Final answer:
Research on decerebrate rats has shown that the brain stem is responsible for basic functions like chewing and swallowing, as these are preserved even after higher brain functions are compromised.
Step-by-step explanation:
Studies using decerebrate rats indicate that the brain stem contains circuits that allow a rat to chew and to swallow. Decerebrate rats still exhibit basic reflexes such as chewing and swallowing because these functions are controlled by brain stem circuits, not by higher brain regions that are disconnected in decerebration. These findings support the idea that the brain stem plays a critical role in regulating the autonomic components of ingestion without requiring input from the forebrain.