Biomedical subjects
Publications and source records attributed to D Finlay.
Literature dealing with the peripheral retina and its 'specialization for motion detection' is reviewed. The data at hand seem to indicate that the central retina is more 'specialized' for motion perception than the peripheral retina. It is clear that motion improves vision for stimuli presented peripherally.
A technique of monocular eye patching was used to measure the response of infants three and four months old to nasally and temporally placed stimuli at various eccentricities in the visual field. The results indicated a field of field of binocular overlap of approximately 60 deg in infants three months old and 80 deg in infants four months old. These figures compare with visual field widths obtained under binocular viewing conditions of at least 140 deg in infants three months old and of at least 150 deg in infants four months old.
Temporal limits of stroboscopic apparent motion in depth have been examined. For monocular viewing the limits are similar to those obtained for motion in the frontal plane, while those for binocular viewing are greatly narrowed. In another experiment the contraction in space over which apparent movement occurs was measured. The results are discussed in terms of a filter representation proposed by Caelli and Finlay.
Pure tone auditory sequences were presented in a successive comparison task to Ss who were required to make judgments as to which sequence was longer. Experiment 1 was designed to test an hypothesis that sequences with small differences in frequency between adjacent tones would be perceived as shorter in duration than would sequences with large differences. Results did not support this hypothesis. Experiment 2 considered a systematic variation of the amount of frequency change in a sequence upon its perceived duration. These data indicated a direct relationship between perceived duration and the amount of stimulus change. A presentation order effect (POE) was found in Experiment 1 but not in Experiment 2 and it was suggested that the presence or absence of a significant POE was related to the ability of the S to store the sequences in memory.
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The authors have earlier found support for the notion that apparent motion (AM) is mediated by a low-pass temporal-frequency filter operating over the spatial domain of the AM sources. Experiments have been carried out to test how this response is changed, or unchanged, through varying the source intensities or contrasts. The results indicate no intensity or contrast effects on the spatiotemporal limits for AM. These results are related to the early formulations of Korte and indicate that there is no amplitude-modulation or contrast-sensitivity function for AM--as there is for threshold movement detection. The filter mechanism seems to be largely restricted to the spatiotemporal domain.
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We present some results which indicate that the known spatiotemporal limits for apparent motion are consistent with the motion being sinusoidal or a result of filtering. Given this we investigated how two such motions interact as a function of their relative temporal phase differences. This was accomplished by inducing two independent motions from complementary coloured event pairs. Results indicated critical phase limits for perceiving the two motions (red and green) which were consistent with the frequency specificity of the effect. The results are discussed within the framework of a filtering process for the perception of apparent motion.
In an earlier paper, Caelli and Finlay demonstrated that the perception of apparent motion was contingent on critical phase relationships between inducing sources, and their spatio-temporal frequency ranges. In their original stimulus red-green centre-surround sources were used and phase-specific inhibition was found at 60 degrees--90 degreee phase angle differences between the complementarily coloured elements. In this experiment we show that, when centre-surround sources are replaced by vertically-horizontally displaced complementary (or identically coloured) sources, symmetrical phase inhibition effects occur with both motions.
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