frequency transcranial magnetic stimulation on smoking cessation: study protocol for a randomized factorial sham-controlled clinical trial

BACKGROUND

Despite the considerable success of comprehensive tobacco control efforts, tobacco use remains one of the greatest preventable causes of death and disease today. Over half of all smokers in the US make quit attempts every year, but over 90% relapse within 12 months, choosing the immediate reinforcement of smoking over the long-term benefits of quitting. Conceptual and empirical evidence supports continued investigation of high frequency repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex in reducing relapse and decreasing cigarette consumption. While this evidence is compelling, an optimal dosing strategy must be determined before a long-term efficacy trial can be conducted. The goal of this study is to determine a dosing strategy for 20 Hz rTMS that will produce the best long-term abstinence outcomes with the fewest undesirable effects.

METHODS

This is a fully crossed, double-blinded, sham-controlled, 3x2x2 randomized factorial study. The three factors are duration (stimulation days: 8, 12, and 16); intensity (900 or 1800 pulses per day); and sham control. Participants (n = 258) will consist of adults (18-65) who are motivated to quit smoking cigarettes and who will be followed for 6 months post-quit. Outcomes include latency to relapse, point prevalence abstinence rates, delay discounting rates, cognitive-behavioral skills acquisition, and multiple measures of potential undesirable effects that impact participant compliance.

DISCUSSION

This study integrates existing theoretical concepts and methodologies from neuropsychology, behavioral economics, brain stimulation, clinical psychology, and the evidence-based treatment of tobacco dependence in the development of a promising and innovative approach to treat tobacco dependence. This study will establish an optimal dosing regimen for efficacy testing. Findings are expected to have a significant influence on advancing this approach as well as informing future research on clinical approaches that combine rTMS with other evidence-based treatments for tobacco dependence and perhaps other addictions.

TRIAL REGISTRATION

Clinical Trials NCT03865472 (retrospectively registered). The first participant was fully enrolled on November 26, 2018. Registration was posted on March 7, 2019.

Mindfulness-Based Relapse Prevention and Transcranial Direct Current Stimulation to Reduce Heavy Drinking: A Double-Blind Sham-Controlled Randomized Trial

BACKGROUND

Mindfulness-based relapse prevention (MBRP) and transcranial direct current stimulation (tDCS) have independently shown benefits for treating alcohol use disorder (AUD). Recent work suggests tDCS may enhance mindfulness. The combination of MBRP and tDCS may provide synergistic benefits and may target both behavioral and neurobiological dysfunctions in AUD. The goal of this double-blind sham-controlled randomized trial was to examine the efficacy of a rolling group MBRP treatment combined with tDCS among individuals interested in reducing their drinking.

METHODS

Individuals who were interested in reducing their alcohol use (n = 84; 40.5% female; mean age = 52.3; 98.9% with current AUD) were randomized to receive active (2.0 milliamps) or sham (0.0 milliamps) anodal tDCS (5 cm × 3 cm electrode) of the right inferior frontal gyrus with the 5 cm × 3 cm cathodal electrode applied to the left upper arm, combined with 8 weeks of outpatient MBRP rolling group treatment. Assessments were conducted at baseline, posttreatment, and 2 months following treatment. The primary outcome was drinks per drinking day, and secondary outcomes were percent heavy drinking days, self-reported craving, alcohol cue reactivity in an alcohol cue task, and response inhibition in a stop signal reaction time task.

RESULTS

Results indicated significant reductions in drinks per drinking day over time, B(SE) = -0.535 (0.16), p = 0.001, and a significant dose effect for number of groups attended, B(SE) = -0.259 (0.11), p = 0.01. There were also significant effects of time and dose for number of groups attended on secondary outcomes of percent heavy drinking days and alcohol cue reactivity. There were no effects of active versus sham tDCS on primary or secondary outcomes.

CONCLUSIONS

Findings from the current study provide initial support for the effectiveness of rolling group MBRP as an outpatient treatment for drinking reduction. The current study did not find additive effects of this tDCS protocol in enhancing MBRP among individuals with drinking reduction goals.

To smoke or not to smoke: Does delay discounting affect the proximal choice to smoke?

BACKGROUND

Delay discounting rate shows robust predictive validity for tobacco use behaviors and is a new therapeutic target in the treatment of tobacco use. Identifying factors that influence relations between delay discounting and the choice to smoke cigarettes is key to the development of effective interventions that target delay discounting to reduce cigarette consumption.

OBJECTIVE

To examine relations between delay discounting, motivational factors, self-efficacy, nicotine dependence level, and the proximal choice to smoke in the context of other commonly rewarding activity choices.

METHODS

In this cross-sectional design, daily smokers (n = 480) from Amazon Mechanical Turk completed a questionnaire that assessed delay discounting rate; motivation, intention, and self-efficacy to quit smoking; nicotine dependence level, and the preference for immediately engaging in multiple commonly rewarding activities. We hypothesized that 1) greater motivation to quit would be associated with lower priority given to smoking; 2) the relation between delay discounting and the priority given to smoking would be mediated by motivation, self-efficacy, and nicotine dependence level.

RESULTS

Greater motivation to quit was significantly associated with a lower priority given to smoking. The relation between delay discounting and the priority given to smoking was marginally mediated by nicotine dependence level (p > .057).

CONCLUSIONS

Motivation to quit influences decision-making by impacting the prioritization of choices. Nicotine dependence is likely to mediate the relation between delay discounting and the choice to smoke. Interventions that target delay discounting to reduce cigarette consumption or prevent relapse need to account for motivation to quit and nicotine dependence level.

eSports: A new window on neurocognitive expertise?

Understanding the neurological changes that take place as expertise develops is a central topic in both cognitive psychology and cognitive neuroscience. Here, we argue that video games, despite previous misconceptions, are an excellent model environment from which one can examine the development of neurocognitive expertise. Of particular relevance we argue is the area of esports, which encompass video/computer games played within the medium of cyberspace competitively and increasingly professionally. The massive scale of participation, controlled environments, structured skill ratings, pervasive social nature, and large repositories of data, together make esports potentially a very fruitful area for scientific research to increase our understanding of a new era of cognitive athletes. This chapter reviews the progress and prospects for esports research with a particular focus on the effects of gaming on neurocognition. We also outline some exciting new avenues and techniques from which we hope to further elucidate the benefits of esports on the brain.

tDCS in Addiction and Impulse Control Disorders

The study of addiction and impulsion control disorders has shown that behaviors of seeking and consumption of addictive substances are subserved by neurobiological alterations specifically related to brain networks for reward, stress, and executive control, representing the brain's adaptation to the continued use of an addictive substance. In parallel, studies using neuromodulation techniques such as transcranial direct current stimulation (tDCS) have demonstrated promising effects in modulating cognitive and motor functions. This review aims to describe the neurobiology of addiction and some of the most relevant cognitive models of addictive behavior and to clarify how tDCS application modulates the intake and craving for several addictive substances, such as food, alcohol, nicotine, cocaine, crack, methamphetamine, and cannabis. We also discuss the positive and null outcomes of the use of this neuromodulatory technique in the treatment of addiction disorders resulting from the use of these substances. The reviewed findings lead us to conclude that tDCS interventions hold several promising clinical avenues in addiction and impulsive control. However, methodological investigations are necessary for undercover optimal parameters before implementing its clinical application.

Effect of Modulating Activity of DLPFC and Gender on Search Behavior: A tDCS Experiment

Studies of search behavior have shown that individuals stop searching earlier and accept a lower point than predicted by the optimal, risk-neutral stopping rule. This behavior may be related to individual risk preferences. Studies have also found correlativity between risk preferences and the dorsolateral prefrontal cortex (DLPFC). As risk attitude plays a crucial role in search behavior, we studied whether modulating the activity of DLPFC, by using a transcranial direct current stimulation (tDCS) device, can change individual search behavior. We performed a sequential search task in which subjects decided when to accept a point randomly drawn from a uniform distribution. A total of 49 subjects (23 females, mean age = 21.84 ± 2.09 years, all right-handed) were recruited at Zhejiang University from May 2017 to September 2017. They repeated the task in 80 trials and received the stimulation at the end of the 40th trial. The results showed that after receiving right anodal/left cathodal stimulation, subjects increased their searching duration, which led to an increase in their accepted point from 778.17 to 826.12. That is, the subjects may have changed their risk attitude to search for a higher acceptable point and received a higher benefit. In addition, the effect of stimulation on search behavior was mainly driven by the female subjects rather than by the male subjects: the female subjects significantly increased their accepted point from 764.15 to 809.17 after right anodal/left cathodal stimulation, while the male subjects increased their accepted point from 794.18 to 845.49, but the change was not significant.

High frequency repetitive transcranial magnetic stimulation treatment for major depression: Dissociated effects on psychopathology and neurocognition

OBJECTIVES

This open-label pilot study explored the effects of a course of accelerated high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) on two neurocognitive domains (decision-making and impulse control) in patients with major depressive disorder (MDD).

METHODS

Participants with MDD and a treatment resistant major depressive episode (n=24) underwent twice-daily HF-rTMS targeted at the left dorsolateral prefrontal cortex (lDLPFC) over two weeks. Psychopathology was assessed by clinician-administered and self-reported measures of depression and anxiety; decision-making was assessed by the Iowa Gambling Task, the Balloon Analog Risk Task and the Game of Dice Task; impulse control was assessed by the Stroop Color-Word Task, the Continuous Performance Task and the Stop-Signal Task.

RESULTS

Depression and anxiety scores significantly improved from pre-post HF-rTMS treatment. However, none of the decision-making or impulse control variables of interest changed significantly from pre-post HF-rTMS. Moreover, there was no correlation between changes in psychopathological symptoms and in neurocognition.

LIMITATIONS

This is a moderately sized open label trial, and the confounds of ongoing psychotropics and illness chronicity can not be excluded in this treatment resistant sample.

CONCLUSIONS

There is dissociation between acute symptomatic benefit after a course of accelerated HF-rTMS applied to the lDLPFC in treatment resistant MDD and performance on tests of decision making and impulse control. Though rTMS appears cognitively safe, additional research is warranted to understand this potential dissociation and its putative clinical implications.

Animal models to improve our understanding and treatment of suicidal behavior

Worldwide, suicide is a leading cause of death. Although a sizable proportion of deaths by suicide may be preventable, it is well documented that despite major governmental and international investments in research, education and clinical practice suicide rates have not diminished and are even increasing among several at-risk populations. Although nonhuman animals do not engage in suicidal behavior amenable to translational studies, we argue that animal model systems are necessary to investigate candidate endophenotypes of suicidal behavior and the neurobiology underlying these endophenotypes. Animal models are similarly a critical resource to help delineate treatment targets and pharmacological means to improve our ability to manage the risk of suicide. In particular, certain pathophysiological pathways to suicidal behavior, including stress and hypothalamic-pituitary-adrenal axis dysfunction, neurotransmitter system abnormalities, endocrine and neuroimmune changes, aggression, impulsivity and decision-making deficits, as well as the role of critical interactions between genetic and epigenetic factors, development and environmental risk factors can be modeled in laboratory animals. We broadly describe human biological findings, as well as protective effects of medications such as lithium, clozapine, and ketamine associated with modifying risk of engaging in suicidal behavior that are readily translatable to animal models. Endophenotypes of suicidal behavior, studied in animal models, are further useful for moving observed associations with harmful environmental factors (for example, childhood adversity, mechanical trauma aeroallergens, pathogens, inflammation triggers) from association to causation, and developing preventative strategies. Further study in animals will contribute to a more informed, comprehensive, accelerated and ultimately impactful suicide research portfolio.

The involvement of the striatum in decision making

Decision making has been extensively studied in the context of economics and from a group perspective, but still little is known on individual decision making. Here we discuss the different cognitive processes involved in decision making and its associated neural substrates. The putative conductors in decision making appear to be the prefrontal cortex and the striatum. Impaired decision-making skills in various clinical populations have been associated with activity in the prefrontal cortex and in the striatum. We highlight the importance of strengthening the degree of integration of both cognitive and neural substrates in order to further our understanding of decision-making skills. In terms of cognitive paradigms, there is a need to improve the ecological value of experimental tasks that assess decision making in various contexts and with rewards; this would help translate laboratory learnings into real-life benefits. In terms of neural substrates, the use of neuroimaging techniques helps characterize the neural networks associated with decision making; more recently, ways to modulate brain activity, such as in the prefrontal cortex and connected regions (eg, striatum), with noninvasive brain stimulation have also shed light on the neural and cognitive substrates of decision making. Together, these cognitive and neural approaches might be useful for patients with impaired decision-making skills. The drive behind this line of work is that decision-making abilities underlie important aspects of wellness, health, security, and financial and social choices in our daily lives.

Transcranial Direct Current Stimulation over the Medial Prefrontal Cortex and Left Primary Motor Cortex (mPFC-lPMC) Affects Subjective Beauty but Not Ugliness

Neuroaesthetics has been searching for the neural bases of the subjective experience of beauty. It has been demonstrated that neural activities in the medial prefrontal cortex (mPFC) and the left primary motor cortex (lPMC) correlate with the subjective experience of beauty. Although beauty and ugliness seem to be semantically and conceptually opposite, it is still unknown whether these two evaluations represent extreme opposites in unitary or bivariate dimensions. In this study, we applied transcranial direct current stimulation (tDCS) to examine whether non-invasive brain stimulation modulates two types of esthetic evaluation; evaluating beauty and ugliness. Participants rated the subjective beauty and ugliness of abstract paintings before and after the application of tDCS. Application of cathodal tDCS over the mPFC with anode electrode over the lPMC, which induced temporal inhibition of neural excitability of the mPFC, led to a decrease in beauty ratings but not ugliness ratings. There were no changes in ratings of both beauty and ugliness when applying anodal tDCS or sham stimulation over the mPFC. Results from our experiment indicate that the mPFC and the lPMC have a causal role in generating the subjective experience of beauty, with beauty and ugliness evaluations constituting two distinct dimensions.

Enhancing decision-making and cognitive impulse control with transcranial direct current stimulation (tDCS) applied over the orbitofrontal cortex (OFC): A randomized and sham-controlled exploratory study

BACKGROUND

Decision-making and impulse control (both cognitive and motor) are complex interrelated processes which rely on a distributed neural network that includes multiple cortical and subcortical regions. Among them, the orbitofrontal cortex (OFC) seems to be particularly relevant as demonstrated by several neuropsychological and neuroimaging investigations.

METHODS

In the present study we assessed whether transcranial direct current stimulation (tDCS) applied bilaterally over the OFC is able to modulate decision-making and cognitive impulse control. More specifically, 45 healthy subjects were randomized to receive a single 30-min session of active or sham anodal tDCS (1.5 mA) applied over either the left or the right OFC (coupled with contralateral cathodal tDCS). They were also assessed pre- and post-tDCS with a battery of computerized tasks.

RESULTS

Our results show that participants who received active anodal tDCS (irrespective of laterality), vs. those who received sham tDCS, displayed more advantageous decision-making (i.e., increased Iowa Gambling Task "net scores" [p = 0.04]), as well as improved cognitive impulse control (i.e., decreased "interference" in the Stroop Word-Colour Task [p = 0.007]). However, we did not observe tDCS-related effects on mood (assessed by visual analogue scales), attentional levels (assessed by the Continuous Performance Task) or motor impulse control (assessed by the Stop-Signal Task).

CONCLUSIONS

Our study potentially serves as a key translational step towards the development of novel non-invasive neuromodulation-based therapeutic interventions directly targeting vulnerability factors for psychiatric conditions such as suicidal behaviour and addiction.

tDCS dans le traitement des addictions : quelles perspectives ?

Les troubles addictifs sont des troubles complexes où les traitements actuellement efficaces restent peu nombreux. Dans ce contexte, la tDCS de part son action neuromodulatrice, sa simplicité d’utilisation et sa faible innocuité pourrait être une option valable à la fois pour mieux comprendre la physiopathologie de ces troubles que comme traitement potentiel. Les comportements addictifs sont marqués par un ensemble de symptômes cognitifs, comportementaux et physiologiques faisant qu’un individu continue à consommer en dépit des conséquences négatives auquel il s’expose. Parmi ces caractéristiques, le craving est particulièrement impliqué dans le maintien des consommations. La neurobiologie du craving implique les régions préfrontales. Cela en fait une cible de choix pour la tDCS. Des études tDCS versus une stimulation placEbo ciblant le cortex préfrontal ont montré une diminution du craving. Ces résultats ont été retrouvé dans une série d’addiction allant du tabac à la methamphetamine en passant par l’alcool et la nourriture. Dans certaines études, cette diminution du craving était associée cliniquement à une diminution des consommations de nourriture ou de cigarettes.

Une autre cible d’action potentielle pourrait être neurocognitive. Les addictions sont marquées par des altérations de la prise de décision, une hypersensibilité à la récompense et une impulsivité importante. Des études très préliminaires chez des sujet dépendants au tabac et au cannabis suggèrent qu’un programme de tDCS ciblant le cortex préfrontal dorsolatéral améliore ces fonctions neuropsychologiques et ainsi indirectement le pronostic de l’addiction. Les données actuelles ne permettent cependant pas de préciser si il existe un maintien à long terme des effets observés. L’intérêt clinique et les paramètres optimaux d’utilisation doivent également être mieux définis. Néanmoins ces premières données suggèrent que la tDCS pourrait permettre le développement de nouvelles approches thérapeutiques dans des troubles où les prises en charge actuelles sont perfectibles.

Focused transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex modulates specific domains of self-regulation

Recent neuroscience theories suggest that different kinds of self-regulation may share a common psychobiological mechanism. However, empirical evidence for a domain general self-regulation mechanism is scarce. The aim of this study was to investigate whether focused anodal transcranial direct current stimulation (tDCS), facilitating the activity of the dorsolateral prefrontal cortex (dlPFC), acts on a domain general self-regulation mechanism and thus modulates both affective and appetitive self-regulation. Twenty smokers participated in this within-subject sham controlled study. Effects of anodal left, anodal right and sham tDCS over the dlPFC on affective picture appraisal and nicotine craving-cue appraisal were assessed. Anodal right tDCS over the dlPFC reduced negative affect in emotion appraisal, but neither modulated regulation of positive emotion appraisal nor of craving appraisal. Anodal left stimulation did not induce any significant effects. The results of our study show that domain specific self-regulation networks are at work in the prefrontal cortex. Focused tDCS modulation of this specific self-regulation network could probably be used during the first phase of nicotine abstinence, during which negative affect might easily result in relapse. These findings have implications for neuroscience models of self-regulation and are of relevance for the development of brain stimulation based treatment methods for neuropsychiatric disorders associated with self-regulation deficits.

The impact of electrical stimulation techniques on behavior

Low-intensity transcranial electrical stimulation (tES) methods are a group of noninvasive brain stimulation techniques, whereby currents are applied with intensities typically ranging between 1 and 2 mA, through the human scalp. These techniques have been shown to induce changes in cortical excitability and activity during and after the stimulation in a reversible manner. They include transcranial direct current simulation (tDCS), transcranial alternating current simulation (tACS), and transcranial random noise stimulation (tRNS). Currently, an increasing number of studies have been published regarding the effects of tES on cognitive performance and behavior. Processes of learning and increases in cognitive performance are accompanied by changes in cortical plasticity. tES can impact upon these processes and is able to affect task execution. Many studies have been based on the accepted idea that by increasing cortical excitability (e.g., by applying anodal tDCS) or coherence of oscillatory activity (e.g., by applying tACS) an increase in performance should be detected; however, a number of studies now suggest that the basic knowledge of the mechanisms of action is insufficient to predict the outcome of applied stimulation on the execution of a cognitive or behavioral task, and so far no standard paradigms for increasing cortical plasticity changes during learning or cognitive tasks have been established. The aim of this review is to summarize recent findings with regard to the effects of tES on behavior concentrating on the motor and visual areas. WIREs Cogn Sci 2014, 5:649-659. doi: 10.1002/wcs.1319 For further resources related to this article, please visit the WIREs website.

CONFLICT OF INTEREST

The authors have declared no conflicts of interest for this article.

The effect of practice on random number generation task: a transcranial direct current stimulation study

Random number generation (RNG) is a procedurally-simple task related to specific executive functions, such as updating and monitoring of information and inhibition of automatic responses. The effect of practice on executive functions has been widely investigated, however little is known on the impact of practice on RNG. Transcranial direct current stimulation (tDCS) allows to modulate, non-invasively, brain activity and to enhance the effects of training on executive functions. Hence, this study aims to investigate the effect of practice on RNG and to explore the possibility to influence it by tDCS applied over dorsolateral prefrontal cortex. Twenty-six healthy volunteers have been evaluated within single session and between different sessions of RNG using several measures of randomness, which are informative of separable cognitive components servicing random behavior. We found that repetition measures significantly change within single session, seriation measures significantly change both within and between sessions, while cycling measures are not affected by practice. tDCS does not produce any additional effect, however a sub-analysis limited to the first session revealed an increasing trend in seriation measure after anodal compared to cathodal stimulation. Our findings support the hypothesis that practice selectively and consistently influences specific cognitive components related to random behavior, while tDCS transiently affects RNG performance.

Neuromodulation of delay discounting, the reflection effect, and cigarette consumption

Cigarette smokers and substance users discount the value of delayed outcomes more steeply than non-users. Higher discounting rates are associated with relapse and poorer treatment outcomes. The left dorsolateral prefontal cortex (DLPFC) exerts an inhibitory influence on impulsive or seductive choices. Greater activity in the prefrontal cortex is associated with lower discounting rates. We hypothesized that increasing activity in the left DLPFC with high frequency repetitive transcranial magnetic stimulation (HF rTMS) would decrease delay discounting and decrease impulsive decision-making in a gambling task as well as decrease cigarette consumption, similar to other studies. In this single-blind, within-subjects design, smokers with no intention to quit (n = 47) and nonsmokers (n = 19) underwent three counterbalanced sessions of HF rTMS (20 Hz, 10 Hz, sham) delivered over the left DLPFC. Tasks were administered at baseline and after each stimulation session. Stimulation decreased discounting of monetary gains (F([3,250]) = 4.46, p < .01), but increased discounting of monetary losses (F([3,246]) = 4.30, p < .01), producing a reflection effect, normally absent in delay discounting. Stimulation had no effect on cigarette consumption. These findings provide new insights into cognitive processes involved with decision-making and cigarette consumption and suggest that like all medications for substance dependence, HF rTMS is likely to be most effective when paired with cognitive-behavioral interventions.

The relationship between impulsivity and craving in alcohol dependent patients

RATIONALE

Impulsivity and craving are both associated with higher relapse rates and a worse prognosis in patients with a substance use disorder, but the relationship between these two phenomena has been largely ignored in the field of alcohol use disorders.

OBJECTIVES

The primary aim of this study was to investigate the relationship between different dimensions of impulsivity and different forms of self-reported craving. Additionally, the influence of the severity of alcohol dependence on impulsivity, craving, and on their relationship was exploed.

METHODS

Impulsivity and craving levels were investigated in 87 abstinent alcohol-dependent (AD) patients using a broad range of self-report questionnaires and behavioral impulsivity measures. Alcohol use was measured by means of the timeline followback method.

RESULTS

Higher scores of emotional craving (Alcohol Urge Questionnaire-AUQ) were significantly related to higher self-reported impulsivity (Barratt Impulsiveness Scale, version 11) and to higher cognitive impulsivity (information sampling task). Additionally, exploratory analyses suggest that these relationships are more pronounced in severe AD patients compared to less severe AD patients. No significant relationships were found between emotional craving (AUQ) and motor impulsivity (stop signal task) or delay discounting and between obsessive-compulsive craving (Obsessive Compulsive Drinking Scale) and measures of impulsivity.

CONCLUSIONS

Emotional craving is related to self-reported impulsivity and to cognitive impulsivity. These relationships seem to be more pronounced in AD patients with severe alcohol dependence. Further research is needed to explore the effect of this relationship on treatment outcome and relapse.