Visual crowding is a dramatic breakdown of object recognition that has been studied extensively as a gateway to determine the mechanisms that underlie normal object recognition. Despite numerous proposed models and mechanisms, a unifying account has yet to be found. Proposed mechanisms reach from purely hierarchical, bottom-up accounts that place crowding early in the processing stream, to high-level attention-based accounts that allow for recurrent processing and top-down feed-back. The aim of the current work was to investigate a range of factors that would help to differentiate between these accounts. Firstly, object-category was studied as a factor that would be expected to modulate crowding if the phenomenon were to affect object recognition during several stages along the processing stream. Secondly, knowledge was studied as a possible source of top-down feedback that, if found to have a direct influence on crowding, would provide evidence against a purely hierarchical account for object recognition. Thirdly, anticipation of flanker-presence was studied as a factor modulating volitional attention-allocation. Observing an influence of anticipation on object recognition under the influence of crowding, would provide support that crowding may be the result of a limitation to focus attention. Finally, object-familiarity was studied as another factor that may modulate crowding via top-down feedback. Of these factors, only object-familiarity was found to have an influence on visual crowding. However, instead of being the result of top-down feedback, hard-wired pathways developed based on repeated exposure might explain the effect of object-familiarity. In summary, none of the studied factors provided univocal evidence to suggest that crowding were to occur at multiple levels of object recognition, or that crowding were to be influenced by higher-level effects. Hence, it may be concluded that a purely hierarchical bottom-up account is sufficient to account for the effects visual crowding exerts on normal object recognition.

El presente texto está organizado de la siguiente forma: en el capítulo 1 me ocupo de presentar las bases sobre las cuales desarrollé esta investigación, tanto las preguntas y problemáticas trabajadas como las 7 herramientas teóricas y metodológicas que he empleado a lo largo de la misma; en el capítulo 2 presento, a través de una descripción detallada, a la Carpeta Negra, para luego desplegar su historia social y material, vista a través de la noción de régimen de valor –que desarrollo más adelante; en el capítulo 3 complemento lo desarrollado anteriormente con algunos debates teóricos sobre la relación entre el arte y la política, primero a partir del análisis de los resultados del trabajo de campo, para luego retomar mi propia descripción e interpretación de la obra. Finalmente, las conclusiones generales de la investigación se encuentran en el quinto apartado. / Tesis

O estudo da acuidade Vernier (VRN) revela a capacidade do sistema visual humano em detectar deslocamentos espaciais de poucos arcos de segundos, menores que a distância entre dois cones foveais adjacentes. Tal fato desperta interesse teórico sobre o tema, além de futuras aplicações na área clínica. A acuidade VRN pode ser medida tanto psicofisicamente quanto eletrofisiologicamente. Para a detecção de quebras de colinearidade (acuidade VRN), alguns autores hipotetizam que as células ganglionares (CGs) M da retina provêem sinal adequado da retina ao córtex, e dão suporte ao desempenho psicofísico da tarefa VRN. Em condições de estímulos semelhantes, as células ganglionares magnocelulares (M) em primatas parecem ter precisão espacial com razão sinal-ruído mais alta do que as células parvocelulares (P) . A dependência ao contraste (C) das células M na precisão espacial, frequência espacial, frequência temporal e velocidade do estímulo é mais similar ao desempenho psicofísico em humanos do que comparados aos dados das células P (Rüttiger et al., 2002; Sun et al., 2004). Nós utilizamos o Potencial Provocado Cortical Visual de Varredura (sVEP) para avaliar esta hipótese no nível de processamento intermediário entre as respostas de célula única na retina e a detecção psicofísica. Nós medimos os limiares corticais VRN em função do contraste (14 participantes, média de 28,21 ± 2,8) e lacunas (9 participantes, média de 29,7 ± 5,9). As quebras verticais VRN na colinearidade foram introduzidas em uma grade de onda quadrada horizontal. O estímulo VRN alternou entre um estado alinhado (grades sem quebras) e desalinhado (grades com quebras) a 6 Hz. Durante cada uma das 10 tentativas, o deslocamento aumentou em passos logarítmicos iguais de 0,5 a 7,5. O limiar VRN foi definido no momento do deslocamento em que a extrapolação linear da média vetorial das respostas em 1F atinge zero uV. Os contrastes testados foram: 4, 8, 16, 32, 64, 80%. Os resultados mostram que (1) aos limiares VRN em Log, medidos com sVEP, com o C em Log, diminuíram de forma linear (com uma inclinação de -0,5), similiares às células ganglionares M mas não P (Sun et al., 2004) e próximo às medidas psicofísicas (Sun et al., 2004; Wehrhahn e Westheimer, 1990); (2) Para C 16% obtivemos limiares de hiperacuidade (menor que 1 arcmin). Em altos contrastes a média do limiar foi de 0,37(erro padrão de 0,06 unidades logarítmicas); (3) Os limiares para o 2F tiveram uma dependência para o contraste diferente, com poucos efeitos para contraste abaixo de 16%. (4) As inclinações das linhas de extrapolação dos sVEP para o 1F1 foram 2 a 3 vezes maiores que as inclinações para 2F; (5) No protocolo controle, deslocamentos bidirecionais e simétricos geraram somente respostas no 2F. Os resultados 3 a 5 implicam que os componentes 1F e 2F derivam de neurônios distintos e fundamentam que respostas no 2F refletem respostas de movimento cortical simétrico. A dependência dos limiares de contraste do sVEP VRN (1F) é similiar aos estudos prévios psicofísicos (Sun et al., 2004; Wehrhahn e Westheimer, 1990), e repete a dependência ao contraste das células M (Sun et al., 2004). Estes resultados fundamentam a hipótese que o córtex extrai informações da posição relativa com precisão de hiperacuidade dos sinais advindos das células M / The human visual system is able to detect spatial displacements of a few arcsec, much smaller than the distance between two adjacent foveal cones. Hyperacuity tasks such as Vernier (VRN) have both theoretical importance as well as clinical application. VRN can be measured psychophysically and with sVEP. Some authors hypothesize that M ganglion cells provide the retinal signal to cortex adequate to support Vernier performance. Under stimulus conditions analogous to detection of Vernier offsets, primate magnocellular (M) ganglion cells appear to have more precise spatial localization (with higher Signal to Noise Ratio) than parvocellular (P) cells, and the dependence of M cell spatial precision on contrast (C), spatial frequency, temporal frequency and stimulus velocity is more similar to human psychophysical performance than comparable data from P cells (Ruttiger et al, 2002; Sun et al., 2003, 2004) (Rüttiger et al., 2002; Sun et al., 2004). We measured the C-dependence of cortical VRN thresholds (thd) using the Sweep VEP (sVEP) to help evaluate this hypothesis at a processing level intermediate between single-cell retinal responses and psychophysical detection. We measured Vernier thds using sVEP as function of constrast (12 young adults, age means 28.21 yrs ± 2.8) and Gaps (9 participants, 29.7 ± 5.9) with normal vision. Vertical VRN breaks in colinearity were introduced to a horizontal squarewave grating. The VRN stimulus alternated between aligned (grating w/o breaks) and misaligned (w/breaks) states at 6 (or 10) Hz. During each of ten, 10-s trials, displacement (D) was increased in equal logarithmic steps from 0.5 to 7.5. Vernier thd was defined as the D at which the rising slope of the vector averaged 1F response extrapolated to zero V. The Cs tested were: 4, 8, 16, 32, 64, 80%. We Found: (1) Log Vernier thd measuered with sVEP decreased linearly with log C similar to M- (but not P-) ganglion cells (Sun et al., 2004) with a slope of -0.5, close to that measured psychophysically (Rüttiger et al., 2002; Sun et al., 2004); (2) For C 16% , thds were true hyperacuities (less than 1). At high C, mean thd was 0.37(S.E = 0.06 log units); (3) Thds for 2F had a different C dependence, with little effect of C below 16 %. Thds for 2F were < 1F thds below 16 % C, but were 1F thds beyond 16 %; (4) The slopes of the sVEP extrapolation lines for 1F were 2-3 times > 2F slopes; (5) In a control protocol, symmetric, bidirectional displacements only generated 2F responses. Results 3-5 imply that the 1F and 2F components derive from distinct neurons, and support the notion that 2F responses reflect symmetric cortical motion responses. The C-dependence of sVEP Vernier (1F) thresholds is similar to prior psychophysics (Sun et al., 2004; Wehrhahn e Westheimer, 1990), and recapitulates Mcell C-dependence (Sun et al., 2004). This results support the hypothesis that cortex extracts relative position information with hyperacuity precision preferentially from M cell signals

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.

Diseñador Gráfico / No autorizada para ser publicada en el Portal de Tesis Electrónicas de la U. de Chile.

Diseñador Gráfico / No autorizada para ser publicada en el Portal de Tesis Electrónicas de la U. de Chile.

Diseñador Gráfico / No autorizada para ser publicada en el Portal de Tesis Electrónicas de la U. de Chile.

The question is addressed of whether the perception of a form is exclusively determined by a prior analysis of its elements, and two major paradigms are reviewed, viz., Gestalt and information processing. Three experiments were carried out. Experiment 1 employed a signal detection task to test the hypothesis that embedding a line segment feature in a unitary figural context would facilitate its detection. The contextual effect found falsified the theory of a one-way causation between analysis of figural elements and form perception. Experiment 2 showed that a necessary condition of this context effect on feature detection is the three-dimensionality of the unitary context. With bi-hemiretinal stimulus presentation Experiment 3 showed a significant context effect in the RVF, but not in the LVF. Some current paradigms are applied to these results; it is argued concurrently that the explanation of phenomena called "perceptual" entails the solution of two problems:, that of determining what constitutes such an explanation, and an adequate theory of the experiential aspect of perceptual phenomena. These are addressed in Appendices A and B. / Arts, Faculty of / Psychology, Department of / Graduate

According to UNESCO’s Universal Declaration on Cultural Diversity there exists a need in light of the “imbalances in flows and exchanges of cultural goods and services at the global level” to enable “all countries, especially developing countries and countries in transition, to establish cultural industries that are viable and competitive at a national and international level” (2001). The dissertation explores ways in which viable cultural industries can be established in developing countries. More specifically, the focus is on the development of film industries in countries in transition. Three national film industries, examined in light of their historical development and contemporary situation, provide the empirical basis for the dissertation’s claims and arguments. The three developing countries under investigation are Bhutan, Mongolia, and Myanmar, and in each case the study traces the historical trajectory of the relevant film industries leading to the mapping of the recent trends and tendencies. The examination of the individual cases foregrounds industrial and commercial challenges and solutions rather than the aesthetic or stylistic properties of specific films. That is, the study seeks to explore how educational practices, production modes, approaches to distribution and exhibition, and cultural policy measures have facilitated or thwarted the emergence of film industries in three developing countries in the Asian region. The approach taken builds on the call for a more inclusive approach to the study of world cinema (Nagib 2006). Equally important is an analytical approach derived from the field of small national cinema studies, one that underscores the need to explore solutions to problems facing filmmakers in countries sharing similar developmental challenges (Hjort & Petrie 2007). Following this conceptual perspective the study aims firstly, through its historical examination, to contribute to expanding the historiography of world cinema, where little to no attention is given to these largely unexplored national cinema cultures. Secondly, following the mapping of the contemporary situation of the institutional and organizational make-up of the film industries in question, the aim is to identify the systematic challenges and opportunities that are embedded in specific film sectors. The approach is applied with the intention of facilitating a constructive discussion that explores and compares proactive strategies. The point ultimately is to identify models that might be more generally relevant and thus transferable across national boundaries.

Museums have the responsibility to meet the needs and expectations of audiences with different backgrounds, including families, students, adults and the elderly. However, the needs of higher education students can easily be overlooked in Hong Kong art museums because their age and educational background fall into different target segments. By the late twentieth century, learning opportunities for higher education students, especially those who were majoring in fine arts, art history and museum studies were inadequate in Hong Kong. In view of the increasing arts programmes offered by tertiary institutions in 2000s Hong Kong, art museums play an important role in developing higher education students’ creativity and critical thinking by making use of their resources and expertise. Collaboration between art museums and universities through curricula is one effective method for strengthening art education at tertiary level in twenty-first century Hong Kong. Based on local and overseas scholarships on museum studies and archival materials in different museums, this dissertation examines both past and current education services provided by art museums in Hong Kong in order to reveal the benefits and difficulties of developing museum-university collaboration. Having interviewed with museum directors, curators and professors, I will present both qualitative and quantitive analyses of the education services provided by four focused institutions, including the University Museum and Art Gallery of the University of Hong Kong, the Art Museum of the Chinese University of Hong Kong, the Hong Kong Museum of Art, and M+. While reviewing learning models and pedagogical methods for higher education in a museum context, successful case studies of museum-university collaboration in overseas institutions, such as the Victoria and Albert Museum in London and the Metropolitan Museum of Art in New York, will also be discussed. I will propose effective methods for strengthening collaboration between art museums and universities in Hong Kong. The research finding of this dissertation will provide feasible plans for museum practitioners, professors and policy makers to enhance the quality of higher education in art-related disciplines and museum services with insightful ideas.