The Nature-Nurture Question – Nurture – The function of the limbic system is to map our nurture experience into the cortex.

nature nurture limbicThe Nature-Nurture question is the big question, It is central for psychiatry, neuroscience, and child development. And of course, the answer is… it is not either/or, but both. But this answer is insufficient on the face of it. We need to understand what nurture really means. And what are we talking about regarding nature? And how do they actually work together?

Unfortunately the exciting explosion of brain science has led to a confusion and faulty assumption about the what constitutes ‘nature’. The operating belief is that specific brain nuclei, neurotransmitters, cortical locations, and genes directly determine our behavior. And whatever is left over that can’t be accounted for, is attributed to ‘nurture’, whatever that is.

The secret of nature/nurture is that the two work together throughout our development in a particular way. It’s not about pitting them against one another. And we have to understand how they work together to see biology in action. The organization of our limbic cortical brain is geared for the creation of human consciousness. The different parts and functions of the brain do not operate in some stand alone way. They all make contributions to the whole.

In this post we will address Nurture. The function of the limbic system is all about processing the environment in the service of the organism. Its function is to process its germane environment. This is, for the first three years of life, the maternal environment. Our fetal and newborn limbic system maps the survival interactions with the maternal environment as it interfaces with the fetus and infant. This brain circuitry is linked to the body, hormones, subcortical brain, and the cortex— the amygdala for impulses of fear and pleasure; the hippocampus for gluing memories; the cingulate gyrus for attention and autonomic functions, such as heart rate and blood pressure; the hypothalamus for regulating the autonomic nervous system; and the thalamus, the relay station from the subcortex. The maturation of the limbic system is progressive and ongoing throughout fetal/ newborn development. By the time we are born, these limbic circuits have developed and are sufficiently organized for the foundational appetites and rudimentary emotions of fear, anger, alarm, sadness, satisfaction, pleasure, hunger, and thirst.

After six short weeks of life, these foundational appetites and rudimentary emotions mature to a sufficiently high level of order to crystallize into a feeling of tenderness and sweetness in the infant. This creates a cohered feeling of the baby. You can feel him in your heart and he can feel you. Yesterday there was no feeling of the baby. And suddenly it is here. But that is not all. From the mappings of maternal responsiveness, the limbic cortex creates a feeling of the mother inside the baby as well.

In fact the rudimentary ‘self’, the rudimentary ‘other’ and the feeling relatedness between them is the beginning of consciousness. The textured depth and seeming aliveness of the feeling of ‘self’ and ‘other’ flows from the brain-body itself. Consciousness is composed of these synthetic brain creations which come from extremely high levels of order of webs of constellations of constellations of constellations of neurons, from perceptions, impulses, appetites, cravings, images, emotions, ideas, and memory.

Under the best of circumstances, there can be no such thing as perfect maternal responsiveness. There can only be good-enough loving for all of us. There is always some element of abuse and deprivation in ordinary life. Mothering can range from minimally problematic all the way to seriously destructive. The mappings of abuse are infused by the limbic system with the serotonin/ adrenaline fight-or-flight response. Likewise, active protection is a natural function of maternal provision. Biological life always has to contend with survival. There is no such thing as a free, safe life. Mother literally keeps her child alive by feeding and protection. She protects her vulnerable child from harm. Protection experience is limbically mapped by good aggression, which is to be differentiated from sadistic aggression. Protective aggression is not directed at the child by the mother. It is in his behalf, and is mapped through the limbic system as safety, reliability, and trust.

The brain maps its experience of ‘nurture’ into a play in the theater of consciousness. This includes not only the actualities of responsiveness, but the actualities of abuse and neglect, and it maps the actualities of protection as well. These three elements comprise the entirety of the maternal environment. The evolving ‘play’ of consciousness reflects the quality of the baby’s nurture experience. Over the course of the next three years, we continue to field and digest maternal/family experience into the cortex. This encompasses the foundational and central impacts of ‘nurture’ on the developing consciousness of the child.

Early on, the limbic cortex is still very immature and does not have high enough levels of symbolic order to create representational images with actual form. Consequently, the original limbic-cortical mappings of nurture create the feelings of the being of the baby and the mother without form. The maturation of our limbic cortex continues until, by the age of three, it achieves high enough levels of order to create a fully formed representational story with representational images of ‘self’ and ‘other’.

However, ‘nurture’ is only half the story. The final form of our representational play is not just a direct rendering of the actual ‘nurture’ experience of the baby and his mother. His developing image of self and his play, are digested and reconfigured by his temperament. Temperament is the ‘nature’ that fields maternal ‘nurture’. Temperament is composed of a set of four genetically determined pairs of elements that order and organize the formation of the play in consciousness. Together ‘nurture’ and ‘nature’ create consciousness which takes form as is a play in the theater of the brain. See – “The Play of Consciousness: Consciousness is biologically organized as a Drama in the Brain”.

In the next blog we will address what constitutes Nature and its operations – the ‘Nature’ blogs

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