This thesis examines how the objects that we visually perceive in the world are coupled to the actions that we make towards them. For example, a whole hand grasp might be coupled with an object like an apple, but not with an object like a pea. It has been claimed that the coupling of what we see and what we do is not simply associative, but is fundamental to the way the brain represents visual objects. More than association, it is thought that when an object is seen (even if there is no intention to interact with it), there is a partial and automatic activation of the networks in the brain that plan actions (such as reaches and grasps). The central aim of this thesis was to investigate how specific these partial action plans might be, and how specific the properties of objects that automatically activate them might be. In acknowledging that perception and action are dynamically intertwining processes (such that in catching a butterfly the eye and the hand cooperate with a fluid and seamless efficiency), it was supposed that these couplings of perception and action in the brain might be loosely constrained. That is, they should not be rigidly prescribed (such that a highly specific action is always and only coupled with a specific object property) but they should instead involve fairly general components of actions that can adapt to different situations. The experimental work examined the automatic coupling of simplistic left and right actions (e.g. key presses) to pictures of oriented objects. Typically a picture of an object was shown and the viewer responded as fast as possible to some object property that was not associated with action (such as its colour). Of interest was how the performance of these left or right responses related to the task irrelevant left or right orientation of the object. The coupling of a particular response to a particular orientation could be demonstrated by the response performance (speed and accuracy). The more tightly coupled a response was to a particular object orientation, the faster and more accurate it was. The results supported the idea of loosely constrained action plans. Thus it appeared that a range of different actions (even foot responses) could be coupled with an object's orientation. These actions were coupled by default to an object's X-Z orientation (e.g. orientation in the depth plane). In further reflecting a loosely constrained perception-action mechanism, these couplings were shown to change in different situations (e.g. when the object moved towards the viewer, or when a key press made the object move in a predictable way). It was concluded that the kinds of components of actions that are automatically activated when viewing an object are not very detailed or fixed, but are initially quite general and can change and become more specific when circumstances demand it.

The development of orienting object features during hand to mouth transport was studied in a group of infants between 6-12 months of age (N=60). The task was to bring a bottle to the mouth. The bottle was presented in six different orientations (up, down, toward, away, left, and right). To measure head movement, a 3D motion capture system (Qualisys) was used. The results revealed that older but not younger infants are able to plan actions based on the functional end of an object. Older infants take less time, are more successful at directing the nipple to the mouth, initially grasp the bottle in an efficient manner more frequently, and move the head less than younger infants. More broadly, the results offer insights into how infants become more efficient in feeding tasks as they get older. / 1 / Wendy P. Jung

We assessed age differences in the ability to resolve competition for figural status in stationary displays using small, enclosed, symmetrical silhouettes that participants classified as depicting "novel'' or "familiar'' shapes. The silhouettes were biased such that the inside was perceived as the shaped figure, and the outside was perceived as a shapeless ground. The critical manipulation was whether a portion of a meaningful object was suggested on the outside of the border of some of the novel silhouettes but not others M(+)Ground and M-Ground novel silhouettes, respectively). This manipulation was intended to induce greater inhibitory competition for figural status from the groundside in M(+)Ground silhouettes than M(-)Ground silhouettes. In previous studies, young adults classified M(+)Ground silhouettes as "novel'' faster than M(-)Ground silhouettes (Trujillo, Allen, Schnyer, & Peterson, 2010), suggesting that young adults may recruit more inhibition to resolve figure-ground when there is more competition. We replicated this effect with young adults in the present study, but older adults showed the opposite pattern and were less accurate in classifying M(+)Ground than M(-)Ground silhouettes. These results extend the evidence for inhibitory deficits in older adults to figure assignment in stationary displays. The (M(+)Ground - M(-)Ground) RT differences were evident in observers' longest responses, consistent with the hypothesis that inhibitory deficits are evident when the need for inhibition is substantial.

There is a large gap between the visual capabilities of biological organisms and visual capabilities of autonomous robots. Even the most simple of flying insects is able to fly within complex environments, locate food, avoid obstacles and elude predators with seeming ease. This stands in stark contrast to even the most advanced of modern ground based or flying autonomous robots, which are only capable of autonomous navigation within simple environments and will fail spectacularly if the expected environment is modified even slightly. This dissertation provides a narrative of the author's graduate research into biologically inspired algorithms for visual perception and navigation with autonomous robotics applications. This research led to several novel algorithms and neural network implementations, which provide improved capabilities of visual sensation with exceedingly light computational requirements. A new computationally-minimal approach to visual motion detection was developed and demonstrated to provide obstacle avoidance without the need for directional specificity. In addition, a novel method of calculating sparse range estimates to visual object boundaries was demonstrated for localization, navigation and mapping using one-dimensional image arrays. Lastly, an assembly of recurrent inhibitory neural networks was developed to provide multiple concurrent object detection, visual feature binding, and internal neural representation of visual objects. These algorithms are promising avenues for future research and are likely to lead to more general, robust and computationally minimal systems of passive visual sensation for a wide variety of autonomous robotics applications.

Evidence suggests that high-level feedback plays an important role in visual perception by shaping the response in lower cortical levels (Sillito et al. 2006, Angelucci and Bullier 2003, Bullier 2001, Harrison et al. 2007). A notable example of this is reflected by the retinotopic activation of V1 and V2 neurons in response to illusory contours, such as Kanizsa figures, which has been reported in numerous studies (Maertens et al. 2008, Seghier and Vuilleumier 2006, Halgren et al. 2003, Lee 2003, Lee and Nguyen 2001). The illusory contour activity emerges first in lateral occipital cortex (LOC), then in V2 and finally in V1, strongly suggesting that the response is driven by feedback connections. Generative models and Bayesian belief propagation have been suggested to provide a theoretical framework that can account for feedback connectivity, explain psychophysical and physiological results, and map well onto the hierarchical distributed cortical connectivity (Friston and Kiebel 2009, Dayan et al. 1995, Knill and Richards 1996, Geisler and Kersten 2002, Yuille and Kersten 2006, Deneve 2008a, George and Hawkins 2009, Lee and Mumford 2003, Rao 2006, Litvak and Ullman 2009, Steimer et al. 2009). The present study explores the role of feedback in object perception, taking as a starting point the HMAX model, a biologically inspired hierarchical model of object recognition (Riesenhuber and Poggio 1999, Serre et al. 2007b), and extending it to include feedback connectivity. A Bayesian network that captures the structure and properties of the HMAX model is developed, replacing the classical deterministic view with a probabilistic interpretation. The proposed model approximates the selectivity and invariance operations of the HMAX model using the belief propagation algorithm. Hence, the model not only achieves successful feedforward recognition invariant to position and size, but is also able to reproduce modulatory effects of higher-level feedback, such as illusory contour completion, attention and mental imagery. Overall, the model provides a biophysiologically plausible interpretation, based on state-of-theart probabilistic approaches and supported by current experimental evidence, of the interaction between top-down global feedback and bottom-up local evidence in the context of hierarchical object perception.

All plane curves can be described at an abstract level by a sequence of five primitive elemental shapes, called "condons", which capture the sequential relations between the singular points of curvature. The condon description provides a basis for enumerating all smooth 2D curves. Let each of these smooth plane be considered as the si lhouette of an opaque 3D object. Clearly an in finity of 3D objects can generate any one of ou r "condon" silhouettes. How then can we p redict which 3D object corresponds to a g iven 2D silhouette? To restrict the infinity of choices, we impose three mathematical properties of smooth surfaces plus one simple viewing constraint. The constraint is an extension of the notion of general position, and seems to drive our preferred inferences of 3D shapes, given only the 2D contour.

Object perception is necessary to our understanding of the visual world, yet its neural mechanism remains poorly understood. The goal of this dissertation is to shed light on this mechanism. Current computational models of object perception suggest that regions on opposite sides of a shared border compete, with the winner perceived as the shaped object and the loser as its locally shapeless background (or ground). Recent behavioral work indicates that the result of this competition is suppression of the ground at the level of object shape--a finding not predicted by models. Here, I present three studies that extend this previous research on ground suppression as a mechanism by which object perception is accomplished. I first show that the amount of suppression applied to the ground depends on the amount of competition for object status (Salvagio, Cacciamani, & Peterson, 2012). I then provide the first neural evidence of ground suppression from shape-level competition at both high and low levels of the visual hierarchy, with the latter arising from top-down feedback (Cacciamani, Scalf, & Peterson, submitted). Finally, I show that semantic information pertaining to the ground is accessed prior to the assignment of object status, but unlike shape information, is not suppressed (Cacciamani, Mojica, Sanguinetti, & Peterson, 2014). Together, the three studies that comprise this dissertation demonstrate that ground suppression arising from shape-level competition underlies object perception. This research contradicts traditional theories stating that objects are processed unidirectionally through the visual system in a single feedforward pass; instead, it supports theories of object perception entailing dynamical feedforward and feedback processes.

The perirhinal cortex (PRC) is a medial temporal lobe (MTL) structure known to be involved in assessing whether an object is familiar (i.e., meaningful) or novel. Recent evidence shows that the PRC is sensitive to the familiarity of both whole object configurations and their parts, and suggests the PRC may modulate part familiarity responses in V2. Here, using functional magnetic resonance imaging (fMRI), we investigated age-related decline in the PRC's sensitivity to part/configuration familiarity and assessed its functional connectivity to visual cortex in young and older adults. Participants categorized peripherally presented silhouettes as familiar ("real-world") or novel. Part/configuration familiarity was manipulated via three silhouette configurations: Familiar (parts/configurations familiar), Control Novel (parts/configurations novel), and Part-Rearranged Novel (parts familiar, configurations novel). "Real-world" judgments were less accurate than "novel" judgments, although accuracy did not differ between age groups. The fMRI data revealed differential neural activity, however: In young adults, a linear pattern of activation was observed in left hemisphere (LH) PRC, with Familiar > Control Novel > Part-Rearranged Novel. Older adults did not show this pattern, indicating age-related decline in the PRC's sensitivity to part/configuration familiarity. A functional connectivity analysis revealed a significant coupling between the PRC and V2 in the LH in young adults only. Older adults showed a linear pattern of activation in the temporopolar cortex (TPC), but no evidence of TPC-V2 connectivity. This is the first study to demonstrate age-related decline in the PRC's representations of part/configuration familiarity and its covariance with visual cortex.

La précision en dessin a été considérablement étudiée chez l'enfant, mais la raison pour laquelle certains adultes sont bien plus précis que d'autres à copier des objets ou des scènes demeure un mystère. Un facteur possible serait l'entrainement : les artistes passent des milliers d'heures à faire des dessins. Le but de cette thèse a été d'explorer dans quelle mesure cet entrainement intensif a pu affecter certains processus de la vision et de la mémoire visuelle. Dans une série d'études, nous avons tout d'abord démontré que l'expertise en dessin n'est pas liée à une perception plus véridique du monde. En effet, les artistes professionnels et les étudiants en Art que nous avons testé n'étaient pas davantage capables de défaire les mécanismes perceptifs automatiques qui corrigent d'ordinaire les effets dus au contexte visuel. Ils étaient autant affectés par les constances visuelles que les novices. Ceci suggère qu'un entrainement en dessin ne pourrait pas affecter des mécanismes perceptifs déjà bien établis, mais plutôt des processus de plus haut ordre, tels que l'analyse visuelle de structure d'objets. Dans deux études, nous avons ensuite cherché à déterminer comment les dessinateurs encodent et intègrent les informations structurelles lorsqu'ils analysent un objet pour le dessiner. Tout d'abord, afin de tester si les artistes avaient une meilleure représentation de formes complexes, nous avons élaboré une tâche de fenêtre contingente dans laquelle les participants devaient classer un objet comme structurellement possible ou impossible alors qu'ils ne pouvaient voir qu'une portion de l'objet centrée sur la position du regard. Les experts étaient capables de faire cette tâche avec de plus petites portions de l'objet. La compétence en dessin serait ainsi liée à la capacité d'intégrer des échantillons d'informations extraits lors de chaque fixation en une représentation interne plus robuste. Nous avons ensuite voulu savoir si la précision en dessin pouvait aussi être liée à l'efficacité de l'encodage des informations structurelles à partir d'une seule fixation (sans mouvements oculaires autorisés), avec l'objet centré soit sur la position de la fixation ou en périphérie visuelle. Nous avons trouvé que les sujets entrainés étaient capables de discriminer des objets impossibles d'objets possibles avec des durées de présentation plus courtes, que ce soit en vision centrale ou périphérique. Enfin, nous avons étudié le rôle de la mémoire visuelle pendant le processus de dessin et cherché à déterminer si les dessinateurs avaient une représentation plus précise de la position des traits de l'objet. Pour cela, nous avons développé une expérience couplant une tâche de dessin sur tablette graphique et une tâche de détection de changement durant laquelle les participants devaient copier une figure sur une tablette graphique. Tout au long du processus de copie, des changements pouvaient intervenir à la fois sur la figure originale et sur la copie, et les participants devaient corriger tout changement détecté, (la figure et le dessin n'étaient visibles qu'en alternance). Nos résultats ont montré que tous nos participants détectaient mieux les changements présents dans la figure originale que dans leur propre dessin. De plus, les experts en dessin était bien meilleurs à détecter les changements, mais seulement lorsque le dessin était impliqué (contrasté avec une simple tâche de détection de changement sans dessin). Pris ensembles, ces résultats démontrent qu'un entrainement intensif en dessin peut affecter des mécanismes perceptifs de haut niveau ainsi que des mécanismes de mémoire visuelle, et non les mécanismes perceptifs basiques déjà bien établis par la longue expérience perceptive que nous partageons tous. / Drawing accuracy has been extensively studied in children, but very little is known of what would make some adults more accurate in copying objects or scenes than many others. One factor may simply be practice: artists have often spent thousands of hours making drawings. The focus of this thesis has been to explore how this intensive practice has affected visual and memory processes. In a series of studies, we first demonstrated that drawing expertise does not relate to a more veridical perception of the world: professional artists and art students were no better than novices at seeing scenes accurately - at undoing the automatic perceptual mechanisms that ordinarily correct for visual context like shadows and depth (visual constancies). This suggests that intensive training in drawing may not affect already well-established perceptual mechanisms, but might affect higher-order processes such as visual analysis of object structure. In a number of studies, we next investigated how trained draftspersons visually encode and integrate structural information when analyzing an object. First, to test whether artists had a more advanced ability to represent complex shapes, we designed a gaze-contingent moving window task where participants had to classify an object as structurally possible or impossible, while only being able to see a portion of the object centered on the gaze position. Experts were able to perform this task with smaller samples of the object. This result suggests that skill in drawing relates to the ability to integrate local samples from each fixation into a more robust internal representation. We then asked whether drawing accuracy could also be related to the encoding efficiency of structural information from a single fixation (no eye movements allowed), with the test object centered at fixation or located in peripheral vision. In this case, we found that experts could discriminate possible vs impossible objects with shorter presentation durations and this was true whether the object was presented at fixation or in the periphery. Finally, we investigated the role of visual memory during the drawing process and whether more skilled participants have a better representation of feature locations. To do so, we designed an interactive pen tablet experiment coupled with a change detection task where participants had to copy a figure on a pen tablet. Throughout the copying process, changes could occur in both the original figure and the copy and participants had to correct any changes they noticed (the figure and the drawing were visible in alternation). We found that all participants detected changes better when they occurred in the original than in their own drawing. Moreover, experts were better at detecting changes, but only when drawing was involved (contrasted with a simple change detection task without drawing). Taken together these results demonstrate that intensive training in drawing affects higher-order perceptual and visual memory mechanisms but not basic perceptual mechanisms that already well grounded on the life-long perceptual experiences that we all share.

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