Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy). Appendices: leaves 95-103. Bibliography: leaves 89-94.

The primary visual cortex (V1) has long been considered the main low level visual analysis area of the brain. The classical view is of a feedfoward system functioning as an edge detector, in which each cell has a receptive field (RF) and a preferred orientation. Whilst intuitive, this view is not the whole story. Although stimuli outside a neuron’s RF do not result in an increased response by themselves, they do modulate a neuron’s response to what’s inside its RF. We will refer to such extra-RF effects as contextual modulation. Contextual modulation is thought to underlie several perceptual phenomena, such as various orientation illusions and saliency of specific features (such as a contour or differing element). This gives a view of V1 as more than a collection of edge detectors, with neurons collectively extracting information beyond their RFs. However, many of the accounts linking psychophysics and physiology explain only a small subset of the illusions and saliency effects: we would like to find a common principle. So first, we assume the contextual modulations experienced by V1 neurons is determined by the elastica model, which describes the shape of the smoothest curve between two points. This single assumption gives rise to a wide range of known contextual modulation and psychophysical effects. Next, we consider the more general problem of encoding and decoding multi-variate stimuli (such as center surround gratings) in neurons, and how well the stimuli can be decoded under substantial noise levels with a maximum likelihood decoder. Although the maximum likelihood decoder is widely considered optimal and unbiased in the limit of no noise, under higher noise levels it is poorly understood. We show how higher noise levels lead to highly complex decoding distributions even for simple encoding models, which provides several psychophysical predictions. We next incorporate more updated experimental knowledge of contextual modulations. Perhaps the most common form of contextual modulations is center surround modulation. Here, the response to a center grating in the RF is modulated by the presence of a surrounding grating (the surround). Classically this modulation is considered strongest when the surround is aligned with the preferred orientation, but several studies have shown how many neurons instead experience strongest modulation whenever center and surround are aligned. We show how the latter type of modulation gives rise to stronger saliency effects and unbiased encoding of the center. Finally, we take an experimental perspective. Recently, both the presence and the underlying mechanisms of contextual modulations has been increasingly studied in mice using calcium imaging. However, cell signals extracted with calcium imaging are often highly contaminated by other sources. As contextual effects beyond center surround modulation can be subtle, a method is needed to remove the contamination. We present an analysis toolbox to de-contaminate calcium signals with blind source separation. This thesis thus expands our understanding of contextual modulation, predicts several new experimental results, and presents a toolbox to extract signals from calcium imaging data which should allow for more in depth studies of contextual modulation.

Esta Tese tem como tema a problemática do fim do antigo ethos e o ocaso das ilusões no mundo moderno com base na reflexão de Giacomo Leopardi (1798-1837) sobre os seus efeitos nefastos. Tal reflexão considera também a problemática da barbárie moderna e pressupõe, igualmente, as formas anteriores da barbárie: a primitiva e a medieval. Na presente investigação não se retorna à questão da ideia de uma filosofia leopardiana ou de uma proposta de sistema no seu interior, pois não se trata, quer da antiga querela de um Leopardi poeta ou filósofo quer de uma exposição pormenorizada acerca de uma filosofia em Leopardi. Nesta investigação adotam-se as seguintes hipóteses interpretativas: i) o Discorso sopra lo stato presente dei costumi deglitaliani, escrito em 1824, contribui para uma compreensão da análise leopardiana acerca do processo de modernização europeia; ii) o Discorso pressupõe uma nova mudança no desenvolvimento da obra leopardiana, da nova crise ocorrida no seu pensamento em 1824, seguida da nova concepção de natureza, não mais aquela amorosa, mas uma natura matrigna, responsável por todos os males e a infelicidade humana; iii) Leopardi aborda elementos fundamentais das mudanças ocorridas no ethos após o processo de modernização europeu com base em um diagnóstico da situação econômica, social, cultural e política italiana; iv) no seu diagnóstico sobre a modernização, ele indica um novo princípio de conservação da vida civil; v) a experiência da modernização, por causa da nova forma de racionalidade e de espiritualização das coisas e do homem, põe em risco a vitalidade humana e conduz a uma nova barbárie: barbárie da sociedade. Ao investigar a experiência filosófica italiana dos séculos XVIII e XIX, Leopardi destaca os rumos tomados pela racionalidade e os riscos identificados por ele de uma barbárie dos novos tempos. Ele denomina o século XIX como século de morte em virtude do desaparecimento da dimensão poética e das ilusões, tão necessárias à conservação da existência humana. Trata-se de uma critica aos novos fenômenos de banalização da vida no mundo moderno e de suas degenerescências: ruína das ilusões, vacuidade dos valores e risco da barbárie da sociedade. / The theme of this thesis is the end of the ancient ethos, the twilight of illusions in the modern world and its adverse effects based on the reflection of Giacomo Leopardi (1798-1837). Such reflection also considers the issue of modern barbarism and presupposes its earlier forms, namely, the primitive and medieval barbarism. This research does not investigate the idea of a Leopardi\'s philosophy nor the proposal of a system inside his philosophy. It does not approach the old quarrel over Leopardi as a poet or as philosopher, nor a detailed exposition of philosophy in Leopardi\'s work. This research adopts the following interpretative hypotheses: i) the Discorso sopra lo stato presente dei costumi deglitaliani, written in 1824, contributes to the understanding of the Leopardi\'s interpretation of the European modernization process; ii) the Discorso presupposes a new change in the development of Leopardi\'s work, because of the new crisis in his thought in 1824, followed by a new conception of nature, which is no longer a loving one, but a natura matrigna, responsible for all evil and human misery; iii) Leopardi addresses the main economic, social, cultural and political changes in the Italian ethos after the European modernization process; iv) His diagnosis of modernization indicates a new principle of the conservation of civil life; v) the experience of modernization endangers human vitality and leads to a new barbarism, because of the new rationality and spiritualization of objects and man, namely, the barbarism of society. Leopardi emphasizes the new forms of rationality and their risks, a new era of barbarism, in his investigation of the philosophical experience of the Italian Eighteenth and Nineteenth centuries. He calls the Nineteenth century the century of death because of the disappearance of the poetic dimension and of the illusions, that are so necessary for the preservation of human existence. This thesis focus a critique of the new phenomena of banalization of life in the modern world and its degeneracies, namely, the end of illusions, vacancy of values and the risk of the society barbarism.

In order to investigate certain anomalies evident in the literature, the performances of three Xhosa groups (rural dwellers, urban dwellers, and undergraduates) of varying degrees of acculturation and a White undergraduate group, each group consisting of 30 subjects, were measured on tests of mode of field approach and susceptibility to the Müller- Lyer and Ponzo illusions. In addition, the effect of the introduction of a mental set, which facilitated the perception of perspective in the Ponzo figure, on susceptibility to the illusion was ascertained. Mode of field approach was measured by a portable version of the Rod-and-Frame Test. Susceptibility to the Müller-Lyer illusion was measured by a conventional movable- slide, subject-adjustable device, while a piece of apparatus which also worked on the movable slide principle and was subject-adjustable was developed to measure susceptibility to the Ponzo illusion. The set to facilitate the perception of perspective in the Ponzo figure was introduced by having subjects match the length of Ponzo contrast lines embodied in a photograph and a line-drawing of a bridge, both of these pictures having strong perspective cues. The subjects were required to perform the tasks in prescribed order. Standardised English or Xhosa instructions were ensured by the use of "programmed" worksheets for each task. Prior to each experimental task, the more unacculturated subjects performed comprehension checks to ensure that they understood the concepts of equal length and verticality. The results of the study suggested that: (i) When groups of differing acculturation levels are tested, there may be a pronounced negative association of field dependence with susceptibility to the Müller-Lyer and Ponzo illusions. In general, the more unacculturated the subject, the more field dependent and the less susceptible to illusions he was. However, there was no evidence which either strongly supported or refuted the relationship between these attributes at the intra-group level. (ii) There is no intra- group association between susceptibility to the Müller-Lyer and to the Ponzo illusions. This would indicate that they are not necessarily generated by similar inference habits or by similar contour properties. (iii) The introduction of a "perspective set" increases susceptibility to the Ponzo illusion only among acculturated subjects, who have well-developed pictorial depth perception skills and who habitually infer depth in inverted - V configurations. (iv) There is a significant association between acculturation and field independence. The unacculturated subjects, presumably because they lack the skills of visual analysis which are engendered by Western culture, were more field dependent than the acculturated subjects. (v) Provided that their degrees of acculturation are more-or-less equivalent, as were those of the two undergraduate groups, there are no differences in mode of field approach or susceptibility to the Müller-Lyer and Ponzo illusion among Xhosa and White subjects. Summary, p. 112.

Au seuil de cette dissertation, que l'on me permette de remercier le docteur D. Niederauer qui, d'abord, accepta de patronner ma these et, ensuite, sut guider mes travaux avec une patience infinie. Mes remerciements vont aussi aux docteurs F. Grover et D. Highnam qui m'aid^rent de leurs precieuses remarques. Je dois enfin exprimer ma gratitude au docteur P. G^rin, professeur a Mount-Saint-Vincent University. Par ses conseils et le re'confort de son amitig, il facilita grandement le premier travail de redaction de cette etude. / Arts, Faculty of / French, Hispanic, and Italian Studies, Department of / Graduate

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Ce mémoire propose une analyse de la figure du journaliste dans illusions perdues de Balzac, figure qui est caractérisée par une vitalité particulière dont le héros, Lucien de Rubempré, est dépourvu. En s'appuyant sur la théorie de l'énergétique balzacienne, nous démontrons que Balzac oppose dans son roman deux éthiques littéraires: celle représentée par le Cénacle (concentration de l'énergie vitale) et celle associée aux milieux journalistiques (dépense de l'énergie vitale). Nous identifions deux lieux de dépense énergétique: les sociabilités et la parole journalistiques. Ce sont ces attributs de la profession journalistique qui expliquent en partie l'échec de la carrière littéraire de Lucien à Paris. Enfin, nous analysons la portée politique de la représentation du journalisme dans le roman de Balzac en démontrant que celle-ci s'inscrit dans une représentation générale du désordre social engendré par le développement des idées politiques libérales, désordre social qui conduit à un antagonisme entre individu et société.

Les silhouettes ambiguës, comme celle du lapin/canard (Jastrow, 1899), ont été étudiées selon plusieurs approches. Toutefois, les figures prises en exemples dans la large majorité des études sont généralement les mêmes. Cette redondance des images ambiguës utilisées pousse à croire qu'elles sont peut-être assez rares. Certaines observations anecdotiques suggèrent cependant qu’elles seraient au contraire relativement fréquentes. C'est ce que cherche à déterminer cette expérience. Nous avons utilisé des modèles tridimensionnels d'animaux projetés de façon aléatoire afin d'en extraire les silhouettes dont la complexité périmétrique a ensuite été modifiée par lissage. Treize sujets ont dû indiquer ce qu'ils percevaient dans l'image. Nous démontrons qu’une silhouette est classée en moyenne dans 1.9079 catégories de base. Nous avons également démontré qu’une diminution de la complexité périmétrique rend d’abord une silhouette plus ambiguë pour éventuellement atteindre un sommet (équivalent à environ six fois la complexité périmétrique d’un disque) à la suite duquel l’ambiguïté chute. / Ambiguous silhouettes such as the duck/rabbit (Jastrow, 1899) have been studied by several approaches. However, the figures taken as examples in the vast majority of studies are generally the same. This redundancy of the ambiguous images used in litterature implies they may be quite rare. On the other hand, anecdotal evidence suggests that they might be relatively frequent. This is what this experiment is trying to establish. We used three-dimensional models of animals from a random point of view to extract silhouettes whose perimetric complexity was subsequently modified by smoothing. Thirteen subjects were asked to indicate what they saw in the image. We show that silhouettes are classified on average with 1.9079 based categories. We also established that a decrease in the perimetric complexity initially makes a more ambiguous figure but that this effect eventually reaches a peak (at a perimetric complexity of approximately 6 times that of a disk) after which ambiguity drops.

Il lavoro di tesi si focalizza su due meccanismi di self-enhancement, le positive illusions e il self-serving bias, e li analizza nel contesto della relazione di coppia, con particolare attenzione all’influenza che una strategia di parenting disfunzionale come l’intrusive parenting esercita su di essi. La tesi si articola in tre studi: il primo ed il secondo studio, adottando un approccio quantitativo, si focalizzano sul costrutto delle positive illusions, mentre il terzo, attraverso un disegno sperimentale, sul costrutto del self-serving bias. / Self-enhancement is a self-motive which pushes individuals to increase positive self-views and to protect their self-concept from negative information. Two mechanisms associated with the self-enhancement motive, positive illusions and the self-serving bias, will be analyzed in the context of couple relationship. Positive illusions deal with the tendency to perceive one’s relationship favorably when compared to the couple relationship of the average other. The self-serving bias relates to the tendency to make internal responsibility attributions for positive events but to make external responsibility attributions for negative events; however, when individuals collaborate with a close partner on an interdependent-outcome task, they refrain from self-serving attributions or even manifest the other-serving bias. These mechanisms serve the purpose of maintaining and protecting a relationship that is central in one’s couple identity. The present work will also focus on the influence that an insidious parental behavior like intrusive parenting exerts on these two biases pro-relationship and, consequently, on couple identity. Study 1 and 2 are dedicated to the examination of couple positive illusions in couples in transition to marriage whereas study 3 investigates the self-serving bias in dating partners.