Early Postural EMG Dynamics During Optic Flow: Effects of Time, Velocity, Retinal Location and Laterality

Background/Objectives: Optic-flow velocity is known to influence postural sway, whereas corresponding electromyographic (EMG) effects may be difficult to detect when muscle activity is averaged over long stimulation periods. We therefore investigated the early temporal organisation of muscle activity following optic-flow onset and examined whether this response was modulated by stimulus velocity, retinal stimulation location, and laterality.

Methods

Surface EMG recordings from the tibialis anterior (TA), soleus (SOL), trapezius descendens (TD), and paraspinal C4 muscles were reanalysed from a previously published dataset of 18 healthy adults exposed to radial optic flow at five velocities and three retinal stimulation configurations. RMS activity was quantified in two consecutive post-stimulus windows, 0-200 ms and 200-400 ms, and analysed using repeated-measures ANCOVA with baseline activity entered as a covariate.