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Title: An investigation of the gaze contingent tilt after-effect
Author: Parwaga, Sandeep
ISNI:       0000 0004 5922 1297
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 2015
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In order to act on the world around us, the brain needs to encode the location of visible objects. This begins with representing the location of visual features on the retina. However, a retinal representation alone does not provide information about the direction of visual features with respect to the head or body whenever the eyes, head and body move. Therefore, successful action requires more than a retinal representation of location. One possibility is that the locations of visible objects may be encoded in retino-centric, head-centric and body-centric frames of reference. To investigate this, we used a well-known visual phenomenon: the tilt aftereffect (TAE). We investigated whether visual feature tilt is represented beyond a retino-centric representation, using a gaze contingent adaptation paradigm. The results of seven experiments yielded four key findings: 1) The TAE was contingent on gaze, suggesting that the TAE is not just retino-centric. We found evidence of a head-centric representation of tilt, but no evidence of a body-centric or world-centric representation of tilt. 2) The gaze contingent TAE showed different characteristics compared to the conventional TAE. While the conventional TAE was sensitive to test stimulus duration, the gaze contingent TAE was not. The gaze contingent TAE was also significantly smaller in aftereffect magnitude. Both TAEs shared similar characteristics with respect to stimulus contrast. 3) We found no evidence that either TAE was modulated by attention. 4) Our findings support the conclusion that the conventional TAE is the result of adaptation of two mechanisms: a tilt sensitive mechanism and a gaze direction encoding mechanism. This result fits with neurophysiological findings of neurons jointly sensitive to tilt and gaze direction (Trotter & Celebrini, 1999). Concluding, our results in this thesis provide psychophysical evidence that our impression of the world is based on head-centric visual representations.
Supervisor: Duke, Philip ; De Lillo, Carlo Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available