Access to social services for undiagnosed rare disease patients in France: A pilot study.

Although the challenge of access to care for undiagnosed rare disease patients is well documented in the literature, little is known about lack of diagnosis preventing access to social services. Yet this has serious consequences for patients and their families because disability associated with rare disease requires frequent and costly multi-disciplinary support. The aim of this research is to explore, in the French context, access to social assistance for rare disease patients. We investigate the link between diagnosis and access to social services to identify potential barriers and unmet needs for patients. Our study is based on a self-administered online questionnaire, adressed to parents or legal representatives of a child under ten years old with a rare disease and development disorders. The survey has been carried out between November 2019 and the end of January 2020 and includes 103 respondents. While our data does not show any differences in the possibility of obtaining a social benefit depending on the diagnosis status, there are differences in the length of time they are granted and in the satisfaction of families with the assistance obtained. Families with an undiagnosed child obtained social assistance for a shorter period on average. They were also more likely to be dissatisfied with the amount of benefit they received. The results of this pilot study need to be confirmed by further extended studies.

10 years of CEMARA database in the AnDDI-Rares network: a unique resource facilitating research and epidemiology in developmental disorders in France.

BACKGROUND: In France, the Ministry of Health has implemented a comprehensive program for rare diseases (RD) that includes an epidemiological program as well as the establishment of expert centers for the clinical care of patients with RD. Since 2007, most of these centers have entered the data for patients with developmental disorders into the CEMARA population-based registry, a national online data repository for all rare diseases. Through the CEMARA web portal, descriptive demographic data, clinical data, and the chronology of medical follow-up can be obtained for each center. We address the interest and ongoing challenges of this national data collection system 10 years after its implementation. METHODS: Since 2007, clinicians and researchers have reported the "minimum dataset (MDS)" for each patient presenting to their expert center. We retrospectively analyzed administrative data, demographic data, care organization and diagnoses. RESULTS: Over 10 years, 228,243 RD patients (including healthy carriers and family members for whom experts denied any suspicion of RD) have visited an expert center. Among them, 167,361 were patients affected by a RD (median age 11 years, 54% children, 46% adults, with a balanced sex ratio), and 60,882 were unaffected relatives (median age 37 years). The majority of patients (87%) were seen no more than once a year, and 52% of visits were for a diagnostic procedure. Among the 2,869 recorded rare disorders, 1,907 (66.5%) were recorded in less than 10 patients, 802 (28%) in 10 to 100 patients, 149 (5.2%) in 100 to 1,000 patients, and 11 (0.4%) in > 1,000 patients. Overall, 45.6% of individuals had no diagnosis and 6.7% had an uncertain diagnosis. Children were mainly referred by their pediatrician (46%; n = 55,755 among the 121,136 total children referrals) and adults by a medical specialist (34%; n = 14,053 among the 41,564 total adult referrals). Given the geographical coverage of the centers, the median distance from the patient's home was 25.1 km (IQR = 6.3 km-64.2 km). CONCLUSIONS: CEMARA provides unprecedented support for epidemiological, clinical and therapeutic studies in the field of RD. Researchers can benefit from the national scope of CEMARA data, but also focus on specific diseases or patient subgroups. While this endeavor has been a major collective effort among French RD experts to gather large-scale data into a single database, it provides tremendous potential to improve patient care.

Secondary actionable findings identified by exome sequencing: expected impact on the organisation of care from the study of 700 consecutive tests.

With exome/genome sequencing (ES/GS) integrated into the practice of medicine, there is some potential for reporting incidental/secondary findings (IFs/SFs). The issue of IFs/SFs has been studied extensively over the last 4 years. In order to evaluate their implications in care organisation, we retrospectively evaluated, in a cohort of 700 consecutive probands, the frequency and burden of introducing the search for variants in a maximum list of 244 medically actionable genes (genes that predispose carriers to a preventable or treatable disease in childhood/adulthood and genes for genetic counselling issues). We also focused on the 59 PharmGKB class IA/IB pharmacogenetic variants. We also compared the results in different gene lists. We identified variants (likely) affecting protein function in genes for care in 26 cases (3.7%) and heterozygous variants in genes for genetic counselling in 29 cases (3.8%). Mean time for the 700 patients was about 6.3 min/patient for medically actionable genes and 1.3 min/patient for genes for genetic counselling, and a mean time of 37 min/patients for the reinterpreted variants. These results would lead to all 700 pre-test counselling sessions being longer, to 55 post-test genetic consultations and to 27 secondary specialised medical evaluations. ES also detected 42/59 pharmacogenetic variants or combinations of variants in the majority of cases. An extremely low metabolizer status in genes relevant for neurodevelopmental disorders (CYP2C9 and CYP2C19) was found in 57/700 cases. This study provides information regarding the need to anticipate the implementation of genomic medicine, notably the work overload at various steps of the process.

Exercise Training for Preventing Dementia, Mild Cognitive Impairment, and Clinically Meaningful Cognitive Decline: A Systematic Review and Meta-analysis.

Background: To assess the effects of long-term exercise on the onset of dementia, mild cognitive impairment (MCI), and other clinically meaningful cognitive decline in the elderly adults. Methods: Systematic review with preplanned meta-analysis. Electronic searches were performed between November 2016 and May 2017. Randomized controlled trials (RCTs) examining the effects of long-term exercise (intervention length 12 months or longer) on the onset of dementia, MCI, or clinically meaningful cognitive decline in older adults without dementia at baseline were eligible. Two authors extracted the data independently. Four binary outcomes were defined: dementia onset, MCI onset, other clinically meaningful cognitive decline, and any of these three outcomes combined. Results: Five studies (n = 2,878 participants randomized) were included in this review. Outcomes' incidence for exercisers and controls were, respectively: 3.7% (n = 949) and 6.1% (n = 1,017) for dementia (three studies), 10.2% (n = 686) and 9.1% (n = 682) for MCI (one study), 14.5% (n = 124) and 15.4% (n = 123) for other clinically meaningful cognitive decline (two studies), and 11.4% (n = 1,073) and 12.5% (n = 1,140) for all outcomes combined. Meta-analyses found no significant effects of exercise for reducing the risk of dementia, MCI, other clinically meaningful cognitive decline, or all outcomes combined. Conclusions: Evidence from RCTs is limited and does not support that exercise reduces the risk of developing clinically important cognitive outcomes. Further long-term exercise RCTs are needed before solid conclusions can be drawn.

Adverse effects of pneumonia on physical functioning in nursing home residents: Results from the INCUR study.

BACKGROUND: Pneumonia is a very common infection in the nursing home, but little is known about its effects on levels of individual functioning. The aim of this study was to examine adverse effects of pneumonia events on physical functioning in nursing home residents. METHODS: Data were used from the INCUR study, a 1-year prospective cohort study of older residents from 13 nursing homes in France. The sample consisted of 716 residents, who were assessed at baseline, 6 and 12 months. Pneumonia diagnosis was based on clinical conditions documented in medical records. Physical functioning was measured by Activities of Daily Living (ADL). Longitudinal associations between pneumonia and physical functioning were explored using Generalized Estimating Equations (GEE). RESULTS: Of 716 participants, 145 (20%) had one or more pneumonia events during 12 months follow-up. Mean age of the participants was 86.0 (SD=7.4)years, and 76% of them were female. Overall, participants had relatively low levels of physical functioning at baseline (Mean ADL=2.4 out of 6, SD=1.8). The GEE analyses adjusted for age, gender, baseline physical functioning, and hospitalization during follow-up showed that pneumonia events had adverse effects on ADL functioning (B=-0.21, SE=0.08, p=0.008). Pneumonia events were mainly associated with loss of independence in transferring from bed to chair and bathing. CONCLUSIONS: In a population of nursing home residents where levels of physical functioning were already relatively low, pneumonia events were associated with loss of physical functioning. These results highlight the importance of preventive interventions aimed at reducing pneumonia in nursing home residents.

Clinical research for older adults in rural areas: the MINDED study experience.

Due to the growing need to make clinical decisions based on valid and objective scientific evidence, the number of randomized controlled trials (RCTs) has increased over the last three decades. Nevertheless, evidence-based medicine has still limited applicability in older adults, because they are often excluded from clinical trials. Evidence-based medicine is even more challenging in rural areas, as its remote environment provides additional barriers. Nevertheless, given the high prevalence of older adults living in rural settings, research in this type of environment has become crucial. This can only be accomplished by considering the multiple additional challenges of these regions. In this paper, we examine potential environmental, procedural, and participants' barriers to the management of a RCT in a rural area. Possible solutions and suggestions are provided based on our experience-from the Multidomain Intervention to preveNt Disability in ElDers (MINDED) project.

Frailty Index and Quality of Life in Nursing Home Residents: Results From INCUR Study.

BACKGROUND: Frailty is a common clinical syndrome in older adults that carries an increased risk for poor health outcomes. The aim of this study was to examine the relationship between frailty and health-related Quality of Life (QoL) in older nursing home patients. METHODS: The study sample consisted of 590 patients aged 65 years or older. QoL was measured with the Visual Analogue Scale. Frailty was assessed using the Frailty Index as proposed by Rockwood and colleagues. RESULTS: Mean age of the participants was 85.9 (standard deviation [SD] 7.6) years, with 73.6% being female. The mean Frailty Index was 0.40 (SD 0.07) and the mean value of QoL was 67.4 out of 100 (SD 25.9). Before and after adjusting for age, and stratification for sociodemographic, and health-related variables, no significant associations between frailty and QoL were reported. CONCLUSION: In our study, the Frailty Index was not associated with QoL in nursing home residents.

Exercise training for managing behavioral and psychological symptoms in people with dementia: A systematic review and meta-analysis.

This systematic review and meta-analysis of randomized controlled trials assessed the effects of exercise on behavioral and psychological symptoms of dementia (BPSD, including depression) in people with dementia (PWD). Secondary outcomes for the effects of exercise were mortality and antipsychotic use. Twenty studies were included in this review (n=18 in the meta-analysis). Most studies used a multicomponent exercise training (n=13) as intervention; the control group was often a usual care (n=10) or a socially-active (n=8) group. Exercise did not reduce global levels of BPSD (n=4. Weighted mean difference -3.884; 95% CI -8.969-1.201; I(2)=69.4%). Exercise significantly reduced depression levels in PWD (n=7). Standardized mean difference -0.306; 95% CI -0.571 to -0.041; I(2)=46.8%); similar patterns were obtained in sensitivity analysis performed among studies with: institutionalized people (p=0.038), multicomponent training (p=0.056), social control group (p=0.08), and low risk of attrition bias (p=0.11). Exploratory analysis showed that the principal BPSD (other than depression) positively affected by exercise was aberrant motor behavior. Exercise had no effect on mortality. Data on antipsychotics were scarce. In conclusion, exercise reduces depression levels in PWD. Future studies should examine whether exercise reduces the use (and doses) of antipsychotics and other drugs often used to manage BPSD.

[Difficulties encountered and solutions provided in the implementation of a multidisciplinary intervention for the prevention of dependency in the older population in rural areas: the MINDED study]. / Difficultés rencontrées et solutions apportées dans la mise en place d'une intervention multidisciplinaire pour la prévention de la dépendance chez les personnes âgées en milieu rural : étude MINDED.

Prevent increased number of dependent elderly has become a new priority for European public health. To achieve this, it is necessary to identify the frail older persons at risk of becoming dependent. Detecting frailty also allows to better understand an old patient's physiological reserves before making a therapeutic decision. To date, research tries to realize simple frailty screening tools allowing the clinician to better target - care provided to old adults during their first consultation. Furthermore, frailty is a reversible syndrome, so a global geriatric evaluation will allow the implementation of an individual program of early multi-domain care. The Multidomain intervention to prevent disability project in elders (MINDED), a randomized trial to prevent disability in elders, aims, in its second phase, to test the feasibility and to verify logistical, methodological and organizational aspects of the multi-domain intervention of the pilot study. In this paper, we shall describe the difficulties encountered and the solutions found during this feasibility phase.

Physical Activity and Amyloid-ß Brain Levels in Elderly Adults with Intact Cognition and Mild Cognitive Impairment.

OBJECTIVES: To examine the associations between amyloid-ß brain deposition and physical activity (PA) in elderly adults without dementia and to investigate whether the association has a dose-response relationship. DESIGN: Cross-sectional study. SETTING: French community-dwelling people. PARTICIPANTS: Elderly adults with normal or mildly impaired cognition (mean age 74.7 ± 4.2; 60.4% female) with available information on current self-reported PA and amyloid-ß brain deposition measured using positron emission tomography (PET) using the PET-ligand florbetapir F 18 (n = 268). MEASUREMENTS: A standardized uptake value ratio (SUVR) was obtained for each subject. Participants were divided according to amyloid plaque cortical retention defined according to a SUVR cutoff of 1.10 (SUVR+ vs SUVR-). RESULTS: Bivariate and multivariate analyses showed that PA was not significantly associated with SUVR. SUVR+ and SUVR- participants did not differ in terms of volume (continuous PA variables) and levels (categorical PA variables) of PA. PA was not correlated with SUVR in apolipoprotein E ε4 carriers or noncarriers. PA was not associated with cognitive function. CONCLUSION: Although PA protects against dementia, there is no solid evidence that this protection involves a reduction in amyloid-ß brain deposition. Further studies are needed to determine whether PA (ideally measured at several time-points using objective measures) is involved in the pathophysiology of Alzheimer's disease.

Frailty Index and Mortality in Nursing Home Residents in France: Results From the INCUR Study.

OBJECTIVE: The objective of this study was to examine whether the capacity of an age-related deficit accumulation index (the so-called Frailty Index [FI] proposed by Rockwood) to predict mortality in a nursing home population. DESIGN, SETTING, AND PARTICIPANTS: Data are from a longitudinal cohort study (ie, the Incidence of pNeumonia and related ConseqUences in nursing home Residents [INCUR]) of 773 older persons (74.4% women) living in 13 French nursing homes. MEASUREMENTS: The FI was computed as the ratio between actual and 30 potential deficits the participant might have presented at the baseline visit (range between 0 [no deficit] and 1 [30 deficits]). Death events were monitored and detected over a 12-month follow-up. The risk of death was estimated using Cox proportional hazards models. RESULTS: Mean age of participants was 86.2 (SD 7.5) years, with a mean FI of 0.35 (SD 0.11). At the end of the follow-up, 135 (17.4%) death events were recorded. A positive association between the FI and mortality (per 0.01 FI increment: age- and gender-adjusted hazard ratio 1.018, 95% confidence interval 1.002-1.035, P = .03) was reported. The use of the traditional 0.25 cut-point for detecting the frailty status is inadequate in this population. CONCLUSION: The FI is able to predict mortality even in very old and complex elders, such as nursing home residents.

How much exercise are older adults living in nursing homes doing in daily life? A cross-sectional study.

Information on the amount of exercise practised by nursing home (NH) residents is scarce. This study aimed at describing NH residents' participation in exercise classes, as well as to examine whether the presence of a professional exercise instructor in the facilities is associated with residents' exercise habits. The cross-sectional data of 5402 residents (median age = 88 years; mostly women (75.2%)) from 163 NHs in France were analysed. Adjusted logistic and linear regressions were performed to examine whether the presence of a professional exercise instructor in the NH was associated with exercise habits: exercise participation, frequency, duration, and levels. From the 5402 participants, 1914 were participating in exercise classes provided in the NH. Most of them had an exercise frequency of 1x/week or less. Median duration of exercise sessions was 45 min. Exercise levels were rated as: highly active (n = 487), intermediately active (n = 1096), and poorly active (n = 331). The presence of a professional exercise instructor working in the facility was significantly associated with exercise participation and with higher exercise frequencies and levels, and session duration. In conclusion, the presence of professional exercise instructors is associated with better exercise habits in NH residents. Improved exercise habits may potentially be translated into better health in this population.

A self-reported screening tool for detecting community-dwelling older persons with frailty syndrome in the absence of mobility disability: the FiND questionnaire.

BACKGROUND: The "frailty syndrome" (a geriatric multidimensional condition characterized by decreased reserve and diminished resistance to stressors) represents a promising target of preventive interventions against disability in elders. Available screening tools for the identification of frailty in the absence of disability present major limitations. In particular, they have to be administered by a trained assessor, require special equipment, and/or do not discriminate between frail and disabled individuals. Aim of this study is to verify the agreement of a novel self-reported questionnaire (the "Frail Non-Disabled" [FiND] instrument) designed for detecting non-mobility disabled frail older persons with results from reference tools. METHODOLOGY/PRINCIPAL FINDINGS: Data are from 45 community-dwelling individuals aged ≥60 years. Participants were asked to complete the FiND questionnaire separately exploring the frailty and disability domains. Then, a blinded assessor objectively measured the frailty status (using the phenotype proposed by Fried and colleagues) and mobility disability (using the 400-meter walk test). Cohen's kappa coefficients were calculated to determine the agreement between the FiND questionnaire with the reference instruments. Mean age of participants (women 62.2%) was 72.5 (standard deviation 8.2) years. Seven (15.6%) participants presented mobility disability as being unable to complete the 400-meter walk test. According to the frailty phenotype criteria, 25 (55.6%) participants were pre-frail or frail, and 13 (28.9%) were robust. Overall, a substantial agreement of the instrument with the reference tools (kappa = 0.748, quadratic weighted kappa = 0.836, both p values<0.001) was reported with only 7 (15.6%) participants incorrectly categorized. The agreement between results of the FiND disability domain and the 400-meter walk test was excellent (kappa = 0.920, p<0.001). CONCLUSIONS/SIGNIFICANCE: The FiND questionnaire presents a very good capacity to correctly identify frail older persons without mobility disability living in the community. This screening tool may represent an opportunity for diffusing awareness about frailty and disability and supporting specific preventive campaigns.

Nutritional status and the incidence of pneumonia in nursing home residents: results from the INCUR study.

OBJECTIVES: To examine the predictive value of the Mini Nutritional Assessment-short form (MNA-SF) and its individual items on the incidence of pneumonia. DESIGN: Prospective observational cohort study over 1-year of follow-up. PARTICIPANTS: A total of 773 older persons (74.4% women) living in 13 French nursing homes from the Incidence of pNeumonia and related ConseqUences in nursing home Residents (INCUR) study. MEASUREMENTS: Nutritional status was assessed using the MNA-SF questionnaire at baseline. Diagnosis of pneumonia was based on clinical conditions retrieved from a medical chart. Cox proportional hazard models were applied to test whether the MNA-SF score and its single components predict pneumonia events over 1 year of follow-up. RESULTS: After 1 year of follow-up, 160 (21%) incident cases of pneumonia were recorded. Mean age of participants was 86.2 (SD 7.5) years. Mean MNA-SF score was 9.8 (SD 2.4), with more than half of the participants (58.7%) being at risk of malnutrition (8-11 points). The total MNA-SF score and its categories did not predict the studied outcome. However, a single component of the MNA-SF score, specifically decreased mobility, was a significant risk factor for pneumonia (hazard ratio 2.289; 95% confidence interval 1.357-3.860; P = .002), independently of potential confounders. CONCLUSIONS: The total MNA-SF score did not predict the incidence of pneumonia. However, decreased mobility was a significant risk factor, implying that individual components of the MNA-SF should be more carefully explored to verify whether they might be used for detecting specific declines of the health status in nursing home residents, thus potentially improving the risk profile estimation of such a complex population.

The Multidomain Intervention to preveNt disability in ElDers (MINDED) project: rationale and study design of a pilot study.

Disability is hardly reversible at old age, negatively impacts on the elders' quality of life, and significantly threatens the sustainability of public health services. Therefore, preventive interventions become necessary for successfully avoiding its onset. The translation of the successful clinical approach represented by the geriatric comprehensive assessment at the community-level and the specific targeting of frailty (a well-established geriatric syndrome) might represent a promising possibility. This approach may allow the implementation of preventive interventions before the irreversible features of disability onset. Unfortunately, there is a lack of evidence on the effectiveness of primary prevention programs against disability in community-dwelling elders. Moreover, the novelty of the topic makes it difficult for the immediate design and conduction of a full-scale trial. For these reasons, a pilot project aimed at obtaining the preliminary information for the design of a subsequent definitive trial is required. In the present article, we describe the objectives, design, and methods of the Multidomain Intervention to preveNt Disability in ElDers (MINDED) project. MINDED is articulated into three sequential phases. First, a screening tool for indentifying non-disabled frail older persons in the community (ideal target population for preventive interventions against disability) will be validated. Then, the organization of a multidisciplinary team in the development and design of a multidomain preventive plan against disability will be verified/optimized. Finally, a randomized controlled trial measuring the effect size of a multicomponent intervention (based on physical exercise, nutrition, and cognitive training) against incident mobility disability versus usual care in community-dwelling frail elders will be conducted.

Energy-related optimal control accounts for gravitational load: comparing shoulder, elbow, and wrist rotations.

We permanently deal with gravity force. Experimental evidences revealed that moving against gravity strongly differs from moving along the gravity vector. This directional asymmetry has been attributed to an optimal planning process that optimizes gravity force effects to minimize energy. Yet, only few studies have considered the case of vertical movements in the context of optimal control. What kind of cost is better suited to explain kinematic patterns in the vertical plane? Here, we aimed to understand further how the central nervous system (CNS) plans and controls vertical arm movements. Our reasoning was the following: if the CNS optimizes gravity mechanical effects on the moving limbs, kinematic patterns should change according to the direction and the magnitude of the gravity torque being encountered in the motion. Ten subjects carried out single-joint movements, i.e., rotation around the shoulder (whole arm), elbow (forearm), and wrist (hand) joints, in the vertical plane. Joint kinematics were analyzed and compared with various theoretical optimal model predictions (minimum absolute work-jerk, jerk, torque change, and variance). We found both direction-dependent and joint-dependent variations in several kinematic parameters. Notably, directional asymmetries decreased according to a proximodistal gradient. Numerical simulations revealed that our experimental findings could be attributed to an optimal motor planning (minimum absolute work-jerk) that integrates the direction and the magnitude of gravity torque and minimizes the absolute work of forces (energy-related cost) around each joint. Present results support the general idea that the CNS implements optimal solutions according to the dynamic context of the action.

Incidence and economical effects of pneumonia in the older population living in French nursing homes: design and methods of the INCUR study.

BACKGROUND: Among the most burdensome clinical conditions occurring in older persons, respiratory infections are particularly relevant. In fact, the onset of pneumonias is associated with a significant worsening of the individual's global health status and significant increase of healthcare costs. The clinical and economical negative consequences of pneumonia may be particularly evident among the frailest groups of elders, in particular those living in nursing home. Nevertheless, specific research on incidence and economical effects of pneumonia in nursing homes residents is still scarce. In the present article, we present the rationale, the design and the methods of the "Incidence of pNeumonia and related ConseqUences in nursing home Resident (INCUR) study, specifically aimed at filling some of the gaps currently present in the field. METHODS/DESIGN: INCUR is an observational longitudinal study recruiting 800 residents across 13 randomly selected nursing homes in France. Multidimensional evaluations of participants are conducted at the baseline, mid-term (at 6 months), and end of the study (at 12 months) visits in order to measure and follow-up their physical function, nutrition, cognition, depression, quality of life, and healthcare costs. Incident pneumonia as well as the onset/recurrence of other major health-related events are monitored during the study follow-up. DISCUSSION: The INCUR study will provide valuable information about older persons living in nursing homes. Results from INCUR study may constitute the basis for the development of future preventive campaigns against pneumonia and its consequences.

Visual gravity influences arm movement planning.

When submitted to a visuomotor rotation, subjects show rapid adaptation of visually guided arm reaching movements, indicated by a progressive reduction in reaching errors. In this study, we wanted to make a step forward by investigating to what extent this adaptation also implies changes into the motor plan. Up to now, classical visuomotor rotation paradigms have been performed on the horizontal plane, where the reaching motor plan in general requires the same kinematics (i.e., straight path and symmetric velocity profile). To overcome this limitation, we considered vertical and horizontal movement directions requiring specific velocity profiles. This way, a change in the motor plan due to the visuomotor conflict would be measurable in terms of a modification in the velocity profile of the reaching movement. Ten subjects performed horizontal and vertical reaching movements while observing a rotated visual feedback of their motion. We found that adaptation to a visuomotor rotation produces a significant change in the motor plan, i.e., changes to the symmetry of velocity profiles. This suggests that the central nervous system takes into account the visual information to plan a future motion, even if this causes the adoption of nonoptimal motor plans in terms of energy consumption. However, the influence of vision on arm movement planning is not fixed, but rather changes as a function of the visual orientation of the movement. Indeed, a clear influence on motion planning can be observed only when the movement is visually presented as oriented along the vertical direction. Thus vision contributes differently to the planning of arm pointing movements depending on motion orientation in space.

Action representation in patients with bilateral vestibular impairments.

During mental actions subjects feel themselves performing a movement without any corresponding motor output. Although broad information is available regarding the influence of central lesions on action representation, little is known about how peripheral damages affect mental events. In the current study, we investigated whether lack of vestibular information influences action representation. Twelve healthy adults and twelve patients with bilateral vestibular damage actually performed and mentally simulated walking and drawing. The locomotor paths implied one (first walking task) and four (second walking task) changes in the walking direction. In the drawing task, participants drew on a sheet of paper a path that was similar to that of the second walking task. We recorded and compared between the two groups the timing of actual and mental movements. We found significant temporal discrepancies between actual and mental walking movements in the group of patients. Conversely, drawing actual and drawing mental durations were similar. For the control group, an isochrony between mental and actual movements was observed for the three tasks. This result denotes an inconsistency between action representation and action execution following vestibular damage, which is specific to walking movements, and emphasizes the role of the vestibular system upon mental states of actions. This observation may have important clinical implications. During action planning vestibular patients may overestimate the capacity of their motor system (imaging faster, executing slower) with harmful consequences for their health.

Muscle fatigue affects mental simulation of action.

Several studies suggest that when subjects mentally rehearse or execute a familiar action, they engage similar neural and cognitive operations. Here, we examined whether muscle fatigue could influence mental movements. Participants mentally and actually performed a sequence of vertical arm movements (rotation around the shoulder joint) before and after a fatiguing exercise involving the right arm. We found similar durations for actual and mental movements before fatigue, but significant temporal discrepancies after fatigue. Specifically, mental simulation was accelerated immediately after fatigue, while the opposite was observed for actual execution. Furthermore, actual movements showed faster adaptation (i.e., return to prefatigue values) than mental movements. The EMG analysis showed that postfatigue participants programmed larger, compared to prefatigue, neural drives. Therefore, immediately after fatigue, the forward model received dramatically greater efferent copies and predicted faster, compared to prefatigue, arm movements. During actual movements, the discrepancy between estimated (forward model output) and actual state (sensory feedback) of the arm guided motor adaptation; i.e., durations returned rapidly to prefatigue values. Since during mental movements there is no sensory information and state estimation derives from the forward model alone, mental durations remained faster after fatigue and their adaptation was longer than those of actual movements. This effect was specific to the fatigued arm because actual and mental movements of the left nonfatigued arm were unaffected. The current results underline the interdependence of motor and cognitive states and suggest that mental actions integrate the current state of the motor system.