A 24-year-old man who lives in Africa presents

with muscle weakness in his legs. His physical exam demonstrates muscle

weakness in all limbs, but his legs are most affected. Testing (polymerase

chain reaction, PCR) confirms poliovirus in his cerebrospinal fluid. Poliovirus

mainly affects second motor neurons of the corticospinal tract and, therefore,

will affect cells whose cell bodies are located in which of the following?