They have characteristics that relate to the area of the brain they point to, and in simple worms are somewhat transferable. Worms, taught to head to the right or left for food or to avoid injury, can have their brains fed to other worms, who then seem to have ingested knowledge. The brain chemicals, not broken down during digestion, migrate in the blood stream to the brain, and being of similar chemical composition in similar worms, attach to the brain pathways of the new host. The chemistry for right or left is specific in these worms, being on one side of the brain or another with some slight differences, and where these differences weigh only slightly they weigh enough to set the ingesting worm to favor connecting to one side of the brain or another. A transferred learned response, proving that the brain works by chemistry, chemical paths and chemical images.
Emotions are chemistry, generated from within.
Sensations, the power of the brain to retain ideas, is also intrinsically allied with chemical reactions. In fact, it forms the base. Hormones stimulate feelings, and homones are created by nervous stimulation of the glands. It is all intertwined. Senses receive light rays or heat, or other such stimuli that create chemical reactions that travel along nerves and are then stored in your brain by chemical changes.