A study of peatland-derived dissolved organic matter from headstream to sea using multiple analytical tools.

The River Thurso, North Scotland, receives substantial terrestrial deliveries of dissolved organic matter (DOM) leached from Europe's most extensive blanket bogs. The relatively short distance between peatlands and coastal ocean offers potential for research to investigate source-to-sea processing of terrigenous dissolved organic carbon (DOC). Here, we determined DOC concentrations in the bulk (< 0.4 µm), truly dissolved (< 5 kDa), and colloidal fraction (5 kDa - 0.4 µm) as well as DOM absorbance and fluorescence spectra during two river catchment surveys and two corresponding coastal plume surveys, in early spring (1st sampling period) and late spring (2nd sampling period). DOC concentrations ranged from 79 to 3799 µM in early spring and from 115 to 5126 µM in late spring. DOM exhibited conservative mixing across the plume in both surveys, but the plume extended further offshore in the second survey due to a pulse of freshwater caused by recent rainfall. Fluorescence excitation-emission matrices (EEMs) and fluorescence indices revealed that the flushed DOM was humic-like, recently synthesized DOM. Coupled with C/N ratio analyses and molecular weight fractionation, the fluorescence indices also provided evidence for the gradual altering of DOM characteristics along the bog - headstream - loch - river continuum. The same analytical tools revealed that seasonal variations occurred within the DOM pool of marine origin, i.e., greater abundance of low-molecular weight bacterial or algal DOM in the late spring survey. The time scale of such variations relative to the flushing time of water through the aquatic continuum should be taken into account when interpreting the DOM property-salinity distributions of major river plumes.

Awakening the control of the ankle dorsiflexors in the post-stroke hemiplegic subject to improve walking activity and social participation: the WAKE (Walking Ankle isoKinetic Exercise) randomised, controlled trial.

BACKGROUND: Stroke is the leading cause of acquired disability in France. While 90% of patients recover the ability to walk, it is often limited with a steady speed of approximately 0.7 m/s. This limitation of walking activity is partly related to a decrease in strength associated with more or less significant spasticity. In particular, it seems that the strength of the dorsiflexor muscles is directly related to walking speed. We hypothesise that a protocol based on gestural repetition targeted at the ankle during the subacute phase potentiates the recovery of motor control, improving walking activity, and participates in recovering better social participation. METHODS: An estimated total of 60 patients with subacute stroke will be recruited to participate in this multicentre, interventional, prospective, randomised controlled trial. All participants will benefit from conventional rehabilitation. In addition, the experimental group will take part in an ankle isokinetic rehabilitation programme for 6 weeks (at least 25 sessions). The control group will receive the same duration of conventional rehabilitation. The primary outcome measure will be a 10-m walking speed at post-intervention. Secondary outcomes will include social participation, walking spatio-temporal parameters, and dorsiflexor strength. Outcome measurements will be taken at baseline, immediately after treatment (6 weeks), then at 6 months and 1 year of follow-up. DISCUSSION: This study aims to provide scientific evidence that a protocol based on an early over-solicitation of the ankle dorsiflexor muscles to promote their "awakening" can serve to achieve a more effective walking activity, which in turn encourages social participation following discharge from the hospital. This protocol should also help optimise physical medicine and rehabilitation practices: the more systematic use of the isokinetic dynamometer as a technique associated with, and integrated into the conventional rehabilitation protocol would allow an objective evaluation of the rehabilitation benefits and should increase the rehabilitation gain in central nervous system disorders. TRIAL REGISTRATION: Limoges University Hospital is the sponsor of this research (Unique Protocol ID: 87RI18_0010) This research is supported by the French Ministry of Health (PHRC 2020-A03328-31) and is conducted with the support of DGOS (PHRC interregional - GIRCI SOHO). The study protocol was approved by the French Human Subjects Protection Review Board (Comité de Protection des Personnes Nord-Ouest III) on February 23, 2021. The trial was registered in the ClinicalTrials.gov registry ( NCT04800601 ) on March 16, 2021.

The effects of low pH on the taste and amino acid composition of tiger shrimp.

Recent research has revealed that shrimp sensory quality may be affected by ocean acidification but we do not exactly know why. Here we conducted controlled pH exposure experiments on adult tiger shrimp, which were kept in 1000-L tanks continuously supplied with coastal seawater. We compared survival rate, carapace properties and flesh sensory properties and amino acid composition of shrimp exposed to pH 7.5 and pH 8.0 treatments for 28 days. Shrimp reared at pH 7.5 had a lower amino acid content (17.6% w/w) than those reared at pH 8.0 (19.5% w/w). Interestingly, the amino acids responsible for the umami taste, i.e. glutamate and aspartic acid, were present at significantly lower levels in the pH 7.5 than the pH 8.0 shrimp, and the pH 7.5 shrimp were also rated as less desirable in a blind quality test by 40 volunteer assessors. These results indicate that tiger shrimp may become less palatable in the future due to a lower production of some amino acids. Finally, tiger shrimp also had a lower survival rate over 28 days at pH 7.5 than at pH 8.0 (73% vs. 81%) suggesting that ocean acidification may affect both the quality and quantity of future shrimp resources.

Controlled Synthesis of Gold Nanoparticles in Copolymers Nanomolds by X-ray Radiolysis.

We show by X-ray and neutron small-angle scattering that gold nanoparticles with controlled sizes and morphologies can be obtained by the metallic reduction of AuCl4- ions trapped in 3D organic molds by X-ray radiolysis. The molds are spherical frozen micelles of polystyrene-b-poly(dimethylaminoethyl methacrylate) (PS-b-PDMAEMA) block copolymer in acidic aqueous solution with a PS spherical core surrounded by a corona of PDMAEMA chains in good solvent. The behavior of micelles is controlled by the [AuCl4-]/[DMAEMA] ratio RAuCl4-/DMAEMA. At low gold concentration, AuCl4- ions condense on the positively charged DMAEMA moieties without changing the behavior of the PDMAEMA chains. At intermediate gold concentration, the ions induce a progressive contraction of the corona's chains and dehydration of micelles. At large gold concentration, the corona becomes a fully dry phase loaded with gold ions, which induces micelle aggregation. Radiolysis of the solution by an intense X-ray beam produces different types of gold nanoparticles with respect to RAuCl4-/DMAEMA and irradiation time. At RAuCl4-/DMAEMA = 0.033, irradiation produces in the first step gold clusters in the micelle corona which in the second step merge to form nanoparticles of a similar size to that of the micelle. Conversely, at RAuCl4-/DMAEMA = 0.33, micelles do not operate as templates but only as nucleation zones and large nanoparticles grow outside the micelles.

Effects of a 6-month self-rehabilitation programme in addition to botulinum toxin injections and conventional physiotherapy on limitations of patients with spastic hemiparesis following stroke (ADJU-TOX): protocol study for a randomised controlled, investigator blinded study.

INTRODUCTION: Home-based self-rehabilitation programmes combined with botulinum toxin injections (BTIs) appear to be a relevant approach to increase the recommended intensive rehabilitation of patients with spasticity following a stroke. The literature highlights a lack of evidence of beneficial effects of this adjuvant therapy to reduce limitations of patients with stroke. The aim of this study is to assess the effects of a 6-month self-rehabilitation programme in adjunction to BTI, in comparison with BTI alone, to reduce limitations of patients with spasticity following a stroke. METHODS AND ANALYSIS: 220 chronic patients will participate to this multicentre, prospective, randomised, controlled, assessor blinded study. All patients will benefit from two successive BTI (3 months apart), and patients randomised in the self-rehabilitation group will perform in adjunction 6 months of self-rehabilitation at home. All patients continue their conventional physiotherapy. The main outcome is the primary treatment goal (PTG), which will be determined jointly by the patient and the medical doctor using Goal Attainment Scaling. Impairments and functions, quality of life, mood and fatigue will be assessed. Botulinum toxin will be injected into the relevant muscles according to the PTG. Patients in the self-rehab group will be taught the self-rehabilitation programme involving respectively 10 min of stretching, 10 min of strengthening and 10 min of task-oriented exercises, corresponding to their PTG. Compliance to the self-rehabilitation programme will be monitored. ETHICS AND DISSEMINATION: Patients will sign written informed consent. Ethical approval was obtained from ethics committee. The results will be disseminated in a peer-reviewed journal and presented at international congresses. The results will also be disseminated to patients. TRIAL REGISTRATION NUMBER: NCT02944929.

Interplay between bulk self-assembly, interfacial and foaming properties in a catanionic surfactant mixture of varying composition.

The self-aggregation, surface properties and foamability of the catanionic surfactant mixture cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate (SOSo) have been investigated to obtain insight on the relation between bulk nanostructures, surfactant packing, and foam stability and aging. Light microscopy, SANS, cryo-TEM, DLS, surface tension, rheometry and direct photography were used to characterize mixtures with varying CTAB molar fraction, xCTAB. In the bulk, self-assembly is richer in the excess CTAB region than in the excess SOSo one. Starting from neat CTAB micelles and on addition of anionic surfactant, there is a change from small ellipsoidal micelles (1 < xCTAB ≤ 0.80) to large rodlike micelles (0.65 ≤ xCTAB ≤ 0.55) and then to vesicles (0 < xCTAB ≤ 0.50), with coexistence regions in between; SOSo-rich mixtures are thus dominated by vesicles. High size polydispersity for the micelles and vesicles is an intrinsic feature of this system. Foam stability is concomitantly impacted by xCTAB. SOSo is a small mobile molecule and so it disrupts foam stability, irrespective of the presence of vesicles. Foams are thus only stable in the CTAB-rich regions, and SANS shows that the shape of micelles and vesicles is unchanged inside the foam. Foam drainage is thereby mostly controlled by the presence of the elongated micelles through the solution viscosity, whereas coarsening is influenced by dense surfactant packing at the gas-liquid interfaces.

Probing foam with neutrons.

Foams are multiscale materials that have an enormous number of uses. As the relevant structural length-scales span from a few nanometres up to millimetres a number of characterisation methods need to be combined to obtain the full material structure. In this review we explain how foams can be explored using Small Angle Neutron Scattering (SANS). We remind the reader of the basics of SANS and contrast variation before we describe the different types of experiments that have been carried out on foams emphasising the specific role of neutrons in learning about the systems. To date SANS has been used to measure different foam structural parameters, such as the film thickness and the bubble size. Several studies have also been carried out to elucidate the organisation of the stabilising objects in the bulk solution. Finally we show how SANS measurements can be used to measure foam composition. Some of the accessible information is unique to SANS experiments, but as the method is still not very widely used on foams the review is also aimed to act as an introduction on how to carry out such measurements on foams.

How exfoliated graphene oxide nanosheets organize at the water interface: evidence for a spontaneous bilayer self-assembly.

In this study, we have characterized graphene oxide films formed at the air-water interface by X-ray reflectivity and grazing incidence X-ray diffraction using synchrotron sources. Surprisingly, the results of both measurements show that at non zero surface pressures, the film is organized as a bilayer of sheets interfaced between air and water with water molecule bridges. Such a spontaneous bilayer structure and its evolution with respect to the surface pressure has been observed for the first time. These results should allow precise control of the density of sheets deposited on the substrate when these films are transferred through the Langmuir Blodgett or Schaefer procedures. Indeed, graphene oxide keeps on attracting more and more attention, increasing the need for the production of well-controlled graphene oxide thin films due to its application in energy devices or in sensor domains.

Alteration of the Copper-Binding Capacity of Iron-Rich Humic Colloids during Transport from Peatland to Marine Waters.

Blanket bogs contain vast amounts of Sphagnum-derived organic substances which can act as powerful chelators for dissolved iron and thus enhance its export to the coastal ocean. To investigate the variations in quantity and quality of these exports, adsorptive cathodic stripping voltammetry (CSV) was used to characterize the metal binding properties of molecular weight-fractionated dissolved organic matter (MW-fractionated DOM) in the catchment and coastal plume of a small peat-draining river over a seasonal cycle. Within the plume, both iron- and copper-binding organic ligands showed a linear, conservative distribution with increasing salinity, illustrating the high stability of peatland-derived humic substances (HS). Within the catchment, humic colloids lost up to 50% of their copper-binding capacity, expressed as a molar ratio to organic carbon, after residing for 1 week or more in the main reservoir of the catchment. Immediately downstream of the reservoir, the molar ratio [L2]/[Corg], where L2 was the second strongest copper-binding ligand, was 0.75 × 10-4 when the reservoir residence time was 5 h but 0.34 × 10-4 when it was 25 days. Residence time did not affect the carbon specific iron-binding capacity of the humic substances which was [L]/[Corg] = (0.80 ± 0.20) × 10-2. Our results suggest that the loss of copper-binding capacity with increasing residence time is caused by intracolloidal interactions between iron and HS during transit from peat soil to river mouth.

Varying the counter ion changes the kinetics, but not the final structure of colloidal gels.

We show that, while the gelation of colloidal silica proceeds much faster in the presence of added KCl than NaCl, the final gels are very similar in structure and properties. We have studied the gelation process by visual inspection and by small angle X-ray scattering for a range of salt and silica particle concentrations. The characteristic times of the early aggregation process and the formation of a stress-bearing structure with both salts are shown to collapse onto master curves with single multiplicative constants, linked to the stability ratio of the colloidal suspensions. The influence of the salt type and concentration is confirmed to be mainly kinetic, as the static structure factors and viscoelastic moduli of the gels are shown to be equivalent at normalized times. While there is strong variation in the kinetics, the structure and properties of the gel at long-times are shown to be mainly controlled by the concentration of particles, and hardly influenced by the type or the concentration of salt. This suggests that the differences between gels generated by different salts are only transient in time.

Precipitating Sodium Dodecyl Sulfate to Create Ultrastable and Stimulable Foams.

Ultrastable foams are made very simply by adding salt (NaCl or KCl) to sodium dodecyl sulfate. The addition of high concentrations of salt leads to the precipitation of the surfactant on the bubble surfaces and as crystals in the interstices between the bubbles. As a consequence, the ageing of the foams is stopped to make them stable indefinitely, or until they are heated above the melting temperature of the crystals. The use of KCl is shown to be much more effective than that of NaCl because potassium dodecyl sulfate has a higher melting temperature and faster rates of crystallization. The crystalline structures have been investigated inside the foam using small angle neutron scattering. The larger lattice spacing of the crystals formed with NaCl in comparison with KCl has been evidenced. These simple temperature stimulable foams could have many potential applications.

Probing structure in submicronic aqueous assemblies of emulsified microemulsions and charged spherical colloids using SANS and cryo-TEM.

The spatial distribution of charged spherical colloids when used as stabilizers of phytantriol-based emulsified microemulsions (EME, L2 symmetry group) is investigated. The coverage of the lipid-based mesophases by the colloids is monitored using small-angle neutron scattering (SANS) in contrast matching conditions and visualized using cryogenic transmission electron microscopy (cryo-TEM) imaging. The results demonstrate that, despite the stability of the emulsion droplets, very few colloids are ever found on the droplets. The stability of the EMEs is suggested to arise from the very slow ripening rates combined with punctual repulsion against coalescence from the isolated charged colloids on the bigger droplet surfaces. We show the possibility of creating a dense cover around the droplets by partially hydrophobizing the colloids by adsorbing a cationic surfactant on their surface. This opens up the possibilities for further modulation of the colloidal coverage in these systems. This is an interesting route for the design of new Colloid-ISAsome assemblies in which dense protective armors could be advantageous such as controlled delivery.

Seasonal variations in surface water chemistry at disturbed and pristine peatland sites in the Flow Country of northern Scotland.

Weekly monitoring of surface water chemistry took place over a one-year period in a small boggy sub-catchment of the River Thurso, northern Scotland. Monitoring started 6 months after the felling to waste of plantation conifers. The chemistry of ground surface waters was monitored at four bog sites situated in former forestry plots as well as one control site situated in an intact bog. The chemistry of the receiving stream (Sleach Water) was monitored at seven points along a 2 km stretch. Dissolved organic carbon and metals were very significantly affected by seasonal factors. On land, seasonal variations accounted for between 35% (Al) and 80% (Fe) of the total variance in the data at the intact bog site, with similar seasonal effects observed at the impacted sites. The amplitude of the seasonal signal was generally much higher at the impacted sites than at the control site. Except for dissolved Al and Mn, the chemical composition of the stream was only marginally influenced by surface runoff from the felled plantation despite evidence of intense seasonal mobilisation of e.g. DOC, K or Fe at or near the ground surface within the felled plots. This was attributed to the presence of a buffer zone between the plantation and the stream. On the other hand, surface inputs from former forestry plots caused measurable increases in stream water [Al] and [Mn]. The likely sources of Al and Mn were the disturbance of the mineral soil that had taken place some 20 years previously as a result of forestry ground preparation and the leaching from the recently felled conifer material, respectively. Such inputs occurred in late autumn or winter for Al and in summer for Mn, thus intensifying their natural seasonal patterns in this peat draining stream.

Safety and self-reported efficacy of botulinum toxin for adult spasticity in current clinical practice: a prospective observational study.

OBJECTIVE: To determine the safety and the self-reported efficacy of botulinum toxin injections for adult spasticity in current clinical practice. DESIGN: A prospective observational study. SUBJECTS: A total of 406 adult patients with focal spasticity received of 1136 series botulinum toxin injections at Bordeaux University Hospital from January 2007 to December 2009. METHODS: Adverse events following botulinum toxin injections were reported. Their severity and the therapeutic efficacy of botulinum toxin injections were estimated with a four-point self-reporting scale (0 to 3). Latency and duration of adverse events and subjective improvement were also noted. RESULTS: The data of 640 series of injections were analyzed. Forty-six (7.2%) adverse events were reported, of which 36 (78%) were local. There were 18 (39%) cases of local muscular weakness with an average duration of 30.0 (SD 38.2) days, and an average severity score of 1.0 (SD 0.97). Among systemic adverse events, there were 8 (17%) cases of excessive fatigue without global muscular weakness and 2 (4%) cases of transitory generalized muscular weakness. The average subjective improvement score was 1.89 (SD 0.97) and was higher for upper, than for lower, limbs (P=0.007). CONCLUSION: Self-reported adverse events following botulinum toxin injections in spasticity are rare, often benign and of short duration in current clinical practice. Botulinum toxin is considered effective by patients in treating spasticity of the upper and lower limbs.

SANS measurements of semiflexible xyloglucan polysaccharide chains in water reveal their self-avoiding statistics.

We explored the behavior and the characteristics of xyloglucan polysaccharide chains extracted from tamarind seeds in aqueous media. The initial solubilization is achieved by using a 0.01 M NaOH solution. The absence of compact aggregates in the solution and the average molecular mass of the individual chains were unambiguously demonstrated by size exclusion chromatography with multi-angle light scattering detection. The composition and the stability of the solution were quantitatively checked over weeks by using liquid state nuclear magnetic resonance with DMSO as internal standard. The conformational characteristics of the chains were measured using nondestructive small-angle neutron scattering (SANS). The unambiguous determination of the Flory exponent (ν = 0.588) by SANS enabled us to directly prove that xyloglucan chains in water behave like semiflexible worm-like chains with excluded volume statistics (good solvent), contrary to most of the neutral water-soluble polymer chains that rather exhibit Gaussian statistics (θ-solvent). In addition to the Flory exponent, the persistence length l(p) and the cross section of the chains were also determined by SANS with utmost precision, with values of 80 and of 7 Å, respectively, which provides a complete description of the conformational characteristics of XG chains at all relevant length scales.

Botulinum toxin treatment in neurological practice: how much does it really cost? A prospective cost-effectiveness study.

Botulinum toxin (BTA) is a safe and effective therapeutic tool for many neurological conditions but few studies have investigated its real cost in neurological practice. We evaluated the daily cost of botulinum toxin type A (BTA) treatment through a cost effectiveness analysis alongside a prospective study of BTA injections at a French University Hospital over a 2-year follow-up period. The data of 3,108 BTA injections performed in 870 adult patients presenting with dystonia, facial hemispasm, or spasticity were entered in the database. Patients were questioned at each visit about the subjective effectiveness of the previous injection. The daily cost of BTA treatment was calculated as the ratio of each session's cost (including all additional costs) to the duration of subjective efficacy. The subjective rating of efficacy duration was 17.3 ± 7.7 weeks for facial hemispasm, 15.4 ± 7.7 for blepharospasm, 14.3 ± 6.7 for cervical dystonia, 14.5 ± 7.8 and 14.1 ± 7.4 weeks for upper and lower limb spasticity, respectively. The daily cost of BTA injections was 0.57 ± 0.20 for facial hemispasm, 0.95 ± 0.30 for blepharospasm, 2.85 ± 0.86 for cervical dystonia, 3.38 ± 1.49 and 3.62 ± 1.81 for upper and lower limb spasticity, respectively. When associated costs were considered, the daily cost of BTA injections was clearly increased (45-93%) in limb spasticity or rigidity but remained only modestly increased (15-37%) in other indications. These results obtained in a large cohort of patients show that BTA treatment has a low daily cost for a long-lasting effect, with a daily cost/benefit ratio that greatly depends on the indications.

Evidence for strong but dynamic iron-humic colloidal associations in humic-rich coastal waters.

This study investigated the physicochemical forms of dissolved iron in the coastal plume (salinity = 28-35) of a small river draining a peat-rich catchment. Speciation information was obtained through a combination of fractionation by crossflow filtration (CFF) along with voltammetric detection of either naturally occurring iron-humic complexes (July survey) or known, synthetic complexes (September survey) formed by titrating the samples with the competing ligand 2-(2-thiazolylazo)-p-cresol (TAC). The majority of colloidal iron (>5000 Da) was present as iron-humic complexes supplied by the river and showing uniform conditional stability constants throughout the plume (log K'(Fe'HS) = 11.3 ± 0.1, i.e. log K(Fe3+HS) = 21.3 ± 0.1). Noncolloidal or soluble iron was strongly complexed to ligands of marine origin with log K'(Fe'HS) = 11.9 ± 0.1. Equilibrium of the total iron pool with the added TAC ligand was achieved in all but the highest salinity sample, albeit more slowly for colloidal than for soluble iron. In addition, measurements of humic like fluorescence suggested that the conformation of colloids could change over time as a result of dissociation of the iron-humic associations. These results are consistent with the concept that iron in coastal waters is strongly but reversibly bound to humic substances and therefore may be available for complexation by siderophore-type ligands released by microorganisms.

Internally self-assembled submicrometer emulsions stabilized by spherical nanocolloids: finding the free nanoparticles in the aqueous continuous phase.

This article reports on the behavior of colloids during the stabilization of internally liquid-crystalline droplets. The ability and limitations of spherical silica colloids to act as stabilizers of liquid-crystalline bulk phases have been demonstrated for monoglyceride/tetradecane/water and phytantriol/tetradecane/water systems using small-angle X-ray scattering and dynamic light scattering as probes. It has been demonstrated that these nanoparticles are very good stabilizers of phytantriol-based phases. In particular, these data showed that they are nondisruptive stabilizers for these bulk phases at ambient temperature. Interestingly, it was shown that the spherical nanoparticles were not able to stabilize the monoglyceride-based bicontinuous cubic phase (Pn3m symmetry group), in contrast with their phytantriol-based counterparts. They were, however, good stabilizers of the monoglyceride-based emulsified microemulsions and inverse micellar cubic phases (Fd3m symmetry group). We then further examined the influence of the concentration of stabilizer on the phytantriol-based dispersed particles. We showed that the scattering signals of the liquid crystal and the nanoparticles are uncorrelated, whatever the identity of the liquid-crystalline phase. A careful analysis method coupled with dynamic light scattering measurements allowed us to determine and discriminate qualitatively the cases with or without free nanoparticles in the continuous phase. The results indicate for the first time fundamental differences in the stabilization by solidlike nanoparticles of emulsified microemulsions and of bicontinuous cubic phases.

Phase behavior of Phytantriol/water bicontinuous cubic Pn3m cubosomes stabilized by Laponite disc-like particles.

The present article reports on the specific effects of temperature on Phytantriol-based cubosomes stabilized by inorganic stabilizers as opposed to organic stabilizers. The ability of Laponite to stabilize Phytantriol-based parent bulk phase is first demonstrated. The sub-micron-sized Laponite-stabilized particles were found to be both physically and chemically stable over time. The temperature-induced behavior, both in heating and cooling directions, of these lipid-based cubosomes has been investigated and compared with their polymer-stabilized counterparts (Pluronic F127). This allows us to extract the particular influence of each stabilizer. Whereas an increased hydration of the cubic structure was evidenced at high pH values, this effect was eliminated to compare the specific influence of both stabilizers on these Phytantriol-based cubosomes. Evidence of differences in the relaxation rates of the internal structures with temperature was found for the two stabilizers, in particular in the cooling direction whilst in the heating direction the two stabilizers could be considered as undisruptive. The origin of this difference is discussed.

Exploring theory of mind after severe traumatic brain injury.

Previous studies have reported a dissociation between social behavioral impairments after severe traumatic brain injury (TBI) and relatively preserved performances in traditional tasks that investigate cognitive abilities. Theory of mind (ToM) refers to the ability to make inferences about other's mental states and use them to understand and predict others' behavior. We tested a group of 15 patients with severe TBI and 15 matched controls on a series of four verbal and non-verbal ToM tasks: the faux pas test, the first-order and second-order false belief task, the character intention task and the Reading the Mind in the Eyes Test. Participants with severe TBI were also compared to controls on non-ToM inference tasks of indirect speech act from the Montreal Evaluation of Communication (M.E.C.) Protocol and empathy (Davis Interpersonal Reactivity Index - I.R.I.) and tests for executive functions. Subjects with TBI performed worse than control subjects on all ToM tasks, except the first-order false belief task. The findings converge with previous evidence for ToM deficit in TBI and dissociation between ToM and executive functions. We show that ToM deficit is probably distinct from other aspects of social cognition like empathy and pragmatic communication skills.