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Abstract:
From a very young age the human visual system can accurately
track moving objects even when they are briefly out of sight due to
occlusion by other surfaces. Previous electrophysiological studies
in non-human primates have shown that neurons in parietal areas and
STS continue to fire even when a moving target disappears. The
continuous firing appears to be due to perceptual memory of the
moving target. The human analogue of lateral intraparietal (LIP) is
not well understood and human motion perception areas, such as
superior temporal sulcus (STS) and MT/V5, differ from that in
monkeys. Thus whether or not the same areas would be responsive to
occluded motion in monkeys and humans is not known. We used fMRI at
1.5 T to compare the neural activations correlated with viewing
motion that is briefly occluded (~3 s), compared to motion that has
ceased for 3 s, and then resumes. Subjects were required to press a
key when the moving ball appeared on the opposite side of a central
occluder. We compared images acquired during the perception of
continuous motion, occlusion, and disappearance. We present data
from composite and individual images, an ROI analysis, and a
timecourse analysis. The results suggest a role for numerous
posterior sites in perceiving and maintaining information on
occluded motion.
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