PSYC 780 Discussion Prenatal Development and Infancy Essay

PSYC 780 Discussion Prenatal Development and Infancy

PSYC 780 Discussion Prenatal Development and Infancy

Posting comments about the week’s material, including any comments you might have made if we were all in class together. I attached the reading material.

Birth, of course, does not mark the beginning of human development; rather, development begins at conception. Although much of prenatal development occurs within the physical domain, developments in the cognitive and psychosocial domains also emerge at this time. Moreover, although these developments are driven by genetic and maturational forces, experiential factors also play an influential role during this period. Within this article, we address some major areas of prenatal development: sensory experience, neurobehavioral functioning, and teratogenic risks. Postnatally, the period of life known as infancy traditionally consists of the first two years following birth, and it is during this period that often dramatic and rapid developments take place in all domains. Some of the most important of these phenomena, including brain development, visual and auditory perception, cognitive development, temperament, and attachment, are reviewed in the remainder of this article. While discussion of the selected topics provides a glimpse into the array of developments occurring during gestation and infancy, they are necessarily limited in their overview of the vast number of changes and issues that have been studied during these earliest phases of life. The reader is thus strongly encouraged to review additional sources for a discussion of subjects such as fetal programming, prematurity, language, and social cognition that are also germane to prenatal and/or infant development.

Prenatal Development
Sensory Development
Even though sensory development begins long before birth, it is inherently difficult to observe the responses expressed by the fetus. Early fetal chemosensory experience has been examined largely in animals, whereas most studies with human fetuses have investigated auditory responsiveness in the second half of gestation. Our primary sources for knowledge about sensory development in human fetuses derive from studies of prematurely born infants and research using sophisticated noninvasive techniques. For example, magnetic fields generated by active neurons in fetal brain tissue can be detected and used to examine a fetus’s response to auditory stimulation (Huotilainen, Kujala, & Hotakainen, 2005; Zappasodi, Tecchio, & Pizzella, 2001). Generally speaking, the senses become functional sequentially between 8 and 26 weeks, with touch developing first, then taste and smell, hearing, and finally vision.

Touch
Sensitivity to touch or pressure begins early in gestation and develops in a cephalocaudal direction (Field, 1990). By about 8 weeks of gestation, the fetus responds to touch on the area around the lips by moving. By 12 weeks, the fetus responds with a grasping movement when fingers are touched. During early gestation, the fetus typically responds by moving away from the source of stimulation. Later in gestation, the fetus tends to move toward the stimulation. For example, touch stimulation on the cheek of a fetus can elicit rooting-like responses, which later help the infant locate the source for nursing. Overall, the sensory abilities to detect touch, along with body motion, appear to be the most developed at birth (Field, 1990).

PSYC 780 Discussion Prenatal Development and InfancyTaste and Smell
Scientists conclude that fetuses have gustatory and olfactory detection. However, with the exception of the taste for sweet, there has been no direct evidence for fetal chemosensory preferences. Flavors and odors from the mother’s diet do pass into the fetus’s amniotic fluid and bloodstream. Thus, the sensation of taste and smell can occur through the fetus’s nose, mouth, and bloodstream. When the fetus engages in breathing movements (beginning at about 10 weeks of gestation), amniotic fluid not only is swallowed but also passes through the nose after the plugs blocking the nostrils dissolve (James, Pillai, & Smoleniec, 1995; Schaal, Orgeur, & Rognon, 1995). Additionally, through blood circulation to the nose and mouth, the fetus has the opportunity to experience different smells and tastes (Schaal, 2005). Following birth, neonatal detection of a variety of odors and flavors is evident, with preferences emerging quickly (e.g., mother’s scent).

Hearing
The fetus’s auditory system develops gradually starting at around 6 weeks of gestation, and by 28 weeks it is sufficiently well developed to enable the fetus to reliably respond to sounds, typically with startle responses and increased heart rate (Lecanuet, Granier-Deferre, & Busnel, 1995). Within the uterine environment, the fetus is regularly exposed to its mother’s voice, gastrointestinal sounds, and heartbeat. During the last trimester, a fetus also appears to hear external sounds that pass through the uterine walls (Fernald, 2004).

Vision
At about 8 weeks of gestation, the lens, eyelids, and muscles controlling eye movement begin to develop. By 15 weeks, the integration of the optic nerve in each eye is complete. By 28 weeks, the development of the visual cortex in the brain resembles that in the adult. Although the fetus can open and blink its eyes for some time, it receives relatively little visual input before birth because of in utero darkness. However, if the fetus is born prematurely at this time, it can already detect changes in brightness (i.e., light and dark; Slater, 2004). Because the neural structure of the eyes and pathways to the brain are still immature, vision appears to be the least sophisticated of the senses and continues to develop substantially after birth.

Neurobehavioral Development and Functioning
The identification of fetal activity patterns and their underlying neural mechanisms is critical not only for understanding the beginnings of human behavior, but also for monitoring the fetus’s healthy development in the functioning of peripheral and central nervous systems. Most knowledge about neurobehavioral development in the fetus has been generated by real-time ultrasound and Dopplerbased electronic fetal monitors (DiPietro, 2005). Four aspects of fetal functioning are typically involved in a multidimensional neurobehavioral assessment: motor activity, heart rate, behavioral state (e.g., from active to inactive), and responsivity to stimulation (DiPietro, 2005).

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Motor Activity
Movements first appear between 7 and 16 weeks of gestation. The development of fetal movements shows an increase in repertoire. Movements include both large generalized movements (e.g., startle, stretch, rotation, and breathing) and movements of specific body parts (e.g., head, eyes, fingers, jaw opening, yawn, and hand-face contact). Initially, movements tend to appear scattered in a random fashion, but gradually the occurrences of movements are more coordinated and clustered together into bursts, and finally into longer periods of fluctuating activity (Robinson & Kleven, 2005). Although there are individual differences in the quantity of movements among fetuses, they occur less frequently but with more vigor during the second half of gestation (DiPietro, Hodgson, & Costigan, 1996). Increasingly longer periods of inactivity are common as fetuses mature. Thus, motor inhibition is believed to also be a significant marker for neurological development.

Fetal Heart Rate
The heart rate in healthy fetuses is almost twice that of adults, fluctuating between 120 and 160 beats per minute. Cycles of increased and decreased variability in baseline heart rate can be observed throughout the day. Whereas spontaneous accelerations indicate responsiveness in the sympathetic nervous system, general trends in the rate and variability of fetal cardiac activity reflect the maturation of the nervous system. Overall, heart rate shows a pattern of decrease in rate and increase in variability during the prenatal period. However, decelerations after 28 weeks tend to be markers of pathology. Contrary to some common beliefs, fetuses’ heart rates are not in synchrony with their mothers’ heart rates. In a quiet and resting condition, a mother’s heart rate does not influence fetal heart rate, or vice versa (DiPietro et al., 2006). Furthermore, the presence of heart rate acceleration coupled with fetal movements is viewed as a sign of fetal well-being. Increases in the coordinated coupling between the two different systems indicate the integration of the central nervous system.

PSYC 780 Discussion Prenatal Development and InfancyBehavioral States
Behavioral states are relatively stable periods characterized by coordinated patterns in the fetus’s eye and motor movements as well as heart rate activity. Beginning at about 28 weeks, the fetus begins to show rest-activity cycles. Four fully developed behavioral states can be detected at around 36 weeks: quiet sleep, active sleep, quiet awake, and active awake (de Vries & Hopkins, 2005). The quiet sleep state features the absence of eye movements and a stable heart rate within a narrow range. The active sleep state is characterized by eye movements, a wider range of heart rate oscillation, and periodic stretches and gross body movements. The state of quiet awake is characterized by the absence of gross body movements, a stable heart rate with a wide range of oscillation, and the absence of heart rate acceleration. The active awake state features the presence of eye movements and continuous, vigorous activities with unstable and large accelerations in heart rate. Compared to neonates, fetuses take a longer time to complete a state change and make fewer transitions between quiet and active sleep states. Because behavioral states are believed to reflect neural functioning, and therefore fetal health, observations of fetal states can be used to discriminate abnormalities in pregnancy and growth retardation.

Responsivity
Fetuses respond to stimulation originating outside of the uterus. Compared to airborne sound stimuli, fetuses respond to vibro-acoustic stimuli (comparable to an electric toothbrush) with greater heart rate accelerations and more body movements. In response to repeated presentation of stimuli, a pattern of decreased response (i.e., habituation) reflects healthy fetuses’ capacity for self-regulation and information processing.

Conclusion
Fetal neurobehavioral development is predictable. Overall, it goes through a transition of rapid changes with decreased heart rate, increased heart rate variability, and increased movement-heart rate coupling between 28 and 32 weeks of gestation, after which the development levels off and a stable pattern is established ( DiPietro, 2005). Because similar patterns of coupling and/or disassociation (e.g., between fetal movement and heart rate) are found among fetuses, it is assumed that these fundamental properties of neurobehavioral development prior to birth are universal (DiPietro et al., 2006). Future research will need to explore the underlying mechanisms and experiential factors that may facilitate or impede fetal development and functioning.

PSYC 780 Discussion Prenatal Development and Infancy Essay

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