Which term describes signals crossing to the opposite side of the brain?

• A. Ipsilateral
• B. Contralateral
• C. Bilateral
• D. Unilateral

Answer: (B)

Contralateral describes signals that cross to the opposite side. In many brain pathways, information and control cross from one hemisphere to the other, so the left hemisphere processes right‑sided body information and issues commands to the right side. For example, motor commands originate in the left motor cortex and travel down pathways that cross to the right side of the body. Conversely, sensory input from the right side of the body is processed by the left somatosensory cortex because of this crossing. The other terms describe different patterns: ipsilateral means staying on the same side, bilateral means involving both sides, and unilateral means on one side only.