Which part of the brain is the largest and is associated with higher brain functions like thought and action?

The cerebrum is indeed the largest part of the brain and is primarily responsible for higher brain functions, including thought processes, reasoning, problem-solving, and voluntary muscle movements. It is divided into two hemispheres and has regions that specialize in different functions, such as the frontal lobe for planning and decision-making, the temporal lobe for hearing and memory, and the parietal lobe for sensory information processing.

This structure is crucial for complex cognitive abilities and is involved in interpreting sensory information and coordinating actions. In contrast, the cerebellum, while important for motor control and coordination, does not handle higher cognitive functions to the same extent. The brainstem regulates basic life functions such as breathing and heart rate, and the thalamus acts as a relay station for sensory information but is not involved in higher cognitive processes. Thus, the primacy of the cerebrum in relation to thought and action makes it the correct answer.