Browsing by Subject "Visual perception"

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    Effects of edge rate on perceived egomotion in a driving environment.
    (2009-12) Rakauskas, Michael E.
    Automobile drivers have a tendency to make judgments of their perceived rate of travel, or egospeed, that are slower than the speed they are actually traveling. This often leads them to drive at faster speeds, which results in increased crash risk for themselves and other vehicles. A driver's egospeed can be affected by visual cues in the environment including Edge Rate (ER) optical effects. The purpose of this research was to examine how speed production would be affected by (1) the presence and distance of roadside (geographic) ER cues; (2) proximal ER cues such as traffic moving at faster, similar, or slower speeds than the driver; and (3) the combined presence of geographic and traffic ER cues. A novel methodology had participants drive at comfortable and ratio speeds while experiencing 10 continuous minutes of each ER condition. Performance was examined in terms of: mean speed choice; ratio speed-production performance (target ratio); speed consistency (speed drift ratio, reliability ratio); and judgments of task difficulty (ease rating). Data suggested that certain cues reduced a driver's comfortable speed of travel: the presence of geographic ER cues; closer-distance geographic ER cues; slower-speed-traffic ER cues; and the pairing of geographic ER with slower-speed-traffic ER cues. Data showed that a reduction in traffic speeds may be produced by increasing the saliency of ER cues in the environment regardless of traffic conditions.
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    Event-related Potential Measurements of Long-term Orientation-specific Contrast Adaptation
    (2019-10) Baek, Yihwa
    The visual system continuously adjusts how it responds to current stimulus based on the history of the incoming stimuli, a process referred to as visual adaptation. Most of the previous studies focused on short-term adaptation effects ranging from milliseconds to minutes. Recent work has showed behavioral effects of long-term adaptation (hours and days), but their neural mechanisms remain unexplored. We aimed to uncover the neural bases of long-term orientation-specific contrast adaptation in an electroencephalography (EEG) experiment. Subjects were deprived of vertical contrast for 4 hours using altered reality goggles, which filtered out vertical energy from the scene in real-time. Event-related potentials (ERPs) in response to vertical and horizontal gratings were recorded before and after the long-term deprivation. We hypothesized that ERP response to vertical stimulation would increase in strength, and might decrease in latency, after the long-term deprivation. Results were analyzed by computing simple amplitudes of response, by comparing model fits to the ERP time courses, and by using the spatial pattern of ERP responses to classify trials by stimulation type. Early ERP components in response to vertical increased in amplitude and decreased in latency following adaptation, relative to responses to horizontal, but these differences were not significant. However, model fitting and classification results both revealed significantly greater differences in ERP responses between vertical and horizontal stimulation following adaptation. Collectively, these results suggest that long-term adaptation changes the amplitude of response in early visual cortex.