Neural Bases Of Behavior
The neocortex, limbic system, and R.A.S. appear to be three interrelated systems which have as their end the integrated and adaptive functioning of the organism in its complex environment. The neocortex is concerned primarily with cognitive aspects of behavior such as perceiving, reasoning, and sensing the environment. The limbic system, in its interaction with neocortical areas, insures that appropriate autonomic and endocrine responses occur in various situations and accounts for the emotional or motivational aspect to behavior. The reticular activating system modulates and integrates the activity of the other two on the basis of information received from the periphery as well as that channeled in from other neural elements.
These developments suggest a new view of the functional organization of the brain. The classical neurophysiologic preparations described earlier in this chapter, decorticate, decerebrate, and other preparations, emphasize the horizontal organization of the central nervous system. In other words, control and organizational complexity was thought of as increasing as one goes rostrally, that is, from the spinal cord toward the cerebral cortex. However, the discovery of the reticular activating system, extending from the upper cord through the brain stem and mid-brain to its thalamic counterparts, suggests a vertical organization. The classical ascending sensory pathways and descending motor pathways are situated on either side of the R.A.S. and richly connected to it along its length. The counterpart of this vertical organization at the forebrain level is the primary sensory 4
Elementary Developmental Dynamisms
The developing individual, from earliest stages, goes through flexible patterns of reactive sequences within an identifiable environment. The order, interaction, and timing of such sequences are subject to analysis. At each phase of development, the organism has certain specific repertoires reflected in his responses to internal as well as external events. Although there is a general tendency to homeostatic balance in processes of successful or defective adaptation to the changing environment, certain systems tend more strongly in one direction. The development process is, of course, intrinsically patterned by genetic factors. In addition, however, this process is also environment-sensitive or interactional. During interactional activity, the organism is itself changed and, in the process, initiates change in the environment. This particular process of interaction between the organism and its environment, which results in a specifiable change in both, is referred to as dynamic. The word dynamic has acquired a certain vague quality because of the tendency in many students to identify the term with one or another theoretical system of metapsychology rather than with observable aspects of behavior. What is the meaning of this dynamic or interactional change with regard to genetic factors? During the past several decades, various investigators have demonstrated that the environment is of particular importance for the expression of certain genetic changes where environment here refers specifically to the distribution of genetic factors at a distance. This is true of all recessive traits, but is true also of certain others which depend not only on the function of a specific gene locus but also on the environmental genetic topography for effective expression, whether the factor itself be recessive or dominant (see Chapter 1).
The Human Organism Before Birth
What are the possibilities for dynamic interactions in the human before birth? How responsive is the organism in utero? Intrauterine development is conventionally visualized as a pretty stable sequence of events guaranteed by a relatively static environment and set by genetic mechanisms. The embryo, on the other hand, would appear to be far more sensitive to the internal and even to the external environment than has previously been assumed. Recent developmental studies support such a statement. The human embryo, for example, is distinctly responsive to touch and pressure stimuli long before birth. During the latter months of gestation, it responds definitely to shifts in body parts, with certain tonic adjustment mechanisms manifested in clear-cut postural responses. It is likely that these are exercised in the fluid-filled amniotic sac, only one evidence for which is the periodic kicking of the organism well before birth. Taste and smell are well developed before birth, and appropriate stimulation evokes responses during the prenatal period. Fully one month before birth, the embryo responds to loud noises. Whether this response is to the pressure wave of the sound disturbance or to the auditory stimulus is not yet known. Pupillary light reflexes may be elicited well before birth in the human. A clear differentiation of light and dark is probable, although there is no evidence for color discrimination during this period. It is thus evident that the organism is reasonably endowed with response repertoires as well as with mechanisms which can well bring it into reactive relationships with a changing environment. To what extent such repertoires come under the systematic control of the relevant variables has not yet been subjected to any systematic study.
The environment of the embryo is provided not only by external events but also by the metabolic milieu of the mother through the fetal circulation. Is there evidence for the existence of biologic adaptations to shifting concentrations of maternal blood constituents as they penetrate the placental barrier during developmental sequences? That significant changes take place in the mother during pregnancy can scarcely be questioned. These include biochemical variations in the steroid hormones, in important biogenic amines, and in certain serum protein components, such as ceruloplasmin. Since the substances mentioned are of great importance as biochemical substrates of behavior in the maturing organism (see Chapter 2), it might be anticipated that they could affect the embryo as well.
Fig. 1. Increase of L-Lysine Decarboxylase activity of an E. coli culture grown on synthetic medium supplemented with L-Lysine. (Based on data by Gale from Monod, Growth, 11:231, 1947.) The evidence for specific chemical adaptations in the developing human before birth is meager. There are, however, certain informative experiments in infrahuman organisms which may be relevant to this problem. An excellent example is provided by certain classical enzymatic adaptations in microorganisms. Let us consider a culture of the bacterium, Escherichia Coli, which has been grown in a lysine-free medium to the point where there is no evidence for the presence of the enzyme, L-Lysine Decarboxylase, in the growth medium. What happens when the amino acid, lysine, is added to such a culture medium? In the course of a relatively brief interval, the enzyme, L-Lysine Decarboxylase, begins to be produced in increasing amounts. The topography of this environmentally elicited enzymatic response follows a typical sigmoidal curve classically characteristic of adaptive enzyme systems (Fig. 1). The evidence suggests that the appearance of this enzyme represents an adaptive response to environmental change where that change is represented by the addition of the amino acid, lysine, to the culture. On the bacterial level, this provides an example of a classic biologic dynamism.
Are such phenomena observable in the developmental adaptations of infrahuman organism at, for example, the vertebrate level? Again, the evidence suggests that they are. The mode of appearance of such activities as cytochrome oxidase (Fig. 2) and succinic dehydrogenase (Fig. 3) in the fetal guinea pig cortex prior to birth follows the same "adaptive" sigmoidal pattern as for the enzymatic activity in E. Coli. Similarly, the appearance of the enzymatic mechanisms supporting the glucose sedoheptulose shunt system in chick embryo brain follows a like pattern, and the same is true for the development of cholinesterase activity (Fig. 4) in chick brain. In the last instance, there is, in The Human Organism before Birth 113; addition, an interesting temporal relationship between the maximal increase in cholinesterase activity and the appearance of synchronized, rhythmic discharges in the electrocorticogram of developing chick brain (Fig. 5). Whether the human embryo, presented with new or unfamiliar substrates under conditions of stress or disease by the maternal circulation (for example, German measles or the recently described Thalidomide) could present favorable conditions for the adaptive stimulation of deviant enzymatic systems or, on the other hand, for the competitive inhibition of normal enzymatic mechanisms during the course of development is still a moot question. Experimental data are few nor are there any unequivocal behavioral evidences to support such postulated dynamic adaptive mechanisms before birth. Nonetheless, it is to be anticipated that current and projected scientific investigations must expand significant and, perhaps, crucial knowledge in this important area.
5 Mother-Infant Interactions, The neonatal period generally is considered to cover the first 30 days of extrauterine existence. If genetic-constitutional as well as environmental factors play substantial roles in the programming of prenatal development, we should expect both species-specific similarities as well as uniquely individual modes of reacting in the newborn organism. Should fundamental similarities or differences between individuals be accepted as more directly related to genetic factors? This question is impossible to answer, but Paul David and Lawrence Snyder, prominent geneticists, have stated, "Genetics has often been defined as the study of heredity, but in its more modern sense, it is better described as the study of the origin, development, and distribution of individual differences."
With regard to general behavioral principles (see Chapter 12), it is important to answer two general questions. First, what are the autonomic as well as skeletal-motor reflex repertoires available to the newborn organism? Second, by what mechanisms can environmental events impinge on and therefore control behavioral responses in the organism?
There are two general groups of mechanisms available to the newborn. The first group includes reflex or innate stimulus-response mechanisms. Patterns involving autonomic functions, as well as skeletal-motor responses involving peripheral receptor, motor effector, and internuncial neuron tie, will be included. The complex interplay of autonomic vegetative reflex responses as modulators of voluntary skeletal-muscle activity in operant behavior is probably a factor of major importance in the establishment and maintenance of individuality. Among examples of reflex mechanisms are those involved in respiration, swallowing, sucking, excretion, temperature regulation, vasomotor integration, and a variety of skeletal-motor activities involved in head, neck, and limb-trunk movements. In addition to such stimulus-response mechanisms, there are also perceptual functions for monitoring, as well as processing, information from the environment. Sensory modalities functioning at, near, and often before birth serve for the reception and transmission of various environmental inputs. Without these perceptual functions, there could be no such thing as environmental control of behavior.
Some developmental psychologists also include two other categories as potentially relevant for the consideration of infant behaviors. One of these is referred to as the primordium of self-awareness, or self-discrimination, in part deriving from postulated intrauterine experience and, in part, from postnatal environmental effects. However, with regard to the primordium of self-awareness, there is neither direct nor inferential evidence available. Finally, something akin to motivation for action, but not precisely identical with the state of deprivation or satiation of the organism, is proposed. Motivation for action popularly includes so called drives or instinctual urges involved with survival, correction of physiologic imbalance, and satisfaction of the organism's demands dictated by its metabolic activities. Debate continues concerning the existence of such drives or urges as also concerning the usefulness of such a conceptual framework. Such postulation is certainly not required for a strict scientific analysis of behavior. If we define instinct, drive, or urge in terms such as Koffka uses - as a response to intrinsic properties of the environmental milieu, its form dependent on the kind of sensorium possessed by the organism, its appearance being the result of maturational inborn patterns rather than of practice - then newborns clearly have such drives because they manifest behavior in response to environmental stimuli. Close scrutiny of this definition, however, leads to the conclusion that it is little more than a restatement of the obvious.
What are the different types of responses available in the intact newborn? First of all, a variety of reflex adaptations are important: 1. The rate and volume of pulsations at the anterior fontanel change in response to a variety of environmental stimuli. These changes can be elicited by fetal stimulation as early as three months before birth. 2. The rate and amplitude of respiratory movements are sensitive to the external environment and, therefore, should come under partial environmental control. 3. Hunger contractions identical to those in the adult have been identified at or shortly after birth. Interestingly enough, there seems to be an inverse relationship between such contractile activity and general bodily motility. 4. Sucking responses are readily elicited by stimulation at or before birth. 5. Muscle-stretch and mass-movement responses are present at or before birth and some of these are of significance for postural maintenance. 6. Stepping and placing reactions, which play an important role in later walking and running, are clearly identifiable in the human at birth.
The reflex-autonomic responses of the newborn organism and young infant should be of major interest to the student of human behavior. The importance of such responses in readying the stage for operant conditioning not only in the infant but also in the more mature organism cannot be overemphasized, as likewise the relevance of such responses to the organism's so called emotional or affective states. The amplitude of skeletal-motor reflex responses and possibly also the stability, durability, and resistance to extinction of operant-conditioned behavior may be intimately affected by such reflex-autonomic phenomena. Bridger and Reiser, for example, have studied heart rate and behavioral responses to tactile stimulation in 40 newborn infants. They noted that as the baseline, prestimulus heart rate of the resting infant increases, the magnitude of change in heart rate following stimulation decreases. At a certain prestimulus level, actual reversal in direction of change occurs. Therefore, if the newborn infant's resting heart rate is sufficiently low, there will be a proportionate rise with stimulation. On the other hand, if the pre-stimulus rate of this same infant is comparatively high, there may actually be a decrease in heart rate following equal stimulation. If one considers only a change in the variable as the indicator of reflex response, then there is no problem in accepting both of these responses as clear-cut and simple reactions to environmental stimulation. However, the fact that there is a change not only in the rate but also in the direction dependent on prestimulus level indicates that two different mechanisms may be involved or that a central and relatively general feedback modulator of such response patterns is involved. Bridger and Reiser found that babies differ with respect to the crossover point at which the stimulus applied produces a changed sign in heart rate response, that is, change from increase to decrease. Certain aspects of this heart rate response are specific to each individual, thus can safely be called idiosyncratic. Among the most individuating of these is the stated crossover level. This level appears to be quite stable from day to day for each individual and during the limited developmental period encompassed by this study.
There are significant individual differences among newborn infants in sucking behavior, sleeping patterns, and crying; in range as well as individual manifestations of sensitivity to environmental stimulation; and in general body motility. Differences also are observed in the range and amplitude of skeletal-reflex responses. Some clinical observers of newborn behavior have suggested that there are two general classes of reactors: those who tend to "act out" and those whose responses are more characteristic of the withdrawing, isolated introvert. In this particular regard, studies of tactile reflex responsivity in newborn infants following stimulation of various erogenous zones (oral, anal, and genital) are of interest. Lustman has recorded the responses of a representative population of newborn infants to light touch. His studies were carried on in a thermoregulated, constant humidity environment (Fig. 6). He reports that responses to manual stimulation of the lips, where the response measured is a change in peripheral skin temperature, vary through a continuous and generally normal distribution. Certain of these infants would be classified as underreactive, certain others as nonreactive, and still others as overreactive. The overreactor shows an elevation of skin temperature, while the underreactor demonstrates a fall in response to the same stimulation. Such individual differences in reflex-autonomic responses to lip stimulation emphasize the importance of intraorganismic factors as they affect such important operant activity as sucking. Lustman himself proposes that such variations may contribute to significant constitutional differences in nursing behavior.
Fig. 6. Magnitude of skin temperature change relative to prestimulus baseline value in response to stimulation of the lips in a group of newborn infants. (From Lustman, S. L., Psychoanalyt. Study of the Child, 11:95, 1956.) Now let us consider perceptual mechanisms available to and operative in the newborn and young infant. 1. The newborn reacts to light in a nonselective way with regard to wave length or the structure of the visual stimulus. There is unsustained and inconsistent pursuit of visual stimuli during the neonatal period. Moreover, it would appear that there is little, if any, sustained classical conditioning to visual stimulation possible during the neonatal period (For a comprehensive and contemporary review of classical conditioning in humans, see Hilgard and Marquis, p. 49). Intense and abrupt stimulation of the infant by light is followed by lid closure, circulatory and respiratory reflex responses, postural changes, and other elements of the startle and clasping response. 2. Intense auditory stimulation of brief duration produces responses analogous to those for visual stimulation. With sustained auditory stimulation, decreased general activity proportional to the intensity of stimulation results. Responses generally do not suggest a qualitative discrimination of frequencies by the neonate. 3. Response to noxious odors is prompt, but such responses are probably not olfactory as such. Facial movements are induced irregularly by nonirritating stimuli accompanied either by avoidance responses or sucking-licking activities. 4. Taste is an excellent modality for studying stimulus-response mechanisms in the newborn, since well-developed sucking reflexes are the behavioral activity affected. There are quantitative as well as qualitative discriminations of taste modalities. Sweetness elicits and maintains sucking; salt inhibits or arrests sucking. Various responses occur to sour or bitter taste, and with these, there are accompanying respiratory and circulatory changes. 5. The newborn infant adapts sluggishly to environmental temperature changes. In the premature infant, a temperature-controlled environment may be essential for survival. Within usual physiologic extremes of temperature, such changes elicit few, if any, reflex responses in the respiratory or circulatory functions. However, greater extremes in temperature do induce such reflex changes, and such extremes also may inhibit sucking. Avoidance responses with inhibition of sucking generally follow cold stimuli, while nuzzling and approach behavior occur in response to warm stimuli. 6. Both touch and pressure stimuli elicit local as well as whole body responses, with the nature and irradiation of the response dependent on the locus of stimulation. 7. Responses to painful stimuli, oddly enough, are meager at birth, although there is a general increase in the magnitude of these during the first seven to ten days. The foot and leg areas are most sensitive to pain, the head area least sensitive. It is interesting to note that, in the adult, the feet remain extremely sensitive to tickle and that tickle is considered a variety of pain sensation by most neurophysiologists.
Richmond, Lustman, and their associates have published an analysis of neonatal responses to auditory stimuli. These investigators studied 46 newborn infants varying from one-half hour to eight days in age. Seven of the group were premature infants from one to 15 days old. The response measured was the palpebral blinking or startle response to a bell sounded at one meter distance. Responses were recorded under four different conditions: light sleep, deep sleep, the fully awake state, and active nursing. It should be mentioned that all 46 infants studied gave positive motor responses to the bell sound, that is, palpebral and/or startle reflexes. The condition of testing, however, influenced the response. Under the condition of active nursing only 17 per cent of the infants responded. In the context of classic psychoanalytic theory, these workers consider active nursing or sucking at the breast as a maximally pleasurable or optimally reinforcing condition, with the opposite extreme, for example, the pain of colic, as the extreme of unpleasantness, discomfort, or aversion. These workers propose that the neonatal organism manifests a differential response to such external stimuli, with maximal response to auditory, tactile, or electrical stimulation under neutral conditions and with virtual disappearance of such responses under conditions of extreme pleasure or distress.
Such data suggest that in the newborn and possibly in the more mature organism not only the physiologic condition of deprivation or of satiation but also the position on the pleasure-pain axis modulate environmental control over operant activity. Factors of this sort may be of major importance in explaining substantial individual variations in operant-conditioned behavior which are not satisfactorily explained on the basis of reinforcement or aversive history alone or in terms of the more complex and largely unspecified aspects of the phylogenetic endowment of the particular organism. Dr. Ferster has proposed, as an alternative explanation of such differential effects, the prepotent influence of certain reinforcers under different conditions, with the immediately prior reinforcement history or schedule being an important determining factor.
There are, in addition, certain species-specific responses of humans, which include clinging contact, crying, and smiling, that have social significance but have not been systematically studied. According to Bowlby and Harlow, such responses are manifested independently of primary drive reduction (satiation) in human as well as subhuman infants. With regard to dependency and security responses in the infant organism, Harlow's studies of affectional behavior in the infant primate (macaque rhesus) emphasize the importance of clinging body contact in the development of behaviors thought to demonstrate an affectional involvement with an artificial mother. Harlow found that nursing or feeding through the artificial mother played either no role or at best a subordinate one in the development of what he calls affectional ties to the substitute, although clinging behavior did develop, probably on the basis of contactual reinforcements. As criteria of affectional involvement, he used contact time, responsiveness to fear-inducing stimuli, responsiveness to oddity or strangeness in the environment, and behavior indicating "motivation to seek and see." He concluded that feeding or nursing very possibly facilitated the early appearance and increased early strength of such affectional behaviors but had no sustained effect on the durability of such responses in later development.
Are certain of the individual differences already described results of genetic determination, or are they, in part, reflections of a varying prenatal environmental history? Is the traumatic experience of birth, stressed by Otto Rank, an important factor? Do the passage from the fluid filled amniotic sac of the uterus to the outer world through the birth canal and the individual vicissitudes of that journey have detectable effects on later behavior? Wile and Davis in 1941 studied the resultant infants of 380 normal births and 100 difficult instrumental births several years after birth. In general, they report that the incidence of so called deviant-reaction patterns, for example, rages, tantrums, excessive fears, tendencies to isolation, tics, nailbiting, food idiosyncrasies, and sustained dependency relationships, was significantly lower throughout in the difficult-birth children as contrasted to the normally-born issues. The only exception to this trend was for general hyperactivity which occurred in a greater percentage of those delivered under difficulty. One critic has suggested that the lower incidence of such behavioral phenomena may be correlated with the fact that children born with difficulty are more frequently solitary children within the family. Evidence available does not support this suggestion since the incidence of developmental disturbances in other studies would appear to be higher among only children than among children within a multiple sibling constellation. Though the observations of Wile and Davis appear paradoxical, they may in fact not be so since many of the deviant patterns selected, for example, extreme pugnacity, rich fantasy life, unhappiness with excessive fears, and nailbiting, are considered by many students of normal development to be questionable indicators of deviation.
What about the effects of premature birth? Shirley, in 1939, studied a sample of 200 children. In those born prematurely, he identified a syndrome or constellation characterized by somewhat greater general emotionality, poorer motor coordination, and greater sensitivity to color, sounds, and textures in comparison with behaviors of children born at full term. Knobloch, Pasamanick, and associates reported a more extensive study in 1956 in which approximately 62 per cent of premature infants showed no departure from normal developmental response patterns at 40 weeks of adjusted age. Defects ranging from minor neurologic deficits to severe intellectual deficit were recorded in the remaining 38 per cent. They contrasted these values with approximately 78 per cent of normal range activities for full term normal controls. These observations have been extended but await independent confirmation.
It is important for the clinical student to remember that the well-established laws and principles of behavioral control (see Part III) must operate in the context of the individual organism.
Reflex responses to given environmental events may run a very wide gamut, though patterned in an idiosyncratic and consistent way. Internal states of the organism may have a notable effect not only on the specific configuration of the operant behavior which appears in the presence of shaping environmental contingencies but also on the durability and resistance to extinction of such behavior.
It is relevant here to recall several classic animal experiments involving sucking behaviors in puppies and feeding activities in rats. Those animals which were exposed early in life to inconsistent or frustrating sucking or feeding experiences, readily identified in operant-conditioning terms as both variable-interval and variable-ratio schedules of reinforcement, showed persistent, pervasive, and sustained sucking activities or hoarding behaviors in later life with relatively little specific stimulus control of such behavior. Dr. Ferster states, for example, that continuously reinforced activities are relatively sensitive to the reinforced contingencies but that such behaviors disappear quickly following termination of reinforcement (see Chapter 12). On the other hand, where the schedule of reinforcement is on an interval or ratio basis, substantially larger amounts of behavior may be maintained over longer periods of time with greater resistance to extinction and with a considerably reduced sum of total reinforcement experiences than is possible under conditions of continuous reinforcement. It is, therefore, obvious that the circumstances favorable to the initial shaping of such activities are quite different from those involved in the ultimate maintenance of already shaped behaviors. It is in this precise behavioral area that we should perhaps seek for more comprehensive explanations of the many persistent "neurotic automatisms" of the organism. Dr. Lawrence Kubie has many times emphasized the central importance of such automatisms in disturbed living. It may well be that the so called rigid inflexibilities of some persons noted during the earliest phases of childhood development, for example, the explosive resistance to changed plans in certain otherwise normal children, are most economically explained in terms of the interaction of the reinforcement schedule with highly individual response sensitivities to environmental stimulation.
6 Further Considerations of Infancy and Early Childhood: The Nurturant Environment and the
- Development Of Behavioral Controls
- Reticular Activating System - Neural Bases Of Behavior
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