#selection pressures

Lifespan

Development

 Introduction

  This chapter develops the ideas of evolutionary neurobiology (= selection pressures) as contextualized in the metanarratives of the social psychology of Russian psychologist Lev Vygotsky. The sociocultural-historical construction of the child’s reality, including the different ways of behaving, speaking, thinking, reading, writing, and using language and symbols, are looked at over the course of different periods of the child’s development. From our first sounds to our first words our speech is public, spoken in the public domain whether others are around or not. From the ages of three to five our pattern of speech changes, and public speech is also private speech, that is, spoken to oneself but as though others are around. Beginning around the age of five private speech is replaced functionally and structurally by different kinds of inner thought including verbal thought, visual thought, semantic thought, contextual thought, and somatic thought. Inner thought is an organic movement of the sociocultural-historical construction that is the individual’s reality, their world, the real-time experiences that are happening and need to be dealt with and responded to. How the individual behaves, speaks, thinks, reads, writes, and uses language and symbols over the course of their lifetime is a product of selection pressures.

 1        History of lifespan development research

      2        Analysis of lifespan development research

      3        Standard model of lifespan development

  a          fertilization to birth

  THE KEY THEME IS SELECTION PRESSURES

  à add in every reference to how the embryo and fetus grow as some reptilian thing.

  [This is all about the genotype bringing about phenotypes whose task it is to adapt successfully to selective pressures and reproduce. Synapses, selection pressures, sociocultural-historical. Ontogeny recapitulates phylogeny.]

  synaptic upregulation and downregulation USE THIS INSTEAD OF SYNAPTOGENESIS

  [IT’S SIMPLY VERY NICE TO MENTION ONE DETAIL EACH WEEK/MONTH OF DEVELOPMENT. NOT THAT THERE ARE “THE MISSING WEEKS”, or maybe some details take a few weeks, “during the seventh through tenth months …”. Do NOT just discuss what’s happening in “only weeks” and “only months”, but give a mixture of the two throughout.]

  [We move from billions of years to sperm and eggs.]

  Our RNA and DNA has mutated over the course of a few billion years with the result of us being here today. The unit of inheritance is in this RNA and DNA. Almost all cells in a person’s body have these units of inheritance in the form of 46 chromosomes, which come in 23 matching pairs, and that are located inside the nucleus. There are 22 pairs of autosomes, and 1 pair of sex chromosomes. The sex chromosome in the sperm determines the sex of the baby.  If the sperm is carrying an X chromosome the baby will be female, and if the sperm is carrying a Y chromosome the baby will be a male. When eggs and sperm are made, these 46 chromosomes divide in half so that the egg contains 22 autosomes and one X chromosome, while the sperm contains 22 autosomes and one "sex-determining" chromosome. After a sperm binds to the plasma membrane of an egg, the sperm’s contents are drawn into the cytosol of the egg. The pronuclei of the sperm and egg now move toward each other while duplicating their DNA. Their nuclear envelopes then disintegrate and their genetic material combines together into a single cell with 46 chromosomes. When these chromosomes join together, genetic recombination takes place in the form of chromosomal crossover. This leads to the offspring having different combinations of genes from their parents, which can be expressed as different alleles such as eye color. In order for this fertilized egg, now called a zygote, to develop into a baby this single cell must divide. Each chromosome makes an identical copy of itself, and the cell divides so that there are now two cells that have the same chromosomes as the original cell. The two new cells repeat this process, the chromosomes duplicate and divide into two new cells, with the result of four cells that are identical to the first original cell. 

Soon after fertilization, the zygote travels down the fallopian tube toward the uterus. At the same time, it will begin dividing rapidly to form a cluster of cells. The inner group of cells becomes the embryo, while the outer group of cells become the membranes that nourish and protect the embryo. By week three the embryo, which is now made of about 500 cells, burrows into the uterine wall for nourishment. The placenta, which provides nourishment, also begins to form.

By about the fourth week the baby is made of three layers of cells. The top layer of cells — the ectoderm —becomes the skin, hair, and nails, as well as the neural tube, where the brain, spinal cord, spinal nerves, and backbone develop. The middle layer of cells — the mesoderm — makes up the major structural components of the body including the voluntary muscles, which underlie all of our actions, the involuntary muscles, which underlie organs such as our heart and blood vessels, respiratory and gastrointestinal systems, and the bones, muscles, kidneys, and much of the reproductive system. The inner layer of cells — the endoderm — includes all of the cell systems which line our organs and vessels, and from which the lungs, intestines, and bladder develop.

  The brainstem consists of phylogenetically older neurons and nuclei and is organized in a somewhat similar manner across a host of species ranging from fish to woman and man. Given its exceedingly long and ancient evolutionary history, not surprisingly, many brainstem functions are present before birth

  Late in the fourth week, the anterior segment of the neural tube forms the three main parts of the brain: the forebrain, midbrain, and the hindbrain. Cells are now undergoing active replication, and cell migration begins to take place, a process that will continue in the postnatal stage. Once migrating nerve cells have reached their final position, they begin to develop two types of extensions from their cell bodies. Dendritic branches emerge from many points along the cell body, providing an increasing surface area for fiber terminals (synaptic terminals) from other neurons. The second major type of cell extension, the axon, will set out on a journey of variable length to establish connections with many other neurons, some adjacent to the cell body of origin, others quite distant. The brain now begins to develop from the inside-out, with the innermost areas developing first and outer areas developing subsequently.

During the fifth week the heart starts to beat and blood circulation begins — making the circulatory system the first functioning organ system. In the sixth week, basic facial features appear as do small buds that will soon grow into arms and legs. By the seventh week the umbilical cord — the link between the baby and the placenta — is now clearly visible. The hindbrain, midbrain, and forebrain further divide into subregions. At week eight the infant develops webbed fingers and toes. During week nine the embryonic tail at the bottom of the baby's spinal cord starts shrinking, helping him or her look less like a tadpole and more like a developing person. The fetus, which is now about one inch, also beings moving around this time. During the tenth week, the baby's brain produces almost 250,000 new neurons every minute. The bones of the baby's skeleton begin to form. If the baby is a boy, his testes will start producing the male hormone testosterone. At week eleven the baby is now officially described as a fetus. The first trimester is now over. The baby is nearly 3 inches long and weighs about 4/5 of an ounce

During the middle of the second trimester, at about the fifth month, the process of synapse formation starts. Neuronal differentiation, dendritic growth, the establishment of synapses, and the myelination of activated brainstem axons which have established dendritic synaptic connections.

The third trimester. By the seventh month synaptic development on the deepest cortical neurons is extensive. At about seven months the cortically re-entrant thalamic brain connections, which mediate sensory input, form. Development of the distinct brain regions significantly happens in the two months preceding birth. While all areas of the brain are formed by birth, their operations are best described as immature. The forebrain (all four lobes) does not begin to functionally mature until near term; for example, eye movement does not appear until around the 38th week (the rudiments of the oculomotor loop).

  b          birth to 24 months

  THE KEY THEME IS SELECTION PRESSURES

  Myelin sheath development, or myelinization as it is called, has a rather well recognized time table in the cerebral hemispheres. Fibers serving the primary sensory (touch, vision, audition etc.) and motor areas are myelinated shortly after birth while those which are involved with more complex associative and cognitive functions myelinate later. It is generally believed that fiber systems of the prefrontal lobes (executive functions, intentions, future planning, etc.) are among the latest to myelinate, a process that may go on into young adulthood.

  4 hours sleeping to 7 minutes awake, and these minutes are often drowsy, for the first few weeks of the babies life.

  [[[At birth and for the ensuing weeks, the forebrain (all four lobes) is so immature that its influences are limited to signaling distress in reaction to hunger or thirst; a function of the immature hypothalamus (Joseph, 1982, 1992, 1999) in conjunction with the midbrain periaqueductal gray (e.g. Larson, Yajima, & Ko, 1994; Zhang, Davis, Bandler, & Carrive, 1994). Although various limbic nuclei become functionally mature over the course of the first several postnatal months and years (Benes, 1994; Joseph, 1992, 1999), the neocortex and lobes of the brain take well over seven, ten, and even thirty years to fully develop and myelinate (Blinkov & Glezer, 1968; Conel, 1939, 1941; Flechsig, 1901; Huttenlocher, 1990; Yakovlev & Lecours, 1967).]]]

  [The sculpting of specific neural pathways fine tunes perception and selective attention, and promotes learning, memory, and language, cognitive and personality development (Joseph, 1982, 1996b, 1999).]

  It is not until well after birth that midbrain development and myelination is nearly complete.

  [this has all the metanarratives:

After birth (neurogenesis as well as synaptogenesis rapidly increases as) synaptic connections within neuronal circuits, and between neural systems, are formed and upregulated or downregulated as a result of the competition for reentry taking place because of the selection pressures faced while adapting in real-time to the changes in environmental and somatic stimuli. Neural systems (maps) that are frequently used are further strengthened by having synaptic upgrades as well as being myelinated, while neural systems that are not used undergo downregulation of synapses and atrophy. The reward system of the brain is already active, ‘learning’ how to appraise stimuli in terms of adaptation, and competition for reentry happens.

  competition for reentry: in this case you explicitly want to connect in neuron atrophying. The infant has many more neurons than that of an adult, but competition will kill off x million each year.]

  Okay, this first paragraph is ‘outside the sequence’:

As the brain is formed, billions of excess neurons and dendrites are produced which in turn form innumerable random interconnections. Over the course of late fetal development and over the first several years of life, billions of these excess dendrites, synapses, and neurons are absorbed, discarded, and die. This process of elimination and programmed cell death is also under environmental control. That is, the maturing, developing brain sheds innumerable excess neurons, dendrites, and random synaptic interconnections, as a function of experience, or lack thereof. Although capable of learning, the increasingly complex behaviors demonstrated by the fetus and neonate, including head turning, eye movements, startle reactions, crying, screaming, and rudimentary smiling, are probably best described as brainstem reflexes (Joseph, 200X).

At birth, the human brain is in a remarkably unfinished state. Although it has almost all the neurons that the brain will ever have, most of these 100 billion neurons are not yet connected in networks. Some neurons are programmed for specific functions-breathing and heartbeat, but most are not yet designated for tasks and are waiting for the experiences in the environment to determine their function. Forming and reinforcing these connections are the key tasks of early brain development. Connections are created by the sensory experiences-seeing, smelling, touching, and especially tasting, stimulate the growth of neural connections. Connections among neurons are formed as the growing child experiences the surrounding world and forms attachments to parents, family members, and other caregivers.

  WHAT HAPPENS BETWEEN BIRTH AND SEVEN MONTHS? Yes, this needs the same scaffolding that womb to birth is receiving.

  Begins to understand “no” by the end of seven months, although still can’t crawl. Indicates executive control begins by eight months. Executive function is subserved by neural circuitry in the prefrontal cortices, with the cingulate cortex, parietal cortex, amygdala, and other cortical structures playing a supporting role. The myelination and synaptic upregulation in these cortical areas results in the infant changing their behavior when a caregiver says “no-no”. Executive function can influence other areas of the brain, in this case the prefrontal cortices downregulate signal reentry for certain behaviors because the reward system of the brain is saying that a certain behavior reduces dopamine, reduces pleasure, and because the PNS body sensation affect is outside a comfortable “non-noticeable” homeostatic range we check ourselves (which means that this response can get automated).

  By ten months the neurons subserving language recognition have started myelinating. Language recognition is subserved by Wernicke’s area, Broca’s area, as well as the declarative, procedural, and emotional memory systems. The myelination of neurons and upregulation of synapses in these cortical areas results in the infant being able to respond to their own name. The automatization of language and behavior is also taking place in the motor, association, and limbic loops. In the motor loops, behavior is automatized via the putamen; in the association loops, learning is automatized via the caudate; in the limbic loop, emotion is automatized via the VS.

By twelve months the neurons subserving spoken language have started myelinating and undergoing synaptic upregulation. Spoken language is subserved by Broca’s area and the supplementary motor area, as well as the declarative, procedural, and emotional memory systems. Previously the infant has merely babbled or made attempts to repeat sounds and simple words, but around twelve months the infant begins to say words like “mama”, “dada”, and “oh-oh”. The automatization of speech takes place through the motor, association, and limbic loops. Beginning at age 18-24 months, the larynx descends in the neck, which allows for a new range of speech articulation. Around 24 months the child can use simple phrases and repeat words overheard in conversation.

Language, speech, and behavior have their roots in the genetic, developmental, and cultural circumstances which the infant is brought up with. The public function of speech is already apparent during the first year of life, when the infant mimics the speech and behavior of the caregivers that are living within a particular sociocultural-historical period.  all speech is part of our sociocultural-historical development, and all speech is communicative whether to others or oneself.

  [And here is a key metanarrative: sociocultural-historical; and the ‘historical’ part is evolution as well as the history of our socialized culture.]

  [AND THIS IS DEVELOPED with the subtext of PHENOTYPIC ADAPTATION TO THE ENVIRONMENT This section grounds all those ideas from the evolution section and from the neural mechanisms]

  [synapses, selection pressures, sociocultural-historical]

  c          two to three years

  [synapses, selection pressures, sociocultural-historical]

  social speech + executive function

  By the age of 2 years old, the brain is about 80% of the adult size. The brain continues to grow for a few years after birth. You may wonder, "How does the brain continue to grow, if the brain has most of the neurons it will get when you are born?". The answer is in glial cells. Glia continues to divide and multiply. Glia carries out many important functions for normal brain function including insulating nerve cells with myelin.

  A baby's brain develops so fast that by age two a child who is developing normally has the same number of connection as an adult.  By age three, a child has TWICE as many brain connections as an adult.

In the first decade of life, a child’s brain forms trillions of connections or synapses. Axons hook up with dendrites, and chemicals called neurotransmitters facilitate the passage of impulses across the resulting synapses. Each individual neuron may be connected to as many as 15,000 other neurons, forming a network of neural pathways that is immensely complex. This elaborate network is sometimes referred to as the brain’s “wiring” or “circuitry.” If they are not used repeatedly, or often enough, they are eliminated. In this way, experience plays a crucial role in “wiring” a young child’s brain.

  At the two year mark the streamlining of synaptic connections begins to happen more rapidly. Selection pressures have increased competition (neuron atrophying) for signal reentry. Since birth executive function and speech production have functionally and structurally proceeded individually, but at about the age of two these meet which results in entirely new selection pressures as well as a new form of behavior. Speech, which till now has been affective-connative, begins to subserve executive function. Executive function now becomes verbalized and speech becomes understandable. This is indicated by the child’s sudden, active curiosity about words and asking about every new thing, “what is this?”. The child feels the need for words and, through questions, actively tries to learn the signs attached to objects. For the child, the word is a property, rather than the symbol, of the object.

The neurobiological substrates of executive function and speech, which have been developing separately, now begin to function together. Take for example a case where a child sees a flower and asks what it is. The curiosity, subserved by the executive functions, upregulates the signals going through the synapses of the limbic loop. The VS appraises these signals as predictive of reward, and motivation happens in the signals transducted through Broca’s area, through the supplementary motor and premotor cortices, through the primary motor cortex whereupon the child asks “what is this?”. The auditory response “flower” is transducted through the auditory cortices, through Wernicke’s and Broca’s areas, while simultaneously the visual image is being synthesized with this sound in the OPT. Within milliseconds this information has been stored as declarative memory by means of the hippocampo-entorhinal cortex, and these signals are being transducted through the association loops of the caudate whereupon this information is automated in procedural memory. If there is any emotional affect to the situation, the information may also be stored in emotional memory.

At this stage of their development their speech is public, speech for others, and is only used when other people are around. This environmental and somatic stimuli is reentered and competition for circuitry takes place due to the selection pressures involved in adapting to the perpetually changing local circumstances. Neurogenesis (really???), synaptogenesis, and myelinogenesis are still happening, and changes in synaptic activity are a result of changes in signal transduction reentry. Their language and behavior is a product of the sociocultural-historical circumstances they are growing up with. Their neuronal circuitry can only subserve the language and customs they have learned to use. In cultures where television is readily available, children are learning language and different behaviors at a faster rate than their peers who don’t have this technology.

  d          three to five years (to the end of four years)

  [synapses, selection pressures, sociocultural-historical]

  social speech + executive function + private speech

  Between three and four years of age the child’s public speech functionally (but not structurally) differentiates. Does Vygotsky agree? NO. Inner thought is forming in tadem with private speech, and the latter is an indication that structural shifts are taking place. Of course it is structural, the frontal lobe has lots of developing still to do.

  Around the age of three children begin to show egocentricism in their speech. From the day they are born, children are unable to see other peoples’ viewpoints and assume that their view of the world is the same as everyone else’s. If a child knows that there is a toy under the pillow, he or she assumes that someone else walking into the room also knows there is a toy under that pillow. Similarly, a child who covers their eyes will say “you can’t see me now, can you?”. Before the age of three this egocentric view was expressed mainly through the child’s behavior, but now it begins to be expressed in speech as well.

Up till now the child’s speech has been public, that is, it has been spoken for others. Between three and four years of age the child’s public speech functionally (but not structurally) differentiates and we begin to observe private speech: speech for oneself. With private speech children start conversing with themselves as they have been doing with others. It happens only in the social realm, and is mostly incomprehensible to other people. It functions only within social situations. (as opposed to a non-social situation, where even alone our world is social) Private speech is not distinguished by the child from speech for others [precisely because there has been no obvious structural change, although inner thought is now forming in tandem with private speech; it does indicate structural shifts]. There are now two sorts of adaptation: public and personal, both of which are adaptations within the sociocultural-historical circumstances the child is developing in relation to, a particular socially constructed reality.

Between the ages of three and four the child’s language ability significantly develops, and by the age of four most people are able to understand much of what is said. The child expresses ideas and feelings rather than just talking about the world around him or her, and is able to say four or five word sentences with some grammatical accuracy. Syntactic processing is done by the procedural memory system and specifically Broca’s area and the supplementary motor area. Selection pressures and synapses. Neurogenesis has reached its peak, but development still continues through increased myelination and synaptic upregulation and downregulation in response to incoming signal transductions. Between the ages of four and five the child’s ability to make grammatically correct sentences significantly develops.

By the age of five the child can define words and answer "why" questions. As with television, cultures that have preschool constructs the sociocultural world the child grows up in. Many children begin to attend preschool around this age, which introduces new selection pressures on the signals competing for reentry. Educational lessons are given which challenge the children to complete various sorts of tasks. If a child faces a difficulty with some task, they will verbalize the problem aloud; that is, the child works out a solution by using private speech. At this age, preschool children “explain” the names of objects by their attributes. (7:7)

  e          five to seven years (to the end of six years)

  INNER THOUGHT HAS ITS ROOTS IN PRIVATE SPEECH, IT IS GROWING OUT OF THIS.

  Whenever you see the word thought by itself, immediately ask “is this inner thought or one of the five types of inner thought?” Do not leave it at the word ‘thought’.

  [synapses, selection pressures, sociocultural-historical]

  social speech + executive function + inner speech (replaces private speech)

  REMEMBER, EXECUTIVE FUNCTION AND PRIVATE SPEECH ARE THE SAME THING

  functional (social vs. private), structural (verbal thought, somatic-cognition), and the neurobiological substrates of functional and structural changes.

  Between birth and the age of three speech is for the public only, then between three and five speech is both for the public and for oneself. Between five and six years of age, private speech begins to disappear and inner thought begins to develop. Inner thought develops due to both functional and structural changes, in their neurobiological substrates, and we now look at each of these changes in turn.

  Inner thought develops through a slow accumulation of functional (adaptation: public sphere and personal sphere) and structural changes.

  FUNCTION

  Inner thought is not speech minus sound, but is an entirely separate speech function.

  Private speech can be considered an intermediary stage between public speech and inner thought, a transition from speech for others to thinking for oneself. It already has the function of inner thought but remains similar to public speech in its expression. Private speech is inner thought in its functions; it is speech on its way inward, intimately tied up with the ordering [governing/self-governance] of the child’s behavior, already partly incomprehensible to others. Speech turns inward because its function changes; it is no longer used only in the pubic realm, whether spoken to others or to oneself, but is now used in a fully private realm. Inner thought branches off from the child’s external speech simultaneously with the differentiation of the public and the private functions of speech.

The developing functional peculiarities of private speech progressively isolate it from external speech, and its vocal aspect fades away.

The function of private speech is similar to that of inner thought: it does not merely accompany the child’s activity; it serves ‘mental’ (socially constructed reality) orientation, conscious understanding; it helps in overcoming difficulties; it is speech for oneself, intimately and usefully connected with the child’s thinking.

The same tasks that the preschooler verbalizes aloud through private speech are now being relegated to non-spoken inner thought in the schoolchild.

  STRUCTURE

  (To what degree are inner thoughts considered as “executive function”? contemplation, judgement, decision-making, comprehending what somebody is saying to us, considering our reply to them, etc.) THEY ARE PARTIALLY DUE TO EXECUTIVE FUNCTION, PARTIALLY DUE TO SPEECH CENTERS ETC. I don’t want to separate these; executive function and inner thought are intricately linked. REMEMBER, EXECUTIVE FUNCTION AND PRIVATE SPEECH ARE THE SAME THING

  With the progressive isolation of speech for oneself, its vocalization becomes unnecessary and meaningless; furthermore, due to its growing structural peculiarities inner thought simply cannot find expression in external speech. In the same way that selection pressures led to private speech, so do new selection pressures lead to the structural peculiarities of inner thought. Inner thought develops partly because we are put in situations where we can not speak aloud and yet the need to speak is there so it gets internalized. We don’t choose to have inner thought; neuronal circuitry is selected and signals continuously reentered that make inner thought happen. It is a new means of adapting to local circumstances.

  [hippocampo-entorhinal cortex retrieves the images, sounds, and contextual stuff whatever stored in the OPT system (The hippocampus supplies context with episodic memories and these is where the visual images that we have come from); Broca’s area retrieves our internal voice (what is commonly termed ‘thinking’ in a narrow sense of the word); DLPFC, OFC, and FPC ‘retrieve’ (retrieve, I mean ‘select’ in terms of circuitry selected to transduct signals) our executive function; neuronal circuitry in the limbic loop is selected according to exactly what signals are being appraised, which involves the amygdala receiving regulation from the HEC (in the guise of images, sounds, and contextual stuff) and OFC (decision-making and ‘mentally’ appraising the images and thoughts), and then sending signals to the VS (innervated by the VTA) and looping again with the amygdala-HEC-OFC; also the DLPFC and OFC are sending signals through the caudate and being assessed in terms of reward and appraisal in that way. The key point to take away here is that the DLPFC and OFC are sending signals through two different loops of the basal ganglia: the DS and the VS. The implications of this will need to be worked out.]

  Verbal thought is closest to “speaking inside our head as we do out loud”. We experience some inner thoughts as a voice coming from inside our head. In this case the speech structures mastered by the child become one of the basic structures of inner thought. In their overlapping parts, inner thought and external speech coincide to produce verbal thought; however, there is no direct correspondence between verbal thought and tongue or larynx movements. What we speak “inside our head” is subserved by a neural substrate for language that retrieves bits of language and imagination from throughout the cortex, and this crosscortical activity is experienced by us as a linear flow of verbal thought spoken inside our head. [rewrite this next bit in terms of competition for signal reentry: Hundreds of thousands of neurons (do you mean synapses?) throughout our brain are operating at a microsecond speed and all we experience is a flow of verbal thoughts spoken inside our head.] Broca’s area retrieves our internal voice (what is commonly termed ‘thinking’ in a narrow sense of the word)

            Visual thought can take place independently of any verbal thought. We experience visual thoughts as images that range from vague and blurry to distinct and vivid. The hippocampo-entorhinal cortex retrieves the images. The hippocampus supplies context with episodic memories and these is where the visual images that we have come from.

            Semantic thought is to a large extent thinking in pure meanings. (The decreasing vocalization of private speech denotes a developing abstraction from sound, the child’s new faculty to “think words” instead of pronouncing them.) This type of inner thought works with semantics, not phonetics. With syntax and sound reduced to a minimum, meaning is more than ever in the forefront. The syntax of meanings in inner speech is no less original than its grammatical syntax. Unlike speech, it does not consist of separate units. When I wish to communicate the semantic thought that today I saw a barefoot boy in a blue shirt running down the street, I do not see every item separately: the boy, the shirt, its blue colour, his running, the absence of shoes. I conceive of all this in one semantic thought, but I put it into separate words. (That is, also making use of visual thought.) A speaker often takes several minutes to disclose one semantic thought. In his mind the whole semantic thought is present at once, but in speech it has to be developed successively. Semantic thought must pass first through meanings and then through words. Neural substrate.

            Contextual thought is the preponderance of the sense of a word over its meaning. Contextual thought has no direct relation to verbal or visual thought. The sense of a word, according to him, is the sum of all the psychological events aroused in our consciousness by the word. It is a dynamic, fluid, complex whole, which has several zones of unequal stability. Meaning is only one of the zones of sense, the most stable and precise zone. A word acquires its sense from the context in which it appears; in different contexts, it changes its sense. Meaning remains stable throughout the changes of sense. The sense of a word, says Paulhan, is a complex, mobile, protean phenomenon; it changes in different minds and situations and is almost unlimited. A word derives its sense from the sentence, which in turn gets its sense from the paragraph, the paragraph from the book, the book from all the works of the author. In contextual thought, the predominance of sense over meaning, of sentence over word, and of context over sentence is the rule. Neural substrate.

            Somatic thought is the understanding of something at the level of our PNS body sensation affect. Whereas contextual thought is a knowing about something, somatic thought is a feeling about something. We have a gut feeling about something, and our body is this understanding. Neural substrate.

The extreme, elliptical economy of inner thought changes the speech pattern almost beyond recognition. This economy can be seen in the different semantic and syntactic peculiarities of inner thought including predication, abbreviation, agglutination, and saturation. The main distinguishing trait about predication is its peculiar syntax. We know what we are thinking about – i.e., we always know the subject and the situation, so we omit subjects and use predicates only. The specific semantic structure of inner speech also contributes to abbreviation. As private speech approaches inner thought, the child uses agglutination more and more as a way of forming compound words to express complex ideas. When several words are merged into one word, the new word not only expresses a rather complex idea but designates all the separate elements contained in that idea. Agglutination can also involve combinations of meanings. Another basic semantic peculiarity of inner thought is the way in which senses of words combine and unite. A single word is so saturated with sense that many words would be required to explain it in external speech.

These different sorts of inner thought are engendered by motivation, i.e., by our desires and needs, our interests and emotions. From the motive springs one or a combination of types of thought through which the object of the motivation is pursued. Our inner thought then finds complementary expression in our speech and behavior. When signals are appraised as most rewarding/suitably adaptive then so will the relevant neuronal circuitry get selected in the hippocampus, speech centers, executive functions (association loops), and emotional affect (limbic loop which includes OFC regulation) which is the PNS body sensation affect. 

  (Thought development is determined by language, i.e., by the linguistic tools of thought and by the sociocultural experience of the child. Essentially, the development of inner thought depends on outside factors; the development of logic (executive function) in the child is a direct function of his public speech. The child’s intellectual growth is contingent on his mastering the social means of thought, that is, language.)

  f           seven to adolescence (hormones start gearing up; 9-10-11-12)

  synaptic upregulation and downregulation USE THIS INSTEAD OF SYNAPTOGENESIS

  [synapses, selection pressures, sociocultural-historical]

  the usage of the word structure to discuss neuronal circuitry (and also mention function)

  This subsection requires the addition of material. What exactly happens around seven?

  Our investigation established that the traits of private speech which make for inscrutability are at their lowest point at three and at their peak at seven. These egocentric traits develop in a reverse direction to the frequency of private speech. While the latter keeps falling and reaches zero at school age, the structural characteristics become more and more pronounced. (7:11)

  At seven, we have speech that in structure and function is totally unlike public speech. (7:11)

  Between the ages of seven and eight speech is almost fully internalized as inner thought.

  Between the ages of eight and nine the egocentric view begins to disappear. Only when entering the so-called concrete-operational stage at age 7-12 (beginning grades 2 – 3), children became capable of decentring and could appreciate viewpoints other than their own. In other words, they were capable of perspective-taking.

  Careful ultramicroscopic studies show that synapse formation proceeds at its highest rate during the first 6-8 years of postnatal life, then plateaus and begins to decrease with the onset of puberty.

  WRITE THIS IN THE CONTEXT “NEW PARENTS” TO PREPARE THEM FOR THEIR CHILD’S AGING.

  By the age of ten the child has nearly the same number of neurons as an adult.

  g          adolescence to young adulthood (hormones start gearing down; 17-18-19-20)

  Adolescence brings new selection pressures.

  h          young adult to adulthood (myelination starts gearing down; 33-34-35-36)

      i           adulthood to old age

  Up until the age of thirty, the brain naturally synthesizes myelin, but after thirty the production of myelin slows down. This means that something like learning a new skill such as a second language might seem more difficult because there is not as much new myelin being made. After the age of forty, genes for the expression of memory and synaptic plasticity begin being downregulated. There are substantial individual differences at work in the neurobiological changes that take place as we age, and the cognitive and behavioral (motor) skills of different people improve and degrade in different ways.

  The adult human brain is believed to consist of at least one hundred billion neurons (nerve cells) and probably five to ten times as many neuroglial (functional support) cells.

  Although neurons continue to be generated and to divide during adulthood, it is through environmentally sculpted attrition and dendritic pruning that specific neural networks are established and formed. The sculpting of specific neural pathways fine tunes perception and selective attention, and promotes learning, memory, and language, cognitive and personality development (Joseph, 1982, 1996b, 1999).