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This thesis presents an empirical analysis of the depth cue of motion parallax. The history of research in this area is described and some recent computational models are outlined which show that parallax information can theoretically provide accurate information about the depth structure of the environment. In contrast to previous empirical work, which failed to demonstrate that motion parallax could be used effectively, the experiments reported in this thesis show that it can be an accurate source of information about depth structure. The characteristics of the processing underlying the use of motion parallax were investigated. Sensitivity to depth surfaces specified by relative motion was high, and it varied as a function of the spatial rate of change of depth. Moreover, the sensitivity function was similar to that measured for stereoscopic depth surfaces. The finding of close similarities between motion parallax and stereoscopic depth was a major theme of the thesis. Strong negative aftereffects followed prolonged viewing of depth surfaces specified by either cue and, in addition, large simultaneous contrast effects were also found. Here, the perceived depth of one area was affected by the depth of the surrounding area. These findings suggest that depth processing from both parallax and stereopsis involves extensive spatial interactions. A model of depth processing was suggested where the basic mechanisms had extended receptive fields which extracted changes in depth, specified either by relative motion or disparity, across local areas. The presence of anisotropies in the perception of depth surfaces showed that there was a differential sensitivity to particular local patterns of relative motion or disparity, which might be due to an asymmetric organisation within depth receptive fields. Finally, the motion parallax and stereoscopic depth processing systems were found to interact, indicating that information from the two sources might come together at some stage. Overall, the empirical findings emphasised the importance of extracting information about the local structure of depth surfaces rather than the depths of individual points.

An animal's own behaviour can give rise to sensory stimulation that is very similar to stimulation of completely external origin. Much of this self-induced stimulation has little informative value to the animal and may even interfere with the processing of externally-induced stimulation. A high-level association area in the temporal cortex of macaque (superior temporal polysensory area, STP) which has been shown to participate in the analysis of visual motion was targeted in a series of experiments in order to investigate whether this brain area discriminates externally- and self-induced stimulation in its visual motion processing. Earlier results in somatosensory processing within this same brain area provided grounds for this presumption The cells studied in here were sensitive to the presence of motion but showed no selectivity for the form of the stimulus. 25% of all visually responsive cells in area STP were classified as belonging to this class of cells. This group of cells was further categorized into unidirectional (39%), bidirectional (4%) and pandirectional (57%) cells. Tuning to direction varied in sharpness. For most cells the angular change in direction required to reduce response to half maximal was between 45 and 70 degrees. The optimal directions of cells appeared clustered around cartesian axes, (up/down, left/right and towards/away). The response latency varied between 35.0-126.4 ms (mean 90.9 ms). On average cell responses showed a transient burst of activity followed by a tonic discharge maintained for the duration of stimulation. 83% of the motion sensitive cells lacking form selectivity responded to any stimuli moved by the experimenter, but gave no response to the sight of the animal's own limb movements. The cells remained, however, responsive to external stimulation while the monkey's own hand was moving in view. Responses to self-induced movements were recovered if the monkey introduced a novel object in its hand into view. That the response discrimination between externally- and self-induced stimulation was not caused by differences in the visual appearance of the stimuli was confirmed in the second experiment where the monkey was trained to rotate a handle connected to a patterned cylinder in order to generate visual motion stimulation over a fixation point. 61% of the tested cells discriminated between pattern motion generated by the monkey and by the experimenter. It was shown that the monkey's motor activity as such (turning a handle without visible cylinder rotation) did not affect the cells' spontaneous activity. Some indication was received to suggest that the discriminative mechanism is using not only (motor) corollary discharges but also proprioceptive input. These results also gave evidence of the plasticity of discriminative processing in STP for the animal's life-time experiences. Finally, the cells were studied for their responsiveness for image motion resulting from movements of external objects and movements of the animal's body (self-motion). 84% of the cells responded only to visual object-motion and failed to respond to visual motion resulting from animal's self-motion. The experiments also revealed that area STP processes visual motion mostly in observer- relative terms, i.e. in reference to the perceiver itself. The results provide one explanation for the functional significance of the convergence of several modalities of sensory (and motor) input in the STP. It is suggested that area STP works as a "neural filter" to separate expected sensory consequences resulting from one's own actions from those that originate from the actions of other animals or environmental events.

Extracting a motion signal for a two-dimensional contour requires the human visual system to derive a velocity vector from the spatially limited receptive fields of motion sensitive cortical cells. An individual cell's response may not specify the contour's true velocity. Models of motion often combine the outputs of different classes of receptive fields to generate a reliable motion signal. Their efficacy was tested by comparing their predictions with human psychophysical performance. The perceived speed of co-linear inclined line segments in horizontal translation was subject to a bias in favour of the local components of the contour. Single tilted lines were also subject to a bias in perceived speed. Experiments investigated the effects of grouping, co-linearity, eccentricity, terminator proximity and stimulus uncertainty on perceived speed and clearly showed that the perceived velocity of line segments is not obtained by a simple averaging process of local velocity signals and veridical velocity signals of line terminators. Variation of the spatial position of terminators was sufficient to abolish the bias in perceived speed of horizontally drifting inclined lines. Neither "vector-average" nor "winner-take-all" rules are sufficient to account for this. The method of integration of one-dimensional components into two-dimensional plaid patterns was explored in two experiments recording thresholds for perceived rotation of drifting plaids. Type II plaids are not subject to the oblique effect found for rotation discrimination thresholds for type IS plaids. Plaid rotation induced by a speed change in one of the components showed that direction perception does not follow a strict interpretation of the "intersection of constraints rule". As current models of motion integration fail to provide a full account of the perceived speed and direction of two-dimensional patterns; higher-order attentional processes should be incorporated into models of motion perception.

In Experiments 1 to 8 an attempt was made to examine the nature of the displacements found in the traditional line bisection test when applied to normal (right-handed), as well as brain lesioned subjects. The problem with this test is that it invariably confounds perceptual and motor components which might both contribute to the observed errors. However, use of the 'landmark task' enables an examination of perceptual effects in isolation. It was found that five out of six neglect patients judged the left half-line of a centrally bisected line as shorter than the right half-line. Moreover, it was consistently shown that cueing strongly influenced judgements in normal and left and right hemisphere lesioned subjects (without neglect) in that it caused them to overestimate the cued part of the line. It was argued that the perception of relative size is subject to systematic distortion as a function of this selective attention within the visual field. Neglect patients may present an abnormal example of this attentionally- induced illusion in that their attentional resources may be abnormally biased towards the ipsilesional space. The result of this imbalance may be to cause, quite directly, a gross abnormality of size perception. Nonetheless one of the neglect patients did not show spatial misperception but spatially misdirected actions, in line with what has been described as directional hypokinesia. Experiments 9 to 12 were designed to demonstrate any possible contribution the right hemisphere might make to visuomotor control, but the data on normal subjects gave little indication of a specific right hemisphere involvement in such tasks. Neither use of a spatial bisection task, nor absence of visual feedback of the moving hand or arm seemed to produce left hand advantages on the dependent measures. On the other hand, RCVA patients proved to be impaired in their reaching behaviour in that they erred systematically to the right of the true target over all three spatial positions, in the absence of visual feedback. The bias was interpreted as a pure example of directional hypokinesia.

Experiments were conducted to examine the differential capabilities of the cerebral hemispheres for the visual perception of motion. Subjects were normal right handed adult male and female humans. Stimuli were viewed binocularly and responses were manual in all studies. Lateralized low contrast real motion was presented using random texture patterns. The task was to correctly detect the direction of motion. The outcome was a significant hemisphere x trials interaction. The right hemisphere improved significantly over trials while the left hemisphere did not. Using random texture patterns in which a small lateralized square was presented in apparent motion, hemispheric superiorities were found to depend on fairly basic stimulus parameters. For low contrast relatively long stimulus field durations, the right hemisphere was significantly superior. For higher contrast apparent motion stimuli with a "masking" ISI, the left hemisphere was significantly better at accurately detecting the direction of motion. V shaped stimuli may be presented in apparent motion so as to be seen as either moving within the stimulus plane, or rotating in depth outside it. The percentage of "space" (i.e., rotation) responses increases as the ISI is lengthened. The hemispheres did not differ significantly in their judgments of motion in depth, therefore, they appear to be employing identically calibrated detection mechanisms. However, female right hemisphere "space" responses remained constant over trials, while analogous male responses decreased linearly. Stimulus parameters which had been shown in earlier experiments to result in hemispheric differences were avoided, and subjects required to identify apparently moving shapes in a random texture background. No hemispheric differences were observed in this detection task. An additional finding was that female subjects tend to more frequently report that sub-vocal verbalization mediated their (manual) responses.

The preparation and initiation of movement has previously been described using a neural accumulation model; this model involves an increase of neural activation in the motor cortex (M1) from baseline to a subthreshold level following a warning signal, which is maintained until presentation of an imperative stimulus (IS). Activity then increases until reaching movement initiation threshold. This model predicts that variability in activation during preparation may influence reaction time (RT) and its variability. The purpose of this thesis project was to determine whether differences in RT/variability of RT during the completion of tasks with varying levels of complexity may be attributable to differences in neural excitability in M1. To test this prediction, transcranial magnetic stimulation (TMS) delivered concurrently with an IS was used to determine neural excitability for movements with different accuracy demands. It was hypothesized that higher accuracy demands would result in lowered amplitude and/or greater variability of neural activation, and consequently slower/more variable RT. Fifteen healthy participants completed a simple RT task involving a targeted wrist extension movement under three different accuracy conditions (easy, moderate, difficult). TMS was delivered concurrently with the IS on 50% of trials during each condition. While pilot testing showed RT differences between accuracy conditions (Appendix A), the data presented here failed to detect significant differences in RT latency (F(2, 28) = .074, p = .929) or variability (F(1.432, 20.053) = .633, p = .538) between conditions . Similarly, no difference in MEP amplitude was observed between difficulty conditions (F(2, 28) = 2.439, p = .106). However, a subset of participants (n = 7) did show significant RT increases between easy and hard conditions (t(6) = 2.531, p = .045), but this subset still failed to show differences in MEP amplitude (t(6) = 1.157, p = .291) or variability (t(6) = 1.545, p = .173), suggesting that preparatory levels at the IS may be similar for movements involving both high and low accuracy demands.

This thesis examines the policies of the socialist movement in the last two decades of the nineteenth century with regard to the education of children. This study is used to both reassess the nature of these education policies and to criticise the validity of the historiographical models of the movement employed by others. This study is thematic and examines the whole socialist movement of the period, rather than a party or an individual and as such draws out the common policies and positions shared across the movement. The most central of these was a belief that progress in what was called the 'moral' and the 'material' must occur simultaneously. Neither the ethical transformation of individuals, nor, the material reformation of society alone would give real progress. Children, for example, needed to be fed as well as educated if the socialist belief in the power of education and the innate goodness of humanity was to be realised. This belief in the unity of moral and material reform effected all socialist policies studied here, such as those towards the family, teachers, and the content of the curriculum. The socialist programme was also heavily centred on the direct democratic control of the education system, the ideal type of which actually existed in this period in the form of school boards. The socialist programme was thus not a utopian wish list but rather was capable of realisation through the forms of the state education machinery that were present in the period. It is argued in this thesis that the removal of this democratic machinery in 1902 crucially de-stabilised this unity of the ethical and the material and was one of the factors that led to the growth of state-centred and bureaucratic socialist solutions.

Resumo: O objetivo dessa tese foi avaliar os efeitos da intrusão ortodôntica no processo de reparação de lesão de furca grau III em cães, e da presença de fator de necrose tumoral alfa (TNFα) e/ou interleucina-1 beta (IL-1ß) na mecanoresposta de células com característica de osteócitos e osteoblastos in vitro. No estudo in vivo, lesões de furca grau III foram criadas em pré-molares inferiores de sete cães. Após 75 dias, as lesões foram aleatoriamente tratadas com cirurgia a retalho (OFD) associada ou não à regeneração tecidual guiada (GTR) e enxerto ósseo autógeno (BA). Após um mês, iniciou-se a intrusão ortodôntica (I) em parte dos dentes tratados pelas duas diferentes abordagens (grupos teste), por meio de ancoragem em miniimplantes. Os cães foram sacrificados após três meses de movimentação e um mês de contenção. Todas as lesões de furca grau III foram reduzidas para grau II ou I nos grupos teste. O mesmo foi observado em 50% das lesões nos grupos controle (sem movimentação). O nível de inserção clínico foi reduzido nos grupos teste, no final da contenção (p<0.01). O grupo OFD+I apresentou maior preenchimento ósseo que os demais grupos (p<0.05), demonstrando superioridade desta associação, no tratamento de lesões de furca grau III, em cães. Esses resultados levantaram a hipótese de que o processo de degradação da membrana e/ou enxerto ósseo interagiria negativamente sobre o processo de reparo quando associado a forças ortodônticas, pois a presença de mediadores inflamatórios estaria intensificada. É conhecido que a alteração tecidual proveniente da movimentação ortodôntica é resultado da ação de mediadores químicos sobre as células dos tecidos periodontais. Portanto, buscamos avaliar in vitro a ação de duas citocinas pró-inflamatórias, TNFα e IL-1ß, sobre células ósseas em presença e ausência de carga mecânica. / Abstract: The aim was to assess the effects of orthodontic intrusion on the healing of class III furcation lesions in dogs, and of the presence of tumor necrosis factor alpha (TNFα) and/or interleukin-1 beta (IL-1ß) on the mechanoresponse of osteocyte and osteoblast-like cells in vitro. In the in vivo study, class III furcation lesions were created in lower pre-molars of seven mongrel dogs. After 75 days, teeth were randomly treated with open flap debridment (OFD) associated or not to guided tissue regeneration (GTR) and bone autograft (BA). After one month, teeth were randomly assigned to orthodontic intrusion using mini-implants anchorage or no movement. Dogs were sacrificed after three months of movement and one month contention. All class III furcations were closed or reduced to class II or I lesions in the intrusion groups while 50% of the class III lesions in non-moved teeth remained unchanged. Clinical attachment level was reduced in the intrusion groups by the end of contention (p<0.01). OFD + I presented smaller soft tissues area and larger bone tissue area than other groups (p<0.05). Orthodontic intrusion with mini-implants anchorage improved healing of class III furcation defects after OFD in dogs. Based on these results we hypothesized that degradation of membrane and/or bone autograft can negatively interfere on repair when associated to orthodontic movement because inflammatory mediators are intensified. It's known that cytokines are present during orthodontic movement which are acting on periodontal cells. Therefore we evaluated in vitro the effects of two pro-inflammatory cytokines, TNFα and IL-1ß, on bone cells in presence or absence of mechanical loading. / Orientador: Joni Augusto Cirelli / Coorientador: Rosemary Adriana Chiérici Marcantonio / Banca: Ana Cláudia Moreira Melo / Banca: Enilson Antonio Sallum / Banca: Ary dos Santos Pinto / Banca: Silvana Regina Perez Orrico / Doutor

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