Les recherches récentes en Neurosciences Affectives apportent des arguments convaincants en faveur du rôle des émotions dans la régulation de nombreux processus sensorimoteurs et cognitifs ayant un fort impact sur la santé mentale et physique.Au cours d’une série d’expériences utilisant des méthodes neuromagnétiques, neurosomatiques et comportementales, nous avons exploré l’impact cérébral, corporel et subjectif de l’information émotionnelle fournie par l'environnement visuel. Dans un premier temps, et pour la première fois en neurosciences, nous avons associé l’enregistrement concomitant de la magnétoencéphalographie (MEG), méthode fonctionnelle permettant une analyse spatiotemporelle fine de l’activité cérébrale, et de l’activité électrodermale, marqueur neurovégétatif robuste de l’activation émotionnelle, lors de la projection de scènes naturelles. Ainsi, en vision centrale, nous avons pu démontrer l’existence d’un lien entre le traitement cérébral précoce des signaux visuels à contenu émotionnel et son impact sur le corps (étude 1); de plus, nous avons déterminé la persistance d’un tel impact en vision périphérique, ce qui a permis d’obtenir des résultats inédits sur un engagement hémisphérique différentiel dans le codage des émotions (étude 2). Dans un second temps, nous avons associé la MEG à une procédure comportementale qui nous a permis d’identifier des effets d’interférence, induits par les stimulations émotionnelles périphériques, dans le codage neurocomportemental des informations présentées au centre du champ visuel (étude 3). Un tel rôle interférant de la valeur émotionnelle pourrait alors aboutir à des inadaptations comportementales. Nous avons donc comparé la performance d’individus sains, anxieux ou présentant une tendance dépressive dans ce paradigme et identifié des patterns hémisphériques asymétriques du codage de l’interférence émotionnelle selon ces variables psychophysiologiques (étude 4).Les recherches présentées dans cette Thèse, à partir de méthodologies et de données neurophysiologiques et comportementales nouvelles, ouvrent des perspectives innovantes sur la compréhension des mécanismes et troubles émotionnels, enjeu majeur de la santé mentale et de ses conséquences neurosomatiques. / Current research in Affective Neuroscience has provided convincing arguments sustaining the role of emotions in regulating many sensory-motor and cognitive processes which have a strong impact on the mental and physical health.In a series of experiments using neuromagnetic, neurosomatic and behavioral methods, we explored the brain-body and the subjective impact of emotional information provided by visual environment. In a first step, and for the first time in neuroscience, we carried out simultaneous recordings of magnetoencephalography (MEG), a functional approach allowing a fine spatiotemporal analysis of brain activity, and electrodermal activity, a reliable autonomic marker of emotional activation, during the screening of natural scenes. Thus, in central vision, we provided evidence of a link between early cerebral processing of emotionally-laden visual cues and its impact on the body (Study 1). In addition, we identified the persistence of such impact in peripheral vision, which yielded new findings on differential hemispheric involvement in the coding of emotions (study 2). In a second step, MEG recordings were conjugated with a behavioral procedure. This new protocol allowed us to identify interference effects, induced by peripheral emotional stimuli, on the neurobehavioral processing of information presented in the center of the visual field (Study 3). Such an interfering role of emotional value could then lead to behavioral maladjustments. We therefore compared the performance of healthy, anxious, or anxious-depressed individuals and identified asymmetrical hemispheric patterns of interference effects following anxious and depressive variables (study 4).The research presented in this thesis, using new neurophysiological and behavioral methodologies, brings innovative perspectives on understanding emotional mechanisms and affective disorders, a major challenge for mental health and its neurosomatic consequences.

No / Identifying a target is more difficult when distracters are present within a zone of interaction around the target. We investigated whether the spatial extent of the zone of interaction scales with the size of the target. Our target was a letter T in one-of-four orientations. Our distracters were four squared-thetas in one-of-two orientations, presented one in each of the four cardinal directions, equidistant from the target. Target-distracter separation was varied and the proportion of correct responses at each separation was determined. From these the extent of interaction was estimated. This procedure was repeated for different target sizes spread over a 5-fold range. In each case, the contrast of the target was adjusted so that its visibility was constant across target sizes. The experiment was performed in the luminance domain (grey targets on grey background) and in the chromatic domain (green target on equiluminant grey background). In the luminance domain, target size had only a small effect on the extent of interaction; these interactions did not scale with target size. The extents of interaction for chromatic stimuli were similar to those for luminance stimuli. For a fixed target visibility, decreasing the duration of the stimulus resulted in an increase in the extent of interaction. The relevance of our findings is discussed with regard to a variety of proposed explanations for crowding. Our results are consistent with an attention-based explanation for crowding.

Master of Science / Psychological Sciences / Lester C. Loschky / A fundamental issue in visual attention is the relationship between the useful field of view (UFOV), the region of visual space where information is encoded within a single fixation, and eccentricity. A common assumption is that impairing attentional resources reduces the size of the UFOV (i.e. “tunnel vision”). However, most research has not accounted for eccentricity-dependent changes in spatial resolution, potentially conflating fixed visual properties with flexible changes in visual attention. Williams (1988; 1989) argued that foveal loads are necessary to reduce the size of the UFOV, producing "tunnel vision". Without a foveal load, it is argued that the attentional decrement is constant across the visual field (i.e. "general interference"). However, other research asserts that auditory working memory (WM) loads produce tunnel vision. To date, foveal versus auditory WM loads have not been compared to determine if they differentially change the size of the UFOV. In two experiments, we tested the effects of a foveal (rotated L vs. T discrimination) task, and an auditory WM (N-back) task on an extrafoveal (Gabor) discrimination task. Gabor patches were scaled for size and processing time to produce equal performance across the visual field under single task conditions, thus removing the confound of eccentricity-dependent differences in visual sensitivity. The results showed that while both foveal and auditory loads reduced Gabor orientation sensitivity, only the foveal load interacted with retinal eccentricity to produce tunnel vision, clearly demonstrating task-specific changes to the form of the UFOV. This has theoretical implications for understanding the UFOV.

Vision provides relevant information for safe locomotion in a variety of environments. During stair locomotion visual information may be important to detect step boundaries, transitions between ground level and stairs, handrail location, and potential hazards. Although there is a large body of literature on the role of vision during locomotion there is relatively little focused on how visual information is used during stair walking. Stairs are related to a significant number of accidents in daily living, and many of these accidents are attributed to visual factors. Therefore, understanding the role of vision during stair walking could provide insight into the mechanisms involved in stair accidents. The purpose of this thesis was to investigate the properties of the visual input used to guide locomotion on stairs. Study 1 was design to describe the gaze patterns during stair locomotion with a specific focus on transitions and handrails. Study 2 investigated the effects of performing concurrent visual and non-visual tasks on walking performance and associated gaze behaviour during stair ascent. Study 3 explored the role of peripheral visual information during visual and non-visual dual tasking. Finally, Study 4 investigated the effects of restricting the lower peripheral visual field to walk on stairs. Studies relied on the measurement in health young adults of: gaze behaviour using an eye tracker, temporal characteristics of walking using foot switches, and reaction time and errors of dual task performance. Overall, the findings of these studies highlight the importance of the lower visual field in guiding stair locomotion and the specific importance for stair transitions. Moreover, foveal vision is not specifically critical to detecting handrails or steps. Results are interpreted in the light of the specialization of the dorsal ventral stream in processing peripheral visual field information. Findings of this thesis provide basic understanding on the role of vision for stair navigation with potential applications in stair-related accident prevention programs and stair design.

Vision provides relevant information for safe locomotion in a variety of environments. During stair locomotion visual information may be important to detect step boundaries, transitions between ground level and stairs, handrail location, and potential hazards. Although there is a large body of literature on the role of vision during locomotion there is relatively little focused on how visual information is used during stair walking. Stairs are related to a significant number of accidents in daily living, and many of these accidents are attributed to visual factors. Therefore, understanding the role of vision during stair walking could provide insight into the mechanisms involved in stair accidents. The purpose of this thesis was to investigate the properties of the visual input used to guide locomotion on stairs. Study 1 was design to describe the gaze patterns during stair locomotion with a specific focus on transitions and handrails. Study 2 investigated the effects of performing concurrent visual and non-visual tasks on walking performance and associated gaze behaviour during stair ascent. Study 3 explored the role of peripheral visual information during visual and non-visual dual tasking. Finally, Study 4 investigated the effects of restricting the lower peripheral visual field to walk on stairs. Studies relied on the measurement in health young adults of: gaze behaviour using an eye tracker, temporal characteristics of walking using foot switches, and reaction time and errors of dual task performance. Overall, the findings of these studies highlight the importance of the lower visual field in guiding stair locomotion and the specific importance for stair transitions. Moreover, foveal vision is not specifically critical to detecting handrails or steps. Results are interpreted in the light of the specialization of the dorsal ventral stream in processing peripheral visual field information. Findings of this thesis provide basic understanding on the role of vision for stair navigation with potential applications in stair-related accident prevention programs and stair design.

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed March 3, 2009). Graduate School of Arts and Sciences, Dept. of Psychology. Includes bibliographical references (p. [80]-91).

Thesis (M.S)--Ohio University, March, 2005. / Includes bibliographical references (p. 94-96)

Thesis (M.S)--Ohio University, March, 2005. / Title from PDF t.p. Includes bibliographical references (p. 94-96)

A practical model is proposed for predicting the detectability of targets at arbitrary locations in the visual field, in arbitrary gray-scale backgrounds, and under photopic viewing conditions. The major factors incorporated into the model include: (i) the optical point spread function of the eye, (ii) local luminance gain control (Weber's law), (iii) the sampling array of retinal ganglion cells, (iv) orientation and spatial-frequency dependent contrast masking, (iv) broadband contrast masking, (vi) and efficient response pooling. The model is tested against previously reported threshold measurements on uniform backgrounds (the ModelFest data set and data from Foley et al. 2007), and against new measurements reported here for several ModelFest targets presented on uniform, 1/f noise, and natural backgrounds, at retinal eccentricities ranging from 0 to 10 deg. Although the model has few free parameters, it is able to account quite well for all the threshold measurements. / text

Metamers of the ventral stream is a model which tries to describe what information we gather from our visual field. It have previously only been tested on static images. This thesis have continued the research and applied it to dynamic images in order to investigate if the model can be seen as a functional representation of our visual field. The results show that the model, at this stage, can not be seen as a fully functional representation of the visual field, but it can be used to determine the detectability of objects in the periphery. It also shows that what we humans perceive as motion is, at least to some extent, merely a change of the statistics in our visual field.