Interpersonal Neurobiology Can Lead to Healthier Communities
When I was first introduced to interpersonal neurobiology (IPNB) 10 years ago it felt like the locked door to a secret room had been opened. As I stepped inside, I saw before me answers to help understand the science of what it means to be human and a way to make sense of our complex nature. Drawing on evidence-based studies across multiple disciplines, IPNB examines the evolution, the development, and the mechanisms of the nervous system, allowing a greater appreciation of our relationships, with others and with ourselves. Focusing on neural systems that organize attachment, emotion, feelings, attunement, and social communication, IPNB attempts to observe how neural structure and experience interact with one another. In other words, IPNB focuses on the importance of relationships, how we connect and are impacted by those connections, and how relationships change the architecture and functioning of the brain. In its essence, IPNB recognizes the brain as a social organ that is built through experience (Cozolino, 2014).
In the following article I will give an overview of neuroanatomy, illustrating both the inborn mechanisms that foster our drive to survive as well as the experience-dependent nature of our brains. I will also describe how feelings and emotions differ, and how they are valuable and inexorable parts of our nervous system, fundamentally linked to the behavioral tendency of all organisms to approach that which is life-sustaining and avoid that which is dangerous. Furthermore, the vast majority of what motivates us is generated below the level of our awareness; we are not nearly as grounded in conscious and compassionate decision-making as we might believe (Sapolsky, 2017). Last, but certainly not least, the particular way that an individual navigates their world depends upon their social connections. Relationships are our natural habitat and the qualities of our human community affects everything from our emotional and biological health to our intellectual abilities (Cozolino, 2017).
I first heard the statement “ontogeny recapitulates phylogeny” (Haeckel, 1892), when I was in college, and I found it fascinating. I became curious about the parallels between individual development and evolutionary history and found myself drawn to the sciences. While the theory of recapitulation is now considered largely defunct, there are aspects that are useful. Indeed, the development of the brain in utero reflects the development of the brain in evolution. In the 1960s, Paul MacLean, a physician and neuroscientist, first described the brain as a three-part system, and in 1990 he published a book called The Triune Brain in Evolution proposing the reptilian, the paleomammalian, and the neomammalian as the different parts (MacLean, 1990). This three-part structure is useful in giving an overview of neuroanatomy and illustrates the way we can observe aspects of our evolutionary history in the developing human being. In reality, this model is static because all three areas have continued to evolve. Nonetheless, it is helpful to look at this simplified view of the brain.
The reptilian brain
The reptilian brain is the most primitive part and is the most activated area of the brain when we are first born. It is located at the base of the brain where the spinal cord first enters the skull. The reptilian brain, which contains the brain stem and cerebellum, is responsible for all of the things a baby can do at birth: cry, eat, sleep, wake, breathe, feel discomfort or pain, or empty its bowel and bladder. The brain stem, along with the hypothalamus (which sits just above the brain stem), work to promote homeostasis in the body through their influence on the nervous system, as well as the endocrine and immune systems, controlling the functioning of the heart and lungs and the energy levels of the body.
The cerebellum, which is included in the reptilian brain, is a perfect example of how MacLean’s model is inadequate in explaining many of the brain’s complexities. Indeed, the cerebellum helps with the very basic functions of balance and coordination of movement, as well as the control of muscle tone and the maintenance of equilibrium (Brodal, 1992). It contains cells responsible for mediating the body’s reactions to threat. One could say that it is the seat of our “automatic pilot”. However, the cerebellum also influences some higher order cortical operations by coordinating important aspects of memory formation and the integration of sensory perceptions (Inhoff, Diener, Rafal, & Ivry, 1989). The outer lobes of the cerebellum work with the association areas of the cerebral cortex, modulating mechanisms involved in motivation, emotional behaviors, and behavioral integration (Berntson & Torello, 1982).[Content protected for subscribers only]