Neuroanatomy of hemispatial neglect and its functional components: a study using voxel-based lesion-symptom mapping

Spatial neglect is a perplexing neuropsychological syndrome, in which patients fail to detect (and/or respond to) stimuli located contralaterally to their (most often right) hemispheric lesion. Neglect is characterized by a wide heterogeneity, and a role for multiple components has been suggested, but the exact nature of the critical components remains unclear. Moreover, many different lesion sites have been reported, leading to enduring controversies about the relative contribution of different cortical and/or subcortical brain regions. Here we report a systematic anatomo-functional study of 80 patients with a focal right hemisphere stroke, who were examined by a series of neuropsychological tests assessing different clinical manifestations of neglect. We first performed a statistical factorial analysis of their behavioural performance across all tests, in order to break down neglect symptoms into coherent profiles of co-varying deficits. We then examined the neural correlates of these distinct neglect profiles using a statistical voxel-based lesion-symptom mapping method that correlated the anatomical extent of brain damage with the relative severity of deficits along the different profiles in each patient. Our factorial analysis revealed three main factors explaining 82% of the total variance across all neglect tests, which suggested distinct components related to perceptive/visuo-spatial, exploratory/visuo-motor, and allocentric/object-centred aspects of spatial neglect. Our anatomical voxel-based lesion-symptom mapping analysis pointed to specific neural correlates for each of these components, including the right inferior parietal lobule for the perceptive/visuo-spatial component, the right dorsolateral prefrontal cortex for the exploratory/visuo-motor component, and deep temporal lobe regions for the allocentric/object-centred component. By contrast, standard anatomical overlap analysis indicated that subcortical damage to paraventricular white matter tracts was associated with severe neglect encompassing several tests. Taken together, our results provide new support to the view that the clinical manifestations of hemispatial neglect might reflect a combination of distinct components affecting different domains of spatial cognition, and that intra-hemispheric disconnection due to white matter lesions might produce severe neglect by impacting on more than one functional domai

Dissociable components of spatial neglect associated with frontal and parietal lesions

Spatial neglect is a complex neuropsychological disorder, in which patients fail to detect and respond to contralesional stimuli. Recent studies suggest that these symptoms may reflect a combination of different component deficits, associated with different lesion substrates. Thus, damage to right lateral prefrontal and inferior parietal regions produce different degrees of left neglect on cancellation and line bisection tasks, respectively. Here we tested for dissociable behaviors across two tasks designed to assess distinct cognitive processes possibly mediating such components, in 14 patients with right focal lesion in either the frontal or parietal lobe. In the “distractor filtering” task, patients had to respond to a visual target presented centrally, with or without a lateralized distractor. Only frontal-lesioned patients showed a marked slowing of reaction times when a central target appeared with a simultaneous right distractor (compared to center and left distractor). In the “spatial coding” task, patients had to detect a target among successive visual stimuli presented horizontally with three sequence conditions (regular/predictive or irregular/non-predictive). Only parietal-lesioned patients were unable to benefit from the predictability of the target position, with similar reaction times across all sequence conditions. By contrast, frontal patients showed faster reaction times on trials with a regular succession of stimuli (compared to random order). Taken together, these results suggest that frontal damage may contribute to left inattention by disrupting top-down control and resistance to distractors on the ipsilesional side, whereas parietal damage may disrupt the maintenance of stable locations in space across gaze shifts or time. This further supports the notion that left neglect may arise as a combined breakdown or impaired connectivity between frontal and parietal mechanisms involved (respectively) in the selective control and memory storage components of spatial attention

Exploiting the Richness of Environmental Waterborne Bacterial Species to Find Natural Legionella pneumophila Competitors

Legionella pneumophila is one of the most tracked waterborne pathogens and remains an important threat to human health. Despite the use of biocides, L. pneumophila is able to persist in engineered water systems with the help of multispecies biofilms and phagocytic protists. For few years now, high-throughput sequencing methods have enabled a better understanding of microbial communities in freshwater environments. Those unexplored and complex communities compete for nutrients using antagonistic molecules as war weapons. Up to now, few of these molecules were characterized in regards of L. pneumophila sensitivity. In this context, we established, from five freshwater environments, a vast collection of culturable bacteria and investigated their ability to inhibit the growth of L. pneumophila. All bacterial isolates were classified within 4 phyla, namely Proteobacteria (179/273), Bacteroidetes (48/273), Firmicutes (43/273), and Actinobacteria (3/273) according to 16S rRNA coding sequences. Aeromonas, Bacillus, Flavobacterium, and Pseudomonas were the most abundant genera (154/273). Among the 273 isolates, 178 (65.2%) were shown to be active against L. pneumophila including 137 isolates of the four previously cited main genera. Additionally, other less represented genera depicted anti-Legionella activity such as Acinetobacter, Kluyvera, Rahnella, or Sphingobacterium. Furthermore, various inhibition diameters were observed among active isolates, ranging from 0.4 to 9 cm. Such variability suggests the presence of numerous and diverse natural compounds in the microenvironment of L. pneumophila. These molecules include both diffusible secreted compounds and volatile organic compounds, the latter being mainly produced by Pseudomonas strains. Altogether, this work sheds light on unexplored freshwater bacterial communities that could be relevant for the biological control of L. pneumophila in manmade water systems

Antiretroviral-naive and -treated HIV-1 patients can harbour more resistant viruses in CSF than in plasma

Objectives The neurological disorders in HIV-1-infected patients remain prevalent. The HIV-1 resistance in plasma and CSF was compared in patients with neurological disorders in a multicentre study. Methods Blood and CSF samples were collected at time of neurological disorders for 244 patients. The viral loads were >50 copies/mL in both compartments and bulk genotypic tests were realized. Results On 244 patients, 89 and 155 were antiretroviral (ARV) naive and ARV treated, respectively. In ARV-naive patients, detection of mutations in CSF and not in plasma were reported for the reverse transcriptase (RT) gene in 2/89 patients (2.2%) and for the protease gene in 1/89 patients (1.1%). In ARV-treated patients, 19/152 (12.5%) patients had HIV-1 mutations only in the CSF for the RT gene and 30/151 (19.8%) for the protease gene. Two mutations appeared statistically more prevalent in the CSF than in plasma: M41L (P = 0.0455) and T215Y (P = 0.0455). Conclusions In most cases, resistance mutations were present and similar in both studied compartments. However, in 3.4% of ARV-naive and 8.8% of ARV-treated patients, the virus was more resistant in CSF than in plasma. These results support the need for genotypic resistance testing when lumbar puncture is performe

Development of the AL-O-A Score for Delirium Screening in Acute Internal Medicine: a Monocentric Prospective Study

Delirium occurs frequently in acute internal medicine wards and may worsen the patient’s prognosis; it deserves a fast, systematic screening tool. OBJECTIVE: Develop a delirium screening score for inpatients admitted to acute internal medicine wards

La norme en neuropsychologie, un concept à facettes multiples

Afin de faciliter l’interprétation des scores des tests, l’utilisation de valeurs normées est devenue la règle en neuropsychologie clinique, parfois au détriment de l’approche clinique. Au vu de l’abondance des outils d’évaluation à disposition, il devient prioritaire de comprendre le plus précisément possible ce que recouvre le concept de normes afin de les utiliser au plus près de la réalité clinique sans en subir la tyrannie. Dans ce but, nous avons réuni un colloque avec différents spécialistes de la question qui nous livrent ici quelques clés de lecture de ce concept. Tout d’abord est présentée une réflexion autour de la normalité, qui s’oppose à la pathologie, à l’aide de normes comparatives ou diagnostiques, tout en utilisant des normes exprimées sous formes de quantiles ou de moyennes. Il sera rappelé qu’une norme est établie pour une population donnée et pour un objectif spécifique. Concernant les tests eux-mêmes, leurs constructions exigent des critères spécifiques, et la discussion s’articule autour des critères de validité et de fidélité, dont l’importance est parfois mal comprise et souvent négligée. Enfin, l’accent est mis sur la diversité des normes pour des tests très largement utilisés, et une tentative de définir des critères communs au sein d’une communauté de spécialistes est proposée

Thoracic splenosis mimicking a pleuropneumonia

International audienc