Orthographically-projected biological motion point-light displays generally contain no information about their in-depth orientation, yet observers consistently prefer the facing-the-viewer (FTV) interpretation (Vanrie, Dekeyser and Verfaillie, 2004). This bias has been attributed to the social relevance of such stimuli (Brooks et al., 2008) although local stimulus properties appear to influence the bias (Schouten, Troje and Verfaillie, 2011). In the present study we investigated the cause of the FTV bias. In Experiment 1 we compared FTV bias for various configurations of stick-figures and depth ambiguous human silhouettes. The FTV bias was not present for silhouettes, but was strongly elicited for most stick-figures. We concluded that local attitude assignments for intrinsic structures of stick-figures are subject to inferences about the flexion of body surfaces, and that a visual bias that assumes surfaces to be convex drives the FTV bias. In Experiment 2 we manipulated silhouettes to permit local attitude assignments by using point-lights on emphasized flexion points. As predicted, the inclusion of intrinsic structures produced FTV bias for silhouettes. The results help to unify various findings regarding the FTV bias. We conclude that the FTV bias emerges during the 2 ½-D sketch stage of visual processing (Marr and Nishihara, 1978). / Thesis (Master, Psychology) -- Queen's University, 2013-08-08 19:06:06.84

<p>Interacting with the world is a two-step process of accurate sensing followed by coordinated movement. Optimization of biologically-inspired robotic systems benefits from the quantification and modeling of natural sensorimotor behavior, including the bottom-up circuits that mediate it and top-down cognitive influences that modulate it. A critical sensorimotor behavior in everyday life is the generation of rapid eye movements, called saccades. By making saccades 2-3 times/second, we scan visual scenes and integrate the incoming visual signals to construct an internal representation of what is around us. Much is still unknown about the neural processes that act on visual input and the nature of the resulting internal construct. To study this, we first created a model with architecture inspired by known visuomotor circuits in the brain. By training the model to achieve visuomotor stability while varying its visual and motor inputs, we found that it converged onto a solution that resembled and explained a dynamic neural process that had been documented electrophysiologically. Second, in a psychophysical experiment, we kept constant the visual stimuli and motor actions but manipulated the expectations of what subjects thought would happen. We found that visual perception systematically changes based on expectation, providing evidence for cognitive influences on visuomotor integration and continuity. Third, we expanded the work to whole-body orienting in an immersive virtual environment. While performing a marksmanship task, subjects learned to precisely intercept moving targets. Analysis and modeling of the dynamics of movement revealed mechanisms of learning in this realistic behavioral context. Taken together, the studies provide a link between the ensemble activity of neurons and perceptual experience, demonstrate that perception is a combination of incoming signals and prior beliefs, and move the field toward the study of perception-action cycles during natural human behavior.</p> / Dissertation

When primates make decisions about sensory signals, their choices are biased by the costs and benefits associated with different possible outcomes. However, much remains unknown about the neuronal mechanisms by which reward information is integrated into the perceptual decision-making process. I used electrophysiological, psychophysical and imaging techniques to explore the effect of reward on sensory representations, whilst humans and monkeys made perceptual judgements about structure-from-motion (SFM) stimuli. Electrical microstimulation of visual area V5/MT in the macaque monkey was used to bias per- ceptual judgements, under different available reward sizes for correct choices. The behavioural effect of microstimulation interacted with available reward, and, in the context of a drift diffu- sion model of decision-making, the results demonstrated that reward must influence sensory processing before visual signals and micro stimulation signals are accumulated in sensorimotor areas. In a parallel human psychophysics experiment, viewers made decisions about SFM stim- uti whilst their choices were biased towards one outcome or the other by unequal pay-offs. A full drift -diffusion model was fitted to human choice and reaction time data. There was a signif- icant effect of reward on model drift rate, a parameter known to be dependent upon evidence represented in sensory brain regions. A second set of experiments used magneto encephalography (MEG) to explore activity in visual , areas in human cortex and the effects of reward. Brain responses to retinotopic visual stimuli were localized with three different MEG source analysis methods, and localization accuracy was evaluated by comparison with fMRI maps obtained in the same individuals. The results demon- strated that the beamformer and minimum norm estimate (MNE) methods were most suitable for investigating early visual activity with MEG. Human brain activity was then recorded with MEG whilst viewers made perceptual judgements about SFM stimuli, under unequal pay-offs. The results revealed an effect of reward size on early MEG responses in the region of the occipi- tal cortex and visual precuneus. Taken together, the experiments presented in this thesis provide consistent evidence that in- formation about reward can influence the processing of sensory information during perceptual decisions.

This study set out to investigate the visuo-spatial component of Baddeley and Hitch's (1974) Working Memory framework. The development of our understanding of this component has been less dramatic than that of its verbal counterpart, the Articulatory Loop. The primary reason for this can be said to be the lack of techniques for investigation (Logie, 1986). This thesis presents one attempt to try to explore the nature of this code and to reveal possible new techniques of investigation. The following are three possible areas of investigation : 1. Is the system spatially or visually based? 2. Does movement have a role in the system? 3. How is information stored? The latter two issues are investigated here. Experiments 1-4 set out to explore the possibility that movement may be involved in the code. These experiments supported the idea that movement has a role to play in spatial coding and more specifically demonstrated that arm movements which are not compatible with the presentation of spatial material can cause disruption. In addition it was shown that when movement identical to that involved in presentation is encouraged at recall subjects show marked improvement in performance. Together these results very strongly suggest that movement should be given prominent reference in the definition of spatial coding and in the description of the visuo-spatial slave system. Another development that came out of these experiments relates to the lack of investigative techniques in the field of visuo-spatial short term memory. The fact that movement has been shown to be important suggests that techniques employed to investigate kinaesthetic memory will aid us in exploring visuo-spatial coding. The second issue in this thesis explored further the nature of the internal code. Research into the nature of coding in visuo-spatial memory had previously argued for the presence of a sequential component. Experiments 1-4 in this thesis had shown that movement had an important role to play in coding. The fact that movement by its very nature would appear to be sequential suggested that there was a strong sequential element in coding within visuo-spatial memory. However, concern was expressed that the materials and presentation format used may have led to sequential coding. This was first explored in experiments 5-8. The results supported the view that the material and presentation format used had led to sequential coding. This was further explored by Experiments 9 and 10 which illustrated that while it may be important under certain conditions, sequentiality is not always a dominant element in coding within the Visuo-Spatial Sketch Pad. This thesis has explored two of the central issues currently interesting theorists of Working Memory and has put forward suggestions for techniques which may in the future help us to advance our knowledge of the visuo-spatial component of the Working Memory framework.

M.A.University of the Witwatersrand, Faculty of Humanities (Fine Arts), 2012 / The ‘Bath Series’ (1983-1988) of Jasper Johns shows the artist’s meditation on his oeuvre of the past thirty years, and the examples of his previous works demonstrate his interest in instabilities of visual perception. The latter are activated when the viewer’s expectation to see conventional representational strategies are destabilized, and figure/ground pictorial space, particularly, becomes ambiguous. This first recorded academic study focusing exclusively on the series as a unit, discovers that figure/ground switching, an ‘Ur-Gestalt’ (Gandelman 1989: 209), appears to be a core energy motivating ambiguous pictorial space in Johns’ art, and constitutes the theoretical component of the research. The practical component is a site specific installation which shows some visual and verbal processes and meditates on the perpetual interaction between the eye and the mind, which is a fundamental concern of Johns (Varnedoe 1996b: 245, 257), as well as of myself. The work invites viewers to experience destabilized conventional visual perceptions and to explore, as Johns said, ‘something new’ (Varnedoe 1996a: 17).

Although it is well known that the pupil responds dynamically to changes in ambient light levels, the results from this dissertation show for the first time that the pupil also responds dynamically to changes in spatially distributed attention. Using a variety of orientating tasks, subjects alternated between focusing attention on a central stimulus and spreading attention over a larger area. Fourier analysis of the fluctuating pupil diameter indicated that: 1) pupil diameter changed at the rate of attention variation, dilating with broadly spread attention and contracting with narrowly focused attention, and 2) pupillary differences required changes in attentional spread; there were no differences in pupil diameter between sustained broad and sustained spread attention. Given that broadly spread attention increases the relative activation of large receptive fields and narrowly focused attention increases the relative activation of small receptive fields (Balz & Hock, 1997), the results of this study indicate that these attentional effects on receptive field activation can be mediated by changes in pupil diameter. That is, under broad attention, the corresponding pupillary dilation observed would increase spherical aberration, blurring the image thereby reducing high spatial frequency information and decreasing the activation of relatively small cortical receptive fields compared to relatively large receptive fields. This increased perception of low spatial frequencies would be beneficial in cases where attention is spread over a large area. Alternatively, under narrow attention the resulting pupillary constriction reduces spherical aberration sharpening the image and preserving high spatial frequency information resulting in a relatively increased response of small receptive fields. / by Lori B. Daniels. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

It is well established that anticipation of the arrival of an expected stimulus is accompanied by rich ongoing oscillatory neurodynamics, which span and link large areas of cortex. An intriguing possibility is that these dynamic interactions may convey knowledge that is embodied by large-scale neurocognitive networks from higher level regions of multi-model cortex to lower level primary sensory areas. In the current study, using autoregressive spectral analysis, we establish that during the anticipatory phase of a visual discrimination task there are rich patterns of coherent interaction between various levels of the ventral visual hierarchy across the frequency spectrum of 8 - 90 Hz. Using spectral Granger causality we determined that a subset of these interactions carry beta frequency (14 - 30 Hz) top-down influences from higher level visual regions V4 and TEO to primary visual cortex. We investigated the functional significance of these top-down interactions by correlating the magnitude of the anticipatory signals with the amplitude of the visual evoked potential that was elicited by stimulus processing. We found that in one third of the extrastriate-striate pairs, tested in three monkeys, the amplitude of the visual evoked response is well predicted by the magnitude of pre-stimulus coherent top-down anticipatory influences. To investigate the dynamics of the coherent and topdown Granger causal interactions, we analyzed the relationship between coherence and top-down Granger causality with stimulus onset asynchrony. This analysis revealed that in an abundance of cases the magnitudes of the coherent interactions and top-down directional influences scaled with the length of time that had elapsed before stimulus onset. / Together these results reveal a complex network of coherent and top-down directional interactions that predict the amplitude of early components of the visual evoked potential in primary visual cortex and vary in strength on the basis of the length of the stimulus onset. / by Craig G. Richter. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Although some research has suggested that very young children are "immune" to functional fixedness (FF), other work has shown that young children form robust associations between objects and their prescribed functions. Across two studies, I investigated (a) the developmental trajectory of FF and (b) its relationship with executive function components (inhibitory control and working memory) in 3- to 6-year old children. Both older and younger children experience FF, but older children use familiar tools more flexibly than younger children (3- and 4-year olds). Furthermore, inhibitory control was related to overcoming FF, indicating that it may be an important cognitive capacity for creative problem-solving. Finally, in a third study, children were instructed to use mental imagery to help them solve the functional fixedness problems. However, these instructions were ineffective at reducing FF compared to a control condition, underscoring the robust nature of object-function relationships in early childhood. / by Sarah R. Bidmead. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980. / Bibliography: leaf 35. / by Steven Yelick. / Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1980.

University of Macau / Faculty of Science and Technology. / Department of Electromechanical Engineering