Étude du partage attentionnel : Analogie entre la production temporelle avec interruption et la double tâche

L’estimation temporelle de l’ordre des secondes à quelques minutes requiert des ressources attentionnelles pour l’accumulation d’information temporelle pendant l’intervalle à estimer (Brown, 2006; Buhusi & Meck, 2009; Zakay & Block, 2004). Ceci est démontré dans le paradigme de double tâche, où l’exécution d’une tâche concurrente pendant l’estimation d’un intervalle mène à un effet d’interférence, soit une distorsion de la durée perçue se traduisant par des productions temporelles plus longues et plus variables que si l’estimation de l’intervalle était effectuée seule (voir Brown, 1997; 2010). Un effet d’interférence est également observé lorsqu’une interruption est attendue pendant l’intervalle à estimer, l’allongement étant proportionnel à la durée d’attente de l’interruption (Fortin & Massé, 2000). Cet effet a mené à l’hypothèse que la production avec interruption serait sous-tendue par un mécanisme de partage attentionnel similaire à la double tâche (Fortin, 2003). Afin d’étudier cette hypothèse, deux études empiriques ont été effectuées dans des contextes expérimentaux associés respectivement à une augmentation et à une diminution de l’effet d’interférence, soit le vieillissement (Chapitre II) et l’entraînement cognitif (Chapitre III). Dans le Chapitre II, la tâche de production avec interruption est étudiée chez des participants jeunes et âgés à l’aide de la spectroscopie proche infrarouge fonctionnelle (SPIRf). Les résultats montrent que l’attente de l’interruption est associée à des coûts comportementaux et fonctionnels similaires à la double tâche. Au niveau comportemental, un allongement des productions proportionnel à la durée d’attente de l’interruption est observé chez l’ensemble des participants, mais cet effet est plus prononcé chez les participants âgés que chez les jeunes. Ce résultat est compatible avec les observations réalisées dans le paradigme de double tâche (voir Verhaegen, 2011 pour une revue). Au niveau fonctionnel, la production avec et sans interruption est associée à l’activation du cortex préfrontal droit et des régions préfrontales dorsolatérales connues pour leur rôle au niveau de l’estimation temporelle explicite (production d’intervalle) et implicite (processus préparatoires). En outre, l’attente de l’interruption est associée à l’augmentation de l’activation corticale préfrontale dans les deux hémisphères chez l’ensemble des participants, incluant le cortex ventrolatéral préfrontal associé au contrôle attentionnel dans la double tâche. Finalement, les résultats montrent que les participants âgés se caractérisent par une activation corticale bilatérale lors de la production sans et avec interruption. Dans le cadre des théories du vieillissement cognitif (Park & Reuter-Lorenz, 2009), cela suggère que l’âge est associé à un recrutement inefficace des ressources attentionnelles pour la production d’intervalle, ceci nuisant au recrutement de ressources additionnelles pour faire face aux demandes liées à l’attente de l’interruption. Dans le Chapitre III, la tâche de production avec interruption est étudiée en comparant la performance de participants assignés à l’une ou l’autre de deux conditions d’exécution extensive (cinq sessions successives) de double tâche ou de production avec interruption. Des sessions pré et post-test sont aussi effectuées afin de tester le transfert entre les conditions. Les résultats montrent un effet d’interférence et de durée d’interférence tant en production avec double tâche qu’en production avec interruption. Ces effets sont toutefois plus prononcés lors de la production avec interruption et tendent à augmenter au fil des sessions, ce qui n’est pas observé en double tâche. Cela peut être expliqué par l’influence des processus préparatoires pendant la période pré-interruption et pendant l’interruption. Finalement, les résultats ne mettent pas en évidence d’effets de transfert substantiels entre les conditions puisque les effets de la pratique concernent principalement la préparation temporelle, un processus spécifique à la production avec interruption. Par la convergence que permet l’utilisation d’un même paradigme avec des méthodologies distinctes, ces travaux approfondissent la connaissance des mécanismes attentionnels associés à l’estimation temporelle et plus spécifiquement à la production avec interruption. Les résultats supportent l’hypothèse d’un partage attentionnel induit par l’attente de l’interruption. Les ressources seraient partagées entre les processus d’estimation temporelle explicite et implicite, une distinction importante récemment mise de l’avant dans la recherche sur l’estimation du temps (Coull, Davranche, Nazarian & Vidal, 2013). L’implication de processus dépendant des ressources attentionnelles communes pour le traitement de l’information temporelle peut rendre compte de l’effet d’interférence robuste et systématique observé dans la tâche de production avec interruption.

A Paradigm Shift in Predoctoral Dental Curricula in Brazil: Evaluating the Process of Change

In 2002, the Brazilian Ministry of Education approved the official curricular guidelines for undergraduate courses in Brazil to be adopted by the nation's 188 dental schools. In 2005-06, the Brazilian Dental Education Association (BDEA) promoted workshops in forty-eight of the schools to verify the degree of transformation of the curriculum based on these guidelines. Among the areas analyzed were course philosophy (variables were v1: knowledge production based on the needs of the Brazilian Public Health System [BPHS]; v2: health determinants; and v3: postgraduate studies and permanent education); pedagogical skills (v4: curricular structure; v5: changes in pedagogic and didactic skills; and v6: course program orientation); and dental practice scenarios (v7: diversity of the scenarios for training/learning; v8: academic health care centers opened to the BPHS; and v9: participation of students in health care delivery for the population). The subjects consisted of faculty members (n=711), students (n=228), and employees (n=14). The results showed an incipient degree of curriculum transformation. The degree of innovation was statistically different depending on the type of university (public or private) for variables I, 2, 4, 5, 6, and 7. Private schools reported a higher level of innovation than public institutions. Resistance to transforming the dental curriculum according to the official guidelines may be linked to an ideological conception that supports the private practice model, continues to have faculty members direct all classroom activities, and prevents students from developing an understanding of professional practice as targeted towards the oral health needs of all segments of society.

Sagittal spinal alignment in paraplegics: a new paradigm for the rehabilitation under neuromuscular electrical stimulation

Study design: Radiographic analysis of sagittal spinal alignment of paraplegics in a standing position under surface neuromuscular electrical stimulation (NMES). Objectives: Describing the radiographic parameters of the sagittal spinal alignment of paraplegics going through a rehabilitation program with NMES. Setting: The University Hospital`s Ambulatory (UNICAMP), Campinas, Sao Paulo, Brazil. Methods: Panoramic X-ray images in profile were taken for 10 paraplegics. All patients participated in the rehabilitation program and were able to perform gait through NMES of the femoral quadriceps muscles. The radiographic parameters used for the analysis were the same as those described in the literature for healthy people. The results were didactically organized into three groups: anatomical shape of the spine, morphology and kinetics of the pelvis and spinopelvic alignment. Results: The physiological curvature of the spine in paraplegics showed average values similar to those described in the literature for healthy patients. The inversion of the pelvic tilt and the increase in the sacral slope were defined by the anterior backward rotation of the pelvis. The existing theoretical mathematical formulas that define lumbar lordosis, pelvic incidence and pelvic tilt showed normal values, despite the anterior intense sagittal imbalance. Conclusions: The adaptive posture of the spine in paraplegics standing through the stimulation of the femoral quadriceps does not allow for a neutral sagittal alignment. This novel radiographic detailed description of the various segments of the spine can be of assistance toward the understanding of the global postural control for such subjects. Spinal Cord (2010) 48, 251-256; doi: 10.1038/sc.2009.123; published online 29 September 2009

Hybrid Method to Assess Sensitive Process Interruption Costs Due to Faults in Electric Power Distribution Networks

This paper shows a new hybrid method for risk assessment regarding interruptions in sensitive processes due to faults in electric power distribution systems. This method determines indices related to long duration interruptions and short duration voltage variations (SDVV), such as voltage sags and swells in each customer supplied by the distribution network. Frequency of such occurrences and their impact on customer processes are determined for each bus and classified according to their corresponding magnitude and duration. The method is based on information regarding network configuration, system parameters and protective devices. It randomly generates a number of fault scenarios in order to assess risk areas regarding long duration interruptions and voltage sags and swells in an especially inventive way, including frequency of events according to their magnitude and duration. Based on sensitivity curves, the method determines frequency indices regarding disruption in customer processes that represent equipment malfunction and possible process interruptions due to voltage sags and swells. Such approach allows for the assessment of the annual costs associated with each one of the evaluated power quality indices.

Integral Piezoactuator System with Optimum Placement of Functionally Graded Material - A Topology Optimization Paradigm

Piezoactuators consist of compliant mechanisms actuated by two or more piezoceramic devices. During the assembling process, such flexible structures are usually bonded to the piezoceramics. The thin bonding layer(s) between the compliant mechanism and the piezoceramic may induce undesirable behavior, including unusual interfacial nonlinearities. This constitutes a drawback of piezoelectric actuators and, in some applications, such as those associated to vibration control and structural health monitoring (e. g., aircraft industry), their use may become either unfeasible or at least limited. A possible solution to this standing problem can be achieved through the functionally graded material concept and consists of developing `integral piezoactuators`, that is those with no bonding layer(s) and whose performance can be improved by tailoring their structural topology and material gradation. Thus, a topology optimization formulation is developed, which allows simultaneous distribution of void and functionally graded piezoelectric materials (including both piezo and non-piezoelectric materials) in the design domain in order to achieve certain specified actuation movements. Two concurrent design problems are considered, that is the optimum design of the piezoceramic property gradation, and the design of the functionally graded structural topology. Two-dimensional piezoactuator designs are investigated because the applications of interest consist of planar devices. Moreover, material gradation is considered in only one direction in order to account for manufacturability issues. To broaden the range of such devices in the field of smart structures, the design of integral Moonie-type functionally graded piezoactuators is provided according to specified performance requirements.

Who fails to complete tuberculosis treatment? Temporal trends and risk factors for treatment interruption in a community-based directly observed therapy programme in a rural district of South Africa

SETTING: Hlabisa Tuberculosis Programme, Hlabisa, South Africa. OBJECTIVE: To determine trends in and risk factors for interruption of tuberculosis treatment. METHODS: Data were extracted from the control programme database starting in 1991. Temporal trends in treatment interruption are described; independent risk factors for treatment interruption were determined with a multiple logistic regression model, and Kaplan-Meier survival curves for treatment interruption were constructed for patients treated in 1994-1995. RESULTS: Overall 629 of 3610 surviving patients (17%) failed to complete treatment; this proportion increased from 11% (n = 79) in 1991/1992 to 22% (n = 201) in 1996. Independent risk factors for treatment interruption were diagnosis between 1994-1996 compared with 1991-1393 (odds ratio [OR] 1.9, 95% confidence interval [CT] 1.6-2.4); human immunodeficiency virus (HIV) positivity compared with HIV negativity (OR 1.8, 95% CI 1.4-2.4); supervised by village clinic compared with community health worker (OR 1.9, 95% CI 1.4-2.6); and male versus female sex (OR 1.3, 95% CI 1.1-1.6). Few patients interrupted treatment during the first 2 weeks, and the treatment interruption rate thereafter was constant at 1% per 14 days. CONCLUSIONS: Frequency of treatment interruption from this programme has increased recently. The strongest risk factor was year of diagnosis, perhaps reflecting the impact of an increased caseload on programme performance. Ensuring adherence to therapy in communities with a high level of migration remains a challenge even within community-based directly observed therapy programmes.

Increasing the efficiency of solute leaching: impacts of flow interruption with drainage of the "preferential flow paths"

Most soils contain preferential flow paths that can impact on solute mobility. Solutes can move rapidly down the preferential flow paths with high pore-water velocities, but can be held in the less permeable region of the soil matrix with low pore-water velocities, thereby reducing the efficiency of leaching. In this study, we conducted leaching experiments with interruption of the flow and drainage of the main flow paths to assess the efficiency of this type of leaching. We compared our experimental results to a simple analytical model, which predicts the influence of the variations in concentration gradients within a single spherical aggregate (SSA) surrounded by preferential flow paths on leaching. We used large (length: 300 mm, diameter: 216 mm) undisturbed field soil cores from two contrasting soil types. To carry out intermittent leaching experiments, the field soil cores were first saturated with tracer solution (CaBr2), and background solution (CaCl2) was applied to mimic a leaching event. The cores were then drained at 25- to 30-cm suction to empty the main flow paths to mimic a dry period during which solutes could redistribute within the undrained region. We also conducted continuous leaching experiments to assess the impact of the dry periods on the efficiency of leaching. The flow interruptions with drainage enhanced leaching by 10-20% for our soils, which was consistent with the model's prediction, given an optimised equivalent aggregate radius for each soil. This parameter quantifies the time scales that characterise diffusion within the undrained region of the soil, and allows us to calculate the duration of the leaching events and interruption periods that would lead to more efficient leaching. Application of these methodologies will aid development of strategies for improving management of chemicals in soils, needed in managing salts in soils, in improving fertiliser efficiency, and in reclaiming contaminated soils. (C) 2000 Elsevier Science B.V. All rights reserved.

Investigation of threat-related attentional bias in anxious children using the startle eyeblink modification paradigm

We used the startle eyeblink modification paradigm to investigate whether clinically anxious children, like high trait-anxious adults, display a bias in favour of threat words compared to neutral words. The present study included 16 clinically anxious children whose diagnostic status was determined using the parent version of a semistructured diagnostic interview as part of a larger childhood anxiety study. The children were presented with threat and neutral words fur 6 s each. A startle-eliciting auditory stimulus - a 100 dBA burst of white noise of 50 ms duration - was presented during the words at lead intervals of 60, 120, 240, or 3500 ms and during intertrial intervals. The overall pattern of startle eyeblink modification indicated inhibition at the 120 and 240 ms lead intervals and facilitation at the 3500 ms lead interval. startle-latency shortening during threat words at the :60 ms lead interval was larger than at other intervals, whereas there was no difference during neutral words. This result reflects an anxiety-related bias in favour of threat words occurring at a very early - and possibly preattentive stage - of information processing.

Effects of reversible inactivation of the medial septum on rat exploratory behavior in the elevated plus-maze using a test-retest paradigm

The effect of intraseptal injections of lidocaine before a first or a second session in the elevated plus-maze, in a test-retest paradigm, was investigated. In addition to gross session analyses, a minute-by-minute analysis of the sessions was used to evaluate both anxiety and memory. Lidocaine injections before the test session produced increases in the frequency of entries, time spent and distance run in the open arms without affecting activity occurring in the closed arms. During the retest session, saline- and lidocaine-treated rats exhibited increased indices of anxiety and lidocaine-treated rats exhibited decreased closed-arm entries. The minute-by-minute analysis showed a faster decrease in anxiety-related behaviors during the test session by saline- than by lidocaine-treated rats and a significant decrease in closed-arm exploration by saline-treated rats, but not by lidocaine-treated ones. Lidocaine injection before the retest session produced increases in the frequency of entries, time spent and distance run in the open arms in the second session when compared with saline-treated rats. Minute-by-minute analysis showed an increase in the time spent in the open arms by lidocaine animals at the beginning of the retest session in comparison to saline animals and a significant decrease in closed-arm exploration by both groups. These results suggest that inactivation of the medial septum by lidocaine affects the expression of unconditioned and conditioned forms of anxiety in the elevated plus-maze and, in a lesser way, the acquisition and retention of spatial information. (C) 2010 Elsevier B.V. All rights reserved.