The impact of luminance on tonic and phasic pupillary responses to sustained cognitive load

Pupillary reactions independent of light conditions have been linked to cognition for a long time. However, the light conditions can impact the cognitive pupillary reaction. Previous studies underlined the impact of luminance on pupillary reaction, but it is still unclear how luminance modulates the sustained and transient components of pupillary reaction – tonic pupil diameter and phasic pupil response. In the present study, we investigated the impact of the luminance on these two components under sustained cognitive load. Fourteen participants performed a novel working memory task combining mathematical computations with a classic n-back task. We studied both tonic pupil diameter and phasic pupil response under low (1-back) and high (2-back) working memory load and two luminance levels (gray and white). We found that the impact of working memory load on the tonic pupil diameter was modulated by the level of luminance, the increase in tonic pupil diameter with the load being larger under lower luminance. In contrast, the smaller phasic pupil response found under high load remained unaffected by luminance. These results showed that luminance impacts the cognitive pupillary reaction – tonic pupil diameter (phasic pupil response) being modulated under sustained (respectively, transient) cognitive load. These findings also support the relationship between the locus-coeruleus system, presumably functioning in two firing modes – tonic and phasic – and the pupil diameter. We suggest that the tonic pupil diameter tracks the tonic activity of the locus-coeruleus while phasic pupil response reflects its phasic activity. Besides, the designed novel cognitive paradigm allows the simultaneous manipulation of sustained and transient components of the cognitive load and is useful for dissociating the effects on the tonic pupil diameter and phasic pupil response

Estimation de l'équivalent en eau de la neige en milieu subarctique du Québec par télédétection micro-ondes passives

The snow cover (extent, depth and water equivalent) is an important factor in assessing the water balance of a territory. In a context of deregulation of electricity, better knowledge of the quantity of water resulting from snowmelt that will be available for hydroelectric power generation has become a major challenge for the managers of Hydro-Québec's generating plant. In fact, the snow on the ground represents nearly one third of Hydro-Québec's annual energy reserve and the proportion is even higher for northern watersheds. Snowcover knowledge would therefore help optimize the management of energy stocks.The issue is especially important when one considers that better management of water resources can lead to substantial economic benefits.The Research Institute of Hydro-Quebec (IREQ), our research partner, is currently attempting to optimize the streamflow forecasts made by its hydrological models by improving the quality of the inputs. These include a parameter known as the snow water equivalent (SWE) which characterizes the properties of the snow cover. At the present time, SWE data is obtained from in situ measurements, which are both sporadic and scattered and does not allow the temporal and spatial variability of SWE to be characterized adequately for the needs of hydrological models. This research project proposes to provide the Québec utility's hydrological models with distributed SWE information about its northern watersheds.The targeted accuracy is 15% for the proposed period of analysis covering the winter months of January, February and March of 2001 to 2006.The methodology is based on the HUT snow emission model and uses the passive microwave remote sensing data acquired by the SSM/I sensor. Monitoring of the temporal and spatial variations in SWE is done by inversion of the model and benefits from the assimilation of in situ data to characterize the state of snow cover during the season. Experimental results show that the assimilation technique of in situ data (density and depth) can reproduce the temporal variations in SWE with a RMSE error of 15.9% (R[subscript 2] =0.76).The analysis of land cover within the SSMI pixels can reduce this error to 14.6% (R[subscript 2] =0.66) for SWE values below 300 mm. Moreover, the results show that the fluctuations of SWE values are driven by changes in snow depths. Indeed, the use of a constant value for the density of snow is feasible and makes it possible to get as good if not better results. These results will allow IREQ to assess the suitability of using snow cover information provided by the remote sensing data in its forecasting models. This improvement in SWE characterization will meet the needs of IREQ for its work on optimization of the quality of hydrological simulations.The originality and relevance of this work are based primarily on the type of method used to quantify SWE and the site where it is applied.The proposed method focuses on the inversion of the HUT model from passive remote sensing data and assimilates in situ data. Moreover, this approach allows high SWE values (> 300 mm) to be quantified, which was impossible with previous methods. These high SWE values are encountered in areas with large amounts of snow such as northern Québec

Caractérisation des propriétés optiques des aérosols troposphériques par télédétection satellitaire et in-situ et validation du modèle climatique canadien GCMIII-CAM

The tropospheric aerosols of the atmosphere play a crucial role in the evolution of the climate. In order to determine with accuracy their influence on the radiative budget of the Earth, it is imperative to develop analysis methods that will allow us to characterize the optical properties of the tropospheric aerosols using remote sensing data.The major problem encountered in this field is the characterization of these properties above the continents. Indeed, the contribution of the surface below the layer of aerosols to the signal measured by the sensor is considerable. Our study seeks to evaluate the potential of two new sensors using two different inversion schemes: POLDER (based on polarization measurements of solar radiation reflected by aerosols) and MODIS (based on measurements above dark dense vegetation target, DDV).The aerosol optical depth ([tau[subscript a[lambda]]]) derived from measurements of the solar photometers of the AERONET-AEROCAN network is used as reference to the comparisons.--Résumé abrégé par UMI

Is Auditory Distraction by Changing-State and Deviant Sounds Underpinned by the Same Mechanism? Evidence from Pupillometry

The mere presence of task-irrelevant auditory stimuli is known to interfere with cognitive functioning. Disruption can be caused by changing auditory distractors (the changing-state effect) or by a sound that deviates from the auditory background (the deviation effect). The unitary account of auditory distraction explains both phenomena in terms of attentional capture whereas the duplex-mechanism account posits that they reflect two fundamentally different forms of distraction in which only the deviation effect is caused by attentional capture. To test these predictions, we exploited a physiological index of attention orienting: the pupillary dilation response (PDR). Participants performed visual serial recall while ignoring sequences of spoken letters. These sequences either comprised repeated or changing letters, and one letter could sometimes be replaced by pink noise (the deviant). Recall was poorer in both changing-state and deviant trials. Interestingly, the PDR was elicited by deviant sounds but not changing-state sounds. This physiological dissociation of the changing-state and the deviation effects suggests they are subtended by distinct mechanisms thereby procuring support for the duplex-mechanism account over the unitary account

Charactéristiques d'une population introduit du Grand brochet, Esox lucius, dans le lac Ramsay, Parc de la Gatineau, Québec, et impact sur l'ichtyofaune

En 1995, la présence du Grand brochet (Esox lucius), une espèce piscivore, a été notée pour la première fois dans le lac Ramsay, Parc de la Gatineau (Québec). Il a été déterminé que l’espèce a été introduite après l’été 1991. Un échantillonnage exhaustif de l’ichtyofaune du lac en 2001 et 2002 a permis de constater que trois des 17 petites espèces de poissons du lac sont probablement disparues: le Mulet perlé (Margariscus margarita), l’Épinoche à cinq épines (Culaea inconstans) et une forme rare de l’Épinoche à trois épines (Gasterosteus aculeatus). Il est prédit que plusieurs autres espèces pourraient disparaître au cours des prochaines années. La croissance du Grand brochet dans le lac Ramsay est comparable aux autres lacs du sud du Québec. En 2001, le rapport femelles:mâles était de 15 : 1, une valeur anormale et inexpliquée.In 1995, the Northern Pike (Esox lucius), a piscivorous fish, was captured for the first time in Ramsay Lake, a small lake of the Gatineau Park (Québec). It was determined that this species was introduced after the summer of 1991. An exhaustive survey of the ichthyofauna of this lake in 2001 and 2002 indicated that three of the 17 small-bodied species of the lake have probably disappeared: the Pearl Dace (Margariscus margarita), the Fivespine Stickleback (Culaea inconstans) and a special form of the Threespine Stickleback (Gasterosteus aculeatus). It is predicted that several other species may be extirpated in the next few years. Northern Pike growth in the lake is comparable to other values obtained for other southern Québec lakes. In 2001, the female:male ratio was highly unbalanced and difficult to explain at 15 : 1. Erratum added

Cognitive conflict in human–automation interactions: A psychophysiological study

The review of literature in sociology and distributed artificial intelligence reveals that the occurrence of conflict is a remarkable precursor to the disruption of multi-agent systems. The study of this concept could be applied to human factors concerns, as man-system conflict appears to provoke perseveration behavior and to degrade attentional abilities with a trend to excessive focus. Once entangled in such conflicts, the human operator will do anything to succeed in his current goal even if it jeopardizes the mission. In order to confirm these findings, an experimental setup, composed of a real unmanned ground vehicle, a ground station is developed. A scenario involving an authority conflict between the partici- pants and the robot is proposed. Analysis of the effects of the conflict on the participants’ cognition and arousal is assessed through heart-rate measurement (reflecting stress level) and eye-tracking techniques (index of attentional focus). Our results clearly show that the occurrence of the conflict leads to perseveration behavior and can induce higher heart rate as well as excessive attentional focus. These results are discussed in terms of task commitment issues and increased arousal. Moreover, our results suggest that individual differences may predict susceptibility to perseveration behavior

Anticipating human error before it happens: Towards a psychophysiological model for online prediction of mental workload

Mental workload is a key factor influencing the occurrence of human error; specifically in remotely-operated vehicle operations. Both low and high mental workload has been found to disrupt performance in a nonlinear fashion at a given task; however, research that has attempted to predict individual mental workload has met with little success. The objective of the present study is to investigate the potential of the dual-task paradigm and prefrontal cortex oxygenation as online measures of mental workload. Subjects performed a computerized object tracking task in which they had to follow a dynamic target with their aircraft. Task difficulty was manipulated in terms of processing load and difficulty of control: two critical sources of workload associated with remotely operating a vehicle. Mental workload was assessed by a secondary concurrent time production task and a functional near infrared spectrometer. Results show that the effects of task difficulty differ across measures of mental workload. This pattern of behavioural and neurophysiologic results suggests that the empirically-based selection of an appropriate secondary task for the measure of mental workload is critical as its sensitivity may vary considerably depending on task factors

Attention Allocation Aid for Visual Search

This paper outlines the development and testing of a novel, feedback-enabled attention allocation aid (AAAD), which uses real-time physiological data to improve human performance in a realistic sequential visual search task. Indeed, by optimizing over search duration, the aid improves efficiency, while preserving decision accuracy, as the operator identifies and classifies targets within simulated aerial imagery. Specifically, using experimental eye-tracking data and measurements about target detectability across the human visual field, we develop functional models of detection accuracy as a function of search time, number of eye movements, scan path, and image clutter. These models are then used by the AAAD in conjunction with real time eye position data to make probabilistic estimations of attained search accuracy and to recommend that the observer either move on to the next image or continue exploring the present image. An experimental evaluation in a scenario motivated from human supervisory control in surveillance missions confirms the benefits of the AAAD.Comment: To be presented at the ACM CHI conference in Denver, Colorado in May 201

Evaluation of head-free eye tracking as an input device for air traffic control

International audienceThe purpose of this study was to investigate the possibility to integrate a free head motion eye-tracking system as input device in air traffic control (ATC) activity. Sixteen participants used an eye tracker to select targets displayed on a screen as quickly and accurately as possible. We assessed the impact of the presence of visual feedback about gaze position and the method of target selection on selection performance under different difficulty levels induced by variations in target size and target-to-target separation. We tend to consider that the combined use of gaze dwell-time selection and continuous eye-gaze feedback was the best condition as it suits naturally with gaze displacement over the ATC display and free the hands of the controller, despite a small cost in terms of selection speed. In addition, target size had a greater impact on accuracy and selection time than target distance. These findings provide guidelines on possible further implementation of eye tracking in ATC everyday activity