Visual Stability and the Motion Aftereffect: A Psychophysical Study Revealing Spatial Updating

Eye movements create an ever-changing image of the world on the retina. In
particular, frequent saccades call for a compensatory mechanism to transform the
changing visual information into a stable percept. To this end, the brain
presumably uses internal copies of motor commands. Electrophysiological
recordings of visual neurons in the primate lateral intraparietal cortex, the
frontal eye fields, and the superior colliculus suggest that the receptive
fields (RFs) of special neurons shift towards their post-saccadic positions
before the onset of a saccade. However, the perceptual consequences of these
shifts remain controversial. We wanted to test in humans whether a remapping of
motion adaptation occurs in visual perception.

The motion aftereffect (MAE) occurs after viewing of a moving stimulus as an
apparent movement to the opposite direction. We designed a saccade paradigm
suitable for revealing pre-saccadic remapping of the MAE. Indeed, a transfer of
motion adaptation from pre-saccadic to post-saccadic position could be observed
when subjects prepared saccades. In the remapping condition, the strength of the
MAE was comparable to the effect measured in a control condition
(33±7% vs. 27±4%). Contrary, after a saccade or
without saccade planning, the MAE was weak or absent when adaptation and test
stimulus were located at different retinal locations, i.e. the effect was
clearly retinotopic.

Regarding visual cognition, our study reveals for the first time predictive
remapping of the MAE but no spatiotopic transfer across saccades. Since the
cortical sites involved in motion adaptation in primates are most likely the
primary visual cortex and the middle temporal area (MT/V5) corresponding to
human MT, our results suggest that pre-saccadic remapping extends to these
areas, which have been associated with strict retinotopy and therefore with
classical RF organization. The pre-saccadic transfer of visual features
demonstrated here may be a crucial determinant for a stable percept despite
saccades.

For the full article visit: Visual Stability and the Motion Aftereffect: A Psychophysical Study
Revealing Spatial Updating
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