Abstract:

PURPOSE ：Motion perception is important for human beings to interplay with environment, such as walking through the street to avoid moving vehicles. Psychophysical researches on human beings reveal that the old people show accumulating deficits in motion perception. Previous studies suggesting decreased neuronal inhibition in visual system accounts for some of the de?cits. However, some visual functions in the old remain the same or even better than young people, suggesting aging a?ect di?erent inhibitory mechanisms di?erently. This research want to prove this assumption.
METHODS: Here we used motion repulsion and drifting gabor direction discrimination paradigms to investigate inhibitory machanism. Motion repulsion refers to the phenomenon observers overestimate the perceived angle when two superimposed dot patterns moving at an acute angle. The misperception has been interpreted as mutual inhibition between nearby direction-tuned neurons within the same cortical area. At high contrast, the drifting gabor direction discrimination threshold increases with the enlargement of the gabor size. This is considered as behavioral manifestation of surround suppression and directed by feedback inhibition from higher cortical regions to primary visual cortex.
RESULTS: We found motion repulsion in elder people was much larger than younger ones. But the increase of motion discrimination threshold with enlargement of drifting gabor size in older group was much less than younger group
CONCLUSIONS: We suggest that the altered motion repulsion in the aged may result from enhanced mutual inhibition in the same area. The decreased change of threshold in the old group is consistent with previous findings. We interpret this result as attenuated feedback inhibition from higher level area to lower level area. Our data indicates that aging a?ect intra-areal inhibition and inter-areal inhibition in visual motion system di?erently.

Key words: aging, motion repulsion, motion discrimination, mutual inhibition, feedback inhibition