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Tracking visible and occluded targets: changes in event related potentials during motion extrapolation
Alexis D J Makin1, Ellen Poliakoff, Wael El-Deredy
1School of Psychological Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Neuropsychologia
|April 8, 2009
Summary
This study used electroencephalography (EEG) to investigate how the brain tracks moving objects. Findings show the brain uses similar systems for visible and occluded targets, relying more on memory when vision is lost.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Visual Perception
Background:
- Tracking visible and occluded moving targets involves overlapping neural systems.
- Visual and stored velocity information guide tracking when targets are visible.
- Occlusion necessitates reliance on stored velocity representations for tracking.
Purpose of the Study:
- To investigate the neural transition to memory-guided tracking after target occlusion using EEG.
- To examine the brain's response during the covert tracking of visible versus occluded targets.
- To determine if the same neural systems are involved in tracking both visible and occluded targets.
Main Methods:
- Electroencephalography (EEG) was employed to record brain activity.
- Participants covertly tracked horizontally moving targets at different velocities (12 or 20 degrees).
- Targets were either continuously visible or disappeared for a short interval.
Main Results:
- Similar positive event-related components were observed over the right occipitoparietal region for both visible and occluded targets.
- The development of this positivity correlated with target location when visible, peaking earlier at 20 degrees.
- Following occlusion, the positive deflection occurred around 200 ms and was not influenced by target velocity or location.
Conclusions:
- The findings support the hypothesis that identical neural systems track both visible and occluded targets.
- The brain's response post-occlusion indicates a cortical registration consistent with increased reliance on memory-guided tracking.
- This study provides neural evidence for the shift towards memory-based processing when visual input is temporarily lost.
