WHAT THE HECK IS THE CALYX OF HELD?

Today people were tweeting about the Calyx of Held.  It sounds like a potentate in medieval times, but this is what Google says."The Calyx of Held is a particularly large synapse in the mammalian auditory central nervous system, so named by Hans Held in his 1893 article Die centrale Gehörleitung because of its resemblance to the calyx of a flower.  Globular bushy cells in the anteroventral cochlear nucleus (AVCN) send axons to the contralateral medial nucleus of the trapezoid body (MNTB), where they synapse via these calyces on MNTB principal cells. These principal cells then project to the ipsilateral lateral superior olive (LSO), where they inhibit postsynaptic neurons and provide a basis for interaural level detection (ILD), required for high frequency sound localization. This synapse has been described as the largest in the brain."

I've never heard of this brain blob.  Now to figure out the definition given above.

Synapse: that little electrical jump of space between the ends of two nerve cells. I always imagine a teeny bolt of lightning crossing.  Three kinds are described according to the elements involved, but never mind. Also, they can send the jump to muscles and organs.

Mammalian means something has changed or been added since reptiles.

Globular bushy cells.  Cells are often "named" by saying what they look like.  These are obviously bushy globs.  Evidently in this context "olive" is the shape, not the color.   

lateral superior olive (LSO)  "Thus, the LSO receives excitatory input from the ipsilateral  [same side] ear and inhibitory input from the contralateral [other side] ear. ... Ipsilateral projections are primarily inhibitory (glycinergic), and the contralateral projections are excitatory."  In other words, this is how you triangulate distance to tell where a sound is coming from.

To understand them, you have to know about them. "The superior olivary complex (or SOC or superior olive) is a collection of brainstem nuclei that functions in multiple aspects of hearing and is an important component of the ascending and descending auditory pathways of the auditory system."

"The mammalian cochlear nucleus (CN) consists of a diverse set of neurons both physiologically and morphologically that are involved in processing different aspects of the sound signal. One class of CN neurons that is located near the entrance of the auditory nerve (AN) to the CN has an oval soma with an eccentric nucleus and a short-bushy dendritic tree and is called a globular/bushy cell (GBC). They contact the principal cells of the medial nucleus of the trapezoid body (MNTB) with the very large calyx of Held that is one of the most secure synapses in the brain. Because MNTB cells provide an inhibitory input to the lateral superior olive, a structure purported to play a role in lateralizing high frequency sounds, GBC physiology is of great interest." 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2518325/

When you consider how poorly I'm grasping all this stuff, please take into consideration that the phone rang twice with a wrong number dialed by a drunk demanding to know where I am, one kitten has just thrust his nose into my coffee cup which luckily is cool rather than hot -- his sister burned her nose yesterday.  One of the two bachelor male cats just beat up on that kitten and had to be chased outside by making terrible sounds and thumping my feet hard.  Household commotion is a continuing hazard for bloggers.

This is what I get out this news about yet another brain part that's barely distinguishable from the mush around it except by shape and location.  Too bad brain parts are not color-coded like those brilliant computer depictions of brain systems we call "the connectome."

This bit is called a "calyx" because it is a cup-shaped structure like that in a flower.  It's kind of a reservoir where things are held. I looked for a definition of the MNTB and got "Merchant Navy Training Board" so I guess the acronym is rather for the preceding phrase in the paragraph:  "medial nucleus of the trapezoid body."  Acronyms do not help explain this stuff.  GBC may refer to "gall bladder cancer" but that doesn't usually happen in the ears.  In this case, it seems to mean "globular bushy cells."

That this complex of the Calyx of Held is so stable and large means that it's not a surprise that Hans discovered it at the end of the 19th century, but also means that it has been conserved and replicated over the millennia since the beginning in early mammals, who evidently survived by listening more than reptiles did.  Good hearing is crucial for both predator and prey, a whole world of meaning for those dependent on it.  Humans ordinarily get deaf in old age, but that doesn't mean much to the species since they are no longer breeding.  That aspect of survival is gone for them except in protecting the young.  Human survival is often due to wisdom accumulated by the old which can be read rather than heard.  This has changed:  loud music is destroying hearing in the young, cultural revolution has discredited whatever is old.  No doubt our survival both as individuals and groups is damaged.

Neither do the young read very much, but turn to the mechanism of sight which is much managed with optical devices, color, flickering, and many other devices.  However, more than ever, the human young are both predators and prey.  I haven't thought about this except for noting the evidence which is extensive and pervasive, mediated by sex, drugs, and family breakdown.

I'm nearing the end of Joseph LeDoux's "The Deep History of Ourselves".  He defines the amygdala as something like the Calyx of Held except in terms of survival reflexes, an unconscious, well-conserved reservoir of information about danger that operates as reflex rather than reflection.  It is not receptive of theories, depending entirely on what has meant survival.  These reflexive salvific impulses are not named or numbered, so far as I know.  They are behavioral rather than structures, so they come and go before anyone can say, "Oh, that reminds me of a . . ."  What?  A boomerang?  A square dance?  Lemmings?

THE HUMAN BODY

What is a human being?  First, body.  We are evolved from worms who developed a spine and then limbs.  At the end of the worm that goes through the world first is the head, which is the sensation seeking-and-absorbing end which guides the creature.  Since it is the battering ram of experience, it is armored with a skull.  In the skull is the guidance and memory system we call the brain.  There are five organ extrusions of the brain, the main input instrumentations that collect information about the surroundings.

The eyes “read” electromagnetic waves of energy called “light.”  Because they are double, they can triangulate distances and speed of movement which is vital for movement.  The ears “read” vibrations of air called “sound” and also contain the main organs of perception for balance.  The nose “reads” molecules, particularly those moving freely in the air and breathed.  The mouth or tongue “reads” the molecular nature of whatever is ingested after pulverizing or in solution.  These two chemical analyzers work together as smell and taste, interwoven.  

Each of these senses claims an area of the brain where each is interpreted, analyzed, possibly censored, embellished, associated with pain or pleasure.  Raw nerve messages become “felt” concepts that guide behavior.  These concepts are not “real” but represent reality.  They are not usually conscious.

An additional sensory organ is the skin, which detects temperature, pressure, texture, friction, moisture and pain.  Just under the skin are muscles that signal contraction, effort, relaxation, the presence of byproducts of effort (lactic acid).  They constantly send information about the body’s position to another specialized area of the brain.  All of these “felt concepts” produced by various sensory systems will grow and connect neurons.  The more a person uses them, the more they create new neurons and connections among them in the brain.  A ballet dancer has ballet embedded in the brain; a tennis player has tennis embedded in the brain.  It is possible to rehearse both in the brain without moving.

The shoulders are an improvised “suspension system” from when humans became upright. The hinging systems allow carrying, throwing, leverage, with fine-tuned control with special elaboration for wrists and hands at the ends of arms.  Again, the hands in particular claim an area of the brain according to how much and in what way they are used.  They become habituated and sensitized according to their use so that manual labor will thicken and to some degree immobilize and desensitize them, while their use for something like braille will make them able to read small bumps.

The main body is divided into zones.  The top is a ribbed bubble for the exchange of gases with the outer atmosphere with a pump to send the key element of oxygen around the body.  Without oxygen the cells stop functioning and eventually will die.  Stretching horizontally across the body under the ribs in a sheet muscle (diaphragm) that acts as a bellows for the lungs.  Lungs and heart are entwined.

The middle zone through the waist contains the largest chemical managing organs: liver, pancreas, spleen, gall bladder, adrenals, kidneys.

The pelvis is a basket or bowl that supports the guts, coiled tubing.  Each soft tube is permeable and sleeved with both many blood-carrying capillaries and a neural system.  From the brain down through the spine and out to all the body contents are two neural systems, one that is voluntary and primarily directly to muscles, and the other called “autonomic” that monitors all the organs that we perceive -- IF we become conscious of them -- as emotion.

In and under the guts are the organs of reproduction and excretion, which in more primitive animals might have been cloacal, combined.  Both sperm and babies are byproducts which must be expelled.  The hips and buttocks are both levers for movement and protection for the pelvis, cushioned by fat, especially in women.

Now let’s go back to the top.  The first early developments of the top of the spine pushing into the world was only a thickening, a knob.  Then came the neural connections of the autonomic system and the segmented, thickened, responsive brain began to invent itself.   The Mid-Brain manages emotions and adjustments. Again, the principle is that everything our ancestors have done has made the brain what it is.  If there was a need pressing on the animal because of doing something repetitiously, the brain -- like the muscles -- responded.  But it was not a deliberate sort of response.  

Rather the increasingly intricate set of directions accumulated in the double helixes of the genes, in turn gathered into chromosomes and embedded in cells that each included captured one-celled bacteria, floating bits of viral code, and the vital mitochondria with their own genetic system.  Methylation, a system of switches that could turn genes on and off, clustering of genes, the ability to wind a helix tighter or looser, and other so-far-undiscovered subtleties, created ongoing variations over time.  Those that contributed to the survival of the individual might be preserved and passed on to progeny.  Those that contributed to the survival of the group persisted in increasing prevalence until they changed the whole nature of the animal.

The same thing happened in a parallel way within the processing of the brain.  The reptile brain gave rise to the mid-brain and that became the substrate of the cerebrum which particularly specialized in the creation of the forebrain where we now detect such granular specializations as “net cells” (mapping) and “mirror” or “spindle cells” (empathy).  Small structures like the two hippocampi, one over each ear, and -- at the core -- the pituitary guidance system that uses circulating chemistry that coordinates with neural impulses.  The list of small specializing bits constantly increases.

The size of a brain makes no difference.  Its complexity gives it enormous potential.  But that potential is shaped from before the moment of birth.  Evolution happens as much by subtraction and deconstruction as by addition and construction.  We can see some of this in the development of the fetus when gills or a tail appear and then disappear.  But the most crucial example in humans is that at birth the brain begins small and dense but then, in response to the senses, carves itself into a “shape” or structure adapted to dealing with that world it encounters.

Culture is an emergent system among the people as they interact with their environment, including each other.  It is supported and limited by the shapes of the brains of the people, but brains can respond to culture in ways that allow them to have new insights -- to carve away or add-on insights and perceptions.  Again, those that contribute to the welfare of the person will persist as “identity” and those that contribute to the survival of the group will become their “civilization” that will continue so long as conditions of the environment don’t collapse.  The environment does change -- sometimes abruptly.

In order to cope with the changes one of the ways that brains change themselves is by using the “scientific method” which is a way of testing reality with hypotheses by accumulating evidence and synthesizing it into new insights.  But another way of changing is to create moments of suspended or deepened function (“liminal”) in which the various parts of the brain are open to reorganization -- though the moment may only reconfirm previous convictions.  These are often highly emotional, not felt as rational, and can be identity changing.  If shared in an effective way (theatre, art, stories), they can change whole cultures.

That’s my story and I’m sticking to it.  Until the next paradigm shift.