Bifurcation analysis of models with uncertain function specification: how should we proceed?

When we investigate the bifurcation structure of models of natural phenomena, we usually assume that all model functions are mathematically specified and that the only existing uncertainty is with respect to the parameters of these functions. In this case, we can split the parameter space into domains corresponding to qualitatively similar dynamics, separated by bifurcation hypersurfaces. On the other hand, in the biological sciences, the exact shape of the model functions is often unknown, and only some qualitative properties of the functions can be specified: mathematically, we can consider that the unknown functions belong to a specific class of functions. However, the use of two different functions belonging to the same class can result in qualitatively different dynamical behaviour in the model and different types of bifurcation. In the literature, the conventional way to avoid such ambiguity is to narrow the class of unknown functions, which allows us to keep patterns of dynamical behaviour consistent for varying functions. The main shortcoming of this approach is that the restrictions on the model functions are often given by cumbersome expressions and are strictly model-dependent: biologically, they are meaningless. In this paper, we suggest a new framework (based on the ODE paradigm) which allows us to investigate deterministic biological models in which the mathematical formulation of some functions is unspecified except for some generic qualitative properties. We demonstrate that in such models, the conventional idea of revealing a concrete bifurcation structure becomes irrelevant: we can only describe bifurcations with a certain probability. We then propose a method to define the probability of a bifurcation taking place when there is uncertainty in the parameterisation in our model. As an illustrative example, we consider a generic predator-prey model where the use of different parameterisations of the logistic-type prey growth function can result in different dynamics in terms of the type of the Hopf bifurcation through which the coexistence equilibrium loses stability. Using this system, we demonstrate a framework for evaluating the probability of having a supercritical or subcritical Hopf bifurcation.

Defining and detecting structural sensitivity in biological models: developing a new framework.

When we construct mathematical models to represent biological systems, there is always uncertainty with regards to the model specification--whether with respect to the parameters or to the formulation of model functions. Sometimes choosing two different functions with close shapes in a model can result in substantially different model predictions: a phenomenon known in the literature as structural sensitivity, which is a significant obstacle to improving the predictive power of biological models. In this paper, we revisit the general definition of structural sensitivity, compare several more specific definitions and discuss their usefulness for the construction and analysis of biological models. Then we propose a general approach to reveal structural sensitivity with regards to certain system properties, which considers infinite-dimensional neighbourhoods of the model functions: a far more powerful technique than the conventional approach of varying parameters for a fixed functional form. In particular, we suggest a rigorous method to unearth sensitivity with respect to the local stability of systems' equilibrium points. We present a method for specifying the neighbourhood of a general unknown function with [Formula: see text] inflection points in terms of a finite number of local function properties, and provide a rigorous proof of its completeness. Using this powerful result, we implement our method to explore sensitivity in several well-known multicomponent ecological models and demonstrate the existence of structural sensitivity in these models. Finally, we argue that structural sensitivity is an important intrinsic property of biological models, and a direct consequence of the complexity of the underlying real systems.

Revising the role of species mobility in maintaining biodiversity in communities with cyclic competition.

One of the most crucial tasks faced by biologists today is revealing the mechanisms which account for biodiversity, yet we are still far from a full understanding of these mechanisms, and in particular the role of spatially heterogeneous population distributions. Recently, the spatially heterogeneous coexistence seen in cyclic competition models--in which species compete as in the game rock-paper-scissors--has brought them to the fore as a paradigm for biodiversity. Research into cyclic competition has so far been focused almost exclusively on stochastic lattice models with discrete space, which ignore several key dynamical aspects. In particular, such models usually assume that species disperse at the same speed. This paper aims to extend our understanding of cyclic competition by applying a reaction-diffusion Lotka-Volterra scheme to the problem, which allows us to vary the mobility of each species, and lets us take into account cyclic competition with more complex underlying mechanisms. In this paper we reveal an entirely new kind of cyclic competition-'conditional' cyclic competition, with a different underlying mechanism to 'classic' cyclic competition-and we show that biodiversity in communities with cyclic competition in fact depends heavily on the ratios between the species mobilities. Furthermore, we show that this dependence can be completely different for conditional and classic cyclic competition. We also present a wide range of spatiotemporal patterns which are formed in the system, including spiral and target waves, spiralling patches, and irregular chaotic patches. We show that the previously unknown case of conditional cyclic competition is host to a scenario of patchy co-invasion, where the spread of the population front takes place via the formation, splitting and propagation of patches of high species density. This is also an example of invasional meltdown because one competitor facilitates the invasion of the other, but unlike well-known cases of invasional meltdown the co-invaders in this system are not mutualists but antagonistic competitors, and the overall result mitigates, rather than amplifies, the damage done to the native ecosystem.

Sex differences in rTMS treatment response: A deep learning-based EEG investigation.

INTRODUCTION: The present study aimed to investigate sex differences in response to repetitive transcranial magnetic stimulation (rTMS) in Major Depressive Disorder (MDD) patients. Identifying the factors that mediate treatment response to rTMS in MDD patients can guide clinicians to administer more appropriate, reliable, and personalized interventions. METHODS: In this paper, we developed a novel pipeline based on convolutional LSTM-based deep learning (DL) to classify 25 female and 25 male patients based on their rTMS treatment response. RESULTS: Five different classification models were generated, namely pre-/post-rTMS female (model 1), pre-/post-rTMS male (model 2), pre-rTMS female responder versus pre-rTMS female nonresponders (model 3), pre-rTMS male responder vs. pre-rTMS male nonresponder (model 4), and pre-rTMS responder versus nonresponder of both sexes (model 5), achieving 93.3%, 98%, 95.2%, 99.2%, and 96.6% overall test accuracy, respectively. CONCLUSION: These results indicate the potential of our approach to be used as a response predictor especially regarding sex-specific antidepressant effects of rTMS in MDD patients.

The roles of COMT val158met status and aviation expertise in flight simulator performance and cognitive ability.

The polymorphic variation in the val158met position of the catechol-O-methyltransferase (COMT) gene is associated with differences in executive performance, processing speed, and attention. The purpose of this study is: (1) replicate previous COMT val158met findings on cognitive performance; (2) determine whether COMT val158met effects extend to a real-world task, aircraft navigation performance in a flight simulator; and (3) determine if aviation expertise moderates any effect of COMT val158met status on flight simulator performance. One hundred seventy two pilots aged 41-69 years, who varied in level of aviation training and experience, completed flight simulator, cognitive, and genetic assessments. Results indicate that although no COMT effect was found for an overall measure of flight performance, a positive effect of the met allele was detected for two aspects of cognitive ability: executive functioning and working memory performance. Pilots with the met/met genotype benefited more from increased levels of expertise than other participants on a traffic avoidance measure, which is a component of flight simulator performance. These preliminary results indicate that COMT val158met polymorphic variation can affect a real-world task.

Evolution of virulence driven by predator-prey interaction: Possible consequences for population dynamics.

The evolution of pathogen virulence in natural populations has conventionally been considered as a result of selection caused by the interactions of the host with its pathogen(s). The host population, however, is generally embedded in complex trophic interactions with other populations in the community, in particular, intensive predation on the infected host can increase its mortality, and this can affect the course of virulence evolution. Reciprocally, in the long run, the evolution of virulence within an infected host can affect the patterns of population dynamics of a predator consuming the host (e.g. resulting in large amplitude oscillations, causing a severe drop in the population size, etc.). Surprisingly, neither the effect of predation on the evolution of virulence within a host, nor the influence of the evolution of virulence upon the consumer's dynamics has been addressed in the literature yet. In this paper, we consider a classical S-I ecoepidemiological model in which the infected host is consumed by a predator. We are particularly interested in the evolutionarily stable virulence of the pathogen in the model and its dependence upon ecologically relevant parameters. We show that predation can prominently shift the evolutionarily stable virulence towards more severe strains as compared to the same system without predation. We demonstrate that the evolution of virulence can result in a succession of dynamical regimes and can even lead to the extinction of the predator in the long run. The presence of a predator can indirectly affect the evolution within its prey since the evolutionarily stable virulence becomes a function of the prey growth rate, which would not be the case in a predator-free system. We find that the evolutionarily stable virulence largely depends on the carrying capacity K of the prey in a non-monotonous way. The model also predicts that in an eutrophic environment the shift of virulence towards evolutionarily stable benign strains can cause demographically stochastic evolutionary suicide, resulting in the extinction of both species, thus artificially maintaining severe strains of pathogen can enhance the persistence of both species.

The effect of coincidental SARS-CoV-2 infection on pre-operative cardiopulmonary exercise testing.

This case report demonstrates the significant impact active infection with SARS-CoV-2 can have on functional capacity evaluated by cardiopulmonary exercise testing, even in minimally symptomatic individuals. A 75-year-old man underwent cardiopulmonary exercise testing before a right hemicolectomy; SARS-CoV-2 was incidentally diagnosed following his test. The patient underwent a period of isolation and recovery before a second pre-operative cardiopulmonary exercise test 6 weeks later. His resting pulmonary function tests did not vary between tests but his peak work, anaerobic threshold, oxygen pulse, pulse oximetry nadir, ventilation perfusion matching and heart rate response to exercise all improved significantly after this recovery period. These are unique results that add to the existing knowledge of the pathophysiology and management of SARS-CoV-2 in the peri-operative setting. While our patient demonstrated dramatic improvement in his functional capacity following 6 weeks of recovery, he remained in a high-risk group for surgery according to our local guidelines. Cardiopulmonary exercise testing has a valuable role in individualised risk assessment and shared decision-making in complex, urgent surgical cases where the benefits of delaying surgery to recover from SARS-CoV-2 infection should be balanced against the potential risks.

Medication status and dual-tasking on turning strategies in Parkinson disease.

BACKGROUND: Parkinson disease (PD) patients have turning impairments that may increase fall risk. Clinics lack specialized kinematic equipment used in gait and turn analysis and require a simple method to evaluate fall risk and advise patients in turning strategy selection. OBJECTIVES: To enhance understanding of PD turning strategies and determine if turning can be assessed using a video-recording and categorization method, we compared 180-degree and 90-degree turns as a function of medication status and dual-tasking (DT). METHODS: 21 PD participants (H&Y stage 1-3) in PD-ON and PD-OFF medication states and 16 controls completed 180-degree and 90-degree turn-tasks with and without DT. Video-recordings of tasks permitted classification of 180-degree turns into Few-Step turns (FST) vs. Multi-Step turns (MST) and 90-degree turns into Step vs. Spin-turns. FST were further sub-classified into Twisting vs. Sideways turns and MST into Backward, Festination, Forward or Wheeling turns. Percentages of subtypes were analyzed across groups by task. RESULTS: IN 180-degree tasks, there was an effect of group: FST vs. MST F(2,55) = 9.578, p < .001. PD participants in the off-medication state (PD-OFF) produced significantly more MST with a larger number of different turning subtypes vs. controls or PD on medication (PD-ON). In 90-degree tasks, controls significantly increased their proportion of Step-turns while DT (p < .001), an adaptation not observed in PD-ON or PD-OFF. CONCLUSIONS: PD turning impairments may stem from an inability to select a unified turning strategy and to adapt to the turning environment, which may be exacerbated in PD-OFF. Video-analysis may prove beneficial in predicting a clinical course for PD patients by revealing features of turning dysfunction.

Brain Injury Lesion Imaging Using Preconditioned Quantitative Susceptibility Mapping without Skull Stripping.

BACKGROUND AND PURPOSE: Identifying cerebral microhemorrhage burden can aid in the diagnosis and management of traumatic brain injury, stroke, hypertension, and cerebral amyloid angiopathy. MR imaging susceptibility-based methods are more sensitive than CT for detecting cerebral microhemorrhage, but methods other than quantitative susceptibility mapping provide results that vary with field strength and TE, require additional phase maps to distinguish blood from calcification, and depict cerebral microhemorrhages as bloom artifacts. Quantitative susceptibility mapping provides universal quantification of tissue magnetic property without these constraints but traditionally requires a mask generated by skull-stripping, which can pose challenges at tissue interphases. We evaluated the preconditioned quantitative susceptibility mapping MR imaging method, which does not require skull-stripping, for improved depiction of brain parenchyma and pathology. MATERIALS AND METHODS: Fifty-six subjects underwent brain MR imaging with a 3D multiecho gradient recalled echo acquisition. Mask-based quantitative susceptibility mapping images were created using a commonly used mask-based quantitative susceptibility mapping method, and preconditioned quantitative susceptibility images were made using precondition-based total field inversion. All images were reviewed by a neuroradiologist and a radiology resident. RESULTS: Ten subjects (18%), all with traumatic brain injury, demonstrated blood products on 3D gradient recalled echo imaging. All lesions were visible on preconditioned quantitative susceptibility mapping, while 6 were not visible on mask-based quantitative susceptibility mapping. Thirty-one subjects (55%) demonstrated brain parenchyma and/or lesions that were visible on preconditioned quantitative susceptibility mapping but not on mask-based quantitative susceptibility mapping. Six subjects (11%) demonstrated pons artifacts on preconditioned quantitative susceptibility mapping and mask-based quantitative susceptibility mapping; they were worse on preconditioned quantitative susceptibility mapping. CONCLUSIONS: Preconditioned quantitative susceptibility mapping MR imaging can bring the benefits of quantitative susceptibility mapping imaging to clinical practice without the limitations of mask-based quantitative susceptibility mapping, especially for evaluating cerebral microhemorrhage-associated pathologies, such as traumatic brain injury.

Quantifying uncertainty in partially specified biological models: how can optimal control theory help us?

Mathematical models in biology are highly simplified representations of a complex underlying reality and there is always a high degree of uncertainty with regards to model function specification. This uncertainty becomes critical for models in which the use of different functions fitting the same dataset can yield substantially different predictions-a property known as structural sensitivity. Thus, even if the model is purely deterministic, then the uncertainty in the model functions carries through into uncertainty in model predictions, and new frameworks are required to tackle this fundamental problem. Here, we consider a framework that uses partially specified models in which some functions are not represented by a specific form. The main idea is to project infinite dimensional function space into a low-dimensional space taking into account biological constraints. The key question of how to carry out this projection has so far remained a serious mathematical challenge and hindered the use of partially specified models. Here, we propose and demonstrate a potentially powerful technique to perform such a projection by using optimal control theory to construct functions with the specified global properties. This approach opens up the prospect of a flexible and easy to use method to fulfil uncertainty analysis of biological models.

Lactoperoxidase-catalyzed inactivation of hexokinase.

The enzymatic activity of hexokinase (ATP : D-hexose 6-phosphotransferase, EC 2.7.1.1) decreased rapidly when the enzyme was exposed to the lactoperoxidase antimicrobial system (consisting of lactoperoxidase, H2O2 and SCN-). Inactivation did not begin until the reaction of one sulfhydryl group per hexokinase monomer was completed. Loss of enzyme activity accompanied the reaction of at least one additional sulfhydryl group per monomer. Covalent incorporation of 14C-labeled SCN- into hexokinase increased as the inactivation reaction progressed. The rate of the hexokinase activity loss dependent on temperature, pH and the presence of glucose and phosphate ion. When H2O2 and SCN- were applied to a Sepharose column bearing covalently attached lactoperoxidase, the column eluate inactivated hexokinase. This demonstrated that the lactoperoxidase molecule itself need not be in contact with hexokinase in order to catalyze hexokinase inactivation. The sulfhydryl-reactive oxidation product of SCN- which is generated by the column is sufficient. The results are consistent with a two-stage reaction in which the exposed, non-essential sulfhydryl groups on the hexokinase molecule react first to produce an enzymatically active but unstable form of hexokinase. This modified form of hexokinase then undergoes a spontaneous, temperature-dependent structural change, which allows reaction of previously shielded, essential sulfhydryl groups. The phenomenon described here suggests a possible mechanism for the antimicrobial effects of the lactoperoxidase system.

Effect of P-wave timing during supraventricular tachycardia on the hemodynamic and sympathetic neural response.

BACKGROUND: Previous studies have shown the importance of the timing of atrial and ventricular systole on the hemodynamic response during supraventricular tachycardia (SVT). However, the reflex changes in autonomic tone during SVT remain poorly understood. METHODS AND RESULTS: Eleven patients with permanent dual-chamber pacemakers were enrolled in the study. Arterial blood pressure (BP), central venous pressure (CVP), and peripheral muscle sympathetic nerve activity (SNA) were recorded during DDD pacing at a rate of 175 bpm (cycle length 343 ms) with an atrioventricular (AV) interval of 30, 200 and 110 ms, simulating tachycardia with near-simultaneous atrial and ventricular systole, short-RP tachycardia (RPPR). Each pacing run was performed for 3 minutes separated by a 5-minute recovery period. All patients demonstrated an abrupt fall in BP, an increase in CVP, and an increase in SNA regardless of the AV interval. The decreases in SBP, DBP, and MAP and the increase in CVP were significantly less during long-RP tachycardia (AV interval 110 ms) than during the other 2 pacing modes (P:<0.05), and the increase in SNA in 7 of the 11 patients was significantly greater during closely coupled atrial and ventricular systole than during long-RP tachycardia (P:<0.05). CONCLUSIONS: These data suggest that the superior maintenance of hemodynamic stability during long-RP tachycardia is accompanied by reduced sympathoexcitation, which is primarily mediated by the arterial baroreceptors, with a modest cardiopulmonary vasodepressor effect.

Who is in the transition gap? Transition from CAMHS to AMHS in the Republic of Ireland.

OBJECTIVE: The ITRACK study explored the process and predictors of transition between Child and Adolescent Mental Health Services (CAMHS) and Adult Mental Health Services (AMHS) in the Republic of Ireland. METHOD: Following ethical approval, clinicians in each of Ireland's four Health Service Executive (HSE) areas were contacted, informed about the study and were invited to participate. Clinicians identified all cases who had reached the transition boundary (i.e. upper age limit for that CAMHS team) between January and December 2010. Data were collected on clinical and socio-demographic details and factors that informed the decision to refer or not refer to the AMHS, and case notes were scrutinised to ascertain the extent of information exchanged between services during transition. RESULTS: A total of 62 service users were identified as having crossed the transition boundary from nine CAMHS [HSE Dublin Mid-Leinster (n=40, 66%), HSE South (n=18, 30%), HSE West (n=2, 3%), HSE Dublin North (n=1, 2%)]. The most common diagnoses were attention deficit hyperactivity disorder (ADHD; n=19, 32%), mood disorders (n=16, 27%), psychosis (n=6, 10%) and eating disorders (n=5, 8%). Forty-seven (76%) of those identified were perceived by the CAMHS clinician to have an 'on-going mental health service need', and of these 15 (32%) were referred, 11 (23%) young people refused and 21 (45%) were not referred, with the majority (12, 57%) continuing with the CAMHS for more than a year beyond the transition boundary. Young people with psychosis were more likely to be referred [χ 2 (2, 46)=8.96, p=0.02], and those with ADHD were less likely to be referred [χ 2 (2, 45)=8.89, p=0.01]. Being prescribed medication was not associated with referral [χ 2 (2, 45)=4.515, p=0.11]. In referred cases (n=15), there was documented evidence of consent in two cases (13.3%), inferred in another four (26.7%) and documented preparation for transition in eight (53.3%). Excellent written communication (100%) was not supported by face-to-face planning meetings (n=2, 13.3%), joint appointments (n=1, 6.7%) or telephone conversations (n=1, 6.7%) between corresponding clinicians. CONCLUSIONS: Despite perceived on-going mental health (MH) service need, many young people are not being referred or are refusing referral to the AMHS, with those with ADHD being the most affected. CAMHS continue to offer on-going care past the transition boundary, which has resource implications. Further qualitative research is warranted to understand, in spite of perceived MH service need, the reason for non-referral by the CAMHS clinicians and refusal by the young person.

Selective parasympathetic denervation following posteroseptal ablation for either atrioventricular nodal reentrant tachycardia or accessory pathways.

Baroreflex gain and coronary sinus norepinephrine and epinephrine levels were measured before and immediately after radiofrequency ablation in the posteroseptal region in 9 patients with atrioventricular nodal reentrant tachycardia or posteroseptal accessory pathways. Arterial baroreflex gain was significantly reduced after radiofrequency ablation (p = 0.046), whereas coronary sinus epinephrine and norepinephrine levels did not change significantly compared with preablation levels.

Evolutionary patterns in life histories of Oxyurida.

The Oxyurida comprises some 850 known species that occur in the intestine of arthropods and vertebrates (one species in annelids). Important arthropod hosts include Diplopoda, Blattodea, Gryllotalpoidea, Passalidae, Scarabaeida and Hydrophilidae. The major vertebrate hosts are lizards, tortoises, primates, rodents and lagomorphs. An underlying characteristic of the group is haplodiploid reproduction and like many haplodiploid groups, pinworms tend to have life histories that involve high levels of inbreeding. Unlike Strongylida, Ascaridida and Spirurida, which have diversified in tissue site and life cycle as well as hosts, pinworms show little variation in these features and have radiated only across host groups. Two explanations are advanced for this. Haplodiploidy and its concomitant inbreeding may act to canalise evolutionary change, although diverse groups such as the Hymenoptera belie this. Alternatively, Strongylida, Ascaridida and Spirurida are presumed to have arisen from skin-penetrating ancestors that were forced to undergo a tissue migration before reaching their primitive tissue site, the gut. This migration demanded they adapt to a variety of tissue sites and thus acted as a preadaptation to further diversification. The Oxyurida, in contrast, probably arose using oral contaminative transmission. The lack of exposure to other tissue sites may therefore have relegated pinworms to their position in the posterior gut.

ITS2 ribosomal RNA indicates Schistosoma hippopotami is a distinct species.

The internal transcribed spacer region of the ribosomal RNA, ITS2, was sequenced from a single specimen of S. hippopotami collected from a pulmonary artery of the hippopotamus, Hippopotamus amphibius in South Africa. The nucleotide sequence was aligned with those of S. mansoni, S. rodhaini, S. haematobium, S. intercalatum, S. curassoni, S. bovis and S. japonicum. Both maximum parsimony and genetic distance analyses were performed on these data sets. Using S. japonicum as outgroup to the African schistosomes, a single most-parasmonious tree was obtained of length 64 steps with a consistency index of 1-S. hippopotami was the sister-group to the remaining African species. This species has lateral-spined eggs and its basal position in the tree suggests that this condition is primitive and that terminal-spined eggs developed secondarily. Molecular data clearly show that S. hippopotami cannot be considered synonymous with S. mansoni. Assuming the hippopotamus is the normal host of S. hippopotami, phylogenetic analysis is consistent with an ancient association between schistosomes and ungulates.

DRD4 dopamine receptor genotype and CSF monoamine metabolites in Finnish alcoholics and controls.

The DRD4 dopamine receptor is thus far unique among neurotransmitter receptors in having a highly polymorphic gene structure that has been reported to produce altered receptor functioning. These allelic variations are caused by a 48-bp segment in exon III of the coding region which may be repeated from 2-10 times. Varying the numbers of repeated segments changes the length, structure, and, possibly, the functional efficiency of the receptor, which makes this gene an intriguing candidate for variations in dopamine-related behaviors, such as alcoholism and drug abuse. Thus far, these DRD4 alleles have been investigated for association with schizophrenia, bipolar disorder, Parkinson's disease, and chronic alcoholism, and all have been largely negative for a direct association. We evaluated the DRD4 genotype in 226 Finish adult males, 113 of whom were alcoholics, many of the early onset type with features of impulsivity and antisocial traits. Genotype frequencies were compared to 113 Finnish controls who were free of alcohol abuse, substance abuse, and major mental illness. In 70 alcoholics and 20 controls, we measured CSF homovanillic acid (HVA), the major metabolite of dopamine, and 5-hydroxyindoleacetic acid (5-HIAA). No association was found between a particular DRD4 dopamine receptor allele and alcoholism. CSF concentrations of the monoamine metabolites showed no significant difference among the DRD4 genotypes. This study of the DRD4 dopamine receptor in alcoholics is the first to be conducted in a clinically and ethnically homogeneous population and to relate the DRD4 genotype to CSF monoamine concentrations. The results indicate that there is no association of the DRD4 receptor with alcoholism.

The psychological impact of MND on patients and carers.

Nineteen patients with Motor Neurone Disease (MND) who had been living with their partners for at least two years prior to the onset of their illness, together with their partners, completed self-report questionnaires to investigate the impact of MND on both patients and carers. Physical disability and impact of the illness on aspects of everyday functioning were related to levels of anxiety and depression in the patients; psychological coping strategies adopted depended to some extent on symptom duration. Carers also demonstrated signs of anxiety and depression, with the latter correlating with aspects of the patients' functional impairment. Perceived strain in carers over caring for the patient correlated with a loss in intimacy in their relationship, which in turn was predicted by patients' cognitive/behavioural and communication changes. Changes in patients' social performance also correlated with the extent to which carers felt that the illness was affecting other areas of their life, the extent to which their partner dominated their thoughts and the extent to which they could control their reactions when thinking about the patient. Satisfaction with formal services and the number of social groups to which carers belonged correlated with carers' self-predicted future ability to cope.

Attributions, strain and depression in carers of partners with MND: a preliminary investigation.

Further examination of the data of Goldstein et al. (J Neurol Sci 160 (1998) S114) on the impact of MND in their spouses/partners on 19 caregivers investigated whether carers' depression and strain scores could be related to their attributional style. Contrary to expectations, carers' scores on a measure of depressed mood were not correlated with measures of internal/external, stable or global attributions. However, perceived strain was greater in carers who viewed their partners' illness as having a more global impact on their lives, and was related to self-perceived control over their thoughts about their partner. Female carers anticipated experiencing less strain and distress in the following year than male carers, even though they did not differ in current strain levels. Male and female carers received similar numbers of formal services. The availability of informal support (family and friends) was associated with reduced anticipation of future strain and distress and with reduced perception of the pervasive impact of their partners' MND on their lives.