The Amazing Human Brain and Human Development

Lesson 4: Communication and Defense

The Brain and Communication

Welcome to Lesson 4 of the Amazing Human Brain. Communication is a complicated process that has taken many, many years to evolve. Now that you've spent the first three lessons learning about the fine points of the physical brain, you'll learn how the brain operates something as intangible as communication.

We will also talk about how different parts of the brain respond to trauma. I asked you to log on to the Message Board with your thoughts about this in Lesson 3. Let's see how close you were.

Humans are Special

Communication between one human and another is the hallmark of our species. Communication was the critical capacity required for survival during the thousands of generations of our evolution. Naked, slow, weak, and without biological armor or weapons, humans survived by living and hunting in groups. Interdependent individuals created a strong, flexible, and adaptive "whole" -- the band, the clan, the tribe.

While physically separate and self-aware, individual humans are linked by the invisible bonds of sensation, perception, and communication into larger biological units, or groups. One individual may belong to many groups -- a couple, a family, and a working group. Each group has a unique set of tasks and a set of rewards for its members. The integrity and function of the group is formed, maintained, and changed by social interaction.

The human brain developed remarkable biological apparatus dedicated specifically to social perception and communication, verbal and non-verbal. These underlying biological properties are continually at play in all human interactions -- sensing, processing, perceiving, storing, and acting on signals from other humans. All human interactions are governed by core principles of communication that are the product of neurobiological processes shaped by thousands of years of evolutionary pressures.

Through the evolutionary process, the remarkable expressive communication capacity of the face was further refined. In fact, facial expression became the most important of all social communication instruments. What else has the capacity to both reflect the internal emotional state of the individual and elicit a specific emotional and social response? The various faces we make can express the full range of human emotions.

Beware of Strangers

During their development, each person creates a catalogue of familiar faces and stores these as templates for familiar/safe. In these familiar faces, the infant and child learn the non-verbal language of the group as surely as they learn the verbal language. An unfamiliar face will elicit a low-level alarm response in any individual. All new faces are judged to be threatening until proven otherwise.

 Two factors provoke this reaction. First, the brain's information matching process is very conservative. All novel situations and new information are judged to be threatening until proven otherwise. The second specific reason that new faces elicit a low-level alarm is that the human brain evolved in a world where, for thousands of generations, the major threats to any individual were other humans.

A new person, a new face in the typical interaction from our history meant that there were other humans around competing for the same water, fruits, game, and cave. This new person was as likely to attack as he was to decide to affiliate or cooperate. Across generations, wariness to new individuals, new groups, and new ideas was selected and built into the circuits of the human brain's alarm response.

Mismatching and Human Behaviors

Templates for faces and facial features of same/safe/familiar, like all other templates for emotional, behavioral, and social functioning, are set during childhood. The tendency to have an alarm response when exposed to an unfamiliar face or mismatched facial features is at the root of many human behaviors.

Despite very minor differences in facial feature placement, almost all people can immediately recognize a Down syndrome child. This matching against previous template faces is at the root of racism (and is a strong argument for placing children of different races together in school and play, allowing them to acquire a diverse set of internal templates for what is same/safe/familiar).

This capacity to match diverse information against previous templates of multi-sensorial input is also at the root of the recognition of deceit. When words do not match body movement, facial expression, or the tone of voice, the brain "senses" a multi-sensory mismatch.

When someone says, "I love you," there are accompanying non-verbal signals validating the verbal information, such as eye contact or facial expression. The same can be said of someone who is telling the truth. Children raised with caregivers who "talk the talk" but don't "walk the walk" (e.g., those exposed to domestic violence or multiple foster homes) internalize patterns of communication and interaction that are distorted and often destructive. This is also how a child learns the mismatched association between intimacy, power, violence, and threat.

Through thousands of generations of evolutionary selection the brain developed its amazing capacity to read non-verbal cues, many of which are communicated via changes in facial expression. The brain has special face and expression recognition capabilities and, through a process of "matching" expressions and faces with existing templates, makes decisions about the familiarity and intent of the specific interaction.

Secondary Cues to Template Recognition

Because we have a limited capacity for categorizing and matching specific faces and facial expressions, the brain utilizes other cues to make decisions about potential friends and enemies. Characteristics such as body movements, postures, or other symbolic trappings of recognition, such as clothes, uniforms, or style of haircut, are used to make secondary decisions about recognition. You may not recognize the face, but the haircut, clothes, or manner of interaction can readily identify someone as "familiar/good" or as "familiar/bad."

This categorizing tendency is the basis for a host of well-described and common phenomenon in human interaction -- including first impressions or using "known" celebrities to sell products or ideas. A classic example of this in the mental health field is transference. This is the phenomenon of attaching multiple attributes of a past relationship to one in the present when only one of those attributes may truly be present (e.g., reacting to a male therapist with the intensity that was present in a paternal relationship).

Children raised in deceitful settings easily lie without detection. They have not internalized the same non-verbal templates associated with deceit as the rest of society has. For these children, the development of sociopathic characteristics is merely an adaptation to the deceitful, inconsistent, and unrewarding world their caregivers have created for them.


I Understand

Central to the invisible biological processes that allow social interaction is communication -- the capacity to perceive and understand others and to express meaning and intention to others. Just as there are parts of the brain responsible for moving, seeing, or hearing, there are systems in our brains dedicated to social affiliation and communication.

Yet Another Brainy Factoid

Although we do have the gift of language, we are not unlike non-human primates when we resort to "hollering" and beating our chests. While humans rely on their words to impart intent, our non-verbal communication (mostly mediated by our faces) is still our primary form of communication. Think about it. How often have we all experienced this -- rolled eyes ever so slightly with the smallest down turn of the mouth at the same time their words say, "Oh, that sounds good." Now what do they really mean? We humans use words to conceal as much as we use them to reveal.

Key Brain Systems Involved in Threat, Fear, and Trauma

A terrified three-year old child huddles, sobbing, in a dark corner of his room after being beaten by a drunken parent for spilling milk. A colicky infant cries for eight hours, left alone, soiled and hungry, by an immature, impaired mother. A seven-year old boy watches his father beat his mother, the most recent of many terrorizing assaults this child has witnessed in his chaotic, violent household.

Terror, chaos, and threat permeate the lives of too many children. Millions of children across the globe each year have tiny pieces of their potential chipped away by fear. When fear is omnipresent, it changes the child. These powerful experiences work to literally change the brain of a frightened child. Fear inhibits exploration, fear inhibits learning, and fear inhibits opportunity.

In order to understand what is happening inside these children, we need to continue our study of the basic organizational and functional properties of the human brain. We've already covered some of the core elements of brain structure and organization that serve as a background for this lesson. Now, let's turn our attention toward some of the key features of the brain that are directly influenced by trauma, neglect, or fear.

In order to understand the traumatized child, we must first understand the fear response. The human brain has a very elaborate and important set of neural systems involved in the response to threat. The abnormal persistent activation of these systems appears to lead to many of the symptoms seen in maltreated children. We'll begin, then, by examining the key brain systems regulating the stress response.

Neurotransmitters and The Stress Response

There are many neurotransmitters involved in the stress response. Some of the most important neurotransmitters are actually clusters of extrinsic neurons. These systems have disproportionate power to regulate human behavior, emotional functioning, and cognition. This is because these systems originate in the brainstem and have connections in virtually all brain areas. The brainstem regulates and mediates hundreds of crucial functions -- including the complexities of the stress response.

The Reticular Activating System (RAS)

The RAS originates in the brainstem and is a network of ascending, arousal-related neural systems. The RAS plays a major role in arousal, anxiety, and the modulation of limbic and cortical processing. These brainstem and midbrain monoamine systems, working together, provide the flexible and diverse functions necessary to modulate the variety of functions involved in anxiety regulation.

Locus Coeruleus

The locus coeruleus (LC) is a critical brain stem nuclei involved in initiating, maintaining, and mobilizing the total body response to threat. The LC plays a major role in determining the value of incoming sensory information, increasing in activity if the information is novel or potentially threatening. Acute stress results in an increase in LC activity. The LC plays a critical role in regulating arousal, vigilance, affect, irritability, locomotion, attention, the response to stress, sleep, and the startle response.


The hippocampus is critical to the process of learning. It takes short-term memory and converts it into long-term memory. It plays a major role in memory, including what we call episodic, declarative, and spatial learning and memory. The hippocampus also plays a key role in various activities of the autonomic nervous and neuroendocrine systems.

Stress hormones and stress-related neurotransmitter systems have the hippocampus as a target. Various hormones (e.g., cortisol) appear to alter hippocampus synapse formation, thereby causing actual changes in gross structure and size. Repeated stress inhibits the development of neurons and atrophy of the hippocampus can occur. These neurobiological changes are related to some of the problems with memory and learning found in stress-related neuropsychiatric syndromes, including post-traumatic stress disorder (PTSD).


In the recent past, the amygdala has emerged as the key brain region in the processing, interpreting, and integration of emotional functioning. The amygdala is where fear learned from past experience is permanently stored. In the same fashion that the LC plays the central role in orchestrating arousal, the amydgala plays the central role of processing afferent and efferent connections related to emotional functioning.

The amygdala receives input directly from sensory systems throughout the brain. The amygdala processes and determines the emotional value of simple sensory input, complex multisensory perceptions, and complex cognitive abstractions. The amygdala orchestrates the response to this emotional information by sending projections to brain areas involved in motor (behavioral), autonomic nervous system, and neuroendocrine areas of the CNS.


The quality and intensity of any emotion, including anxiety, is dependent upon subjective interpretation or cognitive appraisal of the given situation. How an individual cortically interprets the limbic-mediated activity (i.e., their internal state) associated with arousal plays a major role in the subjective sense of anxiety.

Kluver-Bucy syndrome, the result of damage to or surgical ablation of temporal lobes, results in loss of fear for current and previously threatening cues. The general lack of inhibition demonstrated by this syndrome suggests a loss of the capacity to recall cortically stored information related to previous threat, or to efficiently store threat-related cues from new experience.

Other areas of the cortex play a role in threat. Foremost among these are the primary and multimodal association areas, which have direct connection to the amygdala.

Coming Up

We covered an enormous span of material in this lesson. How are you doing? I expect many questions to come up from this lesson, and I cannot urge you enough to use the Message Board for them. Your questions and thoughts will undoubtedly help shed light on the subject for others in the class. I look forward to seeing them.

In the next lesson, we're going to learn how the brain stores experience and how it is changed by those experiences.


Important Neurotransmitters in the Cortex

Do you remember what a neurotransmitter is? It is the chemical that a neuron releases in order to relay information to another cell.

Important neurotransmitters in cortical regions are GABA and glycine. The capacity of benzodiazepines to alter arousal and sensitivity to threat has long been known. The principle pharmacological treatment for many anxiety disorders involves benzodiazepine treatment, targeting GABA receptor complexes.

Scientists Demonstrate Key Role of Amygdala in Emotional Memory

The site of perception of anxiety is likely to be the amygdala. In experiments with laboratory rats, scientists have determined that a rat without an amygdala has no fear of cats! When the "storage bin" for emotional information is missing, the emotion is lost.

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