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Frederic Chavane, Alexandre Reynaud, Guillaume Masson; The role of cortico-cortical interactions during motion integration: a voltage-sensitive dye imaging study in V1 and V2 of the awake monkey. Journal of Vision 2008;8(6):226. doi: 10.1167/8.6.226.
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© ARVO (1962-2015); The Authors (2016-present)
Lateral interactions are crucial mechanisms involved in contextual modulation of visual processing from which motion percept can emerge, such as in the case of apparent motion. Integration of a sequence of static stimuli could evoke motion signal in the visual system through spatio-temporal interactions originating from horizontal intra-cortical interactions or feedback from higher areas. However, horizontal and feedback interactions differ from their spatial and temporal properties, the first pathway being less extended and slower. Using voltage-sensitive dye imaging (VSDI) we investigated what are the cortico-cortical interactions that can shape the emergence of a motion signal in V1, in the awake monkey.
Using VSDI, we observe that local stimuli, containing or not motion information, activate a restricted cortical area followed by horizontal propagation of activity along the cortex at slow speed. In a sequence of two local static stimuli, 2 stroke apparent motion, two waves of activation, the horizontal propagation evoked by the first stimulus and the feedforward activation of the second stimulus, are interacting in V1. This interaction can lead to the emergence of a wave of propagating activity as was observed in the anesthetized cat (Jancke et al 2004). To identify the different roles of the various cortico-cortical interactions in the apparent motion integration, we therefore explored different spatio-temporal parameters of the 2 stroke apparent motion. The observed non-linear cortical interactions were then compared to the activity generated by real motion stimuli. Depending on stimulus characteristics, this cortico-cortical interplay develops a dynamical balance of facilitation and suppression. These non-linearities allow for the emergence of a gradual and smooth wave of normalized activity.
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