The field of study concerned with the structure and function of the brain and nervous system is neuroscience. It examines the nervous system at many levels, from molecules and individual neurons to brain regions, neural circuits, behavior, and consciousness.
Neuroscience developed from older disciplines such as anatomy, physiology, and biology. Modern progress accelerated in the 20th century through advances in electrophysiology, molecular biology, brain imaging, and computing. Researchers now study how neurons communicate at synapses, how networks produce movement and perception, and how the brain supports learning, memory, emotion, and decision-making.
The wrong options are related but narrower or more clinical. Neurosurgery is the surgical treatment of disorders involving the brain, spinal cord, and nerves. Neurology is a medical specialty focused on diagnosing and treating diseases of the nervous system. Neuropsychology studies how brain structure and damage relate to psychological processes and behavior. All may overlap with neuroscience, but none is the broad canonical answer to this definition.
The nervous system includes the central nervous system—the brain and spinal cord—and the peripheral nervous system, which connects it with the rest of the body. Neuroscience therefore covers far more than the brain alone.