Cognitive control enhancement in attention deficit hyperactivity disorder (ADHD) and neurotypical individuals.

Cognitive control, which has been localized to the right inferior frontal gyrus (rIFG) based on functional imaging and brain lesion studies, is impaired in patients with ADHD. The present study aims to investigate whether transcranial direct current stimulation (tDCS) over the rIFG might improve cognitive control in ADHD subjects. We hypothesized poorer performance in a cognitive control task, but not in a control language task, in the ADHD subjects. Crucially, following tDCS, we expected the ADHD group to improve their cognitive control. In a double-blind randomized control trial, 42 participants performed the stop signal task (SST) to index their cognitive control level and the language task. Half of them were randomly assigned to the anodal stimulation condition and half to the sham stimulation. The anodal or sham stimulation was applied over the right IFG. Following the stimulation, the participants reset the two tasks to see whether stimulation improved the (predicted) weaker performance in the ADHD group. Stimulation significantly enhanced cognitive control for both groups, with or without ADHD, in the SST task, but no significant stimulation effects were found for the control task. tDCS seems as a promising tool to improve cognitive control in the general population.

Cognitive control in processing ambiguous idioms: evidence from a self-paced reading study.

Idioms entail a competition between bottom-up and top-down activations of literal and figurative meanings. The present study explored the involvement of cognitive control in processing Hebrew ambiguous idioms. Fifty subjects have completed a self-paced reading task and a response inhibition, stop-signal task (SST). Subjects read 26 matched pairs of almost-identical sentences, which included ambiguous idioms (e.g., "break the ice"). The ambiguity was resolved only in the third part of the sentence, which was either literal ("on the parking lot") or figurative ("with funny stories"). Figurative disambiguation parts were read significantly faster than literal ones. The means of the absolute RT difference between the literal and figurative sentences significantly correlated with the SST cognitive control measure. A comparison between three groups of cognitive control levels validated that "Good inhibitors" in the SST were also faster in processing ambiguities. The paper discusses the generality of cognitive control in linguistic processing.

When a Patient Dies From Suicide: A Survey Among Mental Health Professionals in Israel.

Death of patients by suicide can have powerful impacts on mental health professionals (MHPs). The National Program for the Prevention of Suicidality and Suicide at Israel's Ministry of Health decided to invest in MHPs who have lost patients by suicide. Two hundred and two MHPs completed an online self-report survey regarding their emotional response, professional identity, and clinical practice, and the aid they felt would be supportive following a patient's suicide. Results indicated that 35% of MHP experienced at least one death of a patient by suicide. Respondents experienced difficult emotional reactions, and many felt responsible for the suicide. Nearly 50% reported that the patient's suicide affected their clinical practice. Most respondents reported the need for a support framework and information about the processes following a patient's suicide. It is important to increase awareness of the possibility of losing a patient by suicide and offer an appropriate supportive framework.

Non-linear effects of cathodal transcranial direct current stimulation (tDCS) of the primary motor cortex on implicit motor learning.

Transcranial direct current stimulation (tDCS) of 1 mA for 13 min was reported to create a linear inter-dependency between the intensity and duration of the current and the effects of the stimulation. tDCS on the primary motor cortex (M1) has been shown to have an effect on both motor-evoked potential (MEP) and motor learning. However, recent findings have shown that the known linear effect is invalid in a 2 mA stimulation for 20 min, where cathodal stimulation led to excitability, rather than inhibition, as measured by MEP changes. Here we aim to replicate the non-linear effect of cathodal stimulation over the M1, using a cognitive task. Twenty-two healthy subjects participated in three sessions, where they were administered with a 2 mA anodal and cathodal stimulation for 20 min over the left M1, and a sham stimulation, while performing the serial reaction time task (SRTT). The overall analysis failed to show any effects of either polarity of tDCS on SRTT performance and hence did not replicate previous findings. However, given our goal to replicate the previously reported reversed polarity effects on MEP, we conducted an exploratory analysis to see whether there were any more subtle signs of a change in sign of the cathodal effect compared with anodal. Anodal stimulation led to faster performance than cathodal stimulation before 13 min of stimulation have passed, however, after 13 min, the pattern had switched, and performance under cathodal stimulation was faster. We conclude that cathodal tDCS has a non-linear effect, and the known polarity-dependent effects of tDCS shift after 13 min of stimulation, leading to an increased, rather than decreased, excitability.

Prosaccade and Antisaccade Paradigms in Persons with Alzheimer's Disease: A Meta-Analytic Review.

Persons with Mild Cognitive Impairment (MCI) are at high Alzheimer's Disease (AD) risk but the development of sensitive measures to assess subtle cognitive decline in this population poses a major challenge for clinicians and researchers. Eye movement monitoring is a non-invasive, sensitive way to assess subtle cognitive processes in clinical populations. We conducted a critical review and a meta-analysis of the literature on pro and antisaccade paradigm in AD/MCI. The meta-analysis included 20 studies, all of which used the prosaccade paradigm and 13 of which studied the antisaccade paradigm as well. Our meta-analysis showed that AD but not MCI patients showed longer prosaccade latencies when compared to controls. While antisaccade latencies did not differentiate between patients from controls, antisaccade error rate were significantly increased among patients in comparison to controls in over 87% of the studies. These findings highlight antisaccade error rate as a reliable tool to distinguish inhibition abilities between AD/MCI and healthy older persons.

Seeing the World as it is: Mimicking Veridical Motion Perception in Schizophrenia Using Non-invasive Brain Stimulation in Healthy Participants.

Schizophrenia (Sz) is a mental health disorder characterized by severe cognitive, emotional, social, and perceptual deficits. Visual deficits are found in tasks relying on the magnocellular/dorsal stream. In our first experiment we established deficits in global motion processing in Sz patients compared to healthy controls. We used a novel task in which background optic flow produces a distortion of the apparent trajectory of a moving stimulus, leading control participants to provide biased estimates of the true motion trajectory under conditions of global stimulation. Sz patients were significantly less affected by the global background motion, and reported trajectories that were more veridically accurate than those of controls. In order to study the mechanism of this effect, we performed a second experiment where we applied transcranial electrical stimulation over area MT+ to selectively modify global motion processing of optic flow displays in healthy participants. Cathodal and high frequency random noise stimulation had opposite effects on trajectory perception in optic flow. The brain stimulation over a control site and in a control task revealed that the effect of stimulation was specific for global motion processing in area MT+. These findings both support prior studies of impaired early visual processing in Sz and provide novel approaches for measurement and manipulation of the underlying circuits.

Increasing propensity to mind-wander with transcranial direct current stimulation.

Humans mind-wander quite intensely. Mind wandering is markedly different from other cognitive behaviors because it is spontaneous, self-generated, and inwardly directed (inner thoughts). However, can such an internal and intimate mental function also be modulated externally by means of brain stimulation? Addressing this question could also help identify the neural correlates of mind wandering in a causal manner, in contrast to the correlational methods used previously (primarily functional MRI). In our study, participants performed a monotonous task while we periodically sampled their thoughts to assess mind wandering. Concurrently, we applied transcranial direct current stimulation (tDCS). We found that stimulation of the frontal lobes [anode electrode at the left dorsolateral prefrontal cortex (DLPFC), cathode electrode at the right supraorbital area], but not of the occipital cortex or sham stimulation, increased the propensity to mind-wander. These results demonstrate for the first time, to our knowledge, that mind wandering can be enhanced externally using brain stimulation, and that the frontal lobes play a causal role in mind-wandering behavior. These results also suggest that the executive control network associated with the DLPFC might be an integral part of mind-wandering neural machinery.

Transcranial Direct Current Stimulation over the Parietal Cortex Improves Approximate Numerical Averaging.

The parietal cortex has been implicated in a variety of numerosity and numerical cognition tasks and was proposed to encompass dedicated neural populations that are tuned for analogue magnitudes as well as for symbolic numerals. Nonetheless, it remains unknown whether the parietal cortex plays a role in approximate numerical averaging (rapid, yet coarse computation of numbers' mean)-a process that is fundamental to preference formation and decision-making. To causally investigate the role of the parietal cortex in numerical averaging, we have conducted a transcranial direct current stimulation (tDCS) study, in which participants were presented with rapid sequences of numbers and asked to convey their intuitive estimation of each sequence's average. During the task, the participants underwent anodal (excitatory) tDCS (or sham), applied either on a parietal or a frontal region. We found that, although participants exhibit above-chance accuracy in estimating the average of numerical sequences, they did so with higher precision under parietal stimulation. In a second experiment, we have replicated this finding and confirmed that the effect is number-specific rather than domain-general or attentional. We present a neurocomputational model postulating population-coding underlying rapid numerical averaging to account for our findings. According to this model, stimulation of the parietal cortex elevates neural activity in number-tuned dedicated detectors, leading to increase in the system's signal-to-noise level and thus resulting in more precise estimations.

Applying Transcranial Magnetic Stimulation (TMS) Over the Dorsal Visual Pathway Induces Schizophrenia-like Disruption of Perceptual Closure.

Perceptual closure ability is postulated to depend upon rapid transmission of magnocellular information to prefrontal cortex via the dorsal stream. In contrast, illusory contour processing requires only local interactions within primary and ventral stream visual regions, such as lateral occipital complex. Schizophrenia is associated with deficits in perceptual closure versus illusory contours processing that is hypothesized to reflect impaired magnocellular/dorsal stream. Perceptual closure and illusory contours performance was evaluated in separate groups of 12 healthy volunteers during no TMS, and during repetitive 10 Hz rTMS stimulation over dorsal stream or vertex (TMS-vertex). Perceptual closure and illusory contours were performed in 11 schizophrenia patients, no TMS was applied in these patients. TMS effects were evaluated with repeated measures ANOVA across treatments. rTMS significantly increased perceptual closure identification thresholds, with significant difference between TMS-dorsal stream and no TMS. TMS-dorsal stream also significantly reduced perceptual closure but not illusory contours accuracy. Schizophrenia patients showed increased perceptual closure identification thresholds relative to controls in the no TMS condition, but similar to controls in the TMS-dorsal stream condition. Conclusions of this study are that magnocellular/dorsal stream input is critical for perceptual closure but not illusory contours performance, supporting both trickledown theories of normal perceptual closure function, and magnocellular/dorsal stream theories of visual dysfunction in schizophrenia.

Effects of Transcranial Alternating Current Stimulation on Cognitive Functions in Healthy Young and Older Adults.

Recently, transcranial alternating current stimulation (tACS) has emerged as a tool to enhance human cognitive processes. Here, we provide a brief summary of the rationale behind tACS-induced effects on task-relevant brain oscillations and associated cognitive functions and review previous studies in young subjects that have applied tACS in cognitive paradigms. Additionally, we present pilot data where we administered theta-tACS (6 Hz) over the temporoparietal cortex and a supraorbital reference for 20 min during implicit language learning in healthy young (mean/SD age: 22/2) and older (mean/SD age: 66/4) adults, in a sham-controlled crossover design. Linear mixed models revealed significantly increased retrieval accuracy following tACS-accompanied associative learning, after controlling for session order and learning success. These data provide the first implementation of tACS during cognitive performance in older adults and support recent studies suggesting that tACS in the theta frequency range may serve as a tool to enhance cognition, possibly through direct modulation of task-relevant brain oscillations. So far, studies have been heterogeneous in their designs, leaving a number of issues to be addressed in future research, including the setup of electrodes and optimal stimulation frequencies to be employed, as well as the interaction with age and underlying brain pathologies in specific patient populations.

Beyond words: evidence for automatic language-gesture integration of symbolic gestures but not dynamic landscapes.

Understanding actions based on either language or action observation is presumed to involve the motor system, reflecting the engagement of an embodied conceptual network. We examined how linguistic and gestural information were integrated in a series of cross-domain priming studies. We varied the task demands across three experiments in which symbolic gestures served as primes for verbal targets. Primes were clips of symbolic gestures taken from a rich set of emblems. Participants responded by making a lexical decision to the target (Experiment 1), naming the target (Experiment 2), or performing a semantic relatedness judgment (Experiment 3). The magnitude of semantic priming was larger in the relatedness judgment and lexical decision tasks compared to the naming task. Priming was also observed in a control task in which the primes were pictures of landscapes with conceptually related verbal targets. However, for these stimuli, the amount of priming was similar across the three tasks. We propose that action observation triggers an automatic, pre-lexical spread of activation, consistent with the idea that language-gesture integration occurs in an obligatory and automatic fashion.

Beyond social engagement: cognitive training leads to greater cognitive improvement in older adults.

Aging is often accompanied by a decline in cognitive functions, with memory being particularly affected. Recent studies suggest that cognitive training sessions that teach memory strategies relevant to daily life may benefit seniors who live in the community. However, it is possible that the cognitive improvement observed in these programs results from the social encounters embedded in them. In this study, we aimed to investigate the effect of a social cognitive training group, which met regularly for an extended period, on enhancing cognitive indices compared to a control group that only received social engagement meetings without training. Sixty-six participants with a mean age of 78 took part in 12 sessions of a social engagement group, with or without strategy training. Cognitive performance was assessed before and after training using four memory tasks, two similar to the trained tasks (near-transfer tasks) and two novel (far-transfer tasks). Both groups showed a slight improvement in most of the evaluation tasks, but the cognitive training combined with social engagement group showed a significant improvement in the Word Recall and Verbal Fluency tests compared to the social engagement group without training. Our findings suggest that cognitive training sessions may be a useful tool in promoting cognitive improvement among older adults living in the community, even beyond the improvement obtained from the social engagement that occurs during the training sessions.Trial registration number:NCT05016336. Date of registration: 20 August 2021. Retrospectively registered.

Autonomic nervous system responses to social stimuli among autistic individuals: A systematic review and meta-analysis.

Physiological responses to environmental and social stimuli have been studied broadly in relation to psychological states and processes. This may be especially important regarding autistic individuals, who show disparities in social interactions. However, findings from studies assessing autonomic nervous system (ANS) responses of autistic individuals present contradictions, with reports showing both autonomic disparities and intact autonomic functioning. The current study aimed to review the existing literature and to estimate if there is a difference between autistic individuals and neurotypical (NT) individuals in their autonomic responses to social stimuli. Furthermore, the study examined factors that may moderate this difference, including the type of physiological function measured, the level of participation required, as well as the age and intellectual functioning of the participants. The meta-analysis revealed a small and statistically insignificant overall difference between autistic and NT individuals, albeit with high heterogeneity. A further nested moderator analysis revealed a significant difference between autistic and NT individuals in physiological response that reflects mainly a parasympathetic nervous system (PNS) activity. Another difference was found in physiological response that reflects a combined activity of the sympathetic and parasympathetic systems, but only for experimental tasks that demanded active participation in social interactions. These results suggest a distinctiveness in autonomic regulation of autistic individuals in social situations, and point to the PNS as an important study objective for future investigation.

Post-traumatic growth correlates among parents of children with chronic illnesses: A systematic review and meta-analysis.

Parenting a child with a chronic illness presents a complex journey marked by various challenges, along with possible personal growth following these challenges. In this systematic review we present three meta-analyses, in order to examine the associations of post-traumatic growth (PTG) among parents of children with diverse chronic illnesses, and psychological distress, social support, and resilience. Analyzing 34 studies encompassing a total of 5328 parents, the results reveal several key findings. First, PTG was found to be prevalent among the parents. Second, there was no significant correlation between PTG and psychological distress, suggesting that these two processes may exist independently. Third, a positive correlation was observed between PTG and both social support and resilience-related factors, underscoring the role of these factors in fostering growth among parents of children with chronic illnesses. Additionally, illness type emerged as a moderator, affecting the strength of the above-mentioned correlations with PTG. Specifically, in the case of psychiatric illnesses, correlations of PTG with social support and resilience were stronger than in the context of other illnesses. Overall, this review emphasizes the significance of recognizing and addressing PTG correlates among parents of children with chronic illnesses, offering insights for clinical practice.

Right semantic modulation of early MEG components during ambiguity resolution.

The time-line of lexical ambiguity resolution in bilateral neuronal networks was investigated using magnetoencephalography (MEG) in a semantic decision task. Dominant and subordinate associations of ambiguous words are considered to be processed in the left and right hemispheres, respectively. In the experiment, ambiguous words were followed by dominant or subordinate associations (manipulated between blocks) or by unrelated target words, and participants (N=25) decided whether the words in each pair were related or not. Subordinate meaning blocks elicited greater changes in the magnetic fields relative to dominant ones over the right, but not the left hemisphere (LH) at 150-235 ms from target onset, a time window corresponding to the M/N170 M/EEG component. Beamforming analysis localized the differential right hemisphere (RH) activity at the perisylvian area, including the homologue regions of Broca's and Wernicke's. At a later stage (235-390 ms) there was no significant difference between the two meaning conditions. We suggest that the RH language regions assist the LH in integrating subordinate disambiguating clues to preceding context during the M170 time window.

Modulating lexical and semantic processing by transcranial direct current stimulation.

Here we aim to evaluate the ability of transcranial direct current stimulation (tDCS), which is applied over Wernicke's area and its right homologue, to influence lexical decisions and semantic priming and establish an involvement for temporo-parietal areas in lexical and semantic processing. Thirty-two subjects (17 women) completed a lexical decision task and a semantic priming task while receiving 20 min of bilateral tDCS stimulation (right anodal/left cathodal or left anodal/right cathodal stimulation) or sham stimulation. We hypothesized that right anodal/left cathodal stimulation over temporo-parietal areas would selectively interrupt the typical lexical processing dominance of the left hemisphere and facilitate mediated priming, while left anodal/right cathodal stimulation would selectively facilitate lexical processing and direct priming. Results showed impaired lexical processing under right anodal/left cathodal stimulation in comparison with sham and left anodal/right cathodal stimulation. Results are discussed in light of previous findings and hemispheric lateralization models.

Right but not left angular gyrus modulates the metric component of the mental body representation: a tDCS study.

The parietal lobes contribute to body-space representation. The present work aims at characterizing the functional role of the inferior parietal lobe in body-space representation and at studying the different roles of the angular gyrus in the right and left hemisphere. We conducted three separate transcranial direct current stimulation (tDCS) experiments using "tactile distance task" as an implicit measure of body representation. Whereas anodal tDCS on the right angular gyrus influences vocal reaction times (vRT) for stimuli delivered on the ipsilateral body parts without changes of accuracy, right tDCS improved both vRT and accuracy for tactile stimuli on the contralateral limbs. Sham or left parietal anodal tDCS had no effect. These evidences support the view that right parietal areas have a crucial role in the metric component of the body representation.

When less is more: evidence for a facilitative cathodal tDCS effect in attentional abilities.

Many previous studies reported that the hyperpolarization of cortical neurons following cathodal stimulation (in transcranial direct current stimulation) has resulted in cognitive performance degradation. Here, we challenge this assumption by showing that cathodal stimulation will not always degrade cognitive performance. We used an attentional load paradigm in which irrelevant stimuli are processed only under low but not under high attentional load. Thirty healthy participants were randomly allocated into three interventional groups with different brain stimulation parameters (active anodal posterior parietal cortex [PPC], active cathodal PPC, and sham). Cathodal but not anodal stimulation enabled flanker processing even in high-loaded scenes. A second experiment was carried out to assert whether the improved flanker processing under cathodal stimulation is because of altered attention allocation between center and surround or, alternatively, enhanced attentional resources. In this experiment, the flanker was presented centrally. The results of Experiment 2 replicated Experiment 1's finding of improved flanker processing. We interpret the results from these two experiments as evidence for the ability of cathodal stimulation to enhance attentional resources rather than simply change attention allocation between center and periphery. Cathodal stimulation in high-loaded scenes can act like a noise filter and may in fact enhance cognitive performance. This study contributes to understanding the way the PPC is engaged with attentional functions and explains the cathodal effects, which thus might lead to more efficient brain stimulation protocols.

Mechanisms of magnetic stimulation of central nervous system neurons.

Transcranial magnetic stimulation (TMS) is a stimulation method in which a magnetic coil generates a magnetic field in an area of interest in the brain. This magnetic field induces an electric field that modulates neuronal activity. The spatial distribution of the induced electric field is determined by the geometry and location of the coil relative to the brain. Although TMS has been used for several decades, the biophysical basis underlying the stimulation of neurons in the central nervous system (CNS) is still unknown. To address this problem we developed a numerical scheme enabling us to combine realistic magnetic stimulation (MS) with compartmental modeling of neurons with arbitrary morphology. The induced electric field for each location in space was combined with standard compartmental modeling software to calculate the membrane current generated by the electromagnetic field for each segment of the neuron. In agreement with previous studies, the simulations suggested that peripheral axons were excited by the spatial gradients of the induced electric field. In both peripheral and central neurons, MS amplitude required for action potential generation was inversely proportional to the square of the diameter of the stimulated compartment. Due to the importance of the fiber's diameter, magnetic stimulation of CNS neurons depolarized the soma followed by initiation of an action potential in the initial segment of the axon. Passive dendrites affect this process primarily as current sinks, not sources. The simulations predict that neurons with low current threshold are more susceptible to magnetic stimulation. Moreover, they suggest that MS does not directly trigger dendritic regenerative mechanisms. These insights into the mechanism of MS may be relevant for the design of multi-intensity TMS protocols, may facilitate the construction of magnetic stimulators, and may aid the interpretation of results of TMS of the CNS.

Modulating behavioral inhibition by tDCS combined with cognitive training.

Cognitive training is an effective tool to improve a variety of cognitive functions, and a small number of studies have now shown that brain stimulation accompanying these training protocols can enhance their effects. In the domain of behavioral inhibition, little is known about how training can affect this skill. As for transcranial direct current stimulation (tDCS), it was previously found that stimulation over the right inferior frontal gyrus (rIFG) facilitates behavioral inhibition performance and modulates its electrophysiological correlates. This study aimed to investigate this behavioral facilitation in the context of a learning paradigm by giving tDCS over rIFG repetitively over four consecutive days of training on a behavioral inhibition task (stop signal task (SST)). Twenty-two participants took part; ten participants were assigned to receive anodal tDCS (1.5 mA, 15 min), 12 were assigned to receive training but not active stimulation. There was a significant effect of training on learning and performance in the SST, and the integration of the training and rIFG-tDCS produced a more linear learning slope. Better performance was also found in the active stimulation group. Our findings show that tDCS-combined cognitive training is an effective tool for improving the ability to inhibit responses. The current study could constitute a step toward the use of tDCS and cognitive training as a therapeutic tool for cognitive control impairments in conditions such as attention-deficit hyperactivity disorder (ADHD) or schizophrenia.