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The temporal sequence of evoked and induced cortical responses to implied-motion processing in human motion area V5/MT+

Authors


Dr I.P. Fawcett, as above.
E-mail: fawcetti@aston.ac.uk

Abstract

Previous functional magnetic resonance imaging (fMRI) studies have demonstrated that the human visual motion area V5/MT+ is differentially activated by stimuli in which the presence of motion is implied by the content of static photographs, compared with similar static scenes in which no motion is implied. Here, using a group magnetoencephalography study, we confirm the role of V5/MT+ in the perception of implied motion (IM) by the measurement and localization of task-related evoked and induced oscillatory responses, and demonstrate the temporal sequence of these responses. Within the lateral occipital complex, including V5/MT+, statistically significant differential oscillatory responses to IM and implied-static (IS) stimuli were only found in the beta band (15–20 Hz). An early, evoked, beta power increase (IM > IS) occurred at about 150 ms, whilst a power decrease (IM < IS) occurred at approximately 700 ms. We additionally show that the difference between the early evoked beta responses for the IM and IS conditions only occurs when participants are able to ascertain whether an IM or IS photograph is expected. We therefore hypothesize that the enhanced early response represents covert priming of V5/MT+ for the arrival of a motion stimuli, whilst the late-induced beta power increase for IS stimuli indicates suppression of activity within V5/MT+.

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