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Title: Neuronal mechanisms underlying the perception of slant and binocular orientation
Author: Bridge, Holly
ISNI:       0000 0001 3479 5356
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2000
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When a line is slanted away from a binocular observer, the image of that line has different orientations on the two retinae. This difference has been called an orientation disparity. A mechanism that exploits the orientation disparities in the visual image could form an efficient method of signalling surface slant. Three different experimental techniques are employed here to investigate whether such a mechanism is exploited in the human, and non-human primate visual systems. Modelling The responses of early visual neurons were simulated using a two dimensional version of the disparity selective complex cell model of Ohzawa et al. (1990). This model had no specific mechanism for detecting orientation differences, and had poor sensitivity to slant. Despite this, the model was able to account for all previous physiological data (Blakemore et al., 1972; Nelson et al., 1977; Wieniawa-Narkiewicz et al., 1992). The model was used to generate predictions to enable new physiological recordings to determine whether or not there is a specialised neuronal mechanism that detects orientation differences. Single unit recording Significant differences in preferred monocular orientation were found in around 30% of the orientation selective neurons recorded from V1 in the two awake, behaving monkeys used for this study. When stimulated binocularly, about one third of the orientation selective V1 neurons appeared to respond consistently to the same interocular orientation difference as the monocular orientations were changed. However, rather than forming a population of neurons specifically selective for orientation differences, it is likely that this response was an artefact of not centering the stimulus on the receptive field of neurons tuned for positional disparity. Psychophysics The results of experiments presented here, combined with a critical review of previous psychophysical studies provide no evidence for an independent orientation disparity mechanism. None of the data presented here, using any of the above approaches, support a significant role for interocular orientation differences in the perception of slant.
Supervisor: Parker, Andrew J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Binocular vision ; Vision ; Visual perception