Monitoring the phenology of plant pathogenic fungi: why and how?

Phenology is a key adaptive trait of organisms, shaping biotic interactions in response to the environment. It has emerged as a critical topic with implications for societal and economic concerns due to the effects of climate change on species' phenological patterns. Fungi play essential roles in ecosystems, and plant pathogenic fungi have significant impacts on global food security. However, the phenology of plant pathogenic fungi, which form a huge and diverse clade of organisms, has received limited attention in the literature. This diversity may have limited the use of a common language for comparisons and the integration of phenological data for these taxonomic groups. Here, we delve into the concept of 'phenology' as applied to plant pathogenic fungi and explore the potential drivers of their phenology, including environmental factors and the host plant. We present the PhenoFun scale, a phenological scoring system suitable for use with all fungi and fungus-like plant pathogens. It offers a standardised and common tool for scientists studying the presence, absence, or predominance of a particular phase, the speed of phenological phase succession, and the synchronism shift between pathogenic fungi and their host plants, across a wide range of environments and ecosystems. The application of the concept of 'phenology' to plant pathogenic fungi and the use of a phenological scoring system involves focusing on the interacting processes between the pathogenic fungi, their hosts, and their biological, physical, and chemical environment, occurring during the life cycle of the pathogen. The goal is to deconstruct the processes involved according to a pattern orchestrated by the fungus's phenology. Such an approach will improve our understanding of the ecology and evolution of such organisms, help to understand and anticipate plant disease epidemics and their future evolution, and make it possible to optimise management models, and to encourage the adoption of cropping practices designed from this phenological perspective.

Psychobehavioural profile in narcolepsy type 1 with and without REM sleep behaviour disorder.

REM sleep behaviour disorder (RBD) is common in narcolepsy type 1 (NT1). Abnormalities in the reward system have been observed in NT1, possibly related to impaired orexin projections towards the mesolimbic reward system, but also in RBD when associated with Parkinson's disease. Our study aimed to explore the psychobehavioural profile of NT1 patients with and without RBD compared with healthy controls (HC). Forty patients with NT1 were compared with 20 sex- and age-matched HC. All patients with NT1 underwent a video-polysomnography including a measure of REM sleep without atonia (RSWA). The following neuropsychobehavioural variables were assessed: apathy, impulsivity, depression, cognition, subjective and objective attention, sensation-seeking, and behavioural addictions. The patient population included 22 patients with NT1-RBD and 18 patients with NT1-noRBD. Compared with the healthy controls, patients with NT1 had higher scores of apathy, impulsivity, and depression; a lower score on global cognition, and poorer self-perceived attention. No differences were found between patients with NT1 with and without RBD in all neuropsychological variables, except for impaired objective attention in patients with NT1-RBD. In patients with NT1, a positive correlation was observed between RSWA and both apathy and impulsivity subscale. Moreover, in patients with NT1-RBD, RSWA was positively correlated with depression. Patients with NT1 showed higher depression, apathy, and impulsivity compared with controls. These measures correlate with the severity of RSWA, suggesting a transdiagnostic association between RBD and abnormalities of the reward system at least for patients with NT1.

Volumetric changes and clinical trajectories in Parkinson's disease: a prospective multicentric study.

BACKGROUND: Longitudinal measures of structural brain changes using MRI in relation to clinical features and progression patterns in PD have been assessed in previous studies, but few were conducted in well-defined and large cohorts, including prospective clinical assessments of both motor and non-motor symptoms. OBJECTIVE: We aimed to identify brain volumetric changes characterizing PD patients, and determine whether regional brain volumetric characteristics at baseline can predict motor, psycho-behavioral and cognitive evolution at one year in a prospective cohort of PD patients. METHODS: In this multicentric 1 year longitudinal study, PD patients and healthy controls from the MPI-R2* cohort were assessed for demographical, clinical and brain volumetric characteristics. Distinct subgroups of PD patients according to motor, cognitive and psycho-behavioral evolution were identified at the end of follow-up. RESULTS: One hundred and fifty PD patients and 73 control subjects were included in our analysis. Over one year, there was no significant difference in volume variations between PD and control subjects, regardless of the brain region considered. However, we observed a reduction in posterior cingulate cortex volume at baseline in PD patients with motor deterioration at one year (p = 0.017). We also observed a bilateral reduction of the volume of the amygdala (p = 0.015 and p = 0.041) and hippocampus (p = 0.015 and p = 0.053) at baseline in patients with psycho-behavioral deterioration, regardless of age, dopaminergic treatment and center. CONCLUSION: Brain volumetric characteristics at baseline may predict clinical trajectories at 1 year in PD as posterior cingulate cortex atrophy was associated with motor decline, while amygdala and hippocampus atrophy were associated with psycho-behavioral decline.

Efficacy and safety of clonidine for the treatment of impulse control disorder in Parkinson's disease: a multicenter, parallel, randomised, double-blind, Phase 2b Clinical trial.

BACKGROUND: Impulse control disorders (ICDs) are frequently encountered in Parkinson's disease (PD). OBJECTIVES: We aimed to assess whether clonidine, an α2-adrenergic receptor agonist, would improve ICDs. METHODS: We conducted a multicentre trial in five movement disorder departments. Patients with PD and ICDs (n = 41) were enrolled in an 8-week, randomised (1:1), double-blind, placebo-controlled study of clonidine (75 µg twice a day). Randomisation and allocation to the trial group were carried out by a central computer system. The primary outcome was the change at 8 weeks in symptom severity using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) score. A reduction of the most elevated subscore of the QUIP-RS of more than 3 points without any increase in the other QUIP-RS dimension defined success. RESULTS: Between 15 May 2019 and 10 September 2021, 19 patients in the clonidine group and 20 patients in the placebo group were enrolled. The proportion difference of success in reducing QUIP-RS at 8 weeks, was 7% (one-sided upper 90% CI 27%) with 42.1% of success in the clonidine group and 35.0% in the placebo group. Compared to patients in the placebo group, patients in the clonidine group experienced a greater reduction in the total QUIP-RS score at 8 weeks (11.0 points vs. 3.6). DISCUSSION: Clonidine was well tolerated but our study was not enough powerful to demonstrate significant superiority compared to placebo in reducing ICDs despite a greater reduction of total QUIP score at 8 weeks. A phase 3 study should be conducted. TRIAL REGISTRATION: The study was registered (NCT03552068) on clinicaltrials.gov on June 11, 2018.

Severity of REM sleep without atonia correlates with measures of cognitive impairment and depressive symptoms in REM sleep behaviour disorder.

This study aimed to correlate REM sleep without atonia (RSWA) and neuropsychological data in patients with idiopathic/isolated REM sleep behaviour disorder (iRBD) and those with RBD associated with Parkinson's disease (PDRBD), in order to assess whether higher degrees of RSWA are related to poorer cognitive performance. A total of 142 subjects were enrolled: 48 with iRBD, 55 with PDRBD, and 39 PD without RBD (PDnoRBD). All participants underwent video-polysomnographic recording, clinical and neuropsychological assessment. RSWA was quantified according to two manual scoring methods (Montréal, SINBAR) and one automated (REM atonia index, RAI). Mild cognitive impairment (MCI) was diagnosed according to diagnostic criteria for MCI in Parkinson's disease. The relationship between neuropsychological scores and RSWA metrics was explored by multiple linear regression analysis and logistic regression models. Patients with iRBD showed significantly lower visuospatial functions and working memory, compared with the others. More severe RSWA was associated with a higher risk of reduced visuospatial abilities (OR 0.15), working memory (OR 2.48), attention (OR 2.53), and semantic fluency (OR 0.15) in the iRBD. In the whole group, a greater RSWA was associated with an increased risk for depressive symptoms (OR 3.6). A total of 57(40%) MCI subjects were found (17 iRBD, 26 PDRBD, and 14 PDnoRBD). Preserved REM-atonia was associated with a reduced odds of multi-domain MCI in the whole study population (OR 0.54). In conclusion, a greater severity of RSWA was associated with an increased risk for poor cognitive performance and depressive mood in patients with RBD. Moreover, higher RAI was associated with a lower risk of multi-domain MCI.

Multiple scenarios for sexual crosses in the fungal pathogen Zymoseptoria tritici on wheat residues: Potential consequences for virulence gene transmission.

Little is known about the impact of host immunity on sexual reproduction in fungal pathogens. In particular, it is unclear whether crossing requires both sexual partners to infect living plant tissues. We addressed this issue in a three-year experiment investigating different scenarios of Zymoseptoria tritici crosses according to the virulence ('vir') or avirulence ('avr') of the parents against a qualitative resistance gene. Co-inoculations ('vir × vir', 'avr × vir', 'avr × avr') and single inoculations were performed on a wheat cultivar carrying the Stb16q resistance gene (Cellule) and a susceptible cultivar (Apache), in the greenhouse. We assessed the intensity of asexual reproduction by scoring disease severity, and the intensity of sexual reproduction by counting the ascospores discharged from wheat residues. As expected, disease severity was more intense on Cellule for 'vir × vir' co-inoculations than for 'avr × vir' co-inoculations, with no disease for 'avr × avr'. However, all types of co-inoculation yielded sexual offspring, whether or not the parental strains caused plant symptoms. Parenthood was confirmed by genotyping (SSR markers), and the occurrence of crosses between (co-)inoculated and exogenous strains (other strains from the experiment, or from far away) was determined. We showed that symptomatic asexual infection was not required for a strain to participate in sexual reproduction, and deduced from this result that avirulent strains could be maintained asymptomatically "on" or "in" leaf tissues of plants carrying the corresponding resistant gene for long enough to reproduce sexually. In two of the three years, the intensity of sexual reproduction did not differ between the three types of co-inoculation in Cellule, suggesting that crosses involving avirulent strains are not anecdotal. We discuss the possible mechanisms explaining the maintenance of avirulence in Z. tritici populations and the potential impact of particular resistance deployments such as cultivar mixtures for limiting resistance breakdown.

Intrasubject subcortical quantitative referencing to boost MRI sensitivity to Parkinson's disease.

Several postmortem studies have shown iron accumulation in the substantia nigra of Parkinson's disease patients. Iron concentration can be estimated via MRI-R2∗ mapping. To assess the changes in R2∗ occurring in Parkinson's disease patients compared to controls, a multicentre transversal study was carried out on a large cohort of Parkinson's disease patients (n = 163) with matched controls (n = 82). In this study, 44 patients and 11 controls were removed due to motion artefacts, 21 patient and 6 controls to preserve matching. Thus, 98 patients and 65 age and sex-matched healthy subjects were selected with enough image quality. The study was conducted on patients with early to late stage Parkinson's disease. The images were acquired at 3Tesla in 12 clinical centres. R2∗ values were measured in subcortical regions of interest (substantia nigra, red nucleus, striatum, globus pallidus externus and globus pallidus internus) contralateral (dominant side) and ipsilateral (non dominant side) to the most clinically affected hemibody. As the observed inter-subject R2∗ variability was significantly higher than the disease effect, an original strategy (intrasubject subcortical quantitative referencing, ISQR) was developed using the measurement of R2∗ in the red nucleus as an intra-subject reference. R2∗ values significantly increased in Parkinson's disease patients when compared with controls; in the substantia nigra (SN) in the dominant side (D) and in the non dominant side (ND), respectively (PSN_D and PSN_ND < 0.0001). After stratification into four subgroups according to the disease duration, no significant R2∗ difference was found in all regions of interest when comparing Parkinson's disease subgroups. By applying our ISQR strategy, R2(ISQR)∗ values significantly increased in the substantia nigra (PSN_D and PSN_ND < 0.0001) when comparing all Parkinson's disease patients to controls. R2(ISQR)∗ values in the substantia nigra significantly increased with the disease duration (PSN_D = 0.01; PSN_ND = 0.03) as well as the severity of the disease (Hoehn & Yahr scale <2 and ≥ 2, PSN_D = 0.02). Additionally, correlations between R2(ISQR)∗ and clinical features, mainly related to the severity of the disease, were found. Our results support the use of ISQR to reduce variations not directly related to Parkinson's disease, supporting the concept that ISQR strategy is useful for the evaluation of Parkinson's disease.

Decision making under uncertainty in Parkinson's disease with Rem sleep behavior disorder.

BACKGROUND: REM sleep behavior disorder (RBD) is associated with an increased risk to develop Impulse control disorders (ICDs) in Parkinson's disease (PD), however the mechanisms underlying this putative association are still poorly understood. Decision-making impairment, one major neuro-psychological dimension that may lead to ICDs, has been reported in idiopathic RBD, but has never been assessed in RBD associated with PD. OBJECTIVE: We aimed to assess decision-making abilities under ambiguous situations associated with the presence of RBD in PD patients. METHODS: In this cross-sectional study, 60 non-demented PD patients with (PD-RBD, n = 40) and without (PD-nRBD, n = 20) video polysomnography-confirmed RBD, and 20 healthy controls matched for gender and age were included. All subjects underwent neurological and neuropsychological examination, including Iowa Gambling task designed to asses decision-making under uncertainty. RESULTS: IGT total score did not differ between groups (p = 0.851), however PD-RBD presented, more disadvantageous choices for the last blocks of IGT compared to PD-nRBD (p = 0.001) and to HC (p = 0.012). Progression of scores did not differ between HC and PD-nRBD. Multivariate analyses taking into account the value of scores at baseline, as well as the duration of PD, the duration of treatment, the presence of ICDs and MMSE confirmed those results. CONCLUSION: Decision making under uncertainty is impaired in PD-RBD compared to PD-nRBD and healthy controls, regardless to the duration of disease, treatment, cognitive status and the presence of ICDs. This could reflect an inability to learn from punishment or reward in PD-RBD, and could explain the increased risk to develop ICDs reported in those patients.

Spatiotemporal Changes in Varietal Resistance to Wheat Yellow Rust in France Reveal an Increase in Field Resistance Level During the Period 1985-2018.

Monitoring spatiotemporal changes in varietal resistance and understanding its drivers seem essential to managing plant diseases but require having access to the genetic basis of disease resistance and to its deployment. In this study, we focused on yellow rust (Puccinia striiformis f. sp. tritici) for three decades in France, by using field adult plant resistance levels, Yr race-specific resistance genes of varieties, presence of Puccinia striiformis f. sp. tritici pathotypes and their virulence profiles, and systematic surveys of the acreages of bread wheat varieties available at a yearly survey time and at a district level. Based on these data, we studied spatiotemporal changes in varietal resistance over the period from 1985 to 2018 in 54 French administrative districts (hereafter "departments") by using a set of relevant indicators weighted by the relative acreage proportion of the varieties sown at the department level. Our analyses revealed an increase in varietal resistance over decades that would be due to the accumulation of both quantitative resistance and different race-specific resistance genes. We suggest that, beyond breeders, several actors, including examination offices, agricultural advisory services, and farmers, may have had a substantial influence on these spatiotemporal changes, promoting more resistant varieties and the rapid replacement of newly susceptible varieties by still resistant ones at the beginning of each epidemic.

Two maize cultivars of contrasting leaf size show different leaf elongation rates with identical patterns of extension dynamics and coordination.

Simulating leaf development from initiation to maturity opens new possibilities to model plant-environment interactions and the plasticity of plant architecture. This study analyses the dynamics of leaf production and extension along a maize (Zea mays) shoot to assess important modelling choices. Maize plants from two cultivars originating from the same inbred line, yet differing in the length of mature leaves were used in this study. We characterized the dynamics of the blade and sheath lengths of all phytomers by dissecting plants every 2-3 days. We analysed how differences in leaf size were built up and we examined the coordination between the emergence of organs and phases of their extension. Leaf extension rates were higher in the cultivar with longer leaves than in the cultivar with shorter leaves; no differences were found in other aspects. We found that (i) first post-embryonic leaves were initiated at a markedly higher rate than upper leaves; (ii) below ear position, sheaths were initiated at a time intermediate between tip emergence and appearance, while above the ear position, sheaths were initiated at a high rate, such that the time interval between the blade and sheath initiations decreased for these leaves; and (iii) ear position also marked a change in the correlation in size between successive phytomers with little correlation of size between upper and lower leaves. Our results identified leaf extension rate as the reason for the difference in size between the two cultivars. The two cultivars shared the same pattern for the timing of initiation events, which was more complex than previously thought. The differences described here may explain some inaccuracies reported in functional-structural plant models. We speculate that genotypic variation in behaviour for leaf and sheath initiation exists, which has been little documented in former studies.

The urge to move: From restless legs syndrome to impulse control disorders in Parkinson's disease.

Impulse control disorders (ICDs) in Parkinson's disease (PD) are defined as a failure to resist an "urge" to behave in a way that may be debilitating for oneself or others. The suggested immobilization test (SIT) has been developed to assess the "urge" to move and support the diagnosis of restless legs syndrome (RLS) in the general population and in PD. A clinical association between RLS and ICDs has been shown in PD and in the general population. We hypothesized that there could be a semiological overlap between RLS and ICDs, and conducted SIT in PD patients with and without ICDs. Fifty PD patients with (n = 17) and without (n = 33) current ICDs were included. SIT, videopolysomnography, demographical treatment, and motor, psycho-behavioural and sleep characteristics, including RLS, were recorded. PD patients with ICDs reported increased subjective discomfort during SIT (SD-SIT) compared to those without ICDs (p = .024). Multivariable analysis confirmed ICDs as an independent factor associated with increased SD-SIT in PD, regardless of the presence of RLS, PD severity and dopamine agonist treatment dose. The discomfort measured by SIT might not only reflect the "urge" to move in RLS but also the ICDs in PD, suggesting that ICDs and RLS in PD could share a common phenomenology.

French validation of the questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS).

INTRODUCTION: The management of impulse control disorders (ICDs) in Parkinson's disease (PD) relies on their early identification, allowing adjustment of antiparkinsonian treatment before these manifestations lead to major social, financial or legal consequences. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) is an English-developed and -validated PD-specific rating scale constructed to support the rating of ICDs and related disorders and the assessment of changes in symptom severity over time, but it has not to date been validated in French. METHODS: We conducted an observational, multicenter, cross-sectional study among a subset of patients (n = 280) from the Drug Interacting with Genes in PD (DIG-PD) cohort, aiming to assess psychometric properties of the French version of QUIP-RS: acceptability, internal consistency, factor analysis, reproductibility and hypotheses testing. In addition to this scale, the following measures were applied: MDS-Unified Parkinson's Disease Rating Scale, Mini-Mental State Examination, Frontal Assessment Behavior, and Ardouin Scale of Behavior in Parkinson's Disease (ASBPD). RESULTS: Cronbach's alpha coefficient was 0.72 and ranged from 0.25 to 0.55. Regarding test-retest reliability and inter-rater reliability, the Lin concordance coefficient for items was higher than 0.58. The correlations between QUIP-RS and ASBPD were moderate to high except for dopaminergic addiction and hobbyism (r = 0.41 and 0.40 respectively, p < 0.001). No clinically significant correlation was found between QUIP-RS total score (and items) and other scales. CONCLUSION: The French version of the QUIP-RS appears to be a valid, reliable, and precise instrument for the assessment of ICDs and related disorders in PD. REGISTRATION NUMBER: clinicaltrials.gov number NCT01564992.

Wait and you shall see: sexual delay discounting in hypersexual Parkinson's disease.

Patients with Parkinson's disease may develop impulse control disorders under dopaminergic treatments. Impulse control disorders include a wide spectrum of behaviours, such as hypersexuality, pathological gambling or compulsive shopping. Yet, the neural systems engaged in specific impulse control disorders remain poorly characterized. Here, using model-based functional MRI, we aimed to determine the brain systems involved during delay-discounting of erotic rewards in hypersexual patients with Parkinson's disease (PD+HS), patients with Parkinson's disease without hypersexuality (PD - HS) and controls. Patients with Parkinson's disease were evaluated ON and OFF levodopa (counterbalanced). Participants had to decide between two options: (i) wait for 1.5 s to briefly view an erotic image; or (ii) wait longer to see the erotic image for a longer period of time. At the time of decision-making, we investigated which brain regions were engaged with the subjective valuation of the delayed erotic reward. At the time of the rewarded outcome, we searched for the brain regions responding more robustly after waiting longer to view the erotic image. PD+HS patients showed reduced discounting of erotic delayed rewards, compared to both patients with Parkinson's disease and controls, suggesting that they accepted waiting longer to view erotic images for a longer period of time. Thus, when using erotic stimuli that motivate PD+HS, these patients were less impulsive for the immediate reward. At the brain system level, this effect was paralleled by the fact that PD+HS, as compared to controls and PD - HS, showed a negative correlation between subjective value of the delayed reward and activity of medial prefrontal cortex and ventral striatum. Consistent with the incentive salience hypothesis combining learned cue-reward associations with current relevant physiological state, dopaminergic treatment in PD+HS boosted excessive 'wanting' of rewards and heightened activity in the anterior medial prefrontal cortex and the posterior cingulate cortex, as reflected by higher correlation with subjective value of the option associated to the delayed reward when ON medication as compared to the OFF medication state. At the time of outcome, the anterior medial prefrontal/rostral anterior cingulate cortex showed an interaction between group (PD+HS versus PD - HS) and medication (ON versus OFF), suggesting that dopaminergic treatment boosted activity of this brain region in PD+HS when viewing erotic images after waiting for longer periods of time. Our findings point to reduced delay discounting of erotic rewards in PD+HS, both at the behavioural and brain system levels, and abnormal reinforcing effect of levodopa when PD+HS patients are confronted with erotic stimuli.10.1093/brain/awy298_video1awy298media15983845074001.

A new methodology based on sensitivity analysis to simplify the recalibration of functional-structural plant models in new conditions.

Background and Aims: Functional-structural plant models (FSPMs) describe explicitly the interactions between plants and their environment at organ to plant scale. However, the high level of description of the structure or model mechanisms makes this type of model very complex and hard to calibrate. A two-step methodology to facilitate the calibration process is proposed here. Methods: First, a global sensitivity analysis method was applied to the calibration loss function. It provided first-order and total-order sensitivity indexes that allow parameters to be ranked by importance in order to select the most influential ones. Second, the Akaike information criterion (AIC) was used to quantify the model's quality of fit after calibration with different combinations of selected parameters. The model with the lowest AIC gives the best combination of parameters to select. This methodology was validated by calibrating the model on an independent data set (same cultivar, another year) with the parameters selected in the second step. All the parameters were set to their nominal value; only the most influential ones were re-estimated. Key Results: Sensitivity analysis applied to the calibration loss function is a relevant method to underline the most significant parameters in the estimation process. For the studied winter oilseed rape model, 11 out of 26 estimated parameters were selected. Then, the model could be recalibrated for a different data set by re-estimating only three parameters selected with the model selection method. Conclusions: Fitting only a small number of parameters dramatically increases the efficiency of recalibration, increases the robustness of the model and helps identify the principal sources of variation in varying environmental conditions. This innovative method still needs to be more widely validated but already gives interesting avenues to improve the calibration of FSPMs.

Impulse control disorders in Parkinson's disease patients with RLS: a cross sectional-study.

BACKGROUND: Although dopamine replacement therapy is the main risk factor for the occurrence of Impulse Control Disorders (ICDs) in Parkinson's disease (PD), non-pharmacological risk factors for have also been identified in that population and sleep disorders could be part of them. Our objective is to determine whether Restless Legs Syndrome (RLS), that has been associated with more impulsive choices in general population regardless of dopaminergic therapy, could be associated with a specific psycho-behavioral profile and ICDs in PD. METHODS: Eighty consecutive PD patients were screened for the presence of RLS in a cross-sectional study. Sleep features were evaluated during one video-polysomnography. The frequency of ICDs, according to standard criteria, together with a broad range of psycho-behavioral features using the Ardouin Scale of Behavior in PD, were compared in patients with RLS (PD-RLS, n = 30) versus without RLS (PD-nRLS, n = 50). RESULTS: PD patients with RLS reported significantly more ICDs than those without RLS (50% versus 26%, p = 0.03), especially compulsive eating disorders, and a different psycho-behavioral profile with more hyperdopaminergic behaviors. There was no between group difference for total and dopamine agonists levodopa equivalent doses. However, age and durations of both disease and dopaminergic treatment were greater in the RLS group. Multivariate and propensity score analyses controlling for age, gender, total sleep time, disease severity, dose and duration of treatment, anxiety and depression showed that RLS was an independent predictor of ICDs in PD (OR = 5.91 [1.63; 22.1] and OR = 2.89 [1.63; 6.67] respectively). CONCLUSION: RLS per se could be a risk factor for impulsive behaviors in PD.

Anatomical predictors of cognitive decline after subthalamic stimulation in Parkinson's disease.

We investigated whether pre-operative MRI measures of focal brain atrophy could predict cognitive decline occurring after deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). For that purpose, we prospectively collected data of 42 consecutive patients with PD who underwent bilateral STN-DBS. Normalized brain structure volumes and cortical thicknesses were measured on pre-operative T1-weighted MRI. Patients were tested for their cognitive performances before surgery and 1 year after. After controlling for age, gender, pre-operative disease severity, change in dopaminomimetic dose after surgery and contact location, we found correlations: (1) between the variation of the total Mattis dementia rating scale (MDRS) score and left lateral ventricle volume (p = 0.032), (2) between the variation of the initiation/perseveration subscore of the MDRS and the left nucleus accumbens volume (p = 0.042) and the left lateral ventricle volume (p = 0.017) and (3) between the variation of the backward digit-span task and the right and left superior frontal gyrus thickness (p = 0.004 and p = 0.007, respectively). Left nucleus accumbens atrophy was associated with decline in the initiation/perseveration subscore with the largest effect size (d = - 1.64). Pre-operative left nucleus accumbens volume strongly predicted postoperative decline in the initiation/attention subscore (AUC = 0.92, p < 0.001, 96.3% sensitivity, 80.0% specificity, 92.9% PPV and 92.9% NPV). We conclude that the morphometric measures of brain atrophy usually associated with cognitive impairment in PD can also explain or predict a part of cognitive decline after bilateral STN-DBS. In particular, the left accumbens nucleus volume could be considered as a promising marker for guiding surgical decisions.

Cultivar architecture modulates spore dispersal by rain splash: A new perspective to reduce disease progression in cultivar mixtures.

Cultivar mixtures can be used to improve the sustainability of disease management within farming systems by growing cultivars that differ in their disease resistance level in the same field. The impact of canopy aerial architecture on rain-splash dispersal could amplify disease reduction within mixtures. We designed a controlled conditions experiment to study single splash-dispersal events and their consequences for disease. We quantified this impact through the spore interception capacities of the component cultivars of a mixture. Two wheat cultivars, differing in their aerial architecture (mainly leaf area density) and resistance to Septoria tritici blotch, were used to constitute pure stands and mixtures with 75% of resistant plants that accounted for 80% of the canopy leaf area. Canopies composed of 3 rows of plants were exposed to standardized spore fluxes produced by splashing calibrated rain drops on a linear source of inoculum. Disease propagation was measured through spore fluxes and several disease indicators. Leaf susceptibility was higher for upper than for lower leaves. Dense canopies intercepted more spores and mainly limited horizontal spore transfer to the first two rows. The presence of the resistant and dense cultivar made the mixed canopy denser than the susceptible pure stand. No disease symptoms were observed on susceptible plants of the second and third rows in the cultivar mixture, suggesting that the number of spores intercepted by these plants was too low to cause disease symptoms. Both lesion area and disease conditional severity were significantly reduced on susceptible plants within mixtures on the first row beside the inoculum source. Those reductions on one single-splash dispersal event, should be amplified after several cycle over the full epidemic season. Control of splash-dispersed diseases within mixtures could therefore be improved by a careful choice of cultivars taking into consideration both resistance and architecture.

The combined effect of subthalamic nuclei deep brain stimulation and L-dopa increases emotion recognition in Parkinson's disease.

Deep brain stimulation of the subthalamic nucleus (DBS) is a widely used surgical technique to suppress motor symptoms in Parkinson's disease (PD), and as such improves patients' quality of life. However, DBS may produce emotional disorders such as a reduced ability to recognize emotional facial expressions (EFE). Previous studies have not considered the fact that DBS and l-dopa medication can have differential, common, or complementary consequences on EFE processing. A thorough way of investigating the effect of DBS and l-dopa medication in greater detail is to compare patients' performances after surgery, with the two therapies either being administered ('on') or not administered ('off'). We therefore used a four-condition (l-dopa 'on'/DBS 'on', l-dopa 'on'/DBS 'off', l-dopa 'off'/DBS 'on', and l-dopa 'off'/DBS 'off') EFE recognition paradigm and compared implanted PD patients to healthy controls. The results confirmed those of previous studies, yielding a significant impairment in the detection of some facial expressions relative to controls. Disgust recognition was impaired when patients were 'off' l-dopa and 'on' DBS, and fear recognition impaired when 'off' of both therapies. More interestingly, the combined effect of both DBS and l-dopa administration seems much more beneficial for EFE recognition than the separate administration of each individual therapy. We discuss the implications of these findings in the light of the inverted U curve function that describes the differential effects of dopamine level on the right orbitofrontal cortex (OFC). We propose that, while l-dopa could "overdose" in dopamine the ventral stream of the OFC, DBS would compensate for this over-activation by decreasing OFC activity, thereby restoring the necessary OFC-amygdala interaction. Another finding is that, when collapsing over all treatment conditions, PD patients recognized more neutral faces than the matched controls, a result that concurs with embodiment theories.