When researchers olds and milner (1954) accidently placed electrodes near a rat's the animal kept returning to the place where it had been stimulated?

hypothalamus

Explanation:

In 1954, the researchers Olds and Milner observed that mice with electrodes (wires) that were accidentally introduced into their hypothalamus beat their paws on bars to receive an electrical stimulus in that region. They exhibited self-stimulation behavior so exaggerated that they sometimes stopped eating and sleeping to keep tapping their paws and thus continue to receive the stimuli. It was observed, however, that only a limited number of brain regions triggered such addictive behaviors, other rats received the same electrical stimulation in these regions and exhibited natural water and food consumption behaviors, implying only feelings of reward and motivation.