Which brain structure is responsible for higher-order functions such as thinking and planning?

The cerebral cortex is indeed the correct answer as it plays a crucial role in higher-order functions, including thinking, planning, problem-solving, and decision-making. The cerebral cortex is the outer layer of the brain and is divided into several lobes, each associated with different functions. For instance, the prefrontal cortex, which is part of the frontal lobe, is particularly important for executive functions like strategizing and controlling impulses.

This structure is involved in processing complex information and integrating sensory input with previous knowledge to guide behavior and thinking. Its development is closely linked to the ability to engage in abstract reasoning and future planning, making it essential for tasks that require a high degree of cognitive functioning.

Other brain structures listed, such as the amygdala, medulla, and hippocampus, have their own specific functions. The amygdala is primarily involved in emotional processing, the medulla controls vital autonomic functions such as heart rate and breathing, and the hippocampus is crucial for memory formation. Although all these structures are important for various aspects of behavior and cognition, it is the cerebral cortex that is central to the higher-order cognitive processes highlighted in the question.