Optimum stimulus size for the human brain to respond to motion: A magnetoencephalographic study

► We investigated the effect of stimulus size on the human brain response by magnetoencephalography. ► The peak latency of the motion response decreased with an increment of size up to 16.8 × 22.4 deg, and increased at 44.8 × 57.4 deg for every motion speed set. ► This U-shaped latency change with size appeared for the motion response but not for the response to the counter phase flickering stimulus (stimulus size and temporal frequency were set equal to those of motion).