What are the holes in the rear seat for?

In the middle of the rear seat, there is a thick plastic cover. Looking at the under side of the seat, it seems that its function is to cover 5 holes.

:?: Does anyone know what the holes are for? :?:

Wrong question, because you've misidentified the plastic panel. It isn't there to cover anything. It's there to make it clear nobody's supposed to be sitting there. The i-MiEV is strictly a 4-passenger vehicle, with no space or safety equipment for a middle occupant. In such designs, I believe there's a legal requirement to "disable" the center position - I take it that hunk of plastic was the lowest cost means of satisfying that requirement.

+1