Final answer:
The cortex, specifically the neocortex, has six layers of neurons, the cerebellum has three layers, and the hippocampus has neurons arranged in fields rather than distinct layers.
Step-by-step explanation:
The number of layers of neurons varies among the different brain structures. In the mammalian brain, the cortex, specifically the neocortex, is known for its role in complex brain functions and possesses six distinct layers of neurons. These layers are important for various functions including sensory perception, motor commands, spatial reasoning, and language. The cerebellum, which is essential in the coordination of motor movement and cognitive processes, is organized into three layers known as the molecular, Purkinje, and granular layers. Lastly, the hippocampus, associated with memory and navigation, has a somewhat different organization with neurons arranged in fields such as CA1, CA2, CA3, and the dentate gyrus, rather than distinct layers like those in the cortex.