Temporal Frequency Effects on Speed Sensitivity, Following Adaptation to Local Motion

Student thesis: Master's ThesisMaster of Science (MSc)

Abstract

The ability to perceive and distinguish different speeds is central for our interaction with the world. Getting this right is critical for both success and sometimes even survival, whether judging the velocity of a moving car or hitting a cricket ball.
There is strong evidence indicating that our inaccuracy in perceiving objects' absolute speeds and distinguishing differences of speed between objects, is systematically skewed in various contexts and even influenced by the immediately preceding perceptions. This is because the visual system adapts to the current visual environment by changing the neural responses. Viewing one object in motion affects the perceived speed and speed sensitivity of objects viewed afterwards. Exactly how the visual system adapts is still being debated, a subject explored in this paper.
The present study investigates whether local motion adaptation affects temporal frequency mechanisms to produce changes in speed sensitivity. To examine this we designed three adaptation experiments using moving sinusoidal gratings and plaids, finding that in all but the lowest temporal frequency tested, the speed discimrination thresholds for plaids were significantly higher after adaptation to moving gratings.
In the third experiment using gratings for both the adaptation and test stimuli, there was no difference in speed discrimination thresholds between the adaptation and non-adaptation conditions. These results suggest that the effects of adaptation take place at, or after, the integration of local motion signals. The novel findings are considered in the context of speed tuned and frequency tuned mechanism theories, and indicate that the effects of adaptation on motion perception cannot simply be considered in terms of either speed tuned adaptation or frequency adaptation in isolation.
Date of Award28 Sep 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorChristopher P Benton (Supervisor)

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