The Social Brain

The Mind is Mapped Onto the Head in Phrenology (de Phrenologie (1894) by Friedrich Eduard Bilz (1842-1922): Das neue Naturheilverfahren (75. Jubiläumsausgabe), In the public domain, PD-US
The Mind is Mapped Onto the Head in Phrenology (de Phrenologie‘ (1894) by Friedrich Eduard Bilz (1842-1922): Das neue Naturheilverfahren (75. Jubiläumsausgabe), In the public domain, PD-US

How Does the Brain Make Us Social?

Ever wonder how are our brains arranged to allow us to act as a member of a social group? I will go back to the very origins of a brain to investigate this behavior, describing both anatomy and physiology of simple to very complex neural circuits necessary for us to be social beings. There is an extremely important point I make in this post: nervous tissue is different from all other tissue. Its properties seem to be “pre-designed” to make it uniquely capable of allowing an organism to interact with another in a complicated way.

There are differences in the brain among vertebrates, reflecting the need for “attachment” between two or more animals. There are also levels of attachment seen in brain organization and function, reflecting the fact that social groupings can be more complex. I bring a very different perspective to the discussion, and hope to provoke more discussion with the ideas I present in this post. If we look at all animals on the earth, we see that by far, the default condition in the vertebrate brain is one of an “asocial” animal, whose species consists of members who come together with another of their own kind only when reproducing or defending territory (for which in the latter situation, “together” doesn’t mean an amicable association). For the default condition in the brain, there has to be representation of the self. Why? Because the brain is the ultimate commander who intervenes between the individual and the external environment. It is capable of doing this because it also controls the internal environment. The representation in the brain of another individual in a social interaction has to be done differently from the representation of the self. Thus, in a social situation, as in any situation where the individual must face something outside of its own body, there has to be a duality in the brain between “inside” and “outside”, “self” and “the other”.

Nervous Tissue is Different

The pancreas, below the stomach. Note the arrow to the pancreatic duct stops short of the duct, the branched darker green lines (Wikipedia)
The pancreas, below the stomach. Note the arrow to the pancreatic duct stops short of the duct, the branched darker green lines (Wikipedia)

Part of the function of the brain is to appoint “roles” to each nerve cell, or neuron (see my blog post “Segmentation in the Nervous System”). Unlike any other tissue in the body, nervous tissue cells can behave very differently depending upon to what role they have been assigned. Pancreatic cells have their roles decided for them by the developmental process whereby certain genes are turned on or off to a permanent state. If you move an acinar cell to an area where you have islet cells, that acinar cell, at some point in development, when pancreatic cells have become “determined”, will continue to produce insulin, and the islet cells will continue to produce epinephrine or norepinephrine.

Pancreatic islet (large lighter pink area), surrounded by acinar cells (darker, purple), from Wikipedia
Pancreatic islet (large lighter pink area), surrounded by acinar cells (darker, purple), from Wikipedia

The biological activity of every neuron is essentially the same. There is a difference in what neurotransmitter gets made, but the neurotransmitter that is produced is not nearly as important as the location of the neuron. The location of the neuron dictates the outcome of the action of the neurotransmitter released, unlike that acinar cell in the pancreas, because the neurotransmitter will cause other surrounding neurons to do something different from the neurons that surround a neuron at another location producing the same neurotransmitter. Every cell in the brain gets assigned a role, and is thus representative of a concept, word, object, person, geographic location, event, memory, process, etc. This is what makes the nervous system unique to any other tissue in the body. It is what makes “mirror neurons” possible (Fabbri-Destro 2008, Gallese 2007, Kohler 2002, Rizzolatti 2008),  and  probably is the underlying reason that many think that there is such a thing as “body memory” (van der Kolk, 1994, Pearsall et al, 2005). The concept of “body memory” has gotten some traction from the “cell memory” group, mostly made up of immunologists who wanted to investigate how T-cells and B-cells were able to “remember” antigens brought into the body by foreign cells, and who looked mostly at genetic mechanisms (Dutton et al 1998, Banchereau et al 1998, Bird 2002), but others, lately, have described other mechanisms of “memory” in a variety of cell types  (Harmon 2010, who reviewed two studies: Kim et al 2010 and Polo et al 2010, LiveScience, Wolff et al 1998, Bird 2002, Ball 2008). However, there are a few people who have written in the past that “body memory” is not reliable, or the concept shows poor scientific reasoning (Smith 1993, The Skeptics Dictionary, Skeptic ReportWikipedia’s description is particularly out of date). Although their criticisms are out-of-date for the scientific evidence that has since been presented, their criticisms of people who over-interpret the concept are still valid, (Smith 1993 , “Inherited Memories in Organ Transplant Victims”–Theophanes  has a very good discussion of alternative theories). Examples of some type of mild and rather harmless over-interpretation can be seen at:  “From Healing the Hurt to Living the Dream – IET Does It All” , “About the cellular memory”). There is no doubt however, that research today is starting to fill in the blanks to one aspect of the theory so strongly pointed out by Susan Smith (1993). In particular, van der Kolk (1994) and the collaborative efforts  between Felitti and the CDC, leading to quite a few papers published, show that body and mind are intertwined (also listen to an interview with Felitti on CBC’s Ideas program, in an episode called “All in the Family” ). In fact, these people and many others are treating patients and generating data that shows how even very old emotional traumas can show up in body symptoms much later in life.

Internal vs External Environment

It All Comes Down to The Embryo

As stated in the introduction, the purpose of the brain is to intervene between the internal and external environment. Once you get a bunch of cells joining together, they tend to generate common behaviors at the same time. They also tend to set up signaling properties that are held in common by the same kinds of cells. Thus, cells on the outside of a group will behave differently from those inside the cluster, but cells at the very center of the cluster will usually behave similarly. With differentiation into a multicellular organism, development plays a big role in determining what a cell will do in the adult form (as shown by the example above in the pancreatic acinar cells vs the islet cells).

In all vertebrates, the nervous system is the first organ system to develop, even though it occurs simultaneously (and not coincidentally) with the first steps in formation of an inner gut tube in many species. In all vertebrates, it starts as a flat sheet of epithelial cells that rolls up or forms a groove that causes it to form a hollow tube. The tube then starts to differentiate a “head” end that forms the brain, and a “tail end” that forms the spinal cord. Critical to this tube’s subsequent differentiation is the formation of “segments” (see “Segmentation in the Nervous System“).

Since all vertebrates start out as a single cell layer, which splits into two layers, and then rapidly forms three layers, their very complexity demands that something form to coordinate the individual cellular needs with needs of the whole organism. The two-layer embryo has one epithelial layer facing out from the center of the embryo, and another epithelial layer that will become the interior-most layer of the body. When cells from the outer layer migrate into an area between the two layers, they become very different from either inner or outer layers, filling in the space between of two rapidly differentiating layers, and not becoming epithelia. In fact, many cells in this middle layer stay in a highly mobile form (mesenchyme). That innermost cell-layer will connect the future gut tube to the body formed by the outermost layer.

Even though mammal embryos and many other vertebrates get their nutrition from the mother via a blood vascular system, most will have some functioning cells in the lining of the gut tube, derived from that innermost cell-layer. Their functions will differ from those cells that cover the embryo, protecting it from external environments. At a very early, simple stage of development, easy transport of nutrients can occur across both the innermost layer and the outermost layer, especially before a blood system forms, because the embryo has to function in a water environment as it grows rapidly.

Because these layers rapidly start to differentiate into cells and organs with different functions, the nervous system changes with it to keep up with its role as the ultimate arbiter between inside and outside environments.

What is inside the embryo? Different organs that keep the embryo alive by making sure that every cell gets fed and that every cell’s waste material is removed. What is outside the embryo? Every embryo faces the same things early on. Since vertebrates evolved in a watery environment, that environment is duplicated in the embryonic membranes and sacs that form around the embryo early during development, in every vertebrate, regardless of whether or not the species’ habitat is restricted to land.

During early development, other cells that are exactly like each other are in the inside environment. They compete for food and developmental space. Some die off during the developmental process (apoptosis) because the embryo sets up impossible conditions for their life in certain places (e.g. the webbing between fingers and toes), as the embryo continues to differentiate. As cells differentiate from each other, and form tissues, then organs, and then organ systems, the developing nervous system has to change to keep these organs working together, in spite of the major differences among them.

What is external to the embryo is critical for its survival because that is where the food and oxygen comes from and that is where waste is sent. The needs are pretty much the same when the baby is fully developed, and is born into a world that is very different outside the baby than inside the baby. However, we cannot think of what goes on inside the body as happening completely without regard to the external environment. Even in the embryo, the nervous system readies different parts of it for nutrients that will be entering the embryo from outside. A part of the embryo that normally consumes very little oxygen will have to shut down when new oxygen enters the embryo to feed a highly active part of the body. Internal competition must be managed. No living organism can afford to have its internal mechanisms work independently of external events.

What’s Outside is Inside

No matter what the species of vertebrate, the newborn has to deal with other living organisms. Some of them will become its food, others its enemies or competitors. In responding to any change in external environment, the baby has to change its own internal environment, either in parts or the whole of the body. The purpose of the nervous system hasn’t really changed at all, even after birth, because it still has to arbitrate between the demands of the external and internal environments. It is uniquely capable of doing this because of the method these nervous cells use to do that.

Physiological Needs

During development, many neurons are still stem cells and migrate very readily throughout the nervous system (e.g. neural crest cells). By migrating, they can change their function. By staying, they keep on doing what they always have done before. Some “half-migrate” by extending parts of themselves over sometimes great distances to contact cells that are nowhere near it. Motor neurons keep their cell bodies in the gray matter of the spinal cord and brain, sending axons up or down the neural tube and sometimes out of the Central Nervous System (CNS) to become what we call the Peripheral Nervous System (PNS, cranial or spinal nerves).

Some hypothalamic nuclei. This nucleus is composed of the cell bodies (or the ends of neurons with the cells' nuclei where the DNA is), the darker, purple areas, and the fiber tracts (pink) are where the axons from those cell bodies pass through the hypothalamus to their target areas in the brain. Taken from Wikipedia.
Some hypothalamic nuclei. This nucleus is composed of the cell bodies (or the ends of neurons with the cells’ nuclei where the DNA is), the darker, purple areas, and the fiber tracts (pink) are where the axons from those cell bodies pass through the hypothalamus to their target areas in the brain. Taken from Wikipedia.

Sensory neurons keep their nuclei in ganglia or in “centers” in the CNS and send axons and/or dendrites short or great distances away from the nucleus to sensory receptors in the body (special: eyes, ears, nose, mouth, or general: epithelia, connective tissue that make up all organs of the body).

Other neurons (forming nuclei, or clusters of cell bodies of neurons) may still send axons or dendrites short or great distances, but stay within the CNS. By sending axons to other parts of the nervous system, these cells can change their function by affecting neurons that did not develop near them, keeping their nuclei in one place, and their synapses farther away.

The nervous system is far more dynamic than what is usually described to us in the anatomy books. It is implied that the only way that dynamics are shown in the nervous system is when one neuron fires a signal at one frequency and another neuron at a different frequency. Or the difference lies in the kind of neurotransmitter it sends. Two neurons can also differ in the strength (amplitude) of the signal they send.

There are anatomical changes that most neuroscientists seem to ignore. Not only are some axons myelinated and others not, but some axons can dynamically grow out toward another cell, and not just when the neuron is healing from damage. We have to realize that a very large number of neurons in the brain and spinal cord are not myelinated. The advantage to not being myelinated is that they do not have to be dedicated to synapsing with particular cells in specific regions of the CNS. They can send axons farther or nearer to the cell they originate from, unlike those axons in dedicated fiber tracts. This ability renders a greater plasticity to the brain than we ever realized.

Although many of the physiological needs of the body as represented in the brain can be summed up as maintaining equilibrium in metabolism, responding quickly to a fight-or-flight situation, controlling heart rate, respiratory rate, and blood pressure, producing hormones needed to communicate with the glands in the body, regulating a daily rhythm of eating, sleeping, and arousal, we also need to consider other things. Scientists have suggested that there exists a kind of nervous control over the immune system, calling it the “neuroimmune system” . [not a good link, will update later]. [More on this later]

Social Needs

Mother & Child (Doux Réves) from Wikipedia
Mother & Child (Doux Réves) from Wikipedia

Social needs can be considered as a hierarchy, from the simplest to the most complex. The only social need all vertebrates have is the attachment to the mother, and even that will vary from very little to a lot. A fish who lays a clutch of eggs in anticipation of a male fertilizing them probably has the least attachment to the embryo, since she is probably gone before the egg has reached the multicellular stage of development. Reproduction may be the only contact one animal has with another when life is not threatened by a predator. The brain will have more resources allocated to social interaction than for all other interactions with the environment if the animal belongs to a very social species, as found among primates, whales, dolphins, elephants and colonial animals.


As vertebrates, we all have a brain as an organ responsible for controlling all other parts of the body. It is also responsible for helping the body respond to the external world, and as such, it is critical for our survival. During vertebrate evolution, many aspects of the brain evolved to ensure survival of the organism in different habitats. One of the adaptations of some vertebrates is the formation of areas important for being in social groups. Social groups make sure that survival of an organism doesn’t completely depend upon the same individual. In some of these social species, if more than one individual helps a single member of the group to survive, then all members survive longer. If all members can live longer lives, then more of them can reproduce more often prolonging the chances for survival of the species.

In order for sociality to occur, attachment is necessary. The only way that attachment can occur is if the brain allow representation of a particular person in it, e.g. assigning a cell to the role of that person. Internal biology will reflect external states. The entire nervous system is involved with replicating the environment external to a person so that a model of what the person will experience is made inside the brain with levels of that model present in spinal cord and brain parts.

Levels of attachment can change, e.g. a person to whom you become attracted becomes a mate, a mother gives birth to a child who is essentially a piece of herself. Egg-laying mammals, the Monotremes (platypus and echidna) would form the smallest of attachments to their children among the mammals, although, since the babies share the same genes, and the mother suckles them, that attachment is more than what the salamander has for her children. The salamander lays her eggs and leaves, never to acknowledge her relationship with any of her children again. Placental and pouched mammals form a stronger attachment, since the baby either feeds off the mother inside the body or in the pouch during development.

Egg-laying animals, for the most part have to provide enough nourishment to an egg for a baby to develop to an adult body form while still inside the eggshell. Monotremes allow for a less developed baby to survive after hatching by suckling them. All of the added attention a mother gives to a developing baby demands a stronger attachment. The longer a young animal stays with the mother in life, the stronger yet the attachment must be and the place and role of the cell representing the other person must change, when compared with animals who do not form the same level of attachment. The brain has to dynamically respond to the needs for such attachments. A cell assigned the role of a friend takes on the different role of a spouse. As an egg develops inside the salamander mother, the cell assigned to represent it in the brain never changes its role. After all, it is just one of many, similar to the cells assigned to specific tissues in the arm in the brain.

In mammals, every egg produced gets a single cell in the brain assigned to represent it. As the egg develops, the cell takes on more responsibilities, since it must contact cells in the rest of the brain more often to make sure a greater blood supply to the growing fetus is provided, the mother has to eat more, more resources have to be used to convert the extra food into nutrition allocated for the fetus and not to any other part of the body of the mother.

If the animal is a member of a social group, changes in the animal’s physiology become more obvious to the other members, and they will start to anticipate the arrival of a new group member, with consequent needs for changes in the group. All it takes is a few times when the birth of an individual affects the whole group for individuals to learn all the signals that precede the growth of their group. The same learning takes place inside an individual brain so that anticipation of the change in relationship between mother and child at birth of the child can cause changes in role of the cells inside the brain which are assigned to each person. All cells representing the processes that occur between “person” cells must change as well, leading to a ripple effect in the brain from the cellular level to tissue, to organ, to system, to whole person levels as represented by particular cells in the brain.

Attachment to another individual is critical for survival of all mammals, but obviously evolved before mammals evolved, because we see various kinds of attachment by mothers to the eggs they lay (crocodiles, birds, some amphibians and fish), and attachment by mothers to growing babies (most birds, some reptiles, who care for young until they disperse). As humans, we think of it as the default condition, when it most certainly is not. Because it is not, the brain’s default condition must change in those whose attachment level changes.

So in mammals, who care for their young until adulthood, and some, even longer than that, the default condition has to include this change in attachment level, since survival of an extremely undeveloped infant at birth depends upon it. Since this attachment is not necessarily guaranteed, our social human history shows all sorts of other behaviors to help a baby survive, with or without attachment (e.g. adoption). We can be forgiven if we conclude that attachment is not critical for survival in any animal because we see all kinds of rejected babies survive–but not necessarily in non-human species. However, there are still consequences to having rejected babies in human society (See my blog posting “Special Case of Type I PTSD–Rejected Children”.)

The Third Man is outlined with broken lines.
The Third Man is outlined with broken lines.

The Third Man Factor (or Syndrome)

ABC Nightline on 26 April 2013 did a segment, ‘Guardian Angel’, which highlighted John Geiger’s book, The Third Man Factor: Surviving the Impossible (2009), where he highlighted the phenomenon, first written about by Sir Ernest Shackleton in his quest for the South Pole,

“during that long and racking march of thirty-six hours over the unnamed mountains and glaciers of South Georgia, it seemed to me often that we were four, not three.” –(Shackleton, 1914.)

He spoke of a phenomenon that many others have felt, and have called their guardian angel. It was the feeling that someone else was there when a person was in danger, who guided them to do the right thing that saved their lives. ABC’s Nightline interviewed several people about their near-death experiences. John Geiger researched such instances in his book and came to the conclusion that there is no “thing” external to our bodies, like a guardian angel, but that the feeling comes from within our own brains. He asked someone, who mentioned that he heard a voice telling him what to do, if they actually heard an audible voice, and they had not.

All of these people had used mindfulness, where they became acutely aware of the signals their unconscious brains were sending to the conscious areas. Concepts, images, and sometimes sounds are sent to the conscious prefrontal cortex which are remembered, analyzed, and acted upon without noting the source of the signal. Thus, we might feel that we thought of what to do as a completely conscious act, when it so totally relies on these unconscious signals.

The centers in the brainstem are concerned with our survival at a very basic level. They recommend to the decision-making center in the prefrontal cortex what is needed, based upon past, similar events and internal programs, in the form of circuits, which are wired to do the same thing every time they are triggered. The decision-making center is also getting a lot of signals coming in from many other centers as well, so that the decision is one of a “committee”, not just one member.

Everything we have ever experienced is stored in our brains. If we have difficulty remembering one thing, it is not that we have totally “forgotten” it. We just cannot access those areas where it is stored, either temporarily or permanently. Everything we experience gets stored in many areas, a large majority are in the unconscious parts of the brain and involve every sensory organ which was triggered during the event. They are associated with many other aspects of life as well as other memories. Those associations allow us to learn, and to eventually recall something we are trying to retrieve (e.g. “Go back through all the steps you took”).

The unconscious brain knows when we are in serious trouble, and not because the conscious brain becomes aware of it first. In fact the reverse happens. The unconscious brain (the brainstem and some other parts of the forebrain) becomes aware of the fact that certain centers are not working correctly or are getting signals from the body alerting them of danger, and then sends a signal to the conscious brain, which then analyzes the circumstance consciously.

Finally, you become very aware you are in great danger. Panic may set in, the fight-or-flight response may be triggered, both of which are predominantly made up of unconscious pathways. The decision-making center reaches out to all areas of the brain for input (advice). This will include centers where cells representing people, places, objects, ideas, etc are stored (in many different areas of the brain). These cells have extensive associations with everything we have ever experienced in life, and they check their connections for relevant information. I wrote about their significance in many circuits of the brain at “The Mother-Infant Bond”.

The third man figures in here. Every cell representing a person is known to the conscious brain. Words that person would have said in the past, images that person described to you, and/or sounds that person made or spoke to you about will come to mind. All aspects are stored in different areas of the brainstem. Sometimes these latter aspects of that person arrive at the prefrontal cortex faster than recognition of who the person is, especially in times of danger, since these associations are more important than the person him/herself. It is only upon reflection later, when you know you are, or will be safe, that you remember who said that to you. ——————————————————————————

Sleepwalking and the Social Brain: An Example

Comment on “Lack Of Sleep, Genes Can Get Sleepwalkers Up And About” on Morning Edition 27 Aug 2013 where I comment on possible reasons for sleepwalking in a specific example. I discuss the brain mechanisms that might be responsible for it and how researchers may be missing important clues by not asking the right questions.


NPR reporter Michelle Trudeau interviewed Alon Avidan, a researcher at the UCLA Sleep Disorder Center and Russell Rosenberg of Neural Trials Research in Atlanta, Georgia, on why sleepwalking occurs. Avidan says that it generally occurs at the beginning of a sleep cycle, during non-REM (rapid eye movement) sleep. When they wake up they won’t remember that they sleepwalked. It is as if the brain is partially awakened enough to allow them to move, but not awake enough to recognize that they are moving. She says that sleepwalking results from the brain’s inability to fully wake up.

Rosenberg says that about 10-20% of children will show sleepwalking. For most children, it results from a brain that hasn’t fully matured and they will outgrow it eventually. However, for some adults, the brain doesn’t outgrow it. Furthermore, if one parent sleepwalks, there is a 45% chance that their child will also sleepwalk. They discuss environmental triggers: apnea, stress, not enough sleep, too much alcohol, and sometimes, even the medication prescribed for sleepwalking, like Ambien. Even though they mention stress as a trigger they claim that sleepwalking does not appear to be linked with psychological problems.

Posted on NPR

The TV Show The Doctors (CBS) had an episode sometime this year (2012) where they spoke about “sleep eating” when people ate either real food or odd things during sleep.

Even though the researchers say that sleepwalking doesn’t appear to have a psychological link, they might need to rethink “emotional reason”. There may be something that is similar in both father and daughter in how they feel in certain social circumstances, something that neither would ever think is responsible for sleepwalking, and something that both would consider a “minor” issue.

The “minor issue” is important here because genetically, these people might, for example, share a similar inability to produce enough neurotransmitter in cells responsible for a particular aspect of social life. These cells may only work when in a social interaction, so their deficit is very difficult to detect. An example: The amygdala signals fear in them every time they think any other person might hurt them emotionally. They both might notice some difficulty every time they feel this fear when awake. They might also feel this fear when asleep as the brain repairs any damage resulting from a social interaction, but they won’t remember it. However, a fish doesn’t know it’s in water. Neither is going to suspect they suffer some deficit, unless someone talks about its possibility.

See my blog post “The Social Brain” at for more about this example. Surviving with a minor problem doesn’t mean it won’t have side effects. This only makes it very difficult to determine what the cause is. We have to remember that genes do not CAUSE anything. They are associated with various phenotypic characteristics. That’s all. They all require an environment to trigger their action. Father and daughter are going to share the same environment, if not all the time, for a large percent of the time if he is active in her life.

Extended Comments

When we sleep, especially when we dream during REM sleep, our brains are repairing any part that is damaged. Strong “bad” emotion (fear, anger, rage, depression) can physically damage axons, especially the unmyelinated ones found most often associated with the “fight or flight” centers and other “visceral” centers. In fact, that is the purpose of sleep–to repair. So why do we dream about a social interaction that took place earlier in the day? The brain needs to find all the damage and so asks us to either replay the situation or play it differently to test various circuits critical for social interaction.

Sometimes it has us dream weird things, like we look down and our foot has changed into a golf club. It probably is repairing something in our feet and may use the symbol of a golf club to get us to think (at least semi-consciously) about golf, because for some reason, the brain is associating the concept “golf” with the damage in the foot. Our semi-conscious thought processes demand the use of the conscious brain where images, sounds, smells, are stored and which can process associations much faster and more thoroughly than the brainstem (unconscious brain) can.

In the case of our hypothetical example, because of the lack of signal coming out of certain defective cells in the amygdala, the emotion center in the prefrontal lobe might not send an important signal to the amygdala to shut down when the person is sleeping. Normally, there is a chain of signals involving activation of sleep centers in the brainstem which block the motivation center (putamen) from allowing movement once we fall asleep. In the case of some people who sleepwalk, the amygdala may continue to signal fear to other centers during early sleep, which removes the block on motivation, thus allowing signals from the motor cortex to reach the pons where the movement is carried out.


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Other Related Posts

The Mother Infant Bond
Surgical Approach to Sleep Apnea
Sleep–What it Does
Treating Sleep Disordered Breathing in Kids

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