Componentes sensoriais e atencionais do tempo de reação: efeitos do tamanho, excentricidade e previsibilidade de estímulos visuais

A percepção visual depende do arcabouço sensorial e do processamento atencional. Este trabalho estudou o efeito, sobre o tempo de reação manual (TR), do tamanho, excentricidade e previsibilidade de estímulos visuais. No experimento 1 (n=8), um alvo foi apresentado aleatoriamente em uma de quatro excentricidades diferentes, possuindo três possíveis tamanhos. O experimento 2 (n=12) apresentava configuração similar, porém uma pista indicava o quadrante de maior probabilidade (70%) de apresentação do alvo. Os resultados mostraram um aumento do TR em função da excentricidade do alvo, além de uma diminuição do TR com o aumento do tamanho do alvo e indicação correta da pista. Uma análise das interações sugere uma superposição de mecanismos atencionais e puramente sensoriais compartilhando um estágio comum do processamento visual.

Bias and learning in temporal binding: intervals between actions and outcomes are compressed by prior bias

It has consistently been shown that agents judge the intervals between their actions and outcomes as compressed in time, an effect named intentional binding. In the present work, we investigated whether this effect is result of prior bias volunteers have about the timing of the consequences of their actions, or if it is due to learning that occurs during the experimental session. Volunteers made temporal estimates of the interval between their action and target onset (Action conditions), or between two events (No-Action conditions). Our results show that temporal estimates become shorter throughout each experimental block in both conditions. Moreover, we found that observers judged intervals between action and outcomes as shorter even in very early trials of each block. To quantify the decrease of temporal judgments in experimental blocks, exponential functions were fitted to participants’ temporal judgments. The fitted parameters suggest that observers had different prior biases as to intervals between events in which action was involved. These findings suggest that prior bias might play a more important role in this effect than calibration-type learning processes.

The subjective present and its modulation in clinical contexts

Time is a basic dimension in psychology, underlying behavior and experience. Timing and time perception constitute implicit processes that are often inaccessible to the individual person. Research in this field has shown that timing is involved in many areas of clinical significance. In the projects presented here, we combine timing with seemingly different fields of research, such as psychopathology, perceptual grouping, and embodied cognition. Focusing on the time scale of the subjective present, we report findings from three different clinical studies: (1) We studied perceived causality in schizophrenia patients, finding that perceptual grouping (‘binding’, ‘Gestalt formation’), which leads to visual causality perceptions, did not distinguish between patients and healthy controls. Patients however did integrate context (provided by the temporal distribution of auditory context stimuli) less into perceptions, in significant contrast to controls. This is consistent with reports of higher inaccuracy in schizophrenia patients’ temporal processing. (2) In a project on auditory Gestalt perception we investigated auditory perceptual grouping in schizophrenia patients. The mean dwell time was positively related to how much patients were prone to auditory hallucinations. Dwell times of auditory Gestalts may be regarded as operationalizations of the subjective present; findings thus suggested that patients with hallucinations had a shorter present. (3) The movement correlations of interacting individuals were used to study the non-verbal synchrony between therapist and patient in psychotherapy sessions. We operationalized the duration of an embodied ‘social present’ by the statistical significance of such associations, finding a window of roughly 5.7 seconds in conversing dyads.We discuss that temporal scales of nowness may be modifiable, e.g., by mindfulness. This yields promising goals for future research on timing in the clinical context: psychotherapeutic techniques may alter binding processes, hence the subjective present of individuals, and may affect the social present in therapeutic interactions.

Designing a Computer Vision System for Underwater Robotic Interventions

This thesis deals with the challenging problem of designing systems able to perceive objects in underwater environments. In the last few decades research activities in robotics have advanced the state of art regarding intervention capabilities of autonomous systems. State of art in fields such as localization and navigation, real time perception and cognition, safe action and manipulation capabilities, applied to ground environments (both indoor and outdoor) has now reached such a readiness level that it allows high level autonomous operations. On the opposite side, the underwater environment remains a very difficult one for autonomous robots. Water influences the mechanical and electrical design of systems, interferes with sensors by limiting their capabilities, heavily impacts on data transmissions, and generally requires systems with low power consumption in order to enable reasonable mission duration. Interest in underwater applications is driven by needs of exploring and intervening in environments in which human capabilities are very limited. Nowadays, most underwater field operations are carried out by manned or remotely operated vehicles, deployed for explorations and limited intervention missions. Manned vehicles, directly on-board controlled, expose human operators to risks related to the stay in field of the mission, within a hostile environment. Remotely Operated Vehicles (ROV) currently represent the most advanced technology for underwater intervention services available on the market. These vehicles can be remotely operated for long time but they need support from an oceanographic vessel with multiple teams of highly specialized pilots. Vehicles equipped with multiple state-of-art sensors and capable to autonomously plan missions have been deployed in the last ten years and exploited as observers for underwater fauna, seabed, ship wrecks, and so on. On the other hand, underwater operations like object recovery and equipment maintenance are still challenging tasks to be conducted without human supervision since they require object perception and localization with much higher accuracy and robustness, to a degree seldom available in Autonomous Underwater Vehicles (AUV). This thesis reports the study, from design to deployment and evaluation, of a general purpose and configurable platform dedicated to stereo-vision perception in underwater environments. Several aspects related to the peculiar environment characteristics have been taken into account during all stages of system design and evaluation: depth of operation and light conditions, together with water turbidity and external weather, heavily impact on perception capabilities. The vision platform proposed in this work is a modular system comprising off-the-shelf components for both the imaging sensors and the computational unit, linked by a high performance ethernet network bus. The adopted design philosophy aims at achieving high flexibility in terms of feasible perception applications, that should not be as limited as in case of a special-purpose and dedicated hardware. Flexibility is required by the variability of underwater environments, with water conditions ranging from clear to turbid, light backscattering varying with daylight and depth, strong color distortion, and other environmental factors. Furthermore, the proposed modular design ensures an easier maintenance and update of the system over time. Performance of the proposed system, in terms of perception capabilities, has been evaluated in several underwater contexts taking advantage of the opportunity offered by the MARIS national project. Design issues like energy power consumption, heat dissipation and network capabilities have been evaluated in different scenarios. Finally, real-world experiments, conducted in multiple and variable underwater contexts, including open sea waters, have led to the collection of several datasets that have been publicly released to the scientific community. The vision system has been integrated in a state of the art AUV equipped with a robotic arm and gripper, and has been exploited in the robot control loop to successfully perform underwater grasping operations.

CORRELAÇÕES ENTRE PERCEPÇÃO DA PASSAGEM DO TEMPO, ATENÇÃO DIFUSA E ANSIEDADE

O presente estudo teve como objetivo avaliar aspectos psicofisiológicos da ansiedade em particular a atenção e a percepção da passagem do tempo. Foi aplicada a escala psicométrica de ansiedade do IDATE em 180 alunos do curso de Educação Física da Universidade de São Paulo em sala de aula. Foram selecionados 15 voluntários mais ansiosos e 15 menos ansiosos foi considerado o IDATE traço por apresentar características mais constantes da ansiedade. O experimento 1 foi a tarefa de Tempo Espontâneo onde os participantes deviam bater o dedo no botão A do joystick da forma mais regular e precisa possível por um minuto. Já no experimento 2 os participantes foram orientados a responder o mais rápido possível ao surgimento do estimulo (ponto branco 0,4 grau) com uma luminância de 80 cd/m contra um fundo cinza pressionando o botão A do joystick com qualquer dedo da mão dominante (TRS). Os estímulos eram apresentados randomicamente por 82 posições diferentes na tela do computador. Após tratamento dos dados e analise estatística, o estudo de caráter geral e exploratório apresentado aqui mostra tendências, mas não correlações significativas entre as medidas. Alguns dados, no entanto, chamam a atenção e devem ser considerados no planejamento de experimentos futuros.

A neuromodulação do córtex pré-frontal dorsolateral na percepção de tempo em contexto neutro ou emocionalmente ativo

The time perception is critical for environmental adaptation in humans and other species. The temporal processing, has evolved through different neural systems, each responsible for processing different time scales. Among the most studied scales is that spans the arrangement of seconds to minutes. Evidence suggests that the dorsolateral prefrontal (DLPFC) cortex has relationship with the time perception scale of seconds. However, it is unclear whether the deficit of time perception in patients with brain injuries or even "reversible lesions" caused by transcranial magnetic stimulation (TMS) in this region, whether by disruption of other cognitive processes (such as attention and working memory) or the time perception itself. Studies also link the region of DLPFC in emotional regulation and specifically the judgment and emotional anticipation. Given this, our objective was to study the role of the dorsolateral prefrontal cortex in the time perception intervals of active and emotionally neutral stimuli, from the effects of cortical modulation by transcranial direct current stimulation (tDCS), through the cortical excitation (anodic current), inhibition (cathode current) and control (sham) using the ranges of 4 and 8 seconds. Our results showed that there is an underestimation when the picture was presented by 8 seconds, with the anodic current in the right DLPFC, there is an underestimation and with cathodic current in the left DLPFC, there is an overestimation of the time reproduction with neutral ones. The cathodic current over the left DLPFC leads to an inverse effect of neutral ones, an underestimation of time with negative pictures. Positive or negative pictures improved estimates for 8 second and positive pictures inhibited the effect of tDCS in DLPFC in estimating time to 4 seconds. With this work, we conclude that the DLPFC plays a key role in the o time perception and largely corresponds to the stages of memory and decision on the internal clock model. The left hemisphere participates in the perception of time in both active and emotionally neutral contexts, and we can conclude that the ETCC and an effective method to study the cortical functions in the time perception in terms of cause and effect.

Contributions of Dorsal/Ventral Hippocampus and Dorsolateral/Dorsomedial Striatum to Interval Timing

Humans and animals have remarkable capabilities in keeping time and using time as a guide to orient their learning and decision making. Psychophysical models of timing and time perception have been proposed for decades and have received behavioral, anatomical and pharmacological data support. However, despite numerous studies that aimed at delineating the neural underpinnings of interval timing, a complete picture of the neurobiological network of timing in the seconds-to-minutes range remains elusive. Based on classical interval timing protocols and proposing a Timing, Immersive Memory and Emotional Regulation (TIMER) test battery, the author investigates the contributions of the dorsal and ventral hippocampus as well as the dorsolateral and the dorsomedial striatum to interval timing by comparing timing performances in mice after they received cytotoxic lesions in the corresponding brain regions. On the other hand, a timing-based theoretical framework for the emergence of conscious experience that is closely related to the function of the claustrum is proposed so as to serve both biological guidance and the research and evolution of “strong” artificial intelligence. Finally, a new “Double Saturation Model of Interval Timing” that integrates the direct- and indirect- pathways of striatum is proposed to explain the set of empirical findings.

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.

Monitoring the Time Course of Perception without Awareness: A Comparison of Mirror Masked Words and Nonwords

Mirror masked words are embedded into a context that makes them appear as senseless patterns or as strings of unfamiliar letters. Thus, mirror masked words can be shown for several hundreds of milliseconds without being recognised as words. We sought to further investigate effects of nonsconscious reading by monitoring event-related brain potentials (ERPs) while participants observed mirror masked letter strings. ERPs were recorded while participants observed mirror masked words and nonwords. Data of 15 participants was segmented into periods of quasi-stable field topography (microstates). Microstates for masked words and nonwords were compared using randomization tests, statistical parametric scalp maps and Low Resolution Electromagnetic Tomography (LORETA). ERPs to masked words and nonwords showed significant topographic differences between 136 and 256 ms, indicating that stimuli were nonconsciously discriminated. A LORETA model localised sources of activation discriminating between masked words and nonwords in left operculum, the right superior parietal lobe and right superior temporal gyrus indicating higher current density for nonwords than for words in these areas. ERPs of mirror masked stimuli can indicate unconscious discrimination even in cases where behavioural priming is unreliable. This approach might be useful for investigating differences in early, nonconscious stages of word perception.

Older driver perception-reaction time for intersection sight distance and object detection.

"January 1995."

On the perception of small differences, with special reference to the extent, force and time of movement,

Mode of access: Internet.