Detection of atypical attentional behaviors in young subjects

BACKGROUND

Vigilance ability refers to the accuracy and speed with which a person performs a cognitive-motor task, either voluntarily (endogenous mode) or following a warning stimulus (exogenous mode). In the context of a force production task, our study focuses on the impact of the states of vigilance by proposing an original approach that allows distinguishing between good (inlier) and poor (outlier) participants. We assume that the use of an external signal and duration of the temporal preparation (foreperiod) increase the speed and the precision of motor responses. Our objective is particularly challenging in the context of a limited dataset with a high level of noise.

NEW METHOD

Our original methodological approach consists of coupling the RANSAC (RANdom SAmple Consensus) algorithm with a statistical machine learning algorithm to handle noise.

COMPARISON WITH EXISTING METHODS

Our clustering approach, based on the coupling of RANSAC methodology with ensemble classifiers, overcomes the limitations of conventional supervised algorithms that are either not robust to outliers (such as K-Nearest Neighbors) and/or not adapted to few-shot learning (such as Support Vector Machines and Artificial Neural Networks).

RESULTS

The clustering results were validated in terms of reaction time distributions and force error distributions with respect to participant groups. We show that the use of an external signal and duration of the temporal preparation (foreperiod) increase the speed and the precision of motor responses.

CONCLUSION

Our study has allowed us to detect atypical attentional patterns and succeeds in separating the inliers from the outliers.

Role of the Cerebellum in the Construction of Functional and Geometrical Spaces

The perceptual and motor systems appear to have a set of movement primitives that exhibit certain geometric and kinematic invariances. Complex patterns and mental representations can be produced by (re)combining some simple motor elements in various ways using basic operations, transformations, and respecting a set of laws referred to as kinematic laws of motion. For example, point-to-point hand movements are characterized by straight hand paths with single-peaked-bell-shaped velocity profiles, whereas hand speed profiles for curved trajectories are often irregular and more variable, with speed valleys and inflections extrema occurring at the peak curvature. Curvature and speed are generically related by the 2/3 power law. Mathematically, such laws can be deduced from a combination of Euclidean, affine, and equi-affine geometries, whose neural correlates have been partially detected in various brain areas including the cerebellum and the basal ganglia. The cerebellum has been found to play an important role in the control of coordination, balance, posture, and timing over the past years. It is also assumed that the cerebellum computes forward internal models in relationship with specific cortical and subcortical brain regions but its motor relationship with the perceptual space is unclear. A renewed interest in the geometrical and spatial role of the cerebellum may enable a better understanding of its specific contribution to the action-perception loop and behavior's adaptation. In this sense, we complete this overview with an innovative theoretical framework that describes a possible implementation and selection by the cerebellum of geometries adhering to different mathematical laws.

Influence of Mental Training of Attentional Control on Autonomic Arousal Within the Framework of the Temporal Preparation of a Force Task

While temporal preparation has frequently been examined through the manipulation of foreperiods, the role of force level during temporal preparation remains underexplored. In our study, we propose to manipulate mental training of attentional control in order to shed light on the role of the force level and autonomic nervous system in the temporal preparation of an action. Forty subjects, divided into mental training group (n = 20) and without mental training group (n = 20), participated in this study. The influence of the attentional control and force levels on the autonomic nervous system were measured using the skin conductance response and the heart rate variability; the accuracy of the motor responses was measured using a method derived from machine learning. Behaviorally, only the mental training group reinforced its motor and attentional control. When using short foreperiod durations and high force level, motor and attentional control decreased, consistent with the dominant sympathetic system. This resulted in an increased anticipation rate of responses with a higher reaction time compared to the long foreperiods duration and low force level, in which the reaction time significantly decreased, with enhancement of the expected force level, showing consistency with the dominant parasympathetic system. Interestingly, results revealed a predictive relationship between the sympathovagal balance and motor and attentional control during the long foreperiods and low force level. Finally, results demonstrate that attentional mental training leads to the reinforcement of interactions between the autonomic nervous system and attentional processes which are involved in the temporal preparation of a force task.

Human Exteroception during Object Handling with an Upper Limb Exoskeleton

Upper limb exoskeletons may confer significant mechanical advantages across a range of tasks. The potential consequences of the exoskeleton upon the user's sensorimotor capacities however, remain poorly understood. The purpose of this study was to examine how the physical coupling of the user's arm to an upper limb exoskeleton influenced the perception of handheld objects. In the experimental protocol, participants were required to estimate the length of a series of bars held in their dominant right hand, in the absence of visual feedback. Their performance in conditions with an exoskeleton fixed to the forearm and upper arm was compared to conditions without the upper limb exoskeleton. Experiment 1 was designed to verify the effects of attaching an exoskeleton to the upper limb, with object handling limited to rotations of the wrist only. Experiment 2 was designed to verify the effects of the structure, and its mass, with combined movements of the wrist, elbow, and shoulder. Statistical analysis indicated that movements performed with the exoskeleton did not significantly affect perception of the handheld object in experiment 1 (BF₀₁ = 2.3) or experiment 2 (BF₀₁ = 4.3). These findings suggest that while the integration of an exoskeleton complexifies the architecture of the upper limb effector, this does not necessarily impede transmission of the mechanical information required for human exteroception.

Motor imagery in amyotrophic lateral Sclerosis: An fMRI study of postural control

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ALS is associated with postural control impairment.

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DCM and PEB frameworks help to characterize connectivity patterns during gait.

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Clinical manifestations of ALS are underpinned by selective network dysfunction.

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Altered BG-SMA and SMA-PPC connectivity are observed during imagined gait in ALS.

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Enhanced BG-cerebellar connectivity may represent functional adaptation.

Background

The functional reorganization of brain networks sustaining gait is poorly characterized in amyotrophic lateral sclerosis (ALS) despite ample evidence of progressive disconnection between brain regions. The main objective of this fMRI study is to assess gait imagery-specific networks in ALS patients using dynamic causal modeling (DCM) complemented by parametric empirical Bayes (PEB) framework.

Method

Seventeen lower motor neuron predominant (LMNp) ALS patients, fourteen upper motor neuron predominant (UMNp) ALS patients and fourteen healthy controls participated in this study. Each subject performed a dual motor imagery task: normal and precision gait. The Movement Imagery Questionnaire (MIQ-rs) and imagery time (IT) were used to evaluate gait imagery in each participant. In a neurobiological computational model, the circuits involved in imagined gait and postural control were investigated by modelling the relationship between normal/precision gait and connection strengths.

Results

Behavioral results showed significant increase in IT in UMNp patients compared to healthy controls (P_corrected < 0.05) and LMNp (P_corrected < 0.05). During precision gait, healthy controls activate the model's circuits involved in the imagined gait and postural control. In UMNp, decreased connectivity (inhibition) from basal ganglia (BG) to supplementary motor area (SMA) and from SMA to posterior parietal cortex (PPC) is observed. Contrary to healthy controls, DCM detects no cerebellar-PPC connectivity in neither UMNp nor LMNp ALS. During precision gait, bilateral connectivity (excitability) between SMA and BG is observed in the LMNp group contrary to UMNp and healthy controls.

Conclusions

Our findings demonstrate the utility of implementing both DCM and PEB to characterize connectivity patterns in specific patient phenotypes. Our approach enables the identification of specific circuits involved in postural deficits, and our findings suggest a putative excitatory–inhibitory imbalance. More broadly, our data demonstrate how clinical manifestations are underpinned by network-specific disconnection phenomena in ALS.

Improving Health of People With Multiple Sclerosis From a Multicenter Randomized Controlled Study in Parallel Groups: Preliminary Results on the Efficacy of a Mindfulness Intervention and Intention Implementation Associated With a Physical Activity Program

Objectives: The objective of this study is to investigate the efficacy of psychological Interventions – Mindfulness or Implementation Intention – associated with a Physical Activity program, delivered via internet, in reducing Multiple Sclerosis symptoms.

Method: Thirty-five adults were randomly assigned to one of the three groups: a Mindfulness-Based Intervention group (N = 12), Implementation Intention group (N = 11), and a Control Group (N = 12). All the groups received the same Physical Activity program. The Mindfulness condition group received daily training in the form of pre-recorded sessions while the Implementation group elaborated their specific plans once a week. Mobility, fatigue, and the impact of the disease on the patient’s life were measured. Two measurement times are carried out in pre-post intervention, at baseline and after eight weeks.

Results: Overall, after 8 weeks intervention, results show that there was a significant increase in Walking distance in the three groups. In addition, the within-group analysis showed a statistically significant improvement between pre and post intervention on the physical component of the Disease Impact scale in the Implementation Intention group (p = 0.023) with large effect size, in the Mindfulness-Based Intervention group (p = 0.008) with a medium effect size and in the control group (p = 0.028) with small effect size. In the Implementation Intention group, all physical, psychosocial and cognitive Fatigue Impact subscales scores decreased significantly (p = 0.022, p = 0.023, and p = 0.012, respectively) and the physical component was statistically and negatively correlated (r = −0.745; p = 0.008) when Implementation Intention group practice a mild to moderate physical activity. In the Mindfulness-Based Intervention group, the physical component (MFIS) showed a statistically significant improvement (p = 0.028) but no correlation with moderate-to-vigorous physical activity (MVPA); the control group outcomes did not reveal any significant change.

Conclusion: The results of this study are very encouraging and show the feasibility of Mindfulness interventions associated with physical activity to improve the health of people with MS. Further study should assess Mindfulness interventions tailored to MS condition and using both hedonic and eudemonic measures of happiness.

Partial sleep deprivation affects endurance performance and psychophysiological responses during 12-minute self-paced running exercise

PURPOSE

This study aimed to investigate the effects of partial sleep deprivation (PSD) on physical performance and psychophysiological responses during 12-minute self-paced running exercise.

METHODS

Twenty runners (20.8±1.1 years, 70.6±4.9 kg, 175.1±3.9 cm) performed, in a randomized order, two running self-paced field exercises after a normal sleep night (CONT, bedtime from 22:30 h to 06:30 h) and one night of PSD (bedtime from 00:30 h to 04:30 h). Core temperature and motivation were recorded before exercise. Speed, covered distance, heart rate (HR), rating of perceived exertion (RPE) and respiratory parameters (i.e., minute ventilation (VE), oxygen uptake (VO₂) and carbon dioxide production (VCO₂)) were assessed during exercise. Blood lactate concentration [La] was assessed 2 min after exercise. Simple reaction time (SRT), mood and barrage test (BT) were assessed before and after exercise.

RESULTS

Higher RPE (p=0.01, d=0.90) and lower physical performance (i.e., p=0.001, d=0.59 for running speed and p=0.01, d=0.7 and Δ (%)=-6% for covered distance), following PSD, were obtained compared to CONT. Similarly, PSD attenuated core temperature (p=0.01, d=0.84), HR (p=0.006, ɳp²=0.45), VE (p=0.001, ɳp²=0.73), VO₂ (p=0.001, ɳp²=0.96), BT (p<0.0005, ɳp²=0.86), SRT (p=0.0009, ɳp²=0.44) and mood (p<0.0005). However, VCO₂, [La] and motivation score were not affected by sleep conditions.

CONCLUSION

The decrease of running performance and the increase of physical discomfort after PSD could be the origin of the lower cardio-respiratory responses to the 12-minute self-paced exercise. Effective strategies should be introduced to overcome the deterioration of physical performance and physiological responses after PSD.

Effects of Mental Effort on Premotor Muscle Activity and Maximal Grip Force

The present study sought to evaluate how mental effort modulates premotor activity within forearm muscles in the context of an isometric grasping task. Muscle activity of the flexor digitorum superficialis (FDS) and extensor digitorum communis (EDC) was recorded during the application of maximum grip forces in nineteen healthy adult subjects. Each subject was examined under two experimental conditions: 1) spontaneous initiation of grasp (SI) and 2) focused concentration preceding the initiation of grasp (CA). Two novel parameters, the mean premotor duration (MPD) and the mean premotor power (MPP) were used to distinguish patterns of muscle activity. Here we tested the hypothesis was maximal grip strength is primed by muscle activity during the premotor phase. Our results demonstrate that MPD for each muscle group was significantly longer in the CA condition than for the SI condition (BF₁₀ = 491497) and that MPP was significantly greater in EDC than in FDS (BF₁₀ = 4305). Furthermore, both the MPD and MPP of the EDC were significantly correlated with maximum grip force. These results suggest that the increase of premotor activity consequent to the mental effort (focused concentration) may support internal biomechanical and physiological mechanisms which serve to enhance patterns of neuromuscular synergies.

Neural mechanisms associated with treatment decision making: An fMRI study

Great progress has been made in understanding how people make financial decisions. However, there is little research on how people make health and treatment choices. Our study aimed to examine how participants weigh benefits (reduction in disease progression) and probability of risk (medications' side effects) when making hypothetical treatment decisions, and to identify the neural networks implicated in this process. Fourteen healthy participants were recruited to perform a treatment decision probability discounting task using MRI. Behavioral responses and skin conductance responses (SCRs) were measured. A whole brain analysis were performed to compare activity changes between "mild" and "severe" medications' side effects conditions. Then, orbitofrontal cortex (OFC), ventral striatum (VS), amygdala and insula were chosen for effective connectivity analysis. Behavioral data showed that participants are more likely to refuse medication when side effects are high and efficacy is low. SCRs values were significantly higher when people made medication decisions in the severe compared to mild condition. Functionally, OFC and VS were activated in the mild condition and were associated with increased likehood of choosing to take medication (higher area under the curve "AUC" side effects/efficacy). These regions also demonstrated an increased effective connectivity when participants valued treatment benefits. By contrast, the OFC, insula and amygdala were activated in the severe condition and were associated with and increased likelihood to refuse treatment. These regions showed enhanced effective connectivity when participants were confronted with increased side effects severity. This is the first study to examine the behavioral and neural bases of medical decision making.

The Click Test: A Novel Tool to Quantify the Age-Related Decline of Fast Motor Sequencing of the Thumb

BACKGROUND

The thumb plays a critical role for manual tasks during the activities of daily life and the incidence of neurological or musculoskeletal disorders affecting the voluntary movements of the thumb is high in the elderly. There is currently no tool to assess repetitive motor sequencing of the thumb during ageing.

OBJECTIVES

To report a novel procedure (the Click Test) assessing the effects of ageing on fast motor sequencing of the thumb.

METHOD

Healthy subjects (n = 252; mean age +/- SD: 49.76 +/- 19.97 years; range: 19-89 years; F/M: 151/101) were asked to perform fast repeated flexion/extension movements of the thumb using a mechanical counter.

RESULTS

Motor performances (assessed by the number of clicks during 3 time periods: 15, 30 and 45 sec), significantly decreased as a function of age for both the dominant (age effect; p< 0.0001 for 15, 30 and 45 sec) and the non-dominant hand (p<0.0001 for 15, 30 and 45 sec). The number of clicks was significantly higher in males (gender effect; p<0.001) and was higher on the dominant side as compared to the non-dominant side (handedness effect: p<0.001). The Click Test is characterized by high repeatability (coefficients of variation from 3.20 to 4.47%), excellent intra-rater reliability (intra-class coefficients ICC ranging from 0.89 to 0.98), high inter-rater reproducibility (Pearson's product correlation ranging from 0.85 to 0.96), high internal consistency (Cronbach alpha coefficient=0.95) and is highly correlated in terms of relative performances with the box and block test and the 9-hole peg test (positive linear correlation with the results of the box and block test: p<0.001 for 15, 30 and 45 sec for both the dominant and the non-dominant hand; negative linear correlation with the results of the 9-hole peg test: p<0.001 for 15, 30 and 45 sec for both the dominant and the non-dominant hand).

CONCLUSION

The Click Test is an entirely novel and very low cost tool to reliably discriminate the ageing effects upon the performances during fast repetitive motor sequencing of the thumb. The potential clinical and research applications for motor functions are multiple, especially in acute and chronic neurological disorders affecting the thumb as well as in the field of rheumatology and orthopedics.

[Brain imaging: towards a more detailed knowledge of the central nervous system]

Functional imaging allowed the knowledge of the brain to progress significantly. Recent findings about modeling of the activity and the interactivity measured by functional imaging are presented, they allow to apprehend brain functioning and brain plasticity both in normal and pathophysiological conditions. The study of specific circuits in networks should make it possible to define more realistically the dynamic functioning of the central nervous system which underlies numerous brain functions.

Treatment of peritoneal carcinomatosis from colonic cancer by cytoreduction, peritonectomy and hyperthermic intraperitoneal chemotherapy (HIPEC). Experience of ten years

INTRODUCTION

Peritoneal carcinomatosis (PC) is one of the routes of dissemination of abdominal neoplasms and is generally considered a lethal disease, with a poor prognosis by conventional chemotherapeutic treatments. While systemic chemotherapy has little impact on the treatment of peritoneal disease, some centers have reported encouraging results with cytoreduction and hyperthermic intraperitoneal chemotherapy (HIPEC). This approach is based on surgical cytoreduction of the primary tumour, peritonectomy (stripping of implants on the peritoneal surface) and HIPEC. The rationale of this treatment, after macroscopic disease removal, is to obtain an elevated and persistent drug concentration in the peritoneal cavity, with limited systemic effects. Many studies have reported encouraging results on overall survival (OS) and the disease-free interval in patients affected by PC.

PATIENTS AND METHODS

From October 1997 to November 2008, 411 operations for PC were performed in our institution; in 232 cases, cytoreduction plus HIPEC was carried out. Out of 72 operations for colonic cancer: 40 cytoreductions plus HIPEC, 12 cytoreductions+ EPIC (early postoperative intraperitoneal chemotherapy) and 16 debulking or explorative laparoscopies/laparotomies were performed. For the present study, the 40 patients who had undergone cytoreduction plus HIPEC for PC of colorectal cancer (CRC) were considered.

RESULTS

The complication rate was 55% (22/40) and mortality rate 2.5% (1/40). The specific features of both groups were considered for the survival curves and complication rates, with special reference to the peritoneal carcinomatosis index (PCI; range 0, absence of disease to 39) and completeness of cytoreduction score (CCR; 0, no residual tumor, to CCR 3, residual nodules greater than 25 mm). In Group A, patients operated on prior to 2002, the median survival time was 16.7 months compared to 24.6 months for Group B, those operated on after 2002. The poor survival of Group A seemed to be related to higher PCI and CCR scores.

CONCLUSION

Correct patient selection based on a maximum PCI of 16, associated with complete cytoreduction (CCR-0), produced encouraging results in our experience. To improve this encouraging survival outcome, it is very important to unify the surgical experience of expertise centres. Our results also suggest the need for an integrated approach to this condition to identify the correct aspect of the surgical domain and results that may be influencing the prognosis and the evolution of this patients.

Dysfunction of the attentional brain network in children with Developmental Coordination Disorder: a fMRI study

Children with Developmental Coordination Disorder (DCD) present impaired motor skills, frequently associated with impaired attentional and executive functions. The objective of this study was to assess the impact of DCD on effective connectivity applied to a putative model of inhibition. fMRI was performed in 9 children with DCD and 10 control children (8-13 years old) performing a go-nogo task. As previously reported, children with DCD obtained a similar score for correct inhibitions as controls, but responses were slower and more variable than in controls. Compared to controls, Structural Equation Modeling indicated that: (1) path coefficients from both middle frontal cortex (MFC) and anterior cingulate cortex (ACC) to inferior parietal cortex (IPC) increased in children with DCD particularly in the left hemisphere; (2) path coefficients between striatum and parietal cortex decreased in children with DCD in the right hemisphere. Results suggest that DCD could be characterized by abnormal brain hemispheric specialization during development. Furthermore, connectivity in the MFC-ACC-IPC network could indicate that children with DCD are less able than healthy children to easily and/or promptly switch between go and nogo motor responses. However, children with DCD seem to compensate for this poor efficiency by more actively engaging the ACC to prevent commissions allowing maintenance of a good level of inhibition.

[Cerebral tumours: which images?]

Magnetic resonance imaging became the gold standard examination of pretherapeutic planning and post-treatment follow-up of cerebral tumours, even if computed tomography remains useful. During the last years, many new modalities of magnetic resonance examination arose, thus leading to increase its specificity. Then, spectroscopy allows better understanding of tumoural metabolism, whereas perfusion weighted imaging provides informations on its neovascularisation. Functional cortical activation imaging and diffusion tensor imaging allows delineation of tumoural extension towards eloquent areas and fiber bundles. Last, peroperative magnetic resonance imaging may lead to better control tumour resection during operation. However, while numerous and increasing the specificity of magnetic resonance examination, confrontation to pathology data remains necessary.

Intracranial Fluid Dynamics in Normal and Hydrocephalic States

OBJECTIVE

To present a novel magnetic resonance (MR) method of analysis of cerebrospinal fluid (CSF) flow dynamics.

METHODS

Fifty-one subjects were explored with phase-contrast cine MR imaging. There were 36 volunteers, 9 patients with normal pressure hydrocephalus (NPH), and 6 patients with asymptomatic ventricular dilation (VD). The transfer function XFRA/CSF from the arterial pulse waves (APWs) and the CSF pulse waves (CSFPWs) and the transfer function XFRCSF/SS from the CSF pulse waves (CSFPWs) and the sagittal sinus pulse waves (SSPWs) were studied separately.

RESULTS

There was a significant difference in the amplitude spectrum of the XFRA/CSF of patients with VD and volunteers (P < 0.05) and in that of patients with NPH and volunteers (P = 0.005). The amplitude of the fundamental frequency was higher in the NPH group than in the VD group (P = 0.02). In patients with NPH, the amplitude spectrum of XFRCSF/SS showed an attenuation of the pulse wave components that significantly differed from the observed amplification in healthy subjects (P = 0.009) and patients with VD (P = 0.012).

CONCLUSION

This systems analysis method could help to detect increased venous compliance in VD and decreased venous compliance in NPH.

Differential MRI diagnosis between brain abscesses and necrotic or cystic brain tumors using the apparent diffusion coefficient and normalized diffusion-weighted images

Magnetic Resonance Diffusion-Weighted Imaging (DWI) has been reported to be helpful for the differential diagnosis between abscesses and cystic/necrotic brain tumors. However the number of patients is still limited, and the sensitivity and specificity of the method remain to be confirmed. The primary purpose of this study was to investigate a larger sample of patients, all investigated under the same experimental conditions, in order to obtain statistically significant data. Moreover, there is no consensus about the appropriate values of b required to use to make an accurate diagnosis from DWI. The secondary purpose of this study was to determine the discriminating threshold b values for raw diffusion-weighted images and for normalized diffusion-weighted images. On the basis of 14 abscesses, 10 high-grade gliomas and 2 metastases, we show that the calculation of accurate Apparent Diffusion Coefficient (ADC) values gives a specificity rate of 100%. Without ADC calculation, we show that image normalization is required to make an accurate differential diagnosis, and we highlight the ability of DWI to discriminate between brain abscesses and cystic/necrotic brain tumors using normalized signal intensity at lower b values (503 s/mm(2)) than usual.

Photosynthetic properties of leaves of a yellow green mutant of wheat compared to its wild type

We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O2 evolution of the leaf tissue in saturating light and CO2 was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO2 assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.