Circuits for Presaccadic Visual Remapping.

Saccadic eye movements rapidly displace the image of the world that is projected onto the retinas. In anticipation of each saccade, many neurons in the visual system shift their receptive fields. This presaccadic change in visual sensitivity, known as remapping, was first documented in the parietal cortex and has been studied in many other brain regions. Remapping requires information about upcoming saccades via corollary discharge. Analyses of neurons in a corollary discharge pathway that targets the frontal eye field (FEF) suggest that remapping may be assembled in the FEF's local microcircuitry. Complementary data from reversible inactivation, neural recording, and modeling studies provide evidence that remapping contributes to transsaccadic continuity of action and perception. Multiple forms of remapping have been reported in the FEF and other brain areas, however, and questions remain about reasons for these differences. In this review of recent progress, we identify three hypotheses that may help to guide further investigations into the structure and function of circuits for remapping.

Live volumetric (4D) visualization and guidance of in vivo human ophthalmic surgery with intraoperative optical coherence tomography.

Minimally-invasive microsurgery has resulted in improved outcomes for patients. However, operating through a microscope limits depth perception and fixes the visual perspective, which result in a steep learning curve to achieve microsurgical proficiency. We introduce a surgical imaging system employing four-dimensional (live volumetric imaging through time) microscope-integrated optical coherence tomography (4D MIOCT) capable of imaging at up to 10 volumes per second to visualize human microsurgery. A custom stereoscopic heads-up display provides real-time interactive volumetric feedback to the surgeon. We report that 4D MIOCT enhanced suturing accuracy and control of instrument positioning in mock surgical trials involving 17 ophthalmic surgeons. Additionally, 4D MIOCT imaging was performed in 48 human eye surgeries and was demonstrated to successfully visualize the pathology of interest in concordance with preoperative diagnosis in 93% of retinal surgeries and the surgical site of interest in 100% of anterior segment surgeries. In vivo 4D MIOCT imaging revealed sub-surface pathologic structures and instrument-induced lesions that were invisible through the operating microscope during standard surgical maneuvers. In select cases, 4D MIOCT guidance was necessary to resolve such lesions and prevent post-operative complications. Our novel surgical visualization platform achieves surgeon-interactive 4D visualization of live surgery which could expand the surgeon's capabilities.

Global and local perceptual style, field-independence, and central coherence: an attempt at concept validation

Historically, the concepts of field-independence, closure flexibility, and weak central coherence have been used to denote a locally, rather globally, dominated perceptual style. To date, there has been little attempt to clarify the relationship between these constructs, or to examine the convergent validity of the various tasks purported to measure them. To address this, we administered 14 tasks that have been used to study visual perceptual styles to a group of 90 neuro-typical adults. The data were subjected to exploratory factor analysis. We found evidence for the existence of a narrowly defined weak central coherence (field-independence) factor that received loadings from only a few of the tasks used to operationalise this concept. This factor can most aptly be described as representing the ability to dis-embed a simple stimulus from a more complex array. The results suggest that future studies of perceptual styles should include tasks whose theoretical validity is empirically verified, as such validity cannot be established merely on the basis of a priori task analysis. Moreover, the use of multiple indices is required to capture the latent dimensions of perceptual styles reliably.

Underway measurements of dissolved gases along POLARSTERN cruise track ANT-XXVII/2

We present measurements of pCO2, O2 concentration, biological oxygen saturation (Delta O2/Ar) and N2 saturation (Delta N2) in Southern Ocean surface waters during austral summer, 2010-2011. Phytoplankton biomass varied strongly across distinct hydrographic zones, with high chlorophyll a (Chla) concentrations in regions of frontal mixing and sea-ice melt. pCO2 and Delta O2 /Ar exhibited large spatial gradients (range 90 to 450 µatm and -10 to 60%, respectively) and co-varied strongly with Chla. However, the ratio of biological O2 accumulation to dissolved inorganic carbon (DIC) drawdown was significantly lower than expected from photosynthetic stoichiometry, reflecting the differential time-scales of O2 and CO2 air-sea equilibration. We measured significant oceanic CO2 uptake, with a mean air-sea flux (~ -20 mmol m-2 d-1) that significantly exceeded regional climatological values. N2 was mostly supersaturated in surface waters (mean Delta N2 of +2.5 %), while physical processes resulted in both supersaturation and undersaturation of mixed layer O2 (mean Delta O2phys = 2.1 %). Box model calculations were able to reproduce much of the spatial variability of Delta N2 and Delta O2phys along the cruise track, demonstrating significant effects of air-sea exchange processes (e.g. atmospheric pressure changes and bubble injection) and mixed layer entrainment on surface gas disequilibria. Net community production (NCP) derived from entrainment-corrected surface Delta O2 /Ar data, ranged from ~ -40 to > 300 mmol O2 m-2 d-1 and showed good coherence with independent NCP estimates based on seasonal mixed layer DIC deficits. Elevated NCP was observed in hydrographic frontal zones and regions of sea-ice melt with shallow mixed layer depths, reflecting the importance of mixing in controlling surface water light and nutrient availability.

Document Cohesion Flow: Striving towards Coherence

Text cohesion is an important element of discourse processing. This paper presents a new approach to modeling, quantifying, and visualizing text cohesion using automated cohesion flow indices that capture semantic links among paragraphs. Cohesion flow is calculated by applying Cohesion Network Analysis, a combination of semantic distances, Latent Semantic Analysis, and Latent Dirichlet Allocation, as well as Social Network Analysis. Experiments performed on 315 timed essays indicated that cohesion flow indices are significantly correlated with human ratings of text coherence and essay quality. Visualizations of the global cohesion indices are also included to support a more facile understanding of how cohesion flow impacts coherence in terms of semantic dependencies between paragraphs.

Funções Executivas (Frontal Assessment Battery), Capacidade Visuo Construtiva e Memória (Rey Complex Figure) numa Amostra de Idosos sob Resposta Social

Introdução: As funções executivas (FE) têm sido sistematicamente associadas ao funcionamento dos lobos frontais e sabemos que o declínio cognitivo se associa a piores resultados em provas que avaliam estas funções. Para além de pretendermos analisar se um teste que avalia as FE (Frontal Assessment Battery/FAB) discrimina idosos com/sem declínio cognitivo, avaliado através do Montreal Cognitive Assessment (MoCA) e se existem associações entre os resultados obtidos com a Figura Complexa de Rey-Osterreith/FCR-O (qualidade da cópia, memória de 3 e de 20 minutos) e a presença/ausência de declínio cognitivo, queremos sobretudo analisar se a qualidade e exactidão da cópia (capacidade visuo construtiva) e a memória de 3 minutos na FCR-O se associam ao resultado obtido com a FAB, dado que as duas provas estão supostamente associadas às FE e ao funcionamento dos lobos frontais avaliados com o FAB, por oposição à memória de 20 minutos (supostamente associada à área temporal, não avaliada pela FAB). Não deixámos de considerar, ainda, a associação entre as variáveis sociodemográficas e os resultados na FAB, na FCR-O e no MoCA. Metodologia: A amostra total incluiu 556 idosos (média de idades, M = 80,2; Desvio-padrão, DP = 5,23; variação = 60-100) sob resposta social em diferentes instituições do Concelho de Coimbra que aceitou responder voluntariamente (ou cujos familiares/cuidadores concederam consentimento) a uma bateria de testes (incluindo questões sociodemográficas, a FCR-O, o MoCA e a FAB). Estas variáveis foram estratificadas de acordo com a idade e escolaridade dos idosos e dicotomizadas. Para testar os nossos objetivos recorremos a diferentes sub amostras compostas pelos sujeitos que tinham resultados nas provas cujas associações queríamos testar. Resultados: De acordo com o MoCA, 59,7% dos idosos apresentavam declínio cognitivo, com 73,9% a apresentar défice executivo ligeiro, de acordo com a FAB. Quanto à FCR-O, 24,0% dos idosos apresentavam défice práxico ligeiro a moderado, 73,9% défice mnésico visual a curto prazo leve (3 minutos) e 60.9% défice mnésico visual a longo prazo leve a moderado (20 minutos). Não se verificaram associações estatisticamente significativas entre o género, estado civil e tipo de resposta social e as três variáveis centrais do estudo (MoCA, FAB e FCR-O). Quer a FAB, quer a FCR-O (as três provas: qualidade e exatidão da cópia, memória de 3 e 20 minutos) revelaram associações com a ausência/presença de declínio cognitivo. Considerando as variáveis estratificadas pela idade e escolaridade dos idosos e dicotomizadas, um teste do qui quadrado para a independência mostrou que a prova qualidade da FCR-O não estava associada ao resultado na FAB (com/sem défice executivo), ao contrário da prova memória de 3 minutos da FCR-O, que se mostrou associada a este resultado. A prova memória de 20 minutos da FCR-O voltou a não estar associada à ausência/presença de défice executivo (usando o mesmo teste). Analisando as diferentes provas da FCR-O e a FAB, sem estratificação, correlações de Spearman confirmaram as associações encontradas, mas também entre a prova qualidade da cópia da FCR-O e a FAB. Conclusão/Discussão: Os resultados seguem a literatura quanto à associação entre a prova da FCR-O memória a curto prazo/3 minutos e as funções executivas (associadas aos lobos frontais e testadas através da FAB), por oposição com a memória a longo prazo que aparece, na literatura, como mais associada/ou envolvendo à/a área temporal e que, de facto, não se mostrou associada ao resultado na FAB. Os resultados não são tão claros/consensuais no que toca à prova qualidade da cópia da FCR-O.

Modifications neurométaboliques et microstructurales à la suite d'une commotion cérébrale chez les athlètes féminines.

L’utilisation de méthodes d’investigation cérébrale avancées a permis de mettre en évidence la présence d’altérations à court et à long terme à la suite d’une commotion cérébrale. Plus spécifiquement, des altérations affectant l’intégrité de la matière blanche et le métabolisme cellulaire ont récemment été révélées par l’utilisation de l’imagerie du tenseur de diffusion (DTI) et la spectroscopie par résonance magnétique (SRM), respectivement. Ces atteintes cérébrales ont été observées chez des athlètes masculins quelques jours après la blessure à la tête et demeuraient détectables lorsque les athlètes étaient à nouveau évalués six mois post-commotion. En revanche, aucune étude n’a évalué les effets neurométaboliques et microstructuraux dans la phase aigüe et chronique d’une commotion cérébrale chez les athlètes féminines, malgré le fait qu’elles présentent une susceptibilité accrue de subir ce type de blessure, ainsi qu’un nombre plus élevé de symptômes post-commotionnels et un temps de réhabilitation plus long. Ainsi, les études composant le présent ouvrage visent globalement à établir le profil d’atteintes microstructurales et neurométaboliques chez des athlètes féminines par l’utilisation du DTI et de la SRM. La première étude visait à évaluer les changements neurométaboliques au sein du corps calleux chez des joueurs et joueuses de hockey au cours d’une saison universitaire. Les athlètes ayant subi une commotion cérébrale pendant la saison ont été évalués 72 heures, 2 semaines et 2 mois après la blessure à la tête en plus des évaluations pré et post-saison. Les résultats démontrent une absence de différences entre les athlètes ayant subi une commotion cérébrale et les athlètes qui n’en ont pas subie. De plus, aucune différence entre les données pré et post-saison a été observée chez les athlètes masculins alors qu’une diminution du taux de N-acetyl aspartate (NAA) n’a été mise en évidence chez les athlètes féminines, suggérant ainsi un impact des coups d’intensité sous-clinique à la tête. La deuxième étude, qui utilisait le DTI et la SRM, a révélé des atteintes chez des athlètes féminines commotionnées asymptomatiques en moyenne 18 mois post-commotion. Plus spécifiquement, la SRM a révélé une diminution du taux de myo-inositol (mI) au sein de l’hippocampe et du cortex moteur primaire (M1) alors que le DTI a mis en évidence une augmentation de la diffusivité moyenne (DM) dans plusieurs faisceaux de matière blanche. De iii plus, une approche par région d’intérêt a mis en évidence une diminution de la fraction d’anisotropie (FA) dans la partie du corps calleux projetant vers l’aire motrice primaire. Le troisième article évaluait des athlètes ayant subi une commotion cérébrale dans les jours suivant la blessure à la tête (7-10 jours) ainsi que six mois post-commotion avec la SRM. Dans la phase aigüe, des altérations neuropsychologiques combinées à un nombre significativement plus élevé de symptômes post-commotionnels et dépressifs ont été trouvés chez les athlètes féminines commotionnées, qui se résorbaient en phase chronique. En revanche, aucune différence sur le plan neurométabolique n’a été mise en évidence entre les deux groupes dans la phase aigüe. Dans la phase chronique, les athlètes commotionnées démontraient des altérations neurométaboliques au sein du cortex préfrontal dorsolatéral (CPDL) et M1, marquées par une augmentation du taux de glutamate/glutamine (Glx). De plus, une diminution du taux de NAA entre les deux temps de mesure était présente chez les athlètes contrôles. Finalement, le quatrième article documentait les atteintes microstructurales au sein de la voie corticospinale et du corps calleux six mois suivant une commotion cérébrale. Les analyses n’ont démontré aucune différence au sein de la voie corticospinale alors que des différences ont été relevées par segmentation du corps calleux selon les projections des fibres calleuses. En effet, les athlètes commotionnées présentaient une diminution de la DM et de la diffusivité radiale (DR) au sein de la région projetant vers le cortex préfrontal, un volume moindre des fibres de matière blanche dans la région projetant vers l’aire prémotrice et l’aire motrice supplémentaire, ainsi qu’une diminution de la diffusivité axiale (DA) dans la région projetant vers l’aire pariétale et temporale. En somme, les études incluses dans le présent ouvrage ont permis d’approfondir les connaissances sur les effets métaboliques et microstructuraux des commotions cérébrales et démontrent des effets délétères persistants chez des athlètes féminines. Ces données vont de pair avec la littérature scientifique qui suggère que les commotions cérébrales n’entraînent pas seulement des symptômes temporaires.

Propriedades Psicométricas da Bateria de Avaliação Frontal numa Amostra de Adultos da População Portuguesa

The Frontal Assessment Batery / A Bateria de Avaliação Frontal (FAB) é um teste neuropsicológico, constituído por seis subtestes, cujo objetivo é avaliar a disfunção executiva global, nomeadamente as funções relacionadas com o lobo frontal, tais como a concetualização, flexibilidade mental, programação motora, sensibilidade à interferência, controlo inibitório e autonomia ambiental frontal. De forma a contribuir para o avanço dos estudos normativos em Portugal, esta dissertação tem como objetivo avaliar as propriedades psicométricas da FAB, numa amostra de adultos da população portuguesa. O protocolo abrangeu a seguinte bateria de testes neuropsicológicos: Bateria de Avaliação Frontal, Figura Complexa de Rey, Matrizes Progressivas de Raven e Teste do Desenho do Relógio. A amostra deste estudo incluiu 376 indivíduos, 155 do sexo masculino e 221 do sexo feminino. Os resultados desta investigação sugerem que a pontuação da FAB é influenciada por algumas variáveis sociodemográficas, designadamente a idade, escolaridade, profissões e região. A análise correlacional mostrou que há apenas uma correlação positiva moderada entre a FAB e as Matrizes Progressivas de Raven. Apesar da consistência interna da FAB ser baixa, existe uma estabilidade temporal moderada. Ao finalizar, consideramos que a FAB reúne os requisitos para se apresentar como uma bateria útil e eficaz, demonstrando um grau razoável de estabilidade temporal, mas fraca consistência interna, sugerindo que a FAB não é indicada para amostra não clínica. / The Frontal Assessment Baterry (FAB) is a neuropsychological test, composed of six subtests, whose aim is to assess the overall executive dysfunction, namely functions related to the frontal lobe, such as conceptualization, mental flexibility, motor programming, sensitivity to interference, inhibitory control and environmental autonomy. In order to contribute to the advancement of normative studies in Portugal, this dissertation aim to evaluate the psychometric properties of the FAB, in an adult sample of the portuguese population. The protocol included the following battery of neuropsychological tests: Frontal Assessment Battery, Complex Figure of Rey, Raven's Progressive Matrices and Clock Drawing Test. The sample this study included 376 individuals, 155 male and 221 female. The results of this investigation suggest that FAB is influenced by some sociodemographic variables, namely age, education, profession and region. The correlational analysis showed that there is only a moderate positive correlation between the FAB and the Raven Progressive Matrices. However, also they found low positive correlations between the FAB and the Complex Figure of Rey, and Clock Drawing Test. Although the FAB has a low internal consistency, there is a moderate temporal stability. Finally, we consider that the FAB gathers the requirements to present itself as a useful and effective battery, demonstrating a reasonable degree of temporal stability, but weaker internal consistency, suggesting that the FAB is not indicate for non-clinical sample.

Avaliação breve do défice executivo em pessoas idosas com Acidente Vascular Cerebral: Validação da Bateria de Avaliação Frontal

RESUMO Objetivos: O Acidente Vascular Cerebral (AVC) potencia o desenvolvimento de disfunção executiva, conduzindo a défice no desempenho das tarefas do quotidiano. A avaliação neuropsicológica das funções executivas é importante para desenvolver estratégias de reabilitação adequadas. Assim, são objetivos descrever os dados normativos, precisão de diagnóstico, propriedades psicométricas e análise fatorial da Bateria de Avaliação Frontal (FAB), instrumento breve e de rápida administração, numa amostra de idosos com AVC. Métodos: Inserida no projeto Trajetórias do Envelhecimento de Idosos em Resposta Social, esta investigação conta com uma amostra de 112 pessoas idosas com diagnóstico médico de AVC e 157 pessoas idosas de um subgrupo de controlo sem AVC. Os sujeitos apresentam idades compreendidas entre os 60 e os 100 anos (M = 78,20; DP = 7,57) sendo maioritariamente do sexo feminino (n = 194). A avaliação inclui entrevistas e testes neuropsicológicos agrupados em medidas de funcionamento executivo, medidas cognitivas de referência e medidas clínicas de controlo. Resultados: As variáveis idade e escolaridade interferiram nas pontuações obtidas na amostra clínica, não sendo verificado impacto da variável sexo. Para um ponto de corte de 7, a FAB teve uma sensibilidade de 83,4% e especificidade de 66,1 % (AUC = 0,64); revelou um alfa de Cronbach de 0,79 e correlações fortes com os testes executivos (teste de Stroop, Figura Complexa de Rey, fator Atencional-Executivo do Montreal Cognitive Assessment e Alternância nos testes de Fluência verbal). A análise fatorial confirmatória apontou uma estrutura com um fator. Conclusões: A FAB apresenta boa consistência interna, validade convergente e validade de constructo, aparentando ser uma escala útil para avaliar o défice executivo em pessoas idosas com AVC. Dadas algumas limitações do estudo, que poderão explicar a fraca precisão diagnóstica da FAB, são incentivadas investigações futuras pois a FAB revelou-se um instrumento com propriedades psicométricas promissoras. ABSTRACT Goals: Stroke potentiates the development of executive dysfunction, leading to impairment in performance of daily activities. The neuropsychological assessment of executive functions is important to develop adequate rehabilitation strategies. Thus, describing the normative data, diagnostic accuracy, psychometric properties and factor analysis of the Frontal Assessment Battery (FAB), a brief and easy to administer instrument, in a clinical sample with stroke are objectives of this study. Methods: Being part of the Aging Trajectories of Institutionalized Elderly, this research has a sample 112 elderly people with a medical diagnosis of stroke and a control subgroup of 157 elderly people. The subjects have ages between 60 and 100 years old (M = 78.20, SD = 7.57), mostly females (n = 194). The measurements used include interviews and neuropsychological tests grouped in executive functioning measures, cognitive measures of reference and clinical measures of control. Results: The variables age and education affect the scores obtained in the clinical subgroup, having the variable gender no impact on these. Using a cutoff score of 7, the FAB had a sensitivity of 83.4% and a specificity of 66.1% for screening stroke (AUC = 0.64); showed a Cronbach's α of 0.79, and strong correlations with executive tests (Stroop test, Rey Complex Figure, Attentional-Executive factor of Montreal Cognitive Assessment and Switching in the verbal fluency tests). The confirmatory factor analysis supported a one-factor structure. Conclusions: The FAB presents good internal consistency, convergent, and construct when used for elderly with stroke. Due to some limitations of the study, which may explain the weak discriminant validity, further investigations are encouraged because FAB has showed promising psychometric properties.