Lab rotation project description
Measuring subjective jitter in Motion-induced Spatial Conflict.
The lab rotation will build skills in computer programming, visual psychophysics and EEG recording and frequency analysis. The programme of work would require the student to develop software to display animated stimuli on a computer screen and collect responses of observers from the computer. The aim would be to develop objective masking methods to measure perceived jitter in a display which contains only smooth motion. We think the jitter reflects the operation of a cortical circuit for motion calibration. According to prior pilot experiments the presence of illusory jitter in the MISC display can mask the detection of real jitter. By varying the frequency of the mask while assessing the detection threshold we can precisely measure the frequency of the subjective jitter percept. We will then compare jitter frequency for any particular individual against the resting alpha frequency for that individual.
Arnold, D.H. & Johnston, A. (2003) Motion induced spatial conflict. Nature, 425, 181-184.
Molecules, Cells and Organisms
LR1, LR2, LR3
Linked PhD Project Outline
Individual differences in Motion-induced Spatial Conflict
When a square made up of a red central stripe and green outer stripes moves over a black background it appears to move rigidly. However, when the red and green stripes are set to be isoluminant then the red bar appears to jitter [1, 2]. The jitter frequency is around 10Hz and we have also shown the apparent perceptual jitter generates a MEG signal in visual cortex that is greater than real jitter .
The jitter can be seen for a physically moving pattern in sunlight - so it is not a consequence of the monitor frame rate or an interaction with variable lighting. It is generated through some cyclical process in the brain which we have identified with a motion prediction and verification operation inherent in the calibration of motion computation.
Remarkably individual differences in jitter frequency vary more than one sees when changing stimulus speed in a single individual. The project will ask what are the consequences of individual jitter frequency for motion processing. Since it is difficult to manipulate jitter frequency we will take an individual differences approach, measuring the jitter frequency for different observers and correlating their individual frequency against their performance on other visual motion tasks and their typical EEG alpha frequency .
- Arnold, D.H., and Johnston, A. (2003). Motion-induced spatial conflict. Nature 425, 181-184.
- Arnold, D.H., and Johnston, A. (2005). Motion induced spatial conflict following binocular integration. Vision research 45, 2934-2942.
- Amano, K., Arnold, D.H., Takeda, T., and Johnston, A. (2008). Alpha band amplification during illusory jitter perception. Journal of vision 8, 1-8.
- Minami, S., and Amano, K. (2016). Illusory jitter perceived at the frequency of intrinsic alpha oscillation. Journal of vision 16, 1127-1127.