Two fundamental ways of looking at the brain prevail: one is linked to chemical pathways of the brain, the other is electrical or biophysical law-like properties. One is not more valid than the other. They are just two rooted scientific approaches to understanding brain function.
Eliot Valenstein (2005), a behavioral neuroscientist at the University of Michigan, in his interesting book, The War of the Soups and the Sparks, lays out the discovery process involved in the depiction of the classical neurotransmitters (norepinephrine, dopamine) and the depiction of the sympathetic and parasympathetic systems and their representation in the brain. This insight into the chemical nature of the classical neurotransmitters along with the depiction of the electrophysiological properties set the conditions for understanding the brain.
My focus is on the chemical pathways of the brain and the functional role in the organization of social approach and avoidance behavioral responses (adaptive responses rooted in evolution). Social contact, in addition to the development of motor control, language and other cognitive capacities, are critical factors in our evolution. Cave paintings show a sense of the intellectual quest.
An understanding of the sympathetic and parasympathetic systems represented in both the peripheral and central nervous system underlie social attachments and all forms of regulation. A rich chemical milieu permeates these autonomic peripheral systems that underlie the diverse forms of physiological systems across end organ systems in maintaining long-term physiological stability. Importantly, the chemical messages are richly expressed in the central nervous system.