It is known that primates are sensitive to the velocity of moving objects. We can also remember velocity information after moving objects disappear. This cognitive faculty has been investigated before, however, the literature on velocity memory to date has been fragmented. For example, velocity memory has been disparately described as a system that controls eye movements and delayed discrimination. Furthermore, velocity memory may have a role in motion extrapolation, i.e. the ability to judge the position of a moving target after it becomes occluded. This thesis provides a unifying account of velocity memory, and uses electroencephalography (EEG) to explore its neural basis. In Chapter 2, the relationship between oculomotor control and motion extrapolation was investigated. Two forms of motion extrapolation task were presented. In the first, participants observed a moving target disappear then reappear further along its path. Reappearance could be at the correct time, too early or too late. Participants discriminated reappearance error with a two-alternative forced choice button press. In the second task, participants saw identical targets travel behind a visible occluder, and they attempted to press a button at the exact time that it reached the other side. Tasks were completed under fixation and free viewing conditions. The accuracy of participant's judgments was reduced by fixation in both tasks. In addition, eye movements were systematically related to behavioural responses, and small eye movements during fixation were affected by occluded motion. These three results imply that common velocity memory and pre-motor systems mediate eye movements and motion extrapolation. In Chapter 3, different types of velocity representation were explored. Another motion extrapolation task was presented, and targets of a particular colour were associated with fast or slow motion. On identical-velocity probe trials, colour still influenced response times. This indicates that long-term colour-velocity associations influence motion extrapolation. In Chapter 4, interference between subsequently encoded velocities was explored. There was robust interference between motion extrapolation and delayed discrimination tasks, suggesting that common processes are involved in both. In Chapter 5, EEG was used to investigate when memory-guided tracking begins during motion extrapolation. This study compared conditions where participants covertly tracked visible and occluded targets. It was found that a specific event related potential (ERP) appeared around 200 ms post occlusion, irrespective of target location or velocity. This component could delineate the onset of memory guided tracking during occlusion. Finally, Chapter 6 presents evidence that a change in alpha band activity is associated with information processing during motion extrapolation tasks. In light of these results, it is concluded that a common velocity memory system is involved a variety of tasks. In the general discussion (Chapter 7), a new account of velocity memory is proposed. It is suggested that a velocity memory reflects persistent synchronization across several velocity sensitive neural populations after stimulus offset. This distributed network is involved in sensory-motor integration, and can remain active without visual input. Theoretical work on eye movements, delayed discrimination and motion extrapolation could benefit from this account of velocity memory.

Nous avons expliqué comment le système visuel intègre les informations de mouvement en manipulant la distribution de vitesse locale à l'aide d'une classe bien contrôlée de stimuli de texture aléatoires à large bande appelée Motion Clouds (TM), avec des spectres de fréquence spatio-temporels naturalistes continus. Nos résultats montrent que le gain et la précision des poursuites se détériorent à mesure que la variabilité de la fréquence de stimulation augmente. Dans l'expérience de discrimination de vitesse perceptuelle, nous avons constaté que les MC ayant une largeur de bande légèrement supérieure à la vitesse étaient perçus comme se déplaçant plus rapidement. Cependant, au-delà d'une bande passante critique, la perception d'une vitesse constante a été perdue. Dans une troisième expérience de discrimination, nous avons constaté que pour les contrôleurs multimédias à large bande passante, les participants ne pouvaient plus discriminer la direction du mouvement. Ces résultats suggèrent que lorsqu’on augmente la bande passante de petites à grandes vitesses, l’observateur expérimente différents régimes de perception. Nous avons finalement réalisé une expérience d’échelle de différence de vraisemblance maximale avec nos stimuli MC afin d’étudier ces différents régimes de perception possibles. Nous avons identifié trois régimes dans la plage des valeurs de différence de vitesse testées qui correspondraient à la cohérence de mouvement, à la transparence de mouvement et à l'incohérence complète. / It is still not fully understood how the visual system integrates motion information across different spatial and temporal frequencies, in order to build a coherent percept of the global motion under complex, noisy naturalistic conditions. We addressed this question by manipulating local speed distribution (i.e. speed bandwidth Bv) using a well-controlled class of broadband random-texture stimuli called Motion Clouds (MCs), with continuous naturalistic spatiotemporal frequency spectra (Sanz-Leon et al., 2012,; Simoncini et al., 2012).Our results show that pursuit gain and precision deteriorate as stimulus speed variability increases. In the perceptual speed discrimination experiment, we found that MCs with moderately larger speed bandwidth were perceived as moving faster. However, beyond a critical bandwidth (Bv > 0.5 °/s), the perception of a coherent speed was lost. In a third direction discrimination experiment, we found that for large bandwidth MCs participants could no longer discriminate motion direction. These results suggest that when increasing speed bandwidth from a small to a large range, the observer experiences different perceptual regimes. We finally ran a Maximum Likelihood Difference Scaling (Knoblauch & Maloney, 2008) experiment with our MC stimuli to investigate these different possible perceptual regimes. We identified three regimes across the range of tested values of velocity difference, that would correspond to motion coherency (and speed integration), motion transparency and complete incoherency.

<p>CAL (Computer Assisted Learning) programs are widespread today in schools and families due to the effectiveness of CAL programs in improving students’ learning and task performance. The flourishing of CAL programs in education has brought large amounts of students’ learning data including log data, performance data, mouse movement data, eye movement data, video data, etc. These data can present students’ learning or problem-solving processes and reflect underlying cognitive processes. These data are valuable resources for educators to comprehend students’ learning and difficulties. However, few data analysis methods can analyze and present CAL data for educators quickly and clearly. Traditional video analysis methods can be time-consuming. Current visualization analysis methods are limited to simple charts or visualizations of a single data type. In this dissertation, I propose a visual learning analytic approach to analyze and present students' problem-solving data from CAL programs. More specifically, a visualization system was developed to present students’ problem-solving data, including eye movement, mouse movement, and performance data, to help educational researchers understand student problem-solving processes and identify students’ problem-solving strategies and difficulties. An evaluation experiment was conducted to compare the visualization system with traditional video analysis methods. Seven educational researchers were recruited to diagnose students’ problem-solving patterns, strategies, and difficulties using either the visualization system or video. The diagnosis task loads and evaluators’ diagnosis processes were measured and the evaluators were interviewed. The results showed that analyzing student problem-solving tasks using the proposed visualization method was significantly quicker than using the video method. In addition, diagnosis using the visualization system can achieve results at least as reliable as the video analysis method. Evaluators’ preferences between the two methods are summarized and illustrated in the dissertation. Finally, the implications of the visual analytic approach in education and data visualization areas are discussed. </p>

In recent years interest in L2 reading research has focused largely on word frequency, sentence level, word recognition, and several researchers have begun to use eye tracking to better study reading behaviors. Parshina et al. (under review) have found that high proficiency heritage speakers of Russian read faster in terms of gaze duration and total time and had fewer regressions than low proficiency heritage speakers. The current study focuses on the establishment of benchmarks for L2 Russian readers in terms of first fixation duration, gaze duration, and total time when reading a complete passage, and compares these variables among different proficiency levels. Thirty-two students participated in the study with proficiency levels ranging from Novice to Superior. Subjects completed eye tracking and reading comprehension passages with the use on an eye tracker to asses reading abilities. Results show that all participants read L1 significantly faster than L2 in terms of first fixation duration. Additionally, all proficiency levels read Intermediate passages faster than Advanced passages. These results help establish the first benchmarks for eye tracking in Russian as an L2.

It is a common finding that neurons synchronize their firing rates in a high frequency range above 30 Hz, the so‐called gamma band, if they are involved in the processing of the same stimuli. Furthermore, it was hypothesized that object representations are stored within the cortical networks that are formed of synchronously firing neurons. Consequently, induced gamma band responses in the electroencephalogram were utilized to investigate cortical object representations. A more recent finding by Yuval‐Greenberg et al. questioned this common interpretation. It was shown that miniature eye movements as they occur during fixation are accompanied by small artifacts that mimic activity in the gamma band. The question arose whether induced gamma band responses in the electroencephalogram are a marker of neuronal processing or a mere artifact caused by miniature eye movements. The present thesis aims at providing solutions for this dilemma by investigating whether evoked gamma band responses and steady state visual responses are suitable tools to examine cortical network activity in relation to object recognition. Both measurements are not affected by miniature eye movements. It was found that evoked gamma band responses are particularly qualified to study early processes of object recognition. Furthermore, steady state visual evoked potentials were sensitive to the semantic content of presented stimuli. Therefore they are feasible for studying object recognition, too. Additionally, the present thesis provides the COSTRAP algorithm, a new method to effectively identify and remove the eye movement artifacts related to miniature eye movements. The remaining induced gamma band responses are most certainly of cortical origin. They proved to be sensitive to object recognition and repetition priming. Finally, it was shown that miniature eye movements and cortical gamma band responses can be experimentally dissociated, further underpinning the different methodological importance of induced gamma band response when studying object recognition. In summary, it was shown that the investigation of cortical networks representing object knowledge can also be addressed by evoked gamma band responses and steady state visual responses. Furthermore, it was proven that induced gamma band responses remain a powerful tool in electrophysiological research when studying the neuronal dynamics behind object recognition and other cognitive processing.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第12979号 / 論医博第2105号 / 新制||医||1012(附属図書館) / 32449 / (主査)教授 髙橋 良輔, 教授 佐藤 俊哉, 教授 渡邉 大 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20259号 / 医博第4218号 / 新制||医||1020(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 渡邉 大, 教授 林 康紀, 教授 髙橋 良輔 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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