Predicting and coding sound into action translation in spinal cord injured people.

Motor activation in response to perception of action-related stimuli may depend on a resonance mechanism subserving action understanding. The extent to which this mechanism is innate or learned from sensorimotor experience is still unclear. Here, we recorded EEG while people with paraplegia or tetraplegia consequent to spinal cord injury (SCI) and healthy control participants were presented with action sounds produced by body parts (mouth, hands or feet) that were or were not affected by SCI. Non-action sounds were used as further control. We observed reduced brain activation in subjects affected by SCI at both pre- and post-stimulus latencies specifically for those actions whose effector was disconnected by the spinal lesion (i.e., hand sound for tetraplegia and leg sound for both paraplegia and tetraplegia). Correlation analyses showed that these modulations were functionally linked with the chronicity of the lesion, indicating that the longer the time the lesion- EEG data acquisition interval and/or the more the lesion occurred at a young age, the weaker was the cortical activity in response to these action sounds. Tellingly, source estimations confirmed that these modulations originated from a deficit in the motor resonance mechanism, by showing diminished activity in premotor (during prediction and perception) and near the primary motor (during perception) areas. Such dissociation along the cortical hierarchy is consistent with both previous reports in healthy subjects and with hierarchical predictive coding accounts. Overall, these data expand on the notion that sensorimotor experience maintains the cortical representations relevant to anticipate and perceive action-related stimuli.

The performance monitoring system is attuned to others' actions during dyadic motor interactions.

Interpersonal motor interactions require the simultaneous monitoring of one's own and one's partner's actions. To characterize how the action monitoring system tracks self and other behavior during synchronous interactions, we combined electroencephalography recordings and immersive virtual reality in two tasks where participants were asked to synchronize their actions with those of a virtual partner (VP). The two tasks differed in the features to be monitored: the Goal task required participants to predict and monitor the VP's reaching goal; the Spatial task required participants to predict and monitor the VP's reaching trajectory. In both tasks, the VP performed unexpected movement changes to which the participant needed to adapt. By extracting the neural activity locked to the detection of unexpected changes in the VP's action (other-monitoring) or to the participants' action-replanning (self-monitoring), we show that the monitoring system is more attuned to others' than to one's own actions. Additionally, distinctive neural responses to VP's unexpected goals and trajectory corrections were found: goal changes were reflected both in early fronto-central and later posterior neural responses while trajectory deviations were reflected only in later posterior responses. Altogether, our results indicate that the monitoring system adopts an inherent social mode to handle interpersonal motor interactions.

The evolution of workplace risk for Covid-19 in Canadian healthcare workers and its relation to vaccination: A nested case-referent study.

BACKGROUND: During the early months of the Covid-19 pandemic, studies demonstrated that healthcare workers (HCWs) were at increased risk of infection. Few modifiable risks were identified. It is largely unknown how these evolved over time. METHODS: A prospective case-referent study was established and nested within a cohort study of Canadian HCWs. Cases of Covid-19, confirmed by polymerase chain reaction, were matched with up to four referents on job, province, gender, and date of first vaccination. Cases and referents completed a questionnaire reporting exposures and experiences in the 21 days before case date. Participants were recruited from October 2020 to March 2022. Workplace factors were examined by mixed-effects logistic regression allowing for competing exposures. A sensitivity analysis was limited to those for whom family/community transmission seemed unlikely. RESULTS: 533 cases were matched with 1697 referents. Among unvaccinated HCWs, the risk of infection was increased if they worked hands-on with patients with Covid-19, on a ward designated for care of infected patients, or handled objects used by infected patients. Sensitivity analysis identified work in residential institutions and geriatric wards as high risk for unvaccinated HCWs. Later, with almost universal HCW vaccination, risk from working with infected patients was much reduced but cases were more likely than referents to report being unable to access an N95 mask or that decontaminated N95 masks were reused. CONCLUSIONS: These results suggest that, after a rocky start, the risks of Covid-19 infection from work in health care are now largely contained in Canada but with need for continued vigilance.

Midfrontal Theta Transcranial Alternating Current Stimulation Facilitates Motor Coordination in Dyadic Human-Avatar Interactions.

Synchronous interpersonal motor interactions require moment-to-moment prediction and proactive monitoring of the partner's actions. Neurophysiologically, this is highlighted by an enhancement of midfrontal theta (4-7 Hz) oscillations. In this study, we explored the causal role of midfrontal theta for interpersonal motor interactions using transcranial alternating current stimulation (tACS). We implemented a realistic human-avatar interaction task in immersive virtual reality where participants controlled a virtual arm and hand to press a button synchronously with a virtual partner. Participants completed the task while receiving EEG-informed theta (Experiment 1) or beta (control frequency, Experiment 2) tACS over the frontal midline, as well as sham stimulation as a control. Results showed that midfrontal theta tACS significantly improved behavioral performance (i.e., reduced interpersonal asynchrony) and participants' motor strategies (i.e., increased movement times and reduced RTs), whereas beta tACS had no effect on these measures. These results suggest that theta tACS over frontal areas facilitates action monitoring and motor abilities supporting interpersonal interactions.

A neurodynamic model of inter-brain coupling in the gamma band.

The use of EEG to simultaneously record multiple brains (i.e., hyperscanning) during social interactions has led to the discovery of inter-brain coupling (IBC). IBC is defined as the neural synchronization between people and is considered to be a marker of social interaction. IBC has previously been observed across different frequency bands, including theta [4-7 Hz]. Given the proximity of this frequency range with behavioral rhythms, models have been able to combine IBC in theta with sensorimotor coordination patterns. Interestingly, empirical EEG-hyperscanning results also report the emergence of IBC in the gamma range [>30 Hz]. Gamma oscillations' fast and transient nature makes a direct link between gamma-IBC and other (much slower) interpersonal dynamics difficult, leaving gamma-IBC without a plausible model. However, at the intrabrain level, gamma activity is coupled with the dynamics of lower frequencies through cross-frequency coupling (CFC). This paper provides a biophysical explanation, through the simulation of neural data, for the emergence of gamma inter-brain coupling using a Kuramoto model of four oscillators divided into two separate (brain) units. By modulating both the degree of inter-brain coupling in the theta band (i.e., between-units coupling) and CFC (i.e., intraunit theta-gamma coupling), we provide a theoretical explanation of the observed gamma-IBC phenomenon in the EEG-hyperscanning literature.NEW & NOTEWORTHY The last years were marked by an increasing interest in multiple-brain recordings. However, the inter-brain coupling arising across interacting individuals also sparks debates about the underlying biological mechanisms. The inter-brain coupling in the gamma band [>30 Hz] was particularly criticized for lacking a theoretical framework. Here, by using biologically informed neural simulations with the Kuramoto model, we assess the role of intra- and inter-brain neural dynamics in the emergence of inter-brain synchrony in the gamma band.

Role of the occipito-temporal theta rhythm in hand visual identification.

Neuroimaging and EEG studies have shown that passive observation of the full body and of specific body parts is associated with 1) activity of an occipito-temporal region named the extrastriate body area (EBA), 2) amplitude modulations of a specific posterior event-related potential (ERP) component (N1/N190), and 3) a theta-band (4-7 Hz) synchronization recorded from occipito-temporal electrodes compatible with the location of EBA. To characterize the functional role of the occipito-temporal theta-band increase during the processing of body-part stimuli, we recorded EEG from healthy participants while they were engaged in an identification task (match-to-sample) of images of hands and nonbody control images (leaves). In addition to confirming that occipito-temporal electrodes show a larger N1 for hand images compared with control stimuli, cluster-based analysis revealed an occipito-temporal cluster showing an increased theta power when hands are presented (compared with leaves) and show that this theta increase is higher for identified hands compared with nonidentified ones while not being significantly different between not identified nonhand stimuli. Finally, single trial multivariate pattern analysis revealed that time-frequency modulation in the theta band is a better marker for classifying the identification of hand images than the ERP modulation. The present results support the notion that theta activity over the occipito-temporal cortex is an informative marker of hand visual processing and may reflect the activity of a network coding for stimulus identity.NEW & NOTEWORTHY Hands provide crucial information regarding the identity of others, which is a key information for social processes. We recorded EEG activity of healthy participants during the visual identification of hand images. The combination of univariate and multivariate pattern analysis in time- and time-frequency domain highlights the functional role of theta (4-7 Hz) activity over visual areas during hand identification and emphasizes the robustness of this neuromarker in occipito-temporal visual processing dynamics.

Theta synchronization over occipito-temporal cortices during visual perception of body parts.

Categorical clustering in the visual system is thought to have evolved as a function of intrinsic (intra-areal) and extrinsic (interareal) connectivity and experience. In the visual system, the extrastriate body area (EBA), an occipito-temporal region, responds to full body and body part images under the organizational principle of their functional/semantic meaning. Although frequency-specific modulations of neural activity associated with perceptive and cognitive functions are increasingly attracting the interest of neurophysiologists and cognitive neuroscientists, perceiving single body parts with different functional meaning and full body images induces time-frequency modulations over occipito-temporal electrodes are yet to be described. Here, we studied this issue by measuring EEG in participants who passively observed fingers, hands, arms and faceless full body images with four control plant stimuli, each bearing hierarchical analogy with the body stimuli. We confirmed that occipito-temporal electrodes (compatible with the location of EBA) show a larger event-related potential (ERP, N190) for body-related images. Furthermore, we identified a body part-specific (i.e. selective for hands and arms) theta event-related synchronization increase under the same electrodes. This frequency modulation associated with the perception of body effectors over occipito-temporal cortices is in line with recent findings of categorical organization of neural responses to human effectors in the visual system.

Computer-based versus in-person interventions for preventing and reducing stress in workers.

BACKGROUND: Chronic exposure to stress has been linked to several negative physiological and psychological health outcomes. Among employees, stress and its associated effects can also result in productivity losses and higher healthcare costs. In-person (face-to-face) and computer-based (web- and mobile-based) stress management interventions have been shown to be effective in reducing stress in employees compared to no intervention. However, it is unclear if one form of intervention delivery is more effective than the other. It is conceivable that computer-based interventions are more accessible, convenient, and cost-effective. OBJECTIVES: To compare the effects of computer-based interventions versus in-person interventions for preventing and reducing stress in workers. SEARCH METHODS: We searched CENTRAL, MEDLINE, PubMed, Embase, PsycINFO, NIOSHTIC, NIOSHTIC-2, HSELINE, CISDOC, and two trials registers up to February 2017. SELECTION CRITERIA: We included randomised controlled studies that compared the effectiveness of a computer-based stress management intervention (using any technique) with a face-to-face intervention that had the same content. We included studies that measured stress or burnout as an outcome, and used workers from any occupation as participants. DATA COLLECTION AND ANALYSIS: Three authors independently screened and selected 75 unique studies for full-text review from 3431 unique reports identified from the search. We excluded 73 studies based on full-text assessment. We included two studies. Two review authors independently extracted stress outcome data from the two included studies. We contacted study authors to gather additional data. We used standardised mean differences (SMDs) with 95% confidence intervals (CIs) to report study results. We did not perform meta-analyses due to variability in the primary outcome and considerable statistical heterogeneity. We used the GRADE approach to rate the quality of the evidence. MAIN RESULTS: Two studies met the inclusion criteria, including a total of 159 participants in the included arms of the studies (67 participants completed computer-based interventions; 92 participants completed in-person interventions). Workers were primarily white, Caucasian, middle-aged, and college-educated. Both studies delivered education about stress, its causes, and strategies to reduce stress (e.g. relaxation or mindfulness) via a computer in the computer-based arm, and via small group sessions in the in-person arm. Both studies measured stress using different scales at short-term follow-up only (less than one month). Due to considerable heterogeneity in the results, we could not pool the data, and we analysed the results of the studies separately. The SMD of stress levels in the computer-based intervention group was 0.81 standard deviations higher (95% CI 0.21 to 1.41) than the in-person group in one study, and 0.35 standard deviations lower (95% CI -0.76 to 0.05) than the in-person group in another study. We judged both studies as having a high risk of bias. AUTHORS' CONCLUSIONS: We found very low-quality evidence with conflicting results, when comparing the effectiveness of computer-based stress management interventions with in-person stress management interventions in employees. We could include only two studies with small sample sizes. We have very little confidence in the effect estimates. It is very likely that future studies will change these conclusions.

A simple technique to study embodied language processes: the grip force sensor.

Research in cognitive neuroscience has shown that brain structures serving perceptual, emotional, and motor processes are also recruited during the understanding of language when it refers to emotion, perception, and action. However, the exact linguistic and extralinguistic conditions under which such language-induced activity in modality-specific cortex is triggered are not yet well understood. The purpose of this study is to introduce a simple experimental technique that allows for the online measure of language-induced activity in motor structures of the brain. This technique consists in the use of a grip force sensor that captures subtle grip force variations while participants listen to words and sentences. Since grip force reflects activity in motor brain structures, the continuous monitoring of force fluctuations provides a fine-grained estimation of motor activity across time. In other terms, this method allows for both localization of the source of language-induced activity to motor brain structures and high temporal resolution of the recorded data. To facilitate comparison of the data to be collected with this tool, we present two experiments that describe in detail the technical setup, the nature of the recorded data, and the analyses (including justification about the data filtering and artifact rejection) that we applied. We also discuss how the tool could be used in other domains of behavioral research.

Long COVID-ACOEM Guidance Statement.

ABSTRACT: Persistent symptoms are common after acute COVID-19, often referred to as long COVID. Long COVID may affect the ability to perform activities of daily living, including work. Long COVID occurs more frequently in those with severe acute COVID-19. This guidance statement reviews the pathophysiology of severe acute COVID-19 and long COVID and provides pragmatic approaches to long COVID symptoms, syndromes, and conditions in the occupational setting. Disability laws and workers' compensation are also addressed.

Reported harassment and mental ill-health in a Canadian prospective cohort of women and men in welding and electrical trades.

OBJECTIVES: Experience of psychosocial environments by workers entering trade apprenticeships may differ by gender. We aimed to document perceived harassment and to investigate whether this related to mental ill-health. METHODS: Cohorts of workers in welding and electrical trades were established, women recruited across Canada and men from Alberta. Participants were recontacted every 6 months for up to 3 years (men) or 5 years (women). At each contact, they were asked about symptoms of anxiety and depression made worse by work. After their last regular contact, participants received a "wrap-up" questionnaire that included questions on workplace harassment. In Alberta, respondents who consented were linked to the administrative health database that recorded diagnostic codes for each physician contact. RESULTS: One thousand eight hundred and eighty five workers were recruited, 1,001 in welding trades (447 women), and 884 in electrical trades (438 women). One thousand four hundred and nineteen (75.3%) completed a "wrap up" questionnaire, with 1,413 answering questions on harassment. Sixty percent of women and 32% of men reported that they had been harassed. Those who reported harassment had more frequently recorded episodes of anxiety and depression made worse by work in prospective data. In Alberta, 1,242 were successfully matched to administrative health records. Those who reported harassment were more likely to have a physician record of depression since starting their trade. CONCLUSIONS: Tradeswomen were much more likely than tradesmen to recall incidents of harassment. The results from record linkage, and from prospectively collected reports of anxiety and depression made worse by work, support a conclusion that harassment resulted in poorer mental health.

Availability, use, and impact of workplace mental health supports during the COVID-19 pandemic in a Canadian cohort of healthcare workers.

We investigated the availability and use of workplace mental health (MH) supports during the COVID-19 pandemic in a Canadian cohort of healthcare workers (HCW) and measured anxiety and depression by the Hospital Anxiety and Depression Scale (HADS) completed at four contacts 2020-2022. Reports were available for 4400 HCW working with patients. Half the HCWs had a clinically significant HADS score at one or more contacts Access to MH supports increased during the pandemic, with 94% reporting access to some workplace support by 2022: 47% had made use of at least one support. 25% of those with high HADS scores used no support. Older women and men with depressive conditions were less likely to report use. Reported use of an Employee Assistance Program was associated with a reduction in HADS scores in the following months.

Work Characteristics, Workplace Support, and Mental Ill-Health in a Canadian Cohort of Healthcare Workers During the COVID-19 Pandemic.

OBJECTIVE: The aim of the study was to identify determinants of mental health in healthcare workers (HCW) during the COVID-19 pandemic. METHODS: A cohort of Canadian HCW completed four questionnaires giving details of work with patients, ratings of workplace supports, a mental health questionnaire, and substance use. Principal components were extracted from 23 rating scales. Risk factors were examined by Poisson regression. RESULTS: A total of 4854 (97.8%) of 4964 participants completed ratings and mental health questionnaires. Healthcare workers working with patients with COVID-19 had high anxiety and depression scores. One of three extracted components, 'poor support,' was related to work with infected patients and to anxiety, depression, and substance use. Availability of online support was associated with feelings of better support and less mental ill-health. CONCLUSIONS: Work with infected patients and perceived poor workplace support were related to anxiety and depression during the pandemic.

Determinants of SARS-CoV-2 IgG response and decay in Canadian healthcare workers: A prospective cohort study.

INTRODUCTION: Healthcare workers (HCWs) from an interprovincial Canadian cohort gave serial blood samples to identify factors associated with anti-receptor binding domain (anti-RBD) IgG response to the SARS-CoV-2 virus. METHODS: Members of the HCW cohort donated blood samples four months after their first SARS-CoV-2 immunization and again at 7, 10 and 13 months. Date and type of immunizations and dates of SARS-CoV-2 infection were collected at each of four contacts, together with information on immunologically-compromising conditions and current therapies. Blood samples were analyzed centrally for anti-RBD IgG and anti-nucleocapsid IgG (Abbott Architect, Abbott Diagnostics). Records of immunization and SARS-CoV-2 testing from public health agencies were used to assess the impact of reporting errors on estimates from the random-effects multivariable model fitted to the data. RESULTS: 2752 of 4567 vaccinated cohort participants agreed to donate at least one blood sample. Modelling of anti-RBD IgG titer from 8903 samples showed an increase in IgG with each vaccine dose and with first infection. A decrease in IgG titer was found with the number of months since vaccination or infection, with the sharpest decline after the third dose. An immunization regime that included mRNA1273 (Moderna) resulted in higher anti-RBD IgG. Participants reporting multiple sclerosis, rheumatoid arthritis or taking selective immunosuppressants, tumor necrosis factor inhibitors, calcineurin inhibitors and antineoplastic agents had lower anti-RBD IgG. Supplementary analyses showed higher anti-RBD IgG in those reporting side-effects of vaccination, no relation of anti-RBD IgG to obesity and lower titers in women immunized in early or mid-pregnancy. Sensitivity analysis results suggested no important bias in the self-report data. CONCLUSION: Creation of a prospective cohort was central to the credibility of results presented here. Serial serology assessments, with longitudinal analysis, provided effect estimates with enhanced accuracy and a clearer understanding of medical and other factors affecting response to vaccination.

Excess risk of COVID-19 infection and mental distress in healthcare workers during successive pandemic waves: Analysis of matched cohorts of healthcare workers and community referents in Alberta, Canada.

OBJECTIVES: To investigate changes in risk of infection and mental distress in healthcare workers (HCWs) relative to the community as the COVID-19 pandemic progressed. METHODS: HCWs in Alberta, Canada, recruited to an interprovincial cohort, were asked consent to link to Alberta's administrative health database (AHDB) and to information on COVID-19 immunization and polymerase chain reaction (PCR) testing. Those consenting were matched to records of up to five community referents (CRs). Physician diagnoses of COVID-19 were identified in the AHDB from the start of the pandemic to 31 March 2022. Physician consultations for mental health (MH) conditions (anxiety, stress/adjustment reaction, depressive) were identified from 1 April 2017 to 31 March 2022. Risks for HCW relative to CR were estimated by fitting wave-specific hazard ratios. RESULTS: Eighty percent (3050/3812) of HCWs consented to be linked to the AHDB; 97% (2959/3050) were matched to 14,546 CRs. HCWs were at greater risk of COVID-19 overall, with first infection defined from either PCR tests (OR=1.96, 95%CI 1.76-2.17) or physician records (OR=1.33, 95%CI 1.21-1.45). They were also at increased risk for each of the three MH diagnoses. In analyses adjusted for confounding, risk of COVID-19 infection was higher than for CRs early in the pandemic and during the fifth (Omicron) wave. The excess risk of stress/adjustment reactions (OR=1.52, 95%CI 1.35-1.71) and depressive conditions (OR=1.39, 95%CI 1.24-1.55) increased with successive waves during the epidemic, peaking in the fourth wave. CONCLUSION: HCWs were at increased risk of both COVID-19 and mental ill-health with the excess risk continuing late in the pandemic.

RéSUMé: OBJECTIFS: Étudier l'évolution du risque d'infection et de problèmes de santé mentale (PSM) chez les travailleurs de la santé (TdS), comparé à la population générale, au cours de la pandémie de COVID-19. MéTHODES: Certains TdS de l'Alberta (Canada) participant à une cohorte interprovinciale, ont consenti à ce que la base administrative de santé de l'Alberta (AHDB) nous transmette leurs données de vaccination contre la COVID-19 et de tests d'amplification des acides nucléiques (TAAN). Ceux ayant consenti ont été appariés à un maximum de cinq témoins de population générale. Les diagnostics médicaux (par médecins) de COVID-19 ont été identifiés dans l'AHDB du début de la pandémie jusqu'au 31 mars 2022. Les consultations médicales pour PSM (anxiété, stress/troubles de l'adaptation, dépression) ont été identifiées entre le 1er avril 2017 et le 31 mars 2022. Les rapports de cotes (RC) comparant les TdS aux témoins de la population générale ont été estimés pour chaque vague d'infection. RéSULTATS: Quatre-vingts pourcent (80 %; 3050/3812) des TdS ont donné leur consentement à ce que leurs données nous soient transmises par l'AHDB; 97 % d'entre eux (2959/3050) ont été appariés à 14 546 témoins. Dans l'ensemble, les TdS étaient plus à risque de COVID-19, avec une première infection identifiée soit par les TANN (RC=1,96, IC de 95% 1,76-2,17), soit via les dossiers médicaux (RC=1,33, IC de 95% 1,21-1,45). Ils étaient également plus à risque pour chacun des trois problèmes de SM. Le risque de COVID-19 ajustés pour les facteurs de confusion était plus élevé que chez les témoins au début de la pandémie et durant la cinquième vague (variant Omicron). Les excès de risque de stress/troubles de l'adaptation (RC=1,52, IC de 95% 1,35-1,71) et de dépression (RC=1,39, IC de 95% 1,24-1,55) ont augmenté au fil des vagues de l'épidémie, avec un pic à la quatrième vague. CONCLUSION: Les TdS étaient plus à risque d'infection de COVID-19 et de troubles de santé mentale avec cet excès de risque se prolongeant plus tard dans la pandémie.