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Title: Centre-periphery-difference in low-level vision and its interactions with top-down and sensorimotor processes
Author: Budnik, Ursula
ISNI:       0000 0004 2732 4806
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2011
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There is a profound difference in low-level vision between the retinal centre and the periphery (cpd). That contrast sensitivity declines from centre to the periphery is well established in humans. However, recently TMS on FEF was found to remotely affect visual cortex such that the cpd was reduced. No direct connections between FEF and occipital visual areas are known, but connections between FEF, the pulvinar and the occipital visual areas exist. I examined the cpd pattern in contrast sensitivity after real lesions in FEF and pulvinar areas by estimating visual thresholds. The results showed that real lesions of FEF do not have the same effect as TMS and are consistent with TMS causing subthreshold activation mimicking covert visuospatial attention. The cpd pattern in contrast sensitivity was different between FEF and pulvinar patients. Differences were prominent for foveal processing, while peripheral processing revealed parallel deficits, although these did not reach significance. In the second part of this work I focused on manual visuo-motor processes that have been found to differ between centrally and peripherally presented subliminal primes. For the periphery, when invisible primes are compatible with targets in their motor associations, RT‟s to targets speed up. However, for foveal primes, priming costs (negative compatibility effects (NCE)) can occur with compatible primes and targets. I examined the impact of perceptual sensitivity decline for the absence of NCE in the periphery by equating primes‟ strength via contrast threshold measurements. The results showed that perceptual equation does not equate priming effects. The critical factor, to trigger visuo-motor processes in periphery was found to be the prolonged time of the mask-target interval (SOA). This indicates that the functionally distinct retinal areas can both trigger visuo-motor processes, which are independent from visibility equation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: BF Psychology