Combining telemedicine and in-person visits to deliver care to patients with severe chronic kidney disease (CKD): Lessons learned from COVID-19.

BACKGROUND: Telemedicine has been widely used to deliver healthcare to outpatients during the COVID-19 pandemic. The effectiveness of this modality is unclear in patients with a pre-dialysis stage of chronic kidney disease (CKD). This study aims to describe the clinical characteristics and management of CKD patients receiving telemedicine care during the COVID-19 pandemic. MATERIALS AND METHODS: A retrospective single-center cohort study enrolled outpatients with pre-dialytic stage of CKD from March 9 to June 21, 2020. Telemedicine was proposed for all patients with a stable CKD to reduce the risk of in-hospital transmission whereas in-person visit was performed for patients requiring urgent evaluation. RESULTS: In a 15-week period, 97 patients received 116 nephrological visits. According to the modality of healthcare delivery, the patients were subdivided into telemedicine (66%) and in-person visit (34%) groups. Mean age of all CKD patients was 72.8 ± 12.5 years and males were 50.5% of the population. The average estimated glomerular filtration rate (eGFR) was 14.6 ± 6 mL/min. Patients evaluated by telemedicine had better kidney function (GFR, 16.2 ± 6.4 vs. 13.6 ± 5.9 mL/min/1.73m2; p = 0.037), a lower body mass index (BMI) (24.1 ± 1.7 vs. 30.6 ± 5.7; p = 0.019), and a lower risk of CKD progression (51.1 vs. 25.4%, p = 0.017) than patients requiring in-person visit. Telemedicine-visit patients experienced a significantly lower number of pharmacological changes than patients managed in the ambulatory setting. Telemedicine was also used to conduct 20% of educational meetings on the choice of dialysis modality and 18.9% of pre-eligibility visits for kidney transplantation. CONCLUSION: Telemedicine made it possible to provide care to and maintain close monitoring of 2/3 of patients with pre-dialytic stage of CKD during the COVID-19 pandemic.

Prevalence, clinical course and outcomes of COVID-19 in peritoneal dialysis (PD) patients: a single-center experience.

INTRODUCTION: There are limited data on the effects of COVID-19 on peritoneal dialysis (PD) patients. This study aimed to describe the impact of COVID-19 on the PD population. METHODS: A monocentric retrospective observational study was conducted on 146 consecutive PD patients followed from January 2020 to March 2022 at the University Hospital of Modena, Italy. RESULTS: Twenty-seven (18.4%) PD patients experienced 29 episodes of SARS-CoV-2 infection, corresponding to an incidence rate of 0.16 episodes/patient-year. Median age of COVID-19 patients was 60.4 (interquartile range [IQR] 50.2-66.5) years. In unvaccinated patients (n. 9), COVID-19 was always symptomatic and manifested with fever (100%) and cough (77.7%). COVID-19 caused hospital admission of three (33.3%) patients and two (22.2%) died of septic shock. COVID-19 was symptomatic in 83.3% of vaccinated subjects (n.18) and manifested with fever (61.1%) and cough (55.6%). Hospital admission occurred in 27.8% of the subjects but all were discharged home. Median SARS-CoV-2 shedding was 32 and 26 days in the unvaccinated and vaccinated groups, respectively. At the end of the follow-up, COVID-19 triggered the shift from PD to HD in two subjects without affecting the residual renal function of the remaining patients. Overall, COVID-19 caused an excess death of 22.2%. COVID-19 vaccination refusal accounted for only 1.6% in this cohort of patients. CONCLUSION: COVID-19 incident rate was 0.16 episodes/patient-year in the PD population. About one-third of the patients were hospitalized for severe infection. Fatal outcome occurred in two (7.4%) unvaccinated patients. A low vaccination refusal rate was observed in this population.

Incidence, risk factors and outcome of acute kidney injury (AKI) in patients with COVID-19.

BACKGROUND: Acute kidney injury (AKI) is a severe complication of coronavirus disease-2019 (COVID-19). This study aims to evaluate incidence, risk factors and case-fatality rate of AKI in patients with COVID-19. METHODS: We reviewed the health medical records of 307 consecutive patients with COVID-19 hospitalized at the University Hospital of Modena, Italy. RESULTS: AKI was diagnosed in 69 out of 307 (22.4%) COVID-19 patients. Stages 1, 2, or 3 AKI accounted for 57.9%, 24.6% and 17.3%, respectively. AKI patients had a mean age of 74.7 ± 9.9 years. These patients showed higher serum levels of the main markers of inflammation and higher rate of severe pneumonia than non-AKI patients. Kidney injury was associated with a higher rate of urinary abnormalities including proteinuria (0.44 ± 0.85 vs 0.18 ± 0.29 mg/mg; P = < 0.0001) and microscopic hematuria (P = 0.032) compared to non-AKI patients. Hemodialysis was performed in 7.2% of the subjects and 33.3% of the survivors did not recover kidney function after AKI. Risk factors for kidney injury were age, male sex, CKD and higher non-renal SOFA score. Patients with AKI had a mortality rate of 56.5%. Adjusted Cox regression analysis revealed that COVID-19-associated AKI was independently associated with in-hospital death (hazard ratio [HR] = 4.82; CI 95%, 1.36-17.08) compared to non-AKI patients. CONCLUSION: AKI was a common and harmful consequence of COVID-19. It manifested with urinary abnormalities (proteinuria, microscopic hematuria) and conferred an increased risk for death. Given the well-known short-term sequelae of AKI, prevention of kidney injury is imperative in this vulnerable cohort of patients.

Hypokalemia in Patients with COVID-19.

BACKGROUND: Patients with COVID-19 experience multiple clinical conditions that may cause electrolyte imbalances. Hypokalemia is a concerning electrolyte disorder closely associated with severe complications. This study aimed to estimate prevalence, risk factors and outcome of hypokalemia in a cohort of patients with confirmed COVID-19. METHODS: A retrospective analysis was conducted on 290 non-ICU admitted patients with COVID-19 at the tertiary teaching hospital of Modena, Italy, from February 16 to April 14, 2020. RESULTS: Hypokalemia was detected in 119 out of 290 patients (41%) during hospitalization. Mean serum potassium was 3.1 ± 0.1 meq/L. The majority of patients (90.7%) patients experienced only a mild decrease in serum potassium level (3-3.4 mEq/L). Hypokalemia was associated with hypocalcemia, which was detected in 50% of subjects. Urine potassium-to-creatinine ratio, measured in a small number of patients (n = 45; 36.1%), revealed an increase of urinary potassium excretion in most cases (95.5%). Risk factors for hypokalemia were female sex (odds ratio (OR) 2.44; 95% CI 1.36-4.37; P 0.003) and diuretic therapy (OR 1.94, 95% CI 1.08-3.48; P 0.027). Hypokalemia, adjusted for sex, age and SOFA score, was not associated with ICU transfer (OR 0.52; 95% CI 0.228-1.212; P = 0.131), in-hospital mortality (OR, 0.47; 95% CI 0.170-1.324; P = 0.154) and composite outcome of ICU transfer or in-hospital mortality (OR 0.48; 95% CI 0.222-1.047; P = 0.065) in our cohort of patients. CONCLUSIONS: Hypokalemia was a frequent disorder in subjects with COVID-19. Female sex and diuretic therapy were identified as risk factors for low serum potassium levels. Hypokalemia was unrelated to ICU transfer and death in this cohort of patients.

Awaiting a cure for COVID-19: therapeutic approach in patients with different severity levels of COVID-19.

COVID-19 is an unpredictable infectious disease caused by SARS-CoV-2. The development of effective anti-COVID-19 vaccines has enormously minimized the risk of severe illness in most immunocompetent patients. However, unvaccinated patients and non-responders to the COVID-19 vaccine are at risk of shortand long-term consequences. In these patients, the outcome of COVID-19 relies on an interplay of multiple factors including age, immunocompetence, comorbidities, inflammatory response triggered by the virus as well as the virulence of SARS-CoV-2 variants. Generally, COVID-19 is asymptomatic or mildly symptomatic in young people, but it may manifest with respiratory insufficiency requiring mechanical ventilation in certain susceptible groups of patients. Furthermore, severe SARS-CoV-2 infection induces multiorgan failure syndrome by affecting liver, kidney heart and nervous system. Since December 2019, multiple drugs have been tested to treat COVID-19, but only a few have been proven effective to mitigate the course of the disease that continues to cause death and comorbidity worldwide. Current treatment of COVID-19 patients is essentially based on the administration of supportive oxygen therapy and the use of specific drugs such as steroids, anticoagulants, antivirals, anti-SARS-CoV-2 antibodies and immunomodulators. However, the rapid spread of new variants and the release of new data coming from the numerous ongoing clinical trials have created the conditions for maintaining a continuous updating of the therapeutic management of COVID-19 patients. Furthermore, we believe that a well-established therapeutic strategy along with the continuum of medical care for all patients with COVID-19 is pivotal to improving disease outcomes and restoring healthcare care fragmentation caused by the pandemic. This narrative review, focusing on the therapeutic management of COVID-19 patients, aimed to provide an overview of current therapies for (i) asymptomatic or mildly/moderate symptomatic patients, (ii) hospitalized patients requiring low-flow oxygen, (iii) high-flow oxygen and (iv) mechanical ventilation.

Which criteria should we use to end isolation in hemodialysis patients with COVID-19?

Safe and timely discontinuation of quarantine of in-center hemodialysis (HD) patients with a previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is a challenging issue for the nephrological community because current guidelines for ending isolation do not mention dialysis patients. To prevent potentially fatal outbreaks of coronavirus disease 2019 (COVID-19), a cautionary approach has been adopted by most dialysis units. The criteria for ending the isolation in the HD population generally coincide with those recommended for immunocompromised people. Thus, a test-based strategy relying on two consecutive negative reverse transcriptase-polymerase chain reaction (RT-PCR) nasopharyngeal swabs has been adopted to terminate quarantine. This strategy has the disadvantage of prolonging isolation as RT-PCR positivity does not equate to SARS-CoV-2 infectivity. Consequentially, prolonged positivity of SARS-CoV-2 results in excessive workload for the HD staff who must face an increasing number of COVID-19 patients requiring isolation. This condition leads also to serious implications for the patients and their households including work productivity loss, postponement of health-care appointments and an increased risk of COVID-19 reinfection. To counteract this problem, other diagnostic tests should be used to provide the best care to HD patients. Recent results seem to encourage the use of RT-PCR cycle threshold (Ct) values and rapid antigen tests given their better correlation with cell culture for SARS-CoV-2 than RT-PCR testing. Here, we provide an overview of the current scientific evidence on the tests used to verify the infectiousness of the virus in order to stimulate the nephrological community to adopt a streamlined and pragmatic procedure to end isolation in COVID-19 patients on HD.

Rethinking Chronic Kidney Disease in the Aging Population.

The process of aging population will inevitably increase age-related comorbidities including chronic kidney disease (CKD). In light of this demographic transition, the lack of an age-adjusted CKD classification may enormously increase the number of new diagnoses of CKD in old subjects with an indolent decline in kidney function. Overdiagnosis of CKD will inevitably lead to important clinical consequences and pronounced negative effects on the health-related quality of life of these patients. Based on these data, an appropriate workup for the diagnosis of CKD is critical in reducing the burden of CKD worldwide. Optimal management of CKD should be based on prevention and reduction of risk factors associated with kidney injury. Once the diagnosis of CKD has been made, an appropriate staging of kidney disease and timely prescriptions of promising nephroprotective drugs (e.g., RAAS, SGLT-2 inhibitors, finerenone) appear crucial to slow down the progression toward end-stage kidney disease (ESKD). The management of elderly, comorbid and frail patients also opens new questions on the appropriate renal replacement therapy for this subset of the population. The non-dialytic management of CKD in old subjects with short life expectancy features as a valid option in patient-centered care programs. Considering the multiple implications of CKD for global public health, this review examines the prevalence, diagnosis and principles of treatment of kidney disease in the aging population.

Acid base disorders in patients with COVID-19.

PURPOSE: Acid-base derangement has been poorly described in patients with coronavirus disease 2019 (COVID-19). Considering the high prevalence of pneumonia and kidneys injury in COVID-19, frequent acid-base alterations are expected in patients admitted with SARS-Cov-2 infection. The study aimed to assess the prevalence of acid-base disorders in symptomatic patients with a diagnosis of COVID-19. METHODS: The retrospective study enrolled COVID-19 patients hospitalized at the University Hospital of Modena from 4 March to 20 June 2020. Baseline arterial blood gas (ABG) analysis was collected in 211 patients. In subjects with multiple ABG analysis, we selected only the first measurement. A pH of less than 7.37 was categorized as acidemia and a pH of more than 7.43 was categorized as alkalemia. RESULTS: ABG analyses revealed a low arterial partial pressure of oxygen (PO2, 70.2 ± 25.1 mmHg), oxygen saturation (SO2, 92%) and a mild reduction of PO2/FiO2 ratio (231 ± 129). Acid-base alterations were found in 79.7% of the patient. Metabolic alkalosis (33.6%) was the main alteration followed by respiratory alkalosis (30.3%), combined alkalosis (9.4%), respiratory acidosis (3.3%), metabolic acidosis (2.8%) and other compensated acid-base disturbances (3.6%). All six patients with metabolic acidosis died at the end of the follow-up. CONCLUSION: Variations of pH occurred in the majority (79.7%) of patients admitted with COVID-19. The patients experienced all the type of acid-base disorders, notably metabolic and respiratory alkalosis were the most common alterations in this group of patients.

The frail world of haemodialysis patients in the COVID-19 pandemic era: a systematic scoping review.

BACKGROUND: Patients undergoing in-centre haemodialysis (HD) are particularly exposed to the dire consequences of COVID-19. The present systematic scoping review aims to identify the extent, range, and nature of articles related to COVID-19 and maintenance HD: it reports specifically the prevalence of the COVID-19 pandemic in the HD population, implementation of strategies for the prevention, mitigation and containment of the COVID-19 pandemic in HD centres, demographic and clinical characteristics, and outcomes of the pediatric and adult HD patients. METHODS: A multi-step systematic search of the literature in Pubmed, Scopus, Ovid Medline, Embase and Web of Science, published between December 1, 2019, and January 30, 2021 was performed. Two authors separately screened the titles and abstracts of the documents and ruled out irrelevant articles. A report of the papers that met inclusion criteria was performed; then, a descriptive analysis of the characteristics of the included articles and a narrative synthesis of the results were performed. RESULTS: The review process ended with the inclusion of 145 articles. Most of them were based on single-centre experiences, which spontaneously developed best practices. Most studies were conducted in high-income countries (69.7%) and a part of them (9.6%) were not in English. Prevalence of COVID-19 among dialysis patients accounted for 0%-37.6%. Preventive measures were reported in 54% of the included articles, with particular emphasis on education, triage, hygiene, and containment measures. Patients experienced a heterogeneous spectrum of symptoms that led 35%-88.2% of them to hospital admission. Median and mean hospital length of stay ranged from 8 to 28.5 and 16.2 to 22 days, respectively. Admission to intensive care units varied widely across studies (from 2.6% to 70.5%) and was associated with high mortality (42.8%-100%). Overall, prognosis was poor in 0%-47% of the hospitalized patients. CONCLUSIONS: This systematic scoping review provides an overview of the current knowledge on the impact of COVID-19 on the frail world of HD patients. Furthermore, it may help to implement the existing strategies of COVID-19 prevention and provide a list of unmet needs (safe transport, testing, shelter). Finally, it may be a stimulus for performing systematic reviews and meta-analyses which will form the basis for evidence-based guidelines.

Clinical Presentation, Renal Histopathological Findings, and Outcome in Patients with Monoclonal Gammopathy and Kidney Disease.

Monoclonal gammopathies are associated with acute and chronic kidney injury. Nephrotoxicity of the secreted monoclonal (M)-protein is related to its biological properties and blood concentration. Little is known about epidemiology, clinical manifestations, and outcome of monoclonal gammopathies in patients with kidney disease. We retrospectively collected data about demographics, clinical manifestations, and renal histological lesions of all patients (n = 1334) who underwent kidney biopsy between January 2000 and March 2017. Monoclonal gammopathy was detected in 174 (13%) patients with a mean age of 66.4 ± 13.1 years. The spectrum of monoclonal gammopathies comprised monoclonal gammopathy of undetermined significate (MGUS) (52.8%), multiple myeloma (MM) (25.2%), primary amyloidosis (AL) (9.1%), smoldering MM (SMM) (4%), non-Hodgkin lymphoma (NHL) (6.8%), and Hodgkin lymphoma (HL) (1.7%). Monoclonal gammopathy of renal significance (MGRS) accounted for 6.5% in patients with MGUS and 14.2% in patients with SMM. Evaluation of kidney biopsy revealed that M-protein was directly involved in causing kidney injury in MM (93.1%). MM was the only gammopathy significantly associated with an increased risk of kidney injury (odds ratio [OR] = 47.5, CI 95%, 13.7-164.9; P ≤ 0.001). While there were no significant differences in the progression toward end-stage renal disease or dialysis (P = 0.776), monoclonal gammopathies were associated with a different risk of death (P = 0.047) at the end of the follow-up. In conclusion, monoclonal gammopathy was a frequent finding (13%) in patients who underwent kidney biopsy. M-protein was secreted by both premalignant (56.8%) and malignant (43.2%) lymphoproliferative clones. Kidney biopsy had a key role in identifying MGRS in patients with MGUS (6.5%) and SMM (14.2%). Among monoclonal gammopathies, only MM was significantly associated with biopsy-proven kidney injury. The rate of end-stage renal disease or dialysis was similar among monoclonal gammopathies, whereas NHL, MM, and SMM showed a higher rate of deaths.

Twenty-four-hour serum creatinine variation is associated with poor outcome in the novel coronavirus disease 2019 (COVID-19) patients.

BACKGROUND: The prognostic value of within-day sCr variation serum creatinine variation is unknown in the setting of the novel coronavirus disease 2019 (COVID-19). We evaluated the prognostic significance of 24-hour serum creatinine variation in COVID-19 patients. METHODS: A monocentric retrospective analysis was conducted in COVID-19 patients not admitted to the intensive care unit. Three groups were subdivided based on 24 hours serum creatinine variation from admission. In the stable kidney function group, 24-hour serum creatinine variation ranged from +0.05 to -0.05 mg/dL; in the decreased kidney function group, 24-hour serum creatinine variation was >0.05 mg/dL; in the improved kidney function group, 24-hour serum creatinine variation was <-0.05 mg/dL. RESULTS: The study population included 224 patients with a median age of 66.5 years and a predominance of males (72.3%). Within 24 hours of admission, renal function remained stable in 37.1% of the subjects, whereas it displayed improved and deteriorated patterns in 45.5% and 17.4%, respectively. Patients with decreased kidney function were older and had more severe COVID-19 symptoms than patients with stable or improved kidney function. About half of patients with decreased kidney function developed an episode of acute kidney injury (AKI) during hospitalization. Decreased kidney function was significantly associated with AKI during hospitalization (hazard ratio [HR], 4.6; 95% confidence interval [CI], 1.9-10.8; p < 0.001) and was an independent risk factor for 30-day in-hospital mortality (HR, 5.5; 95% CI, 1.1-28; p = 0.037). CONCLUSION: COVID-19 patients with decreased kidney function within 24 hours of admission were at high risk of AKI and 30-day in-hospital mortality.

Peritoneal dialysis in the time of coronavirus disease 2019.

In the current setting of global containment, peritoneal dialysis (PD) and home haemodialysis are the best modalities of renal replacement therapy (RRT) to reduce the rate of transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Considering the shorter and easier training programme of PD compared to home haemodialysis, PD appears a practical solution for patients with end-stage renal disease to reduce the risk of hospital-acquired infection. PD offers the advantage of minimizing the risk of viral transmission through interpersonal contact that commonly occurs during the haemodialysis session and while travelling from home to the haemodialysis facility using public transport services. To overcome barriers to health care access due to the containment measures for this emerging disease, telemedicine is a useful and reliable tool for delivering health care without exposing patients to the risk of contact. However, novel issues including handling of potentially infected dialysate, caregivers' infectious risk and adequacy of PD in critically ill patients with acute respiratory distress syndrome remain to be clarified. In conclusion, PD should be preferred to the other modalities of RRT during the coronavirus disease 2019 (COVID-19) outbreak because it can be a solution to cope with the increased number of infected patients worldwide.

Hemolytic Anemia as Presentation of T-Cell Large Granular Lymphocytic Leukemia After Kidney Transplantation: A Case Report.

T-cell large granular lymphocytic (T-LGL) leukemia is a rare clonal proliferation presenting with cytopenia, splenomegaly, and autoimmune manifestations. It has rarely been described in recipients of solid organ transplants. We report the clinical case of a young kidney transplant recipient that developed T-LGL leukemia 3 years after kidney transplantation. The disorder manifested with a severe form of autoimmune hemolytic anemia in the absence of other laboratory abnormalities. The anemia was successfully treated with an intense course of corticosteroids ands witch of immunosuppressive therapy from a calcineurin inhibitor to sirolimus, a mammalian target of rapamycin inhibitor. Our case shows that autoimmune hemolytic anemia can be a life-threatening manifestation of T-LGL disease. The antiproliferative effects of sirolimus may be useful in the treatment of symptoms of T-LGL leukemia in kidney transplantation.

Incidence of nephrogenic systemic fibrosis after administration of gadoteric acid in patients on renal replacement treatment.

PURPOSE: Nephrogenic system fibrosis (NSF) is a rare complication detected in patients with renal insufficiency exposed to gadolinium-based contrast agents (GBCAs). The aim of our study is to evaluate the prevalence of NSF in a cohort of patients on renal replacement treatment who underwent GBCA-enhanced magnetic resonance imaging (MRI). METHOD: We retrospectively reviewed all the charts of kidney transplant (KT) recipients, patients on hemodialysis (HD) and peritoneal dialysis (PD) who received a uniform protocol for contrast material enhanced-MRI with gadoteric acid at our center from January 2004 to December 2017. RESULTS: Three-hundred forty-four patients (44.1% on HD, 11.3% on PD and 44.4% KT recipients) underwent 551 gadoteric acid-enhanced MRI. The median age of the patients was 58 years (IQR, 45-70 years) and 65.1% were men. Sixty-three patients (18.3%) had skin punch biopsy after integumentary assessment performed by a dermatologist. No cases of NSF were detected after a median follow-up of 4.5 years (IQR, 1.9-8.2 years). During this period of observation, 116 (33.7%) patients died and 11 (3.1%) were lost at follow-up. CONCLUSIONS: None of the patients exposed to gadoteric acid developed NSF. Our results, in line with more recent studies, suggest that the use of gadoteric acid, a macrocyclic GBCA, appears safe even in chronic kidney disease (CKD) patients receiving dialysis.

Clinical outcome of kidney transplantation in HIV-infected recipients: a retrospective study.

Kidney transplantation is a safe and effective option for HIV-positive (HIV+) patients. We conducted a retrospective study on HIV+ kidney transplant recipients who underwent transplantation from March 2008 to September 2016. Inclusion criteria for transplantation were CD4+ T-cell count ≥200 per mm3 and undetectable HIV load. The current study reports the outcome of 19 HIV+ recipients, mostly of Caucasian origin (79%) with a median age of 50 years (interquartile range [IQR], 42-52), who were followed up for a median period of 2.4 years (IQR, 1.2-4.6) after transplantation. Compared with HIV-negative (HIV-) controls, HIV+ recipients had similar one- and three-year graft and patient survival, but significantly lower five-year patient survival (P = 0.03). The differences in graft outcome became less evident with the analysis of death-censored graft survival rates. Cumulative incidence of allograft rejection at one year was 32.9%. Rates of infections were not particularly elevated and HIV replication remained well controlled in all but one patient. A high prevalence of metabolic and endocrine complications (68%) was reported after transplantation. Further studies are needed to evaluate long-term outcomes of HIV+ recipients who underwent kidney transplantation.

Proactive Control Strategies for Overt and Covert Go/NoGo Tasks: An Electrical Neuroimaging Study.

Proactive and reactive inhibition are generally intended as mechanisms allowing the withholding or suppression of overt movements. Nonetheless, inhibition could also play a pivotal role during covert actions (i.e., potential motor acts not overtly performed, despite the activation of the motor system), such as Motor Imagery (MI). In a previous EEG study, we analyzed cerebral activities reactively triggered during two cued Go/NoGo tasks, requiring execution or withholding of overt or covert imagined actions, respectively. This study revealed activation of pre-supplementary motor area (pre-SMA) and right inferior frontal gyrus (rIFG), key nodes of the network underpinning reactive inhibition of overt responses in NoGo trials, also during MI enactment, enabling the covert nature of the imagined motor response. Taking into account possible proactive engagement of inhibitory mechanisms by cue signals, for an exhaustive interpretation of these previous findings in the present study we analyzed EEG activities elicited during the preparatory phase of our cued overt and covert Go/NoGo tasks. Our results demonstrate a substantial overlap of cerebral areas activated during proactive recruitment and subsequent reactive implementation of motor inhibition in both overt and covert actions; also, different involvement of pre-SMA and rIFG emerged, in accord with the intended type (covert or overt) of incoming motor responses. During preparation of the overt Go/NoGo task, the cue is encoded in a pragmatic mode, as it primes the possible overt motor response programs in motor and premotor cortex and, through preactivation of a pre-SMA-related decisional mechanism, it triggers a parallel preparation for successful response selection and/or inhibition during the response phase. Conversely, the preparatory strategy for the covert Go/NoGo task is centered on priming of an inhibitory mechanism in rIFG, tuned to the instructed covert modality of motor performance and instantiated during subsequent MI, which allows the imagined response to remain a potential motor act.

Correction: Proactive Control Strategies for Overt and Covert Go/NoGo Tasks: an Electrical Neuroimaging Study.

[This corrects the article DOI: 10.1371/journal.pone.0152188.].

Motor Inhibition during Overt and Covert Actions: An Electrical Neuroimaging Study.

Given ample evidence for shared cortical structures involved in encoding actions, whether or not subsequently executed, a still unsolved problem is the identification of neural mechanisms of motor inhibition, preventing "covert actions" as motor imagery from being performed, in spite of the activation of the motor system. The principal aims of the present study were the evaluation of: 1) the presence in covert actions as motor imagery of putative motor inhibitory mechanisms; 2) their underlying cerebral sources; 3) their differences or similarities with respect to cerebral networks underpinning the inhibition of overt actions during a Go/NoGo task. For these purposes, we performed a high density EEG study evaluating the cerebral microstates and their related sources elicited during two types of Go/NoGo tasks, requiring the execution or withholding of an overt or a covert imagined action, respectively. Our results show for the first time the engagement during motor imagery of key nodes of a putative inhibitory network (including pre-supplementary motor area and right inferior frontal gyrus) partially overlapping with those activated for the inhibition of an overt action during the overt NoGo condition. At the same time, different patterns of temporal recruitment in these shared neural inhibitory substrates are shown, in accord with the intended overt or covert modality of action performance. The evidence that apparently divergent mechanisms such as controlled inhibition of overt actions and contingent automatic inhibition of covert actions do indeed share partially overlapping neural substrates, further challenges the rigid dichotomy between conscious, explicit, flexible and unconscious, implicit, inflexible forms of motor behavioral control.