Neural Pathways of Bonding and Relationships

To quote the well-known and beloved book, The Body Keeps Score, which discusses the neuroscience and psychology behind intergenerational hurt and trauma, “If your parents’ faces never lit up when they looked at you, it’s hard to know what it feels like to be loved and cherished.” From a neurological point of view, the importance of mother’s love cannot be underestimated. Numerous studies on attachment and the human brain prove the initial bonding of mother-offspring attachment underlies the quality of bonding in relationships for the rest of one’s life. These relationships include close friends, other family members, mentors, sports teams, etc., and, importantly, bonding in romantic partnerships. Every relationship makes use of the same complex neural network (reward-motivation, embodied simulation, and mentalization) involved in mother-offspring bonding - involving the neurotransmitters, oxytocin (OT) and dopamine (DA). When we are held lovingly as a child, when we are cared for and understood deeply by our caregivers, we neurologically and emotionally form the capacity to establish and foster healthy relationships into adulthood. But what happens to those who experience neglect or adverse trauma in these “critical periods” of development? Will those neglected ever have the neural capacity to know how to give love, and importantly, how to be loved?

Before diving into those questions, let us review briefly the neural mechanisms and complex brain systems involved in attachment. When a relationship begins to form, oxytocin neurons in the hypothalamus (located between the thalamus and pituitary gland at base of the brain) release oxytocin in the posterior lobe of the pituitary glands (located under the hypothalamus), which then enters the bloodstream - spreading throughout the body. Although oxytocin is mainly known as the “cuddle hormone,” it works together with other neurotransmitter pathways, such as those releasing dopamine, to form relationships - increasing feelings of trust, love, empathy, and compassion. These neurotransmitter pathways dictate both the time of pair-bonding and whether we have the neural plasticity (capacity) to form new attachments. When we experience love, cortisol release, dopamine (pleasure and motivation), oxytocin (trust and attachment), vasopressin (sexual arousal and attraction), obsessive thinking and aggression are typically high. In contrast, our pain sensitivity decreases, as well as sadness, fear/anxiety. Other important neurological systems in attachment involve the nucleus accumbens (important for pleasure-reward pathways, located in the basal forebrain, where dopamine is projected from the ventral tegmental area, and where oxytocin receptor-containing inputs are received), the amygdala (important for emotion and fear), the anterior cingulate cortex (important for emotional expression, attention, and mood regulation, located along the midline of the cortex), and the striatum (important for hardwiring connections of bonding for behavior and senses, receives dopamine inputs from VTA for pleasure-reward pathways, and is the interface between the cerebral cortex and other parts of the brain).

The 3 major complex systems involved in attachments are: embodied simulation (the synchronized behavior and understanding of what another person is feeling; being able to emulate another’s emotions in order to respond appropriately), mentalizing (conceptualizing a larger picture of what is occurring in the relationship, imbued with beliefs, thoughts, and intentions with others to create a sense of togetherness), and reward-motivation (supports attachment-related motivational behaviors such as social orienting, social seeking, and maintaining contact). 

Several studies such as the Harry Harlow experiment and Romanian orphans study demonstrate how neglect between mother-offspring attachment can facilitate feelings of isolation, unsafeness, and insecurity later in life. 

Key findings in the Neurobiology of Human Attachments Model: 

1. Later relationships are framed and supported by neurobiological systems from mother-offspring attachment in early life.

2. Behavioral synchrony of nonverbal actions with physiological responses are key to forming human attachment. If a mother does not treat her child with loving behavior, the child will often struggle with giving and receiving this behavior in later relationships.

3. Oxytocin is essential in mothering, fathering, coparenting, romantic partnership, and close friendships. OT and DA together spark bonding, motivation, and vigor in human attachments.

4. Quality of human attachments in our lives are critical to our health, well-being, and life span.

5. Attachment patterns are carried through generations on the hormonal level. Behavior patterns from childhood organize OT availability and location of OT receptors, shaping the infant’s brain and ability to parent the next generation.

6. Physical proximity in mother-offspring attachment is also essential in full development of infant’s brain for need of social affiliation and to be formed as a mature, “situated organ.”

7. Later human bonds can IMPLICATE neural plasticity of the brain and attachments by reorganizing OT availability that was formed during mother-offspring attachment in early life. Later benevolent and healthy attachments can repair neural networks hindered by negative early life experiences.