Modulating OFC Activity With tDCS Alters Regret About Human Decision-Making

Regret is a common emotion in daily life. Humans always regret their decision-making choices if the chosen outcome is bad. Neuroscientific studies suggest that the orbitofrontal cortex (OFC) influences feelings of regret. We used a transcranial direct current stimulation (tDCS) device to study the role of regret in participants’ decision-making by modulating the activity of the OFC. The two-wheel-of-fortune gamble task was used in our experimental design, and we asked the participants to rate their feelings of regret after the computer presented the obtained and unobtained outcomes. The experimental results revealed that the effect of stimulation type was significant, which indicated that the influence of the OFC in regret was modulated by tDCS. Furthermore, based on post hoc analyses (Bonferroni), regret was lower in those who received left anodal/right cathodal stimulation than in those who received sham stimulation, which revealed that modulating the activity of the OFC reduced the emotional intensity of regret. In addition, an inverted U-shaped curve characterized the mean ratings of regret over time.

Are People Altruistic When Making Socially Responsible Investments? Evidence From a tDCS Study

Socially responsible investment (SRI) is an emerging philosophy that integrates social and environmental impacts into investment considerations, and it has gradually developed into an important form of investment. Previous studies have shown that both financial and non-financial motivations account for SRI behaviors, but it is unclear whether the non-financial motive to adopt SRI derives from investors’ altruism. This study uses neuroscientific techniques to explore the role of altruism in SRI decision-making. Given that existing evidence has supported the involvement of the right temporoparietal junction (rTPJ) in altruism and altruistic behaviors, we used transcranial direct current stimulation (tDCS) to temporarily modulate activity in the rTPJ and tested its effect on charitable donations and SRI behaviors. We found that anodal stimulation increased the subjects’ donations, while cathodal stimulation decreased them, suggesting that tDCS changed the subjects’ levels of altruism. More importantly, anodal stimulation enhanced the subjects’ willingness to make SRIs, while cathodal stimulation did not have a significant impact. These findings indicate that altruism plays an important role in SRI decision-making. Furthermore, cathodal stimulation changed the subjects’ perceived effectiveness of charitable donation but not that of socially responsible fund. This result may help explain the inconsistent effects of cathodal stimulation on charitable donations and SRI behaviors. The main contribution of our study lies in its pioneering application of tDCS to conduct research on SRI behaviors and provision of neuroscientific evidence regarding the role of altruism in SRI decision-making.

The Effect of Different tDCS Protocols on Drug Craving and Cognitive Functions in Methamphetamine Addicts

Background and objective: Drug craving is considered to be a major problem in addiction treatment. Neuroimaging research has revealed various areas for drug craving, among which two key areas are the dorsolateral prefrontal cortex (DLPFC) and the cerebellum. The DLPFC is involved in different cognitive tasks like the inhibitory control over seductive options harboring the promise of immediate reward. The cerebellum considered to be related to cognition and memory and gets activated by drug-related cues. Therefore based on the previous researches we decided to study the effects of applying tDCS on six different protocols in reducing Drug Craving and increasing Cognitive Functions in Methamphetamine Addicts. Methods: The present study is a semi-experimental, with pre/post-test, and a control group. Based on a simple sampling method, 15 male methamphetamine addicts in two rehabilitation centers in Tehran were recruited. The participants were 18-65 years old with a minimum 12-month history of methamphetamine dependence. Visual Analog Scale (VAS), The Go/No-Go Task and The N-Back Task was administered before and after single session of tDCS. tDCS applied on six protocols which were: 1. The right DLPFC anodal and the left DLPFC cathodal stimulation 2. The right DLPFC cathodal and the left DLPFC anodal stimulation 3. The right DLPFC anodal and the right arm cathodal stimulation 4. The left DLPFC anodal and the left arm cathodal stimulation 5. The right cerebellar hemisphere (O2) anodal and the left cerebellar hemisphere (O1) cathodal stimulation 6. The right cerebellar hemisphere (O2) cathodal and the left cerebellar hemisphere (O1) anodal stimulation. The data were analyzed by covariance method using SPSS-22 software Results: Study results indicated while single session tDCS effects on craving were not significant, it increased cognitive inhibition especially in protocol 2: The right DLPFC cathodal and the left DLPFC anodal stimulation Conclusion and discussion: Single session of tDCS has an insignificant effect on craving but it can increase cognitive inhibition significantly. These findings extend the results of previous studies on the effects of brain stimulation for drug craving reduction in other drug type settings.

The Role of the Mirror System in Influencing Musicians’ Evaluation of Musical Creativity: A tDCS Study

Evidence reported in the literature suggests that the mirror system not only plays a role in recognizing motor action but also fosters a better understanding of other people because it helps an individual assume another’s perspective. This led to the idea, supported by research findings, that people with higher empathy scores should show higher activation of the mirror system. Recently, it has been hypothesized that a purely auditory mirror system exists. In this study, we aimed to explore the possibility that this system might play a particular role for musicians. Specifically, this system would impact their response to a new piece of music by using non-invasive brain stimulation to modulate the activation of the mirror system. A sample of 40 young musicians was involved in this study. Half of the participants were randomly assigned to a cathodal stimulation condition, while the other half was used as a control. After listening to a new piece of music, participants were asked to rate the creativity of the piece (by focusing on how interesting, innovative, and exciting the piece was) as well as their general emotional response to it. Their empathy levels were also assessed using the Interpersonal Reactivity Index (IRI). Results showed that the cathodal stimulation of the mirror system negatively affected both the perception of creativity (level of innovation) and the emotional response to the music. There was no significant difference in the ratings of how interesting the piece was perceived. The effect was mediated by the individuals’ level of empathy. Specifically, empathic concern and fantasy dimensions increased the evaluation of creativity. Results also showed that participants reported less emotion with a negative valence in the cathodal stimulation condition.

Limb apparent motion perception: modification by tDCS, and clinically or experimentally altered bodily states

Limb apparent motion perception (LAMP) refers to the illusory visual perception of a moving limb upon observing two rapidly alternating photographs depicting the same limb in two different postures. Fast stimulus onset asynchronies (SOAs) induce the more visually guided perception of physically impossible movements. Slow SOAs induce the perception of physically possible movements. According to the motor theory of LAMP, the latter perception depends upon the observers’ sensorimotor representations. Here, we tested this theory in two independent studies by performing a central (study 1) and peripheral (study 2) manipulation of the body’s sensorimotor states during two LAMP tasks. In the first sham-controlled transcranial direct current stimulation between-subject designed study, we observed that the dampening of left sensorimotor cortex activity through cathodal stimulation biased LAMP towards the more visually guided perception of physically impossible movements for stimulus pairs at slow SOAs. In the second, online within-subject designed study, we tested three participant groups twice: (1) individuals with an acquired lower limb amputation, either while wearing or not wearing their prosthesis; (2) individuals with body integrity dysphoria (i.e., with a desire for amputation of a healthy leg) while sitting in a regular position or binding up the undesired leg (to simulate the desired amputation); (3) able-bodied individuals while sitting in a normal position or sitting on one of their legs. We found that the momentary sensorimotor state crucially impacted LAMP in all groups. Taken together, the results of these two studies substantiate the motor theory of LAMP.

Cerebellar tDCS alters the perception of optic flow

Studies have shown that the cerebellar vermis is involved in the perception of motion. However, it is unclear how the cerebellum influences motion perception. tDCS is a non-invasive brain stimulation technique that can reduce (through cathodal stimulation) or increase neuronal excitability (through anodal stimulation). To explore the nature of the cerebellar involvement on large-field global motion perception (i.e., optic flow-like motion), we applied tDCS on the cerebellar midline while participants performed an optic flow motion discrimination task. Our results show that anodal tDCS improves discrimination threshold for optic flow perception, but only for left-right motion in contrast to up-down motion discrimination. This result was evident within the first 10 minutes of stimulation and was also found post-stimulation. Cathodal stimulation did not have any significant effects on performance in any direction. The results show that discrimination of planar optic flow can be improved with tDCS of the cerebellar midline and provide further support for the role of the human midline cerebellum in the perception of optic flow.

Immediate and after effects of transcranial direct-current stimulation in the mouse primary somatosensory cortex

Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique consisting in the application of weak electric currents on the scalp. Although previous studies have demonstrated the clinical value of tDCS for modulating sensory, motor, and cognitive functions, there are still huge gaps in the knowledge of the underlying physiological mechanisms. To define the immediate impact as well as the after effects of tDCS on sensory processing, we first performed electrophysiological recordings in primary somatosensory cortex (S1) of alert mice during and after administration of S1-tDCS, and followed up with immunohistochemical analysis of the stimulated brain regions. During the application of cathodal and anodal transcranial currents we observed polarity-specific bidirectional changes in the N1 component of the sensory-evoked potentials (SEPs) and associated gamma oscillations. On the other hand, 20 min of cathodal stimulation produced significant after-effects including a decreased SEP amplitude for up to 30 min, a power reduction in the 20–80 Hz range and a decrease in gamma event related synchronization (ERS). In contrast, no significant changes in SEP amplitude or power analysis were observed after anodal stimulation except for a significant increase in gamma ERS after tDCS cessation. The polarity-specific differences of these after effects were corroborated by immunohistochemical analysis, which revealed an unbalance of GAD 65–67 immunoreactivity between the stimulated versus non-stimulated S1 region only after cathodal tDCS. These results highlight the differences between immediate and after effects of tDCS, as well as the asymmetric after effects induced by anodal and cathodal stimulation.

Effect of Modulating DLPFC Activity on Antisocial and Prosocial Behavior: Evidence From a tDCS Study

Antisocial behavior and prosocial behavior in the condition of inequality have long been observed in daily life. Understanding the neurological mechanisms and brain regions associated with antisocial and prosocial behavior and the development of new interventions are important for reducing violence and inequality. Fortunately, neurocognitive research and brain imaging research have found a correlation between antisocial or prosocial behavior and the prefrontal cortex. Recent brain stimulation research adopting transcranial direct current stimulation or transcranial magnetic stimulation has shown a causal relationship between brain regions and behaviors, but the findings are mixed. In the present study, we aimed to study whether stimulation of the DLPFC can change participants’ antisocial and prosocial behavior in the condition of inequality. We integrated antisocial and prosocial behavior in a unified paradigm. Based on this paradigm, we discussed costly and cost-free antisocial and prosocial behavior. In addition, we also measured participants’ disadvantageous and advantageous inequality aversion. The current study revealed an asymmetric effect of bilateral stimulation over the DLPFC on costly antisocial behavior, while such an effect of antisocial behavior without cost and prosocial behavior with and without cost were not observed. Moreover, costly antisocial behavior exhibited by men increased after receiving right anodal/left cathodal stimulation and decreased after receiving right cathodal anodal/left anodal stimulation compared with the behavior observed under sham stimulation. However, subjects’ inequality aversion was not influenced by tDCS.

The polarity specific nature of single session high-definition transcranial direct current stimulation to the cerebellum and prefrontal cortex on motor and non-motor task performance

The cerebellum has an increasingly recognized role in higher order cognition. Advancements in noninvasive neuromodulation techniques allows one to focally create functional alterations in the cerebellum to investigate its role in cognitive functions. To this point, work in this area has been mixed, in part due to varying methodologies for stimulation, and it is unclear whether or not transcranial direct current stimulation (tDCS) effects on the cerebellum are task or load dependent. Here, we employed a between-subjects design using a high definition tDCS system to apply anodal, cathodal, or sham stimulation to the cerebellum or prefrontal cortex (PFC) to examine the role the cerebellum plays in verbal working memory, inhibition, motor learning, and balance performance, and how this interaction might interact with the cortex (i.e. PFC). We predicted performance decrements following anodal stimulation and performance increases following cathodal stimulation, compared to sham. Broadly, our work provides evidence for cerebellar contributions to cognitive processing, particularly in verbal working memory and sequence learning. Additionally, we found the effect of stimulation might be load specific, particularly when applied to the cerebellum. Critically, anodal simulation negatively impacted performance during effortful processing, but was helpful during less effortful processing. Cathodal stimulation hindered task performance, regardless of simulation region. The current results suggest an effect of stimulation on cognition, perhaps suggesting that the cerebellum is more critical when processing is less effortful but becomes less involved under higher load when processing is more prefrontally-dependent.

The Influence of Pre-Supplementary Motor Area Targeted High-Definition Transcranial Direct Current Stimulation on Inhibitory Control

The neural underpinnings of inhibitory control, an executive cognitive control function, has been a topic of interest for several decades due to both its clinical significance and the maturation of cognitive science disciplines. Behavioral, imaging, and electrophysiological studies suggest that the pre-supplementary motor area (preSMA) serves as a primary hub in a network of regions engaged in inhibition. High-definition transcranial direct current stimulation (HD-tDCS) allows us to modulate neural function to assess cortical contribution to cognitive functioning. The present study targeted HD-tDCS modulation of preSMA to affect inhibition. Participants were randomly assigned to receive 20 min of Sham, Anodal, or Cathodal stimulation prior to completing a semantically cued go/nogo task while electroencephalography (EEG) data were recorded. Both anodal and cathodal stimulation improved inhibitory performance as measured by faster reaction times and increased (greater negative) N2 event-related potentials (ERPs). In contrast, the Sham group did not show such changes. We did not find support for the anodal/cathodal dichotomy for HD neural stimulation. These findings constitute an early investigation into role of the preSMA in inhibitory control and in exploring application of HD-tDCS to the preSMA in order to improve inhibitory control.