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Compassion is a key motivator of altruistic behavior, but little is known about individuals’ capacity to cultivate compassion through training. We examined whether compassion may be systematically trained by testing whether (a) short-term compassion training increases altruistic behavior and (b) individual differences in altruism are associated with training-induced changes in neural responses to suffering. In healthy adults, we found that compassion training increased altruistic redistribution of funds to a victim encountered outside of the training context. Furthermore, increased altruistic behavior after compassion training was associated with altered activation in brain regions implicated in social cognition and emotion regulation, including the inferior parietal cortex and dorsolateral prefrontal cortex (DLPFC), and in DLPFC connectivity with the nucleus accumbens. These results suggest that compassion can be cultivated with training and that greater altruistic behavior may emerge from increased engagement of neural systems implicated in understanding the suffering of other people, executive and emotional control, and reward processing.

Frontoparietal cortex is involved in the explicit processing (awareness) of stimuli. Frontoparietal activation has also been found in studies of subliminal stimulus processing. We hypothesized that an impairment of top-down processes, involved in recurrent neuronal message-passing and the generation of long-latency electrophysiological responses, might provide a more reliable correlate of consciousness in severely brain-damaged patients, than frontoparietal responses. We measured effective connectivity during a mismatch negativity paradigm and found that the only significant difference between patients in a vegetative state and controls was an impairment of backward connectivity from frontal to temporal cortices. This result emphasizes the importance of top-down projections in recurrent processing that involve high-order associative cortices for conscious perception.

Temporal interference (TI) stimulation is a novel neuromodulation technique that overcomes the depth limitations of traditional transcranial electrical stimulation while avoiding the invasiveness of deep brain stimulation. Our previous behavioral research has demonstrated the effects of multi‐target TI stimulation in enhancing working memory (WM) performance, however, the neural mechanisms of this special form of envelope modulation remain unclear. To address this issue, here we designed this randomized, double‐blind, crossover study, which consisted of a task‐based functional magnetic resonance imaging (fMRI) experiment, to explore how offline TI stimulation modulated brain activity and behavioral performance in healthy adults. We conducted a 2 × 2 within‐subjects design with two factors: stimulation (TI vs. Sham) and time (pre vs. post). Participants received two stimulation protocols in a random order: TI (beat frequency: 6 Hz, targeting middle frontal gyrus [MFG] and inferior parietal lobule [IPL]) and sham stimulation. Neuroimaging data of a WM task with different cognitive loads were acquisited immediately before and after stimulation. We found TI stimulation significantly improved d′ in the high‐demand WM task. Whole‐brain analysis showed the significant time‐by‐stimulation interactions in two main clusters in IPL and precuneus with lower activation after TI stimulation. The generalized psychophysiological interaction (gPPI) analysis revealed a significant interaction in task‐modulated connectivity between MFG and IPL, with improvement observed after TI stimulation. Notably, this increasing functional connectivity induced by TI stimulation was positively correlated with better behavioral performance. Overall, our findings show specific effects of TI stimulation on brain activation and functional connectivity in the frontoparietal network and may contribute to provide new perspectives for future neuromodulation applications. Our finding showed that frontoparietal TI stimulation enhanced working memory performance. Compared to sham stimulation, TI stimulation reduced the parietal activation, but increased coupling in the frontoparietal network. Moreover, the changes of connectivity predicts behavioral performance. This study may contribute to provide new perspectives for future neuromodulation applications.

Animal studies using selective serotonin reuptake inhibitors (SSRIs) and learning paradigms have demonstrated that serotonin is important for flexibility in executive functions and learning. SSRIs might facilitate relearning through neuroplastic processes and thus exert their clinical effects in psychiatric diseases where cognitive functioning is affected. However, translation of these mechanisms to humans is missing. In this randomized placebo-controlled trial, we assessed functional brain activation during learning and memory retrieval in healthy volunteers performing associative learning tasks aiming to translate facilitated relearning by SSRIs. To this extent, seventy-six participants underwent three MRI scanning sessions: (1) at baseline, (2) after three weeks of daily associative learning and subsequent retrieval (face-matching or Chinese character–noun matching) and (3) after three weeks of relearning under escitalopram (10 mg/day) or placebo. Associative learning and retrieval tasks were performed during each functional MRI (fMRI) session. Statistical modeling was done using a repeated-measures ANOVA, to test for content-by-treatment-by-time interaction effects. During the learning task, a significant substance-by-time interaction was found in the right insula showing a greater deactivation in the SSRI cohort after 21 days of relearning compared to the learning phase. In the retrieval task, there was a significant content-by-time interaction in the left angular gyrus (AG) with an increased activation in face-matching compared to Chinese-character matching for both learning and relearning phases. A further substance-by-time interaction was found in task performance after 21 days of relearning, indicating a greater decrease of performance in the placebo group. Our findings that escitalopram modulate insula activation demonstrates successful translation of relearning as a mechanism of SSRIs in human. Furthermore, we show that the left AG is an active component of correct memory retrieval, which coincides with previous literature. We extend the function of this region by demonstrating its activation is not only stimulus dependent but also time constrained. Finally, we were able to show that escitalopram aids in relearning, irrespective of content.

Parietal alpha activity shows a specific pattern of phasic changes during working memory. It decreases during the encoding and recall phases but increases during the maintenance phase. This study tested whether online rTMS delivered to the parietal cortex during the maintenance phase of a working memory task would increase alpha activity and hence improve working memory. Then, 46 healthy volunteers were randomly assigned to two groups to receive 3‐day parietal 10 Hz online rTMS (either real or sham, 3600 pulses in total) that were time‐locked to the maintenance phase of a spatial span task (180 trials in total). Behavioral performance on another spatial span task and EEG signals during a change detection task were recorded on the day before the first rTMS (pretest) and the day after the last rTMS (posttest). We found that rTMS improved performance on both online and offline spatial span tasks. For the offline change detection task, rTMS enhanced alpha activity within the maintenance phase and improved interference control of working memory at both behavioral (K score) and neural (contralateral delay activity) levels. These results suggested that rTMS with alpha frequency time‐locked to the maintenance phase is a promising way to boost working memory. We have found that 3 days of parietal 10 Hz rTMS resulted in offline alpha oscillation entrainment and improved working memory. This study is the first to demonstrate that targeting parietal alpha oscillation can noninvasively modulate working memory.

Spontaneous brain activity at rest is highly organized even when the brain is not explicitly engaged in a task. Functional connectivity (FC) in the alpha frequency band (α, 8–12 Hz) during rest is associated with improved performance on various cognitive and motor tasks. In this study we explored how FC is associated with visuo-motor skill learning and offline consolidation. We tested two hypotheses by which resting-state FC might achieve its impact on behavior: preparing the brain for an upcoming task or consolidating training gains. Twenty-four healthy participants were assigned to one of two groups: The experimental group (n = 12) performed a computerized mirror-drawing task. The control group (n = 12) performed a similar task but with concordant cursor direction. High-density 156-channel resting-state EEG was recorded before and after learning. Subjects were tested for offline consolidation 24h later. The Experimental group improved during training and showed offline consolidation. Increased α-FC between the left superior parietal cortex and the rest of the brain before training and decreased α-FC in the same region after training predicted learning. Resting-state FC following training did not predict offline consolidation and none of these effects were present in controls. These findings indicate that resting-state alpha-band FC is primarily implicated in providing optimal neural resources for upcoming tasks. •Learning and offline consolidation of mirror-drawing skills are evaluated.•EEG resting-state predicts learning but not offline consolidation.•Modulations of resting state are apparent at the alpha-band in left parietal areas.•Alpha-band resting-state provides the optimal neural resources for upcoming tasks.

Measuring the brain’s response to transcranial magnetic stimulation (TMS) with electroencephalography (EEG) offers unique insights into the cortical circuits activated following stimulation, particularly in non-motor regions where less is known about TMS physiology. However, the mechanisms underlying TMS-evoked EEG potentials (TEPs) remain largely unknown. We assessed TEP sensitivity to changes in excitatory neurotransmission mediated by n-methyl-d-aspartate (NMDA) receptors following stimulation of non-motor regions. In fourteen male volunteers, resting EEG and TEPs from prefrontal (PFC) and parietal (PAR) cortex were measured before and after administration of either dextromethorphan (NMDA receptor antagonist) or placebo across two sessions in a double-blinded pseudo-randomised crossover design. At baseline, there were amplitude differences between PFC and PAR TEPs across a wide time range (15–250 ms), however the signals were correlated after ~80 ms, suggesting early peaks reflect site-specific activity, whereas late peaks reflect activity patterns less dependent on the stimulated sites. Early TEP peaks were not reliably altered following dextromethorphan compared to placebo, although findings were less clear for later peaks, and low frequency resting oscillations were reduced in power. Our findings suggest that early TEP peaks (<80 ms) from PFC and PAR reflect stimulation site specific activity that is largely insensitive to changes in NMDA receptor-mediated neurotransmission.

Transcranial alternating current stimulation (tACS) has been reported to improve associative memory (AM) by modulating the frequency of neural oscillations in the brain; however, whether gamma-frequency (> 30 Hz) tACS in the left posterior parietal lobe (PPC) can enhance memory retention in AM remains unclear. This study aimed to investigate whether memory retention in AM could be improved after gamma-frequency tACS of the left PPC. We used a randomly assigned, double-blind, repeated-measures, sham-control design, in which 28 healthy adult participants were assigned to receive a single 20-min session of gamma-frequency (60 Hz) tACS or sham stimulation. The memory learning task consisted of studying and testing 50 unrelated word pairs three times on day 1. The number of correct responses in the cued recall task was measured at three time points: days 1, 7, and 28. The results revealed a significant difference in the number of correct responses between the interventions on day 7 and day 28. These data suggest that gamma-frequency tACS stimulation of the left PPC enhances the long-term retention of AM in healthy adults.

Associative memory (AM) is the ability to remember and retrieve multiple items bound together. Previous studies aiming to modulate AM by various transcranial electric stimulation (tES) techniques were inconclusive, although overall suggestive that tES could be a tool for AM enhancement. However, evidence from a direct comparison between different tES techniques is lacking. Here, in a sham-controlled cross-over experiment, we comparatively assessed the effects of three types of tES—anodal tDCS, theta-band transcranial alternating current stimulation (tACS), and theta-oscillatory tDCS (otDCS), delivered over the left posterior parietal cortex, during a short-term digit-color AM task with cued-recall. The effects were tested in 40 healthy young participants while both oscillatory tES were delivered at a previously determined individual theta frequency (4–8 Hz). All three active stimulations facilitated the overall AM performance, and no differences could be detected between them on direct comparison. However, unlike tDCS, the effects of which appeared to stem mainly from the facilitation of low-memory demand trials, both theta-modulated tACS and otDCS primarily promoted AM in high memory demand trials. Comparable yet differential effects of tDCS, theta tACS, and otDCS could be attributed to differences in their presumed modes of action.

Third parties punish, sacrificing personal interests, offenders who violate either fairness or cooperation norms. This behavior is defined altruistic punishment and the degree of punishment typically increases with the severity of the norm violation. An opposite and apparently paradoxical behavior, namely anti-social punishment, is the tendency to spend own money to punish cooperative or fair behaviors. Previous fMRI studies correlated punishment behavior with increased activation of brain areas belonging to the reward system (e.g. the ventromedial prefrontal cortex, VMPFC), the mentalizing (e.g. the temporoparietal junction, TPJ) and central-executive networks. In the present study, we aimed at investigating the causal role of VMPFC and TPJ in punishment behaviors through the application of anodal transcranial direct current stimulation (tDCS). Sixty healthy participants were randomly assigned to three tDCS conditions: (1) anodal tDCS over VMPFC, (2) anodal tDCS over right TPJ (rTPJ), (3) sham stimulation. At the end of the stimulation, participants played a third-party punishment game, consisting in viewing a series of fair or unfair monetary allocations between unknown proposers and recipients. Participants were asked whether and how much they would punish the proposers using their own monetary endowment. To test membership effects, proposers and recipients could be either Italian or Chinese. Anodal tDCS over VMPFC increased altruistic punishment behavior whereas anodal tDCS over rTPJ increased anti-social punishment choices compared with sham condition, while membership did not influence participant's choices. Our results support the idea that the two types of punishment behaviors rely upon different brain regions, suggesting that reward and mentalizing systems underlie, respectively, altruistic and anti-social punishment behaviors. •Altruistic punishment and antisocial punishment rely upon different brain regions.•Anodal tDCS influences punishing behaviors.•VMPFC and TPJ are implicates in altruistic and antisocial punishment.•Reward and mentalizing systems, underlie altruistic and anti-social punishment.