PRE- AND PERINATAL BRAIN DEVELOPMENT
AND ENCULTURATION: A BIOGENETIC STRUCTURAL APPROACH
Charles D. Laughlin
There now exists ample evidence from various quarters that the perceptual/cognitive competence of the pre- and perinatal human being is significantly greater than was once thought. The author reviews some of the evidence of this emerging picture of early competence and discusses its importance both as evidence of the biogenetic structural concept of "neurognosis," and for a theory of enculturation. To this end he draws upon the literature of pre- and perinatal psychology, especially that of developmental neuropsychology, psychobiology and social psychophysiology. He concludes by suggesting some of the implications of these data for a theory of enculturation.[key words: brain and culture, enculturation, neural development, pre- and perinatal psychology, innate knowledge, infancy, fetal experience]
Charles D. Laughlin is professor of anthropology at Carleton University, Ottawa, Canada. He has done ethnographic fieldwork among the So of northeastern Uganda and among Tibetan lamas in Nepal and India. He completed postdoctoral studies in neurophysiology at the Institute of Neurological Sciences, University of Pennsylvania. He is co-author of Biogenetic Structuralism (1974), The Spectrum of Ritual (1979), Extinction and Survival in Human Populations (1978), Science AS Cognitive Process (1984), and Brain, Symbol and Experience (1990). He is editor of both the Neuroanthropology Network Newsletter and the Pre- and Peri-Natal Psychology Journal.
The literature in pre- and perinatal psychology (including aspects of cognitive psychology, developmental psychology, developmental neuropsychology, psychobiology, social psychobiology and clinical psychology) now provides ample evidence that the perceptual and cognitive2 competence of the fetus and infant is significantly greater than was once thought. This evidence suggests that neurocognitive development in the pre- and perinatal human being produces structures that make the world of experience "already there" for the advanced fetus, neonate and infant. For instance, objects, relations between objects, faces and speech sounds appear to be already meaningful to the neonate (see below). This conclusion has major implications for ethnographic research and ethnological theories of enculturation. It is the purpose of this paper to review some of this evidence and to point out some of the ethnographic and ethnological implications.
Because the review portion of the paper will cover a wide spectrum of research and findings, treatment of any particular aspect of development will be unfortunately superficial. For instance, some of the findings mentioned here are in fact controversial in the literature. Furthermore, as the methods vary widely within the different approaches -- ranging from clinical records to animal research, from ethnographic fieldwork to double-blind experimentation, from neuroanatomical dissection to electrophysiological recording -- space does not allow us to discuss the pros and cons of the methods used to generate these data. Rather, we have cast our net widely in the field of pre- and perinatal psychological information and are relying upon building a general picture of the evidence relevant to the issue of enculturation. Beyond this, we leave it to the reader to follow-up methodological and theoretical points of interest and controversy.
The discussion will be presented within the framework of biogenetic structural theory, because current findings in pre- and perinatal psychological research tend to confirm a central tenet of that theory -- a pivotal concept termed neurognosis, or neurognostic structure (see d'Aquili, Laughlin and McManus 1979: 8, Laughlin and d'Aquili 1974: Chapter 5, Laughlin, McManus and d'Aquili 1990: Chapter 2).3 According to the theory, a principal function of the human nervous system is the construction of a system of models of the world. These models develop from rudimentary neural structures produced in the course of neurogenesis, mostly (but not entirely) during gestation and early infancy. These initial models of the world are largely predetermined in organization by the genotype and function as nascent knowledge about the world (hence, "neuro-gnosis," or knowledge inherent in the nascent structure of a neural system; e.g., knowledge about faces, speech sounds, objects, movement, etc.). It is neurognosis that mediates the "already there" world of experience for the human fetus, and that later operates as a preadaptation (what Chisholm and Heath 1987:61-62 call a "facultative adaptation") for the detection and interpretation of patterned energies encountered after birth and later in life.
When the notion of neurognosis was initially formulated in the early 1970's, there were relatively scant direct data to offer as examples of these models and their development. But times have changed, and there now exists ample evidence from various quarters that tends to confirm the existence and importance of neurognosis, and for the very early interaction between the neurognostic models and the world. It is therefore timely to introduce the notion of neurognosis into a revised consideration of the nature of enculturation.
We do not mean to imply that the fetus, or even the neonate is learning "culture" in the normal sense of that term; i.e., customs, roles, behaviors, attitudes, norms, ritual procedures, semantic fields, etc. Rather, it seems important to focus on the capabilities of the pre- and perinatal human being which establish anlagen (i.e., affective/arousal biases, perceptual/cognitive foundations, precursors, requisite initial structures, learning tendencies, aspects of temperament, etc.) upon which the development of "enculturation" (in the old sense of the term) is grounded (see Piaget 1971, 1985, Oyama 1985:4). But in order to turn thinking in this direction, we must drop any dualistic (i.e., "nature" vs. "nurture") notions of learning before and after the transmission of culture. It is our view that the neurognostically rich experience and development of the pre- and perinatal human being produce transformations in neurophysiological structures that in turn form the earliest roots of enculturation (Laughlin 1990). Early experience and development lay the foundations for the later learning we usually associate with the idea of "culture." And insofar as a society conditions the environment of the pre- and perinatal human being in such a way as to bias early experience and development, it is reasonable to suggest that the application of a new sense of the term "enculturation" is appropriate.
PRE- AND PERINATAL COMPETENCE
It now seems probable that a kind of consciousness4 is present in the prenatal child at least as soon as a functioning neural substrate for experience is in place; "substrate" being defined here as the cortical and subcortical structures requisite to the occurrence of perception, which includes at least simple intentionality (i.e., attention, cathecting energy to an object), constitution of sensory objects, neurognosis, and learning (defined here as development of neurognostic structures in interaction with the world). Although adult consciousness is certainly more complex than that of the prenatal child and is probably largely cortical in organization (Doty 1975: 797-798), this does not mean that the prenatal child need be wholly "cortical" to experience, to be conscious, or to learn. Rather, it means that as soon as a presiding, intentional, cybernetically active neural network is present in the developing nervous system, the child may be said to be experiencing.5 The incorporation of cortical processing into the neural systems mediating experience would appear to emerge sometime during the last trimester of gestation.
It is critical to understand that the consciousness of a human being develops. Consciousness does not magically come into existence from nowhere at some point in life and remain fixed in its qualities and its organization thereafter. Rather, the extent and range of functions comprising consciousness at any particular point in its maturation will be determined in large part by the organization of the individual's nervous system and its cognized environment.6Our notion of cognized environment is similar in some respects to the phenomenological concept of the "lifeworld" (Schutz and Luckman 1973, Husserl 1970), and differs only in that our concept implies a world of experience produced by neurobiological networks of the brain. We originally borrowed the terms "cognized" and "operational environments" from Rappaport (1968), but have substantially altered their meaning within biogenetic structural theory (see d'Aquili, Laughlin and McManus 1979: 12ff, Laughlin and Brady 1978: 6ff, Rubinstein, Laughlin and McManus 1984: 21ff, and Laughlin, McManus and d'Aquili 1990: Chapter 3). For one thing, Rappaport does not imply as we do a neurocognitive substrate to the cognized environment. For another thing, Rappaport equates the operational environment with that described by science, whereas we treat scientific descriptions as cognized environments. And this development, particularly during gestation, is in part determined by the genotype (Imbert in Mehler and Fox 1985) and unfolds in intimate interaction with the operational environment -- that is, with the actual nature of the individual organism and its world.7 The process of development of the nervous system, and its conscious network, tends toward greater differentiation of structure and function, and a greater hierarchy of control functions (Powers 1973, Gottlieb 1983: 6, Piaget 1985, Laughlin, McManus and d'Aquili 1990:Chap. 9).8 Of course, development of the organization of consciousness continues for years after birth; e.g., development of the prefrontal areas of the cortex mediating the "higher cognitive functions," is not mature until the later teens or older (Becker, Isaac and Hynd 1987).
The Prenatal Child.
The available data indicate that the cognized environment of the prenatal child is indeed one of rich sensory experience (Bornstein in Mehler and Fox 1985), and that it is behaviorally very active, at least by the beginning of the second trimester.
This does not mean that the consciousness of the prenatal human being is the same experientially or structurally as that of an adult, or even that of a postnatal child. It is not, nor could it be, for the component systems of the network of cells producing consciousness are maturing at a rapid rate, especially during the second and third trimester of prenatal life and the first six months or so after birth. There are also considerable individual differences in the rate of development.
Table 1 presents a summary of some of what we know about the course of prenatal physiological and psychological development.9Furthermore, the data pertaining to when various functions arise in the course of prenatal development are often spotty or inconclusive. Anthropologists should be wary of considering any point of initial development of a function as fixed, for the tendency has been for the age of emergence of any particular function to be pushed back to earlier stages as new and more sensitive techniques of observation and experimentation are acquired. Also, it would be well to keep in mind three other factors when evaluating these data: (1) the almost inevitably ethnocentricity of these studies; the subjects are usually Euroamerican in origin, (2) many of whom have undergone hospital births and obstetrical procedures, and (3) the experimental research upon which conclusions are based frequently do not reflect the "real life," naturalistic situations so valued by ethnology (see also Murray and Trevarthen 1985: 180, Edgerton 1974). This summary is uncomfortably sparse and although the rate of development of the brain, both within the human species and across primate species, is known to be quite uniform (see Dobbing and Sands 1973, Sacher 1982), the phase of gestation during which any particular function first begins to actually manifest itself is often uncertain. However, the summary will give the reader a quick sense of the course of prenatal neurobiological and psychological development.
A rough summary of the landmarks of neurophysiological and psychological development during human prenatal life by approximate month and week of gestation. Sources of data: Verny (1982), Chamberlain (1983), Larroche (1966), Walton in Stave (1978), Rosen and Galaburda in Mehler and Fox (1985), Busnel and Granier-Deferre (1983), Hollander (1979), Balashavo (1963), Klosovskii (1963), Parmelee and Sigman (1983), Spreen et al. (1984), Kjellmer (1981), DeCasper and Fifer (1980), Moore (1982), Barrett (1982), articles in Gootman (1986).
Month Week What Is Known About Brain and Consciousness:
0 0 -Conception.
1 -Blastocyst implanted in the uterine wall.
2 -Ectoderm forms from which the nervous system will differentiate; beginning of "embryo" stage.
3 -Nervous system begins to form; neural groove and tube, then optic vesicles and auditory placode present; acoustic ganglia appear; formation of cortical plate where cells of cortex produced.
4 -Neuroectoderm complete and begins differentiation into neural tissue; spinal cord, rhombencephalon, mesencephalon, diencephalon and telencephalon are all evident; rapid growth of the brain; heart begins to beat; autonomic nervous system (ANS) begins to form (cells migrate from neural crest to form sympathetic ganglia and trunk, cells from brain stem and spinal cord form parasympathetic nerves, including cranial nerves III, VII, IV and X); olfactory placodes arise.
5 -Blood vessels begin to penetrate neural tissue; optic vesicle appears; cerebral vesicles distinct; ear begins to form; cerebral hemispheres begin to bulge.
6 -Primordium of cerebellum; cochlea appear; hypothalamus differentiates within diencephalon; nerve plexuses present; sympathetic ganglia forming segmental masses.
7 -First contralateral head flexion; telencephalon transforms to the cerebral hemispheres; basal ganglia appear; first commissure fibres form (anterior and hippocampal commissures); middle ear ossicles appear; sympathetic chains of the ANS more developed; nerve fibers invade optic stalk; eyelids forming.
8 -Sub-cortical synapses; cerebral cortex begins to obtain typical cells; movement of head, arms and trunk easily; rudimentary beginnings of most bodily organs apparent; taste buds apparent; end of "embryo" stage and beginning of "fetal" stage; fetus looks more "human."
2 9 -Vestibular system immature, but operating; fully functioning kidneys secreting urea and uric acid into amniotic fluid; visual system, esp. the retina, develops rapidly between 2nd and 4th months; sensory nerves have developed and now contact the skin; face has human appearance.
10 -Main parts of the brain differentiated; corpus callosum incomplete; cortex individualized within the mantle, but only four layers; lower visual pathway in place; adrenal medulla and the paraganglia of the ANS differentiated; spinal cord attains definitive internal structure.
12 -Fetus clearly moving - grasping, sucking, squinting; increased heart rate in response to touch by amniocentesis needle; swallowing and tongue movements; anterior corpus callosum forms; all parts of brain (except sulci) present by 12th week; first evidence of adrenal medulla chromaffin cells; neuroglial cells begin to differentiate.
3 13 -Primary cortical sulci begin to appear; formation of major nuclear groups of the limbic system between 3rd and 4th months; hypothalamic-pituitary-adrenal axis active.
14 -Taste apparatus in place.
15 -Corpus callosum complete; functional retinae; mothers first detect signs of life between 15 and 20 weeks.
16 -Frowning, grimacing; squinting if eyelids touched; beginning of cortical cell migration; cerebral hemispheres conceal much of the brain.
18 -Gag reflex; hippocampus begins to differentiate.
19 -Cortical layers begin to form; different cortical functional areas may be distinguished; primitive body language indicating aversion to noxious stimuli (e.g., amniocentesis needle, ultrasound).
20 -Cortical dendritic branching and synapsing begins; hair cells in organ of Corti develop; produces catecholamines (related to ANS functioning) in increasing amounts from before now to end of gestation.
21 -Audible crying.
5 22 -Sensitive to touch as any 1 year old; aversive reactions to cold water injected into mother's stomach; myelinization begins; associative learning demonstrated (music w/relaxation) for fetuses between 22 and 36 weeks.
24 -Main mass of cortical cells in place and major convolutions form (frontal lobes poorly developed); hearing structures all in place; listening constantly, but immaturely, and keyed to mother's heartbeat; pupillary response.
25 -Moves in rhythm to orchestra drum; vestibular system fully mature.
6 26 -Six layers of cortex evident by this time, and different areas clearly distinguishable by type of cells and cell layers; no more cortical cells will be produced; premature infant can survive because lungs can breathe on their own, capable of directing rhythmic breathing and regulating body temperature; memories from roughly 6 months on; discriminates mother's attitudes and feelings and reacts to them; eyelids can open and retinal fovea begin to form.
27 -Limited dendritic branching on pyramidal cells in visual cortex.
28 -Primary sulci deeper and better defined and secondary sulci begin to appear; neural circuits nearly as complex as a newborn; possible awareness (?).
29 -Asymmetries in cortex first visible.
30 -Myelinization of cerebellum begins.
32 -EEG data showing all primary and secondary cortical association areas working; EEG's become distinct for sleep and wake; REM sleep apparent; clear evidence of visual attention.
34 -Habituation demonstrated in fetuses; active visual attention reported; significant dendritic branching of both pyramidal and stellate cells in visual cortex.
8 35 -Cortical cells same as full term, but with less dendritic branching; evidence of visual recognition memory.
9 39+ -Full term; auditory system reasonably mature; stories read to baby in utero recognized after birth.
Encapsulating a bit, among the various sensory systems of the human nervous system, the somatosensory system (mediating tactile sense) begins to develop first, followed in turn by the vestibular (position in space), the auditory and finally the visual systems. All of these systems become functional during gestation (Gottlieb 1971, 1976b). Furthermore, the cerebral cortex is in place and functioning before birth, providing the substrate for many of the precocious perceptual/cognitive functions now being documented for the neonate (see Visser et al. 1985, Weiskrantz 1988: 69-70, Kagan 1984:31-50).
Of special interest to anthropologists is the development of the prefrontal cortex. Anatomically, this area is intimately connected to subcortical limbic and autonomic structures (mediating motivation and emotion), brain stem reticular activating systems (mediating arousal), posterior sensory and association cortex (producing sensory phenomena), and the frontal and cerebellar motor areas (controlling behavior). Prefrontal cortex is known to service intentionality, modulate affect and behavior, constitute temporal relations and plan goal-directed cognitive and motor activity (Fuster 1980, Stuss and Benson 1986, Laughlin 1988).
Unfortunately, our understanding of the functions and development of the prefrontal lobes is far from complete, and the developmental neuropsychology required to clear the picture has only just begun to emerge (Fuster 1980, Stuss and Benson 1986). It is instructive, however, that just as with other cognitive functions of the nervous system, the age at which prefrontal synaptic development and rudimentary functioning is considered to begin is being moved back into early infancy, and some authorities would go so far as to say near birth (Diamond 1988, Welsh and Pennington 1988). And it is becoming apparent that different components of the prefrontal complex of functional areas mature at different rates (Nonneman et al. 1984). It seems likely that some prefrontal functions actually begin to emerge in prenatal life, perhaps beginning with the selective augmentation of sensory input from competing modalities, a function of attention known to operate in all sensory modalities (Robinson and Petersen 1986). Moreover, it is entirely possible that rudimentary intentional functions are mediated during part of the gestation period by the dorsal-medial nucleus of the thalamus, the most phylogenetically recent area of the thalamus, and an area with intimate reciprocal interconnections with the prefrontal cortex (Stuss and Benson 1986).
LEARNING AND THE ENVIRONMENT OF THE WOMB
The universality of sequencing and emergence of cognitive and perceptual functions in prenatal life are due mainly to two factors: (1) the brains of all people seem to develop anatomically in a relatively invariant manner during pre- and early perinatal life (Sacher 1982, Turkewitz and Kenny 1982, Larroche 1966, Glassman and Wimsatt 1984), and (2) the womb provides a relatively similar environment for all humans. But although the neurobiological development of the fetus is genetically regulated, it also appears that the influence of the environment upon the development of cognitive and perceptual structures begins at some point in prenatal life (see Gottlieb 1976b and Barrett 1981 for reviews), and accelerates throughout the pre- and perinatal period. We now know that most of the activity of the sensory neural cells at every hierarchical level involves abstraction of patterns in the ever-changing perceptual field, and projection of these (as re-cognition) upon events occurring in the world (Hubel and Weisel 1962, E.J. Gibson 1969, J.J. Gibson 1979, Barlow and Mollon 1982, Imbert in Mehler and Fox 1985). As Ashby (1960: Chapter 5) has noted, the adaptive functions of the brain produce a stability of structural boundaries and functional limits.
Moreover, a range of environmental factors are known to influence the development of children in the womb -- mother's diet and fetal malnutrition, toxins in the environment, availability of oxygen, noise, mother's endocrinal, immunological and emotional states, mother's attitude toward pregnancy and birth, mother's movement, mother's tobacco, alcohol and drug consumption, and other stressors have an effect upon both the child's experience and its neural development (see Verny 1982, Sontag 1941, Schell 1981, Klosovskii 1963, Joffe 1969, 1978, Stave 1978, Maurer and Maurer 1988: 16-20, Dobbing 1974, Chisholm 1983: 135ff, Dhopeshwarkar 1983, Streissguth et al. 1989, Winick 1976, Elkington 1985, Stott 1971, 1973, Martin 1981, Lewin 1982). In addition there are some suggestive data from animal studies that indicate that the extent of enrichment or impoverishment of the maternal environment may have a determinant effect upon the complexity of dendritic branching of the fetal cortex, thus indicating in physiological terms the possibility of "intrauterine education" (M.C. Diamond 1988:91), a possibility acknowledged and even institutionalized in some cultures (e.g., Japan, see Nakae 1983; Mohave Indians, see Devereux 1964: 267; and Ashanti, see Hogan 1968).
Fetuses may well become "sensitized" to the speech of their mothers and others while in the womb, and are quite capable of some types of associative learning by at least the fifth month of gestation (Busnel and Granier-Deferre 1983). It is also significant that areas of the left hemisphere of the cortex associated with language processing are observed to be larger than homotopical areas of the right hemisphere as early as the 29th week of gestation (Rosen and Galaburda in Mehler and Fox 1985: 315), indicating that the neural substrate for the processing of speech and language may be present in utero.
Part of early learning involves establishing an emotional set relative to objects in the world, and to the world of phenomena as a whole. Some theorists consider "emotion" to be a strictly cortical-level, cognitive interpretation of lower order processes (e.g., Maurer and Maurer 1988). On the contrary, our view is that stress-related affective and arousal states mediated by discrete interconnections of hypothalamic, autonomic, adrenal medulla, brain stem reticular, limbic, and motor "fight and flight" systems that develop early in prenatal life may establish responses to recurrently stressful stimuli such as maternal anxiety and stress, noise and alarming speech sounds, noxious vibrations and movements (see relevant discussion by Gellhorn in Gellhorn 1968: 144ff; also McKinnon, Baum and Morokoff 1988, Levenson 1988, Hofer 1974, Brazelton and Yogman 1986:1, Chisholm and Heath 1987:55-61). In other words, subcortical and peripheral nervous system orientations toward the world of experience may be established prenatally before the cortical processes involved in adult emotion have fully matured, and which come to establish a biased orientation, or characteristic "tuning" of cortical connections when they do mature. It is now known that most, if not all of the basic human emotions are present and being expressed by the perinatal child just after birth (Campos et al. 1983).
Studies of changes of heart rate, blood pressure and peripheral vasomotor tone suggest that the fetus and newborn are endowed with extremely reactive autonomic nervous systems that respond to a wide range of stimuli in the environment (Rogers and Richmond 1978, Hofer 1974), including their mother's ANS activity while still in the womb (Jost and Sontag 1944). A number of theorists have held that a bivalent approach-with-interest/withdrawal-with-disgust emotional response to objects is present from birth and provides the initial motivation for exploration of the physical and social world (Schneirla 1959, Izard 1977, Fox 1985).
It seems reasonable that one of the most important sets of associations being made during the pre- and perinatal period of growth and learning over which culture likely exercises significant influence is that developing between sensory experiences and affect/arousal -- in other words, between perceptions/cognitions about sensory objects and their interrelations on the one hand and autonomic/limbic activity on the other hand (see Campos and Barrett 1984). Yet our understanding of this very crucial relationship is hampered to some extent by at least two factors, one methodological and the other theoretical. The methodological problem has to do with the difficulty of directly measuring autonomic activity relative to sensory events in the human fetus. It is difficult to design non-intrusive methods of measuring autonomic activity in any sophisticated way. As a consequence, the data about the development of autonomic functioning during gestation is rudimentary at best. Moreover, even when there are correlational data indicating an effect from mother to fetus, it is difficult to pinpoint the physiological mechanisms involved (but see Mednick et al. 1971).
The theoretical hurdle is easier to circumvent. The tendency has been to think of cognitive-perceptual structures as operating at a level above and somewhat removed from the more primitive and generalized limbic and autonomic systems mediating affect and arousal; again, a residue of inherent "nature" vs. "nurture" thinking in science. Steps toward a more integrated view of energy allocation in the nervous system were taken years ago by W.R. Hess (see Hess 1964:34; Akert 1981:119-121) in his notion that the entire brain and endocrine system is a binary one comprised of ergotropic (adaptational) and trophotropic (vegetative and organizational) subsystems, each represented at every hierarchical level of neuroendocrinal and somatic organization. Hess' model was explored and elaborated by Ernst Gellhorn and his associates (Gellhorn 1967, 1968, Gellhorn and Loofbourrow 1963) in the study of emotions. Gellhorn was just extending the theory to a consideration of states of consciousness (Gellhorn and Kiely 1972), and was just beginning to generate some controversy (Mills and Campbell 1974), when he died (Kiely 1974). A few researchers have since carried on where the Gellhorn group left off in the study of adult states of consciousness (see e.g., Davidson 1976, Lex 1979, Laughlin, McManus and d'Aquili 1990, Fischer 1971, 1986), but to our knowledge no one has explored the relevance of ergotropic-trophotropic balance, or "tuning" for an understanding of pre- and perinatal development. A study of these relationships would be of immense value in constructing an integrated theory of the cultural influences upon the development of affect and arousal states in early life.
James Chisholm and his associates have made a significant start in this direction by studying cross-culturally the influence of maternal ANS activity on newborn and infant ANS activity (Chisholm 1981, 1983, Chisholm, Woodson and da Costa 1978, Chisholm and Heath 1987). Chisholm (1983: 135ff) has reviewed the cross-cultural data showing a correlation between the elevated blood pressure on the part of pregnant women (as early as the second trimester), or women in labor, and the later high stress level (as indicated by irritability) on the part of their newborns (see also Barrett 1982: 279). Moreover, Chisholm and Heath (1987:56-61) have reviewed the psychophysiological evidence indicating the long term effects of prenatal stress (see also Sameroff and Chandler 1975).
Of corollary interest, here is reason to believe that, as in rats, early infant stress may result in higher physical stature in human males cross-culturally (Landauer and Whiting 1964). There is also the suggestion that extraordinary stressing may be incorporated within childhood initiation ceremonies to bring about culturally required transformations in autonomic and endocrinal balance or "tuning" (e.g., scarification, circumcision, torture, ordeal; Morinis 1985; Gellhorn and Kiely 1972, Lex 1979).
Development is a complex process, of course, and the data for long-term psychological and cultural effects of intrauterine stress are frequently conflicting and confusing (see Kagan 1984:26-72, 1989:7, 95-100 for a critique of this issue). But based on clinical data -- data that are often ignored by "hard science" experimentalist reviews of stress-related phenomena -- it seems likely that a long-term, often generalized stressful and emotional orientation may develop for some individuals while in the womb toward either specific aspects of experience (e.g., noise, maternal affect and psychopathology), or experience generally (say, due to chronic pain or toxicity; Chamberlain 1983, 1987, 1989, Grof 1976, 1979, 1985).
It is extremely difficult to obtain direct evidence of attention or "awareness" in prenatal life, and yet it is possible to make grounded speculations about their origins. For example, if one assumes a correlation between conjugate saccades (rapid scanning eye movements) and attention, this function is operating by at least the 28th week of gestation, and probably earlier. And if one assumes that some form of awareness is requisite for memory (operating by at least the 25th week), then this would push the beginning of awareness back even further (e.g., Ploye 1973). In any event, the child is exquisitely sensitive to its environment, and the range of visual, auditory, biochemical, emotional and somaesthetic stimuli arising in its cognized environment is remarkable (see Ploye 1973, Liley 1972, Schell 1981, Sontag 1941, Fries 1977).
Learning and Birth
Unless interrupted by cesarean section, birth is a tremendous event in the life of every person (Stave in Stave 1978). Recent evidence has shown that there is a naturally enhanced sympathoadrenal activity that occurs in the fetus/neonate as a consequence of which adrenal catecholamines are released into the bloodstream during the birth process (Lagercrantz and Bistoletti 1973). Sudden release of endorphins prior to birth may have a regulatory effect upon respiration after birth (Moss 1986), and may well be a factor in producing the experience had by the fetus/neonate during a "natural" birth.
The suspicion in some quarters is that this enhanced excitation of the child's circulation, respiration and metabolism during birth helps the child to establish a normal somatic adaptation to its new circumstances, as well as to protect itself from potential hypoxia and hypercapnia during the actual birth (articles by Jones and by Silver and Edwards in Parvez and Parvez 1980). And conservative interpretations of experimental research to the contrary (e.g., Maurer and Maurer 1988), there is considerable clinical (Chamberlain 1983, 1987, 1989, Verny 1982, 1987, Janov 1972, 1983, Laing 1982, Cheek 1974, Grof 1976, 1979, 1985, 1988), pediatric (Brazelton and Als 1979, Brazelton, Koslowski and Tronick 1977, Sanders-Phillips, Strauss and Gutberlet 1988, Blackbill et al. 1974, Rose 1981), and ethnographic (Neumann 1963, Eliade 1958, Trevathan 1987, Laughlin 1985, 1989) data to indicate that just how the culture patterns the birth process may leave lasting positive or negative, and even traumatic effects upon later psychological development. We do know that newborns and early infants are capable of visual memories, and that such memories may be long-term and difficult to disrupt (Watson 1967, Fagan 1984c). It seems likely that painful stimuli and negative emotions may be constellated around images of visual, auditory and tactile experiences to leave long-term memories of the birth experience -- producing in memory something on the order of Stanislav Grof's (1976) "COEX systems."
A study by Niles Newton (1970) shows that there is a cross-cultural correlation between the psychological environment of birth and the ease and speed of birth. Easier labors seem to be associated with acceptance of birth as natural and non-frightening, and with a comfortable and supportive social environment. Newton tested this finding experimentally on mice and found the same association. And, of course, cultural influences upon the birth process and the treatment of the neonate are found to vary enormously cross-culturally (Brazelton, Koslowski and Tronick 1977, Liedloff 1975, Trevathan 1987, Kay 1982, MacCormack 1982, Ford 1945, 1964, Eibl-Eibesfeldt 1983, Mead and Newton 1967, Jordan 1978), thus indicating an enormous range of possible birth experiences from the neonate's point of view.
PERCEPTION AND LEARNING IN THE PERINATAL CHILD
Interaction between the developing nervous system and the environment becomes even more important during postpartum development and with age. The growth of the brain is rapid and dramatic during the first months of infancy. The brain of the neonate at birth weighs roughly 300 to 350 grams and will reach 80% of its adult weight of 1250 to 1500 grams by the age of four years (Spreen et al. 1984: 29).
Virtually all of the neural cells that one will ever have in one's life are present by the seventh month of gestation.10 Most of the dramatic brain development during the last trimester of prenatal life, and during early postnatal life involves the growth of interconnections between neural cells, selection and elimination among these connections (Oppenheim and Haverkamp 1986, Changeux 1985 and in Mehler and Fox 1985, Purves 1988, Bronson 1982), growth of glial (support) cells (Bronson 1982), and myelinization of certain classes of fibers (Yakovlev and Lecours 1967). The most intense phase of dendritic branching and synapse formation occurs after birth.
A cautionary note is worth interjecting here: Much has been made in the past about the presumed greater plasticity of the infant brain compared with the adult brain (the so-called Kennard principle). The implication of this rather "tabula rasa" view has been that the organization of the infant brain is so immature and malleable that functions can be readily spared and taken up by alternative tissues if damage is sustained. There is now a growing body of data to suggest that the opposite situation may be the case, that under certain circumstances the infant brain may be more susceptible to disruption than the adult brain (see Will and Eclancher 1984). Of related interest are data indicating that the neonatal and infant cortex is already thoroughly lateralized in its functions, even prior to language competence and fully developed handedness (Kinsbourne and Hiscock 1983). This is not to say that flexibility does not exist in the very young nervous system. It clearly does, if one is to take Edelman's (1987, 1989) group selection model, or Changeux's (1985) selectivity model as accurate pictures of early neurogenesis. Plasticity may be most usefully conceived as degrees of freedom of structural transformation constrained by the neurognosis of the particular tissues involved.
Table 2 presents a summary of some of what is known about perinatal development to the postpartum age of six months.