Neurodevelopment

“ The increasing frequency of nervous disorders among school children, particularly in the older countries, is probably due in part to these circumstances. If we consider the brain of the child of seven or eight years, our conclusions are strengthened that he should not be engaged in reading and writing. At this age the brain has attained almost its full weight, and is therefore large in proportion to the body. Its development is, however, very incomplete, particularly as regards its associative elements—that is, the so-called association fibers and apperception centers. ”

“ When the brain and nervous system are both young, there are few neural connections established, and the organism is plastic to all stimuli. As the individual grows older, connections once made tend to be repeated and to be, as it were, unconsciously preferred by the nervous system. The capacity to form habits is most pronounced in the young child in whose nervous structure no one action rather than another has yet had a chance to be ingrained. The more connections that are made, the more habits that are acquired, the less, in a sense, can be made. ”

“ In other words, is there nothing in that infant, or in the adult which he becomes, but a brain and a nervous system of a highly organized and complex physical structure adapted to receive impressions on itself from without? Are the experiences which have been enjoyed by the progenitors of the human infant or by preceding organisms registered in his brain, and is his capacity of intelligence dependent on his having inherited the same or nearly the same volume of brain as that which was possessed by his progenitors? ”

“ When, however, an infant is born, though physically fully developed, with face fully formed, but acephalous, without brain—that is, when an arrest [332] of development has taken place—the babe cannot live, it cannot breathe, because the principal part of the nervous system is wanting—the medulla oblongata, cerebrum and cerebellum, etc.—though the lungs, heart, and all other organs are perfectly developed. This arrest of development may take place at any time. It is thus that congenital malformations are produced. Idiots are thus formed, or any other inferior formation of brain may take place. ”

“ Education should be so arranged as to develop the brain by a natural process—not from within outward; not from the centre to the periphery; not from above downward; but as the nervous system itself develops in its evolution from a lower to a higher order of animals, from the simple to the more complex and more elaborate. Any system of education is wrong, and is calculated to weaken and worry an impressionable nervous system, which attempts to overturn or change this order of the progress of a true development of the brain. ”

“ They originate in nests of characteristic large cells located in the cerebral cortex and are regarded as paths, though not the only ones, through which volitional impulses are conveyed from the brain. They seem to control certain of the finer and more delicate movements of the body.
Great Complexity in Associations and More Neurons in the Brain of Man Than of Other Animals.—It has already been noted that as animals stand higher in the scale of life while the general plan of their neural elements remain the same, there is increasing complexity in the number and connections of the neurons. ”

“ The new growth takes shape from the new thoughts: the old is lost in the steady waste, and the child is reformed, physically as well as morally and mentally. That the nervous tissue of the cerebrum should be thus the instrument of the mind need not surprise us when we think how the muscles and joints of the tumbler, the vocal organs of the singer, the finger-ends of the watchmaker, the palate of the tea-taster, grow to the uses they are steadily put to; and, much more, both in the case of brain and of bodily organs, grow to the uses they are earliest put to. ”

“ It was then necessary that the nervous cerebral system should be adapted, by its early development, to the great degree of action which it is then to have. In fact, all the organs that receive external impressions, the nerves that transmit them, and the brain that perceives them, are really in the infant when awake in permanent excitement, who in the midst of the same objects as the adult, fatigues these organs three times as much as he to whom a great part of these external objects is indifferent, because they have heretofore excited him. ”

“ This would seem to indicate that the greater mental activities of higher animals depend more on richness in complex associations than on mere increase in number of neurons. The latter, however, is by no means unimportant as may be seen in man, for instance, in whom it is estimated that the cerebral cortex, that is, that part of his brain in which his more complex mental processes transpire, contains some nine billion more nerve cells than does the corresponding region of the brain of an anthropoid ape. ”

“ When the mind dwells on one subject to the exclusion of all others, we call such a condition monomania. If we have an excessive development of mind, and deficient support of body, the result is corporeal derangement. It is unfortunate for any child to inherit unusually large brain endowments, unless he is possessed of a vigorous, robust constitution. Such training [pg 181] should be directed to that body as will encourage it to grow strong, hearty, and thrifty, and enable it to support the cerebral functions. ”

“ For healthy and efficient action, the brain should be primarily sound; as this organ is subject to the same general laws as other parts of the body. If the brain of the child is free from defects at birth, and acquires no improper impressions in infancy, it will not easily become diseased in after life. But, if the brain has inherited defects, or has acquired a proneness to disease by mismanagement in early life, it will more easily yield to influences that cause diseased action. The hereditary tendency to disease is one of the most powerful causes that produce nervous and mental affections. ”

“ Work and Waste of Brain Tissue Necessary––This, speaking broadly, is the rationale of the matter: just as actually as we sew or write through the instrumentality of the hand, so the child learns, thinks, feels, by means of a material organ––the very delicate nervous tissue of the cerebrum. Now this tissue is constantly and rapidly wearing away. The more it is used, whether in the way of mental effort or emotional excitement, the more it wears away. Happily, rapid new growth replaces the waste, wherefore work and consequent waste of tissue are necessary. ”

“ In ordinary discourse we use the words brain and mind as interchangeable terms, because it is quite evident that where there is lack of intelligence there is deficiency in the brain and where there is a high degree of intelligence there is a correspondingly high development of brain. The immense advance in recent times in our knowledge of the physiology of cerebral process serves more and more to emphasize the entire and absolute dependence of mind on brain, and particularly of the higher processes of mind on the development of the cells and fibres of the cerebral cortex. ”

“ In man, for example, there are certain characteristics, types and groupings of nerve-cells which are reproduced generation after generation with remarkable fidelity. This means that in so far as these represent the mental make-up of the individual, his mentality is continuously linked with others which have gone before. The new-born child has all the nerve-cells in its brain that it will ever have but the ultimate linkages of the finer connectives between them, or at least the pathways of travel, remain in large measure to be made. ”

“ Who would have imagined that the nervous system is a modified portion of the primitive epidermis? In the absence of proofs furnished by the concurrent testimony of embryologists during the last thirty or forty years, who would have believed that the brain arises from an unfolded tract of the outer skin, which, sinking down beneath the surface, becomes imbedded in other tissues and eventually surrounded by a bony case? Yet the human nervous system in common with the nervous systems of lower animals is thus originated. ”

“ From these reports it is plain to be seen that for all mental development an hereditary physical growth of the cerebrum is indispensable. If the sensuous impressions experienced anew in each case by each human being, and the original movements, were sufficient without the development of the cerebral convolutions and of the gray cortex, then these microcephalous beings, upon whom the same impressions operated as upon other new-born children, must have had better brains and must have learned more. ”

“ Medical science has, in late years, gone so far as to prove that there must be an advance growth or change in the brain cells years before action or change in character become the result of such development. For all we know, every deed in our careers is the result of some such mental change, and as there are more super-sensitive nerves from the brain to the hand, it may then follow that such changes and subsequent actions in our lives may be written in our hands even long years in advance. ”

“ No one is much surprised when an automobile, equipped with a mechanism much simpler than the nervous system, refuses to respond properly.
The child is born without knowledge but with certain tendencies, instincts, capacities and potential strength or weakness. His nervous system and his brain may be good or bad—most likely neither very good nor very bad. All of his actions both as a child and as a man are induced by stimulation from without. He feels, tastes, sees, hears or smells some object, and his nerves carry the impression to his brain where a more or less correct registration is made. ”

“ Relatively large in bulk at birth, and reaching usually its full mass in the first fourteen years of life, the human brain possesses throughout childhood vast silent areas, big with future potentialities, areas in which the cells are slowly ripening to function. Even after full growth in size is reached, many more years must pass before capacity for the higher mental functions or for the complete control of such functions has developed. It must be borne in mind that, throughout this period of immaturity, errors of nutrition or defective stimulation may interfere with function. ”

“ Likewise the child's first attempts to feed himself or do any one of the thousand little things about which he is so awkward, are partial failures not so much because he has not had practice as because his nervous machinery connected with those movements is not yet developed sufficiently to enable him to be accurate. His brain is in a condition which Flechsig calls "unripe." How, then, shall the undeveloped cells and system ripen? How shall the undeveloped cells and fibers grow to full maturity and efficiency? ”

“ It is assumed as a matter of course that the brain itself is there, which, to carry out our analogy, means that the crude soil or earth is there. Sufficient quantity and adequate quality of nerve tissue must be regarded as prerequisite. If the brain has been damaged in any way during development or birth, if it has been smashed up in any way, or if it has failed to evolve the minimum number of healthy nerve cells, the endocrine influence becomes negligible. ”

“ We may, however, notice here that, as in his nervous organization, no distinctly new parts are discoverable, but only general growth and development, and especially vast increase in the size and working capacity of the cerebrum, together with improved lines of communication between the different parts of the brain, so in the psychical manifestations which this enlarged and better-developed brain exhibits, no faculties are discovered beyond what these various developments in structure render possible. Does man possess intelligence? ”

“ Some of the higher brain centers do not yet exist at all, while others are in too incomplete a state for service. The various sensations which the baby experiences—heat, light, contact, motion, etc.—are so many stimuli to the development of these centers. If the stimulus is too great, the development is sometimes unduly hastened, with serious results, which show themselves chiefly in later life. The child who is brought up a noisy room, is constantly talked to and fondled, is likely to develop prematurely, to talk and walk at an early age ”

“ A peculiar fact relating to these convolutions is observed by all anatomists: mental [pg 99] development is always accompanied by an increasing dissimilarity between their proportional size.
The cerebral hemispheres may be injured or lacerated without any pain to the patient. The effect seems to be one of stupefaction without sensation or volition. A well-developed brain is a very good indication of intelligence and mental activity. That the cerebrum is the seat of the reasoning powers, and all the higher intellectual functions, is proved by three facts. ”

“ In the human organism physical variation has well-nigh stopped, or is confined to insignificant features, save in the grey surface of the cerebrum. The work of cerebral organization is chiefly completed after birth, as we see by contrasting the smooth ape-like brain-surface of the new-born child with the deeply-furrowed and myriad-seamed 57surface of the adult civilized brain. The plastic period of adolescence, lengthened in civilized man until it has come to cover more than one third of his lifetime, is thus the guaranty of his boundless progressiveness. ”