Rocks in our heads, the eyes and rolling in bed

So when these rocks break loose or too many are produced, they can fall out of the vestibule and go into the semicircular canals where they are not supposed to be.  When this happens, our eyes spin like crazy (nystagmus) and that makes us feel dizzy.  This nystagmus is usually perceived as spinning and often times occurs with any movement of the head...especially rolling in bed.