Visual perception in space and time ? mapping the visual field of temporal resolution
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To characterize temporal aspects of information processing in the human visual field, we studied the topographical distribution of temporal and non-temporal performance parameters in 95 normally sighted subjects. Visual field maps of double-pulse resolution thresholds (DPR) (the minimum detectable temporal gap between two light stimuli) and simple visual reaction times (RT) (measuring the speed of reaction to a light stimulus) were compared to maps of luminance thresholds determined by standard perimetry. Thus, for the first time, the topography of a visual variable without temporal constraints (perimetry) could be compared to visual variables in the temporal domain, with (RT) and without (DPR) motor reaction. The goal of the study was to obtain and to describe the pattern of co-variation of performance indicators. In all three measures, performance was best in the central visual field and dropped significantly towards the periphery. Although the correlation between DPR and RT was significant, shared variance was low, and we observed large topographical differences between these two temporal-performance variables. In contrast, DPR and perimetric thresholds correlated more substantially, and visual field maps were similar. The Gestalt of DPR maps shares characteristics of basic visual processing (e.g., light sensitivity), but it also reflects top-down influences, i.e., from spatial attention. Although the correlation between DPR and RT suggests common characteristics between these two temporal variables, the topographic distributions reveal significant differences, indicating separate underlying processing mechanisms.
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D. A. Poggel, Generation Research Program (GRP), Human Science Center, Ludwig-Maximilians University Munich, Prof.-Max-Lange-Platz 11, 83646 Bad Toelz, Germany