Cortical activations associated with spatial remapping of finger touch using EEG.

The spatial coding of tactile information is functionally essential for touch-based shape perception and motor control. However, the spatiotemporal dynamics of how tactile information is remapped from the somatotopic reference frame in the primary somatosensory cortex to the spatiotopic reference frame remains unclear. This study investigated how hand position in space or posture influences cortical somatosensory processing. Twenty-two healthy subjects received electrical stimulation to the right thumb (D1) or little finger (D5) in three position conditions: palm down on right side of the body (baseline), hand crossing the body midline (effect of position), and palm up (effect of posture). Somatosensory-evoked potentials (SEPs) were recorded using electroencephalography. One early-, two mid-, and two late-latency neurophysiological components were identified for both fingers: P50, P1, N125, P200, and N250. D1 and D5 showed different cortical activation patterns: compared with baseline, the crossing condition showed significant clustering at P1 for D1, and at P50 and N125 for D5; the change in posture showed a significant cluster at N125 for D5. Clusters predominated at centro-parietal electrodes. These results suggest that tactile remapping of fingers after electrical stimulation occurs around 100-125 ms in the parietal cortex.

Why is there an error negativity on correct trials? A reappraisal.

In healthy subjects, the Error Negativity (Ne) was initially reported on errors and on partial errors, only. Later on, application of the Laplacian transformation to EEG data unmasked a Ne-like wave (Nc) that shares a main generator with the Ne, suggesting that the Nc is just a small Ne. However, the reason why a small Ne would persist on correct responses remains unclear. Now, sometimes, subthreshold EMG activations in the muscles corresponding to correct responses (not strong enough to reach the response threshold) can precede full-blown correct responses. These "partially correct" activities seem to correspond to (force) execution errors, as they evoke a sizeable Ne. Within the frames of the Reward Value and Prediction Model or of the Predicted Response-Outcome model we propose that the action monitoring system evokes a Ne/Nc on correct responses because, even when a correct choice has been made, the accuracy of response (force) execution cannot be fully predicted. If this interpretation is correct, it can be assumed that, once these execution errors have been corrected, the correctness of the (full-blown) correcting response is highly predictable. Consequently, they should evoke a smaller Nc/Ne than "pure" correct responses. We show, that for the response thresholds set in the present experiment, the correcting response of the trials containing a partially correct activation evoke no identifiable Nc at all. Therefore it seems that there usually is an Error Negativity on correct trials because the correctness of response (force) execution cannot be fully predicted.

'Hidden' anger as a risk factor for operational health: An exploratory approach among French military personnel.

Military personnel are repeatedly exposed to multiple stressors, and are sometimes characterized by high levels of anger. Evidence suggests that this anger can become dysfunctional, and impact the health status of populations chronically exposed to stress. In particular, rumination (understood as perseverative thoughts about a past event), provides a theoretical framework for investigating how anger may impact stress regulation abilities in military personnel declared fit for deployment. This exploratory study aimed therefore to examine the impact of the anger profile on psychological suffering in terms of burnout and post-traumatic stress disorder (PTSD), along with the reactivity of the autonomic nervous system, measured as cardiac variability. One hundred and seventeen French soldiers were tested before deployment to Operation BARKHANE. Anger rumination, burnout, and PTSD symptoms were assessed using questionnaires, and cardiac variability was measured as the questionnaires were completed. The results revealed two profiles related to anger trait and anger rumination. Burnout and PTSD scores were higher among military personnel with high levels of anger trait and rumination, and this group also had lower parasympathetic activity and flexibility after completing the questionnaires. These results suggest that there may be a link between an angry profile and psychological suffering, notably burnout and PTSD. Rumination could be involved in this link, as it is associated with poor adaptation to stress in a military context. Prospective researches including post-deployment will establish whether this ruminative response can account for the relationship between problematic anger, stress regulatory capacities and psychological health in military populations.

Highlighting of the interactions of MYD88 and NFKB1 SNPs in rats resistant to decompression sickness: toward an autoimmune response.

Decompression sickness (DCS) with neurological disorders includes an inappropriate inflammatory response which degenerates slowly, even after the disappearance of the bubbles. There is high inter-individual variability in terms of the occurrence of DCS that could have been mastered by the selection and then the breeding of DCS-resistant rats. We hypothesized the selection of single-nucleotide polymorphisms (SNPs) linked to autoimmunity operated upon a generation of a DCS-resistant strain of rats. We used the candidate gene approach and targeted SNPs linked to the signaling cascade that directly regulates inflammation of innate immunity transiting by the Toll-like receptors. Twenty candidate SNPs were investigated in 36 standard rats and 33 DCS-resistant rats. For the first time, we identify a diplotype (i.e., with matched haplotypes)-when coinherited-that strengthens protection against DCS, which is not strictly homozygous and suggests that a certain tolerance may be considered. We deduced an ideal haplotype of six variants from it (MyD88_50-T, _49-A, _97-C coupled to NFKB_85-T, _69-T, _45-T) linked to the resistant phenotype. Four among the six identified variants are located in pre- and/or post-transcriptional areas regulating MyD88 or NFKB1 expression. Because of missense mutations, the other two variants induce a structural change in the NFKB1 protein complex including one damage alteration according to the Missense3D algorithm. In addition to the MyD88/NFKB1 haplotype providing rats with a strong resistance to DCS, this also highlights the importance that the immune response, here linked to the genetic heritage, can have in the development of DCS and offer a new perspective for therapeutic strategies.

Quantitative analysis of early-stage EEG reactivity predicts awakening and recovery of consciousness in patients with severe brain injury.

BACKGROUND: Decisions of withdrawal of life-sustaining therapy for patients with severe brain injury are often based on prognostic evaluations such as analysis of electroencephalography (EEG) reactivity (EEG-R). However, EEG-R usually relies on visual assessment, which requires neurophysiological expertise and is prone to inter-rater variability. We hypothesised that quantitative analysis of EEG-R obtained 3 days after patient admission can identify new markers of subsequent awakening and consciousness recovery. METHODS: In this prospective observational study of patients with severe brain injury requiring mechanical ventilation, quantitative EEG-R was assessed using standard 11-lead EEG with frequency-based (power spectral density) and functional connectivity-based (phase-lag index) analyses. Associations between awakening in the intensive care unit (ICU) and reactivity to auditory and nociceptive stimulations were assessed with logistic regression. Secondary outcomes included in-ICU mortality and 3-month Coma Recovery Scale-Revised (CRS-R) score. RESULTS: Of 116 patients, 86 (74%) awoke in the ICU. Among quantitative EEG-R markers, variation in phase-lag index connectivity in the delta frequency band after noise stimulation was associated with awakening (adjusted odds ratio=0.89, 95% confidence interval: 0.81-0.97, P=0.02 corrected for multiple tests), independently of age, baseline severity, and sedation. This new marker was independently associated with improved 3-month CRS-R (adjusted ß=-0.16, standard error 0.075, P=0.048), but not with mortality (adjusted odds ratio=1.08, 95% CI: 0.99-1.18, P=0.10). CONCLUSIONS: An early-stage quantitative EEG-R marker was independently associated with awakening and 3-month level of consciousness in patients with severe brain injury. This promising marker based on functional connectivity will need external validation before potential integration into a multimodal prognostic model.

Communicating and reading emotion with masked faces in the Covid era: A short review of the literature.

Face masks have proven to be key to slowing down the SARS-Cov2 virus spread in the COVID-19 pandemic context. However, wearing face masks is not devoid of "side-effects", at both the physical and psychosocial levels. In particular, masks hinder emotion reading from facial expressions as they hide a significant part of the face. This disturbs both holistic and featural processing of facial expressions and, therefore, impairs emotion recognition, and influences many aspects of human social behavior. Communication in general is disrupted by face masks, as they modify the wearer's voice and prevent the audience from using lip reading or other non-verbal cues for speech comprehension. Individuals suffering from psychiatric conditions with impairment of communication, are at higher risk of distress because masks increase their difficulties to read emotions from faces. The identification and acknowledgement of these "side-effects" on communication are necessary because they warrant further work on adaptive solutions that will help foster the use of face masks by the greatest number.

The heartbeat evoked potential does not support strong interoceptive sensibility in trait mindfulness.

The enhancement of body awareness is proposed as one of the cognitive mechanisms that characterize mindfulness. To date, this hypothesis is supported by self-report and behavioral measures but still lacks physiological evidence. The current study investigated relation between trait mindfulness (i.e., individual differences in the ability to be mindful in daily life) and body awareness in combining a self-report measure (Multidimensional Assessment of Interoceptive Awareness [MAIA] questionnaire) with analysis of the heartbeat evoked potential (HEP), which is an event-related potential reflecting the cortical processing of the heartbeat. The HEP data were collected from 17 healthy participants under five minutes of resting-state condition. In addition, each participant completed the Freiburg Mindfulness Inventory and the MAIA questionnaire. Taking account of the important variability of HEP effects, analyses were replicated with the same participants three times (in three distinct sessions). First, group-level analyses showed that HEP amplitude and trait mindfulness do not correlate. Secondly, we observed that HEP amplitude could positively correlate with self-reported body awareness; however, this association was unreliable over time. Interestingly, we found that HEP measure shows very poor reliability over time at the individual level, potentially explaining the lack of reliable association between HEP and psychological traits. Lastly, a reliable positive correlation was found between self-reported trait mindfulness and body awareness. Taken together, these findings provide preliminary evidence that the HEP might not support the increased subjective body awareness in trait mindfulness, thus suggesting that perhaps objective and subjective measures of body awareness could be independent.

Impact of skull-to-brain conductivity ratio for high resolution EEG source localization.

Objective. To measure the impact of skull-to-brain conductivity ratios on interictal spikes source localizations, using high resolution EEG (HR EEG). In previous studies, two ratios were mainly employed: 1/80 and 1/40. Consequences of the employed ratios on source localization results are poorly studied.Methods. Twenty patients with drug-resistant epilepsy were studied using HR EEG (sixty-four scalp electrodes). For each patient, three-layers realistic head models based on individual MRI were elaborated using boundary element model. For each interictal spike, source localization was performed six times, using six skull-to-brain conductivity ratios (1/80, 1/50, 1/40, 1/30, 1/20 and 1/10), exploring all the spectrum of values reported in the literature. We then measured distances between the different sources obtained and between the sources and the anterior commissure (in order to estimate sources depth).Results. We measured a mean distance of 5.3 mm (sd: 3 mm) between the sources obtained with 1/40 versus 1/80 ratio. This distance increased when the discrepancy between the two evaluated ratios increased. We measured a mean distance of 14.2 mm (sd: 4.9 mm) between sources obtained with 1/10 ratio versus 1/80 ratio. Sources localized using 1/40 ratio were 4.3 mm closer to the anterior commissure than sources localized using 1/80 ratio.Significance. Skull-to-brain conductivity ratio is an often-neglected parameter in source localization studies. The different ratios mainly used in the litterature (1/80 and 1/40) lead to significant differences in source localizations. These variations mainly occur in source depth. A more accurate estimation of skull-to-brain conductivity is needed to increase source localization accuracy.Abbreviations. ECD: equivalent current dipole; EIT: electric impedance tomography, HR EEG: High resolution Electroencephalography, IIS: Inter ictal spikes, MEG: Magnetoencephalography, MRI: Magnetic resonance imaging, mS/m: milli-Siemens/m, S/m: Siemens/m, SD: Standard deviation.

The Effectiveness of Vagus Nerve Stimulation in Drug-Resistant Epilepsy Correlates with Vagus Nerve Stimulation-Induced Electroencephalography Desynchronization.

Introduction: VNS is an adjunctive neuromodulation therapy for patients with drug-refractory epilepsy. The antiseizure effect of VNS is thought to be related to a diffuse modulation of functional connectivity but remains to be confirmed. Aim: To investigate electroencephalographic (EEG) metrics of functional connectivity in patients with drug-refractory epilepsy treated by vagus nerve stimulation (VNS), between VNS-stimulated "ON" and nonstimulated "OFF" periods and between responder (R) and nonresponder (NR) patients. Methods: Scalp-EEG was performed for 35 patients treated by VNS, using 21 channels and 2 additional electrodes on the neck to detect the VNS stimulation. Patients were defined as VNS responders if a reduction of seizure frequency of ∼50% was documented. We analyzed the synchronization in EEG time series during "ON" and "OFF" periods of stimulation, using average phase lag index (PLI) in signal space and phase-locking value (PLV) between 10 sources. Based on graph theory, we computed brain network models and analyzed minimum spanning tree (MST) for responder and nonresponder patients. Results: Among 35 patients treated by VNS for a median time of 7 years (range 4 months to 22 years), 20 were R and 15 were NR. For responder patients, PLI during ON periods was significantly lower than that during OFF periods in delta (p = 0.009), theta (p = 0.02), and beta (p = 0.04) frequency bands. For nonresponder patients, there were no significant differences between ON and OFF periods. Moreover, variations of seizure frequency with VNS correlated with the PLI OFF/ON ratio in delta (p = 0.02), theta (p = 0.04), and beta (p = 0.03) frequency bands. Our results were confirmed using PLV in theta band (p < 0.05). No significant differences in MST were observed between R and NR patients. Conclusion: The correlation between VNS-induced interictal EEG time-series desynchronization and decrease in seizure frequency suggested that VNS therapeutic impact might be related to changes in interictal functional connectivity. Impact statement Electroencephalography (EEG) desynchronization has been proposed to be a mechanism for antiepileptic effect of vagus nerve stimulation (VNS). We measured interictal EEG time-series synchronization during stimulated (ON) and nonstimulated (OFF) periods in epileptic patients treated by VNS. Phase lag index differences between ON and OFF periods were measured in delta, theta, and beta bands only in responder patients. To our knowledge, our study is the first to statistically correlate interictal cortical desynchronization during ON periods with reduction in seizure frequency. Our result supports the hypothesis that the antiseizure effect of VNS is mediated by cortical desynchronization.

Toward a Refined Mindfulness Model Related to Consciousness and Based on Event-Related Potentials.

Neuroimaging, behavioral, and self-report evidence suggests that there are four main cognitive mechanisms that support mindfulness: (a) self-regulation of attention, (b) improved body awareness, (c) improved emotion regulation, and (d) change in perspective on the self. In this article, we discuss these mechanisms on the basis of the event-related potential (ERP). We reviewed the ERP literature related to mindfulness and examined a data set of 29 articles. Our findings show that the neural features of mindfulness are consistently associated with the self-regulation of attention and, in most cases, reduced reactivity to emotional stimuli and improved cognitive control. On the other hand, there appear to be no studies of body awareness. We link these electrophysiological findings to models of consciousness and introduce a unified, mechanistic mindfulness model. The main idea in this refined model is that mindfulness decreases the threshold of conscious access. We end with several working hypotheses that could direct future mindfulness research and clarify our results.

Dopamine and response selection: an Acute Phenylalanine/Tyrosine Depletion study.

The role of dopaminergic system in decision-making is well documented, and evidence suggests that it could play a significant role in response selection processes. The N-40 is a fronto-central event-related potential, generated by the supplementary motor areas (SMAs) and a physiological index of response selection processes. The aim of the present study was to determine whether infraclinical effects of dopamine depletion on response selection processes could be evidenced via alterations of the N-40. We obtained a dopamine depletion in healthy volunteers with the acute phenylalanine and tyrosine depletion (APTD) method which consists in decreasing the availability of dopamine precursors. Subjects realized a Simon task in the APTD condition and in the control condition. When the stimulus was presented on the same side as the required response, the stimulus-response association was congruent and when the stimulus was presented on the opposite side of the required response, the stimulus-response association was incongruent. The N-40 was smaller for congruent associations than for incongruent associations. Moreover, the N-40 was sensitive to the level of dopaminergic activity with a decrease in APTD condition compared to control condition. This modulation of the N-40 by dopaminergic level could not be explained by a global decrease of cerebral electrogenesis, since negativities and positivities indexing the recruitment of the primary motor cortex (anatomically adjacent to the SMA) were unaffected by APTD. The specific sensitivity of N-40 to ATPD supports the model of Keeler et al. (Neuroscience 282:156-175, 2014) according to which the dopaminergic system is involved in response selection.

On-line action monitoring of response execution: An electrophysiological study.

In between-hand choice-RT-tasks, small incorrect EMG activations occurring before the correct response ("partial errors") are assumed to reflect the detection, inhibition and correction of erroneous hand selection, revealing the existence of an action monitoring system, acting "on-line". Now, EMG activations of the correctly selected hand muscles, too small to reach the response threshold, may also occur before these hand muscles produce an overt correct response ("partial corrects"). We hypothesized that partial corrects reflect incorrect execution of correctly selected responses. We found 1) that response force was smaller on trials preceding a partial correct trial and 2) that the Error Negativity, a performance sensitive ERP, assumed to reveal "on-line" action monitoring, was larger for partial corrects than for correct trials. This also suggests that the competence of the action monitoring system is not restricted to selection errors but also extends to execution errors.

Recreational Diving Practice for Stress Management: An Exploratory Trial.

Background: Within the components of Scuba diving there are similarities with meditation and mindfulness techniques by training divers to be in a state of open monitoring associated with slow and ample breathing. Perceived stress is known to be diminished during meditation practice. This study evaluates the benefits of scuba diving on perceived stress and mindful functioning. Method: A recreational diving group (RDG; n = 37) was compared with a multisport control group (MCG; n = 30) on perceived stress, mood, well-being and mindfulness by answering auto-questionnaires before and after a 1-week long UCPA course. For the diving group, stability of the effects was evaluated 1 month later using similar auto-questionnaires. Results: Perceived stress did not decrease after the course for the MCG [ The divers showed a significant reduction on the perceived stress score (p < 0.05) with a sustainable effect (p = 0.01)]. An improvement in mood scale was observed in both groups. This was associated to an increase in mindfulness abilities. Conclusions: The practice of a recreational sport improves the mood of subjects reporting the thymic benefits of a physical activity performed during a vacation period. The health benefits of recreational diving appear to be greater than the practice of other sports in reducing stress and improving well-being.

Dopamine precursors depletion impairs impulse control in healthy volunteers.

The aim of the present study was to decipher the role of the dopamine system in impulse control. Impulsive actions entail (i) activation of the motor system by an impulse, which is an urge to act and (ii) a failure to suppress that impulse, when inappropriate, in order to prevent an error. These two aspects of action impulsivity can be experimentally disentangled in conflict reaction time tasks such as the Simon task, which measures susceptibility to acting on spontaneous impulses (as well as the proficiency of suppressing these impulses). In 12 healthy volunteers performing a Simon task, dopamine availability was reduced with an amino acid drink deficient in the dopamine precursors, phenylalanine and tyrosine. Classic behavioral measures were augmented with an analysis of the electromyographic activity of the response effectors. Electromyography allows one to detect covert activations undetectable with strictly behavioral measures and further reveals the participants' ability to quickly suppress covert activations before they result in an overt movement. Following dopamine depletion, compared with a placebo condition, participants displayed comparable impulse activation but were less proficient at suppressing the interference from this activation. These results provide evidence that the dopamine system is directly involved in the suppression of maladaptive response impulses.

The N-40: an electrophysiological marker of response selection.

A frontocentral electrophysiological wave occurring before the response, the N-40, has been reported in response choice situations compared to no-choice situations. This was interpreted as reflecting response selection. The gradual sensitivity of the N-40 to the demands put on response choice was tested by manipulating stimulus-response (S-R) congruence so as to influence response selection processes. After Laplacian transformation, an N-40 clearly emerged and was larger for incongruent (more demanding) than for congruent (less demanding) S-R associations. The N-40, which possibly reflects SMA activation, thus provides information about the implementation of response selection in the brain.

Sleep deprivation affects the sensitivity of proactive and reactive action monitoring: a behavioural and ERP analysis.

We studied the impact of sleep deprivation on action monitoring. Each participant performed a Simon task after a normal night of sleep and after 26 h of awakening. Reaction time (RT) distributions were analyzed and the sensitivity of the error negativity (Ne/Ne like) to response correctness was examined. Results showed that (1) the Simon effect persisted for the longest RTs only after sleep deprivation and (2) the sensitivity of the Ne/Ne like to correctness decreased after sleep deprivation, especially on incongruent trials. This suggests that after sleep deprivation (1) the ability to inhibit prepotent response tendencies is impaired and (2) the sensitivity of a response monitoring system as revealed by the error negativity is less sensitive to performance. In conclusion, action monitoring was affected by sleep deprivation as revealed by distributional analyses and the sensitivity of the Ne/Ne like to performance, which may be attributed to the fragility of prefrontal structures to sleep deprivation.