Suppressive traveling waves shape representations of illusory
motion in primary visual cortex of awake primate.
Sandrine Chemla, Alexandre Reynaud, Matteo diVolo, Yann Zerlaut,
Laurent Perrinet, Alain Destexhe and Frédéric
Journal of Neurosscience 39: 4282-4298, 2019.
How does the brain link visual stimuli across space and time?
Visual illusions provide an experimental paradigm to study these
processes. When two stationary dots are flashed in close spatial
and temporal succession, human observers experience a percept of
apparent motion. Large spatiotemporal separation challenges the
visual system to keep track of object identity along the apparent
motion path, the so-called "correspondence problem". Here, we use
voltage-sensitive dye imaging in primary visual cortex (V1) of
awake monkeys to show that intracortical connections within V1 can
solve this issue by shaping cortical dynamics to represent the
illusory motion. We find that the appearance of the second stimulus
in V1 creates a systematic suppressive wave traveling toward the
retinotopic representation of the first. Using a computational
model, we show that the suppressive wave is the emergent property
of a recurrent gain control fed by the intracortical network. This
suppressive wave acts to explain away ambiguous correspondence
problems and contributes to precisely encode the expected motion
velocity at the surface of V1. Together, these results demonstrate
that the nonlinear dynamics within retinotopic maps can shape
cortical representations of illusory motion. Understanding these
dynamics will shed light on how the brain links sensory stimuli
across space and time, by preformatting population responses for a
straightforward read-out by downstream areas.
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