The right side of the brain controls motor activity on the left side of the body because nerve tracts decussate in the 00:40 Biology Chapter 8 The right side of the brain controls motor activity on the left side of the body because nerve tracts decussate in the A. pons. B. midbrain. C. thalamus. D. medulla oblongata. Answer: thalamus Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+