Thesis (Ph. D.)--Columbia University, 1956. / eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--Columbia University, 1956.

Thesis (Ph. D.)--University of California, San Diego, 2009. / Title from first page of PDF file (viewed Oct. 7, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 57-58).

Critical flicker fusion (CFF) functions are reported during the course of dark adaptation under various states of cone and rod adaptation. Also, measurements were made of the stimulus intensity necessary to just perceive flicker for a wide range of frequencies. The resulting data clearly demonstrate a rod-cone interaction causing a suppression of the threshold. Our results reproduce the familiar rod and cone branches of the CFF function, and confirm the assertion that CFF is dependent upon state of retinal adaptation. Intensities necessary for flicker detection were recorded at various frequencies during the cone plateau. However, the very same frequencies required as much as 1.5 Log units more intensity when recorded after complete rod recovery. We were able to detect the cone-rod interference only at the time when the rods begin to significantly contribute to the threshold. Our data suggest a channel whereby the rods have an accessible mechanism of directly influencing the cone signal as well as the total contribution to a threshold. The probable retinal area of this interaction is also discussed. Results are reported from a rod monochromat and six color normals. This study discusses other stimulus properties which could also reveal the rod-cone suppression. / Master of Science

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on Sept. 3, 2009). Includes bibliographical references (p. 45-52).

Caffeine's effect on the visual system was investigated. Twelve male and twelve female subjects (aged 18 - 25 years) were measured for Critical Flicker Frequency (CFF) thresholds at 15 levels of retinal illuminance (-1.0 to 3.0 log trolands) in each of four caffeine dosage conditions (0, 200mg, 400mg, 600mg). Variables of interest included dosage, gender, left and right eye differences, and time after ingestion. Significant results were found for dosage (p=.000), gender (p=.001), and eye differences (p=.000). Interactions were found for gender and dosage (p=.000), and gender and eye differences (p=.043). Implications of these findings are discussed in terms of caffeine's effect on the Central Nervous System (CNS) and corresponding effects on the visual system. It is concluded that ingestion of caffeine causes increased sensitivity of the visual system as displayed through lower Critical Flicker Frequency thresholds. / Master of Science

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from first page of PDF file (viewed on June 10, 2009). Includes bibliographical references.

No description available.

abstract: The experience of language can, as any other experience, change the way that the human brain is organized and connected. Fluency in more than one language should, in turn, change the brain in the same way. Recent research has focused on the differences in processing between bilinguals and monolinguals, and has even ventured into using different neuroimaging techniques to study why these differences exist. What previous research has failed to identify is the mechanism that is responsible for the difference in processing. In an attempt to gather information about these effects, this study explores the possibility that bilingual individuals utilize lower signal strength (and by comparison less biological energy) to complete the same tasks that monolingual individuals do. Using an electroencephalograph (EEG), signal strength is retrieved during two perceptual tasks, the Landolt C and the critical flicker fusion threshold, as well as one executive task (the Stroop task). Most likely due to small sample size, bilingual participants did not perform better than monolingual participants on any of the tasks they were given, but they did show a lower EEG signal strength during the Landolt C task than monolingual participants. Monolingual participants showed a lower EEG signal strength during the Stroop task, which stands to support the idea that a linguistic processing task adds complexity to the bilingual brain. Likewise, analysis revealed a significantly lower signal strength during the critical flicker fusion task for monolingual participants than for bilingual participants. Monolingual participants also had a significantly different variability during the critical flicker fusion threshold task, suggesting that becoming bilingual creates an entirely separate population of individuals. Future research should perform analysis with the addition of a prefrontal cortex electrode to determine if less collaboration during processing is present for bilinguals, and if signal complexity in the prefrontal cortex is lower than other electrodes. / Dissertation/Thesis / Masters Thesis Psychology 2019

Existem evidências que jogar videogames de ação (AVG) aperfeiçoa habilidades perceptuais, atentivas e cognitivas, como por exemplo, recuperação mais rápida da atenção visual e aprimoramento das dinâmicas temporais da percepção visual. Estudos correlacionais sugerem que estes aprimoramentos temporais se aplicam também ao processamento visual de baixa ordem, contudo evidências mais contundentes são necessárias. Ademais, no campo da multimídia computacional estudos apontam que a resolução temporal na qual o videogame é apresentado na tela, correspondente a taxa de quadros por segundo (QPS), afeta o desempenho e o entretenimento de jogadores. Entretanto ainda não se sabe como aspectos técnicos dos AVG, como a taxa de QPS, influenciam nos aperfeiçoamentos cognitivos citados anteriormente. Para esclarecer tais lacunas, delineou-se um estudo para verificar se AVG jogados em diferentes QPS afetam a recuperação temporal da atenção, medidos pela tarefa de Supressão Atencional (SA), e se há alterações nos limiares da resolução temporal visual, medidas através da frequência crítica de fusão e oscilação da visão (CFF). Trinta e dois (16M, 16F) participantes não jogadores de videogame voluntariaram-se para um experimento longitudinal. Inicialmente os voluntários foram separados em quatro grupos (4M, 4F) e todos eles no primeiro dia foram submetidos a uma tarefa de mensuração de CFF na região visual central e uma tarefa de SA. No dia seguinte e depois nos sete dias conseguintes dois grupos, intitulados experimentais, realizaram um treinamento com videogames de ação, sendo que cada um dos grupos treinou em diferentes resoluções temporais, um a 15 QPS e outro a 120 QPS. Simultaneamente um terceiro grupo, treinou com um videogame controle sem elementos de ação. E o quarto grupo, controle, não teve treinamento. O total de tempo de treinamento foi de 10 horas, distribuído em 8 dias, exceto para o grupo sem treino. No dia posterior ao último dia de treinamento todos os participantes foram submetidos novamente a tarefas de SA e CFF. De modo geral o CFF aumentou para todos os participantes entre pré e pós-teste, particularmente para o grupo sem treino, não houve efeito de grupo. Desempenho no SA melhorou somente no para lag2 (212ms) para participantes que treinaram AVG na taxa de QPS mais baixa. Estes resultados sugerem que treinamento com AVG não aumenta o limiar do CFF na região visual central, se não o oposto, e que o aprimoramento temporal da atenção beneficia-se com um treinamento com AVG em baixa resolução temporal, mas não de alta taxa de QPS, ao menos nas 10 horas iniciais de treino / Action video game play enhances perceptual, attentional, and cognitive skills, such as leading to faster recovery of visual attention over time and improvement of temporal dynamics of visual perception. Correlational data suggest that these temporal enhancements extend to low-level vision processes, but stronger evidence is needed. Also, in the multimedia computing field it was pointed out that video game screen frame rate affects players performance and enjoyment, but it is unclear how such technical aspects of the games play a role in cognitive augmentations. To shed more light on these issues, we tested whether action video game play and the frame rate at which they are played affects flicker detection in the central visual field and performance in attentional blink task. Thirty two (16 M, 16F) non-video game players volunteered to a longitudinal experiment. They were randomly split into four groups (4M, 4F). All of the groups performed a critical flicker-fusion frequency task (by method of limits) and attentional blink task at the first day of the experiment. Two experimental groups underwent action video-game training with different screen frame-rate caps each (15 and 120 frames per second, respectively). And one control group trained with a control game and a second control group had no training. The total amount of time in video-game training was 10 hours (75 min per day for consecutive 8 days), except for the no-training group. On the 10th day, all participants performed the flicker-detection and attentional blink tasks (post-test). Generally, critical flicker-fusion thresholds increased at the post-test for all groups, particularly for the non-training group, there were no group effect. Only marginal increased were observed in lag 2 for participant trained in low-frame-rate action video games. Our data suggest that playing video games do not increase flicker sensitivity threshold, it may actually prevent increase. And lower frame rate training produce transfer effects to Attentional Blink task, but not the higher frame rate training, at least in the first 10 hours