Human fetal movement: spontaneous oscillations near one cycle per minute.

Spectral analysis of spontaneous fluctuations in human fetal movement revealed strong oscillations at frequencies between 0.24 and 0.90 cycle per minute, which are much higher than those of the cyclic alternation of quiet and active states in the fetus and neonate. Oscillations at frequencies up to 2.88 cycles per minute were also detected, but they were usually much weaker. The prominent peaks in the fetal movement spectra are in the frequency range of recently reported neonatal motor rhythms, and indicate the existence of a cyclic process controlling spontaneous motor output that oscillates near one cycle per minute and begins to function in utero.

Transcutaneous oxygen tension during nonnutritive sucking in preterm infants.

The effects of nonnutritive sucking on transcutaneous oxygen tension, heart rate, and respiratory rate were studied sequentially in 14 sleeping preterm infants breathing room air. Transcutaneous oxygen tension increased during nonnutritive sucking in infants between 32 and 35 weeks postconceptional age, but not in those between 36 and 39 weeks. This response was not associated with a change in respiratory rate or sleep state, although heart rate tended to increase. These data offer further support for the beneficial effects of nonnutritive sucking in preterm infants.

Increasing arterial carbon dioxide tension: influence on transcutaneous carbon dioxide tension measurements.

Despite widespread use of transcutaneous PCO2 (TcPCO2) monitoring, the precise relationship between TcPCO2 and PaCO2 remains unclear. It has been widely assumed that theoretical correction of TcPCO2 (combining temperature correction with a constant metabolic factor of 4 mm Hg) accounts for the elevation of TcPCO2 over PaCO2. To test this assumption, TcPCO2 was measured with a 44 degrees C electrode and compared to PaCO2 in 60 normotensive infants with cardiorespiratory disease during the first four +/- six days of life (mean +/- SD) (range one to 36 days). During hypocapnea, from PaCO2. In contrast, during normocapnea, theoretically corrected TcPCO2 exceeded PaCO2 by 5 +/- 4 mm Hg (P less than .001), and similarly during hypercapnea, theoretically corrected TcPCO2 exceeded PaCO2 by 9 +/- 6 mm Hg (P less than .001). These data suggest that, as PaCO2 increases, there may be an imbalance between tissue CO2 production and removal, resulting in a progressively increasing gradient between TcPCO2 and PaCO2. Clarification of the relationship between TcPCO2 and PaCO2 should enhance the interpretation of TcPCO2 measurements in infants.

An intrinsic source of behavioral regulation that influences discrete responses to cues important for the initiation of suckling.

The present experiment investigated the relationship between motor activity and oral grasping of an artificial nipple in newborn rats. Pups orally grasped the artificial nipple, and they performed more and longer oral grasps in the latter portion of the nipple presentation. Motor activity was cyclical, and this cyclicity was evident before and during presentation of the artificial nipple. The onset of an oral grasp response was preceded by a period of relatively low motor activity, and the termination of a grasp was followed by relatively high motor activity. The newborn rat pup's intrinsic oscillations in motor activity may regulate the expression of discrete responses to cues important for the initiation of suckling.

Structure and irregularity in the spontaneous behavior of young infants.

Persistent, irregular fluctuations in spontaneous motor activity are common in the young of many vertebrate species, but whether the irregularity is intrinsic to the dynamics of motor activation or the result of random perturbations is not known. Analysis of the second-by-second variation in the general body movement of awake human infants 1 and 3 months after birth revealed low dimensional structure in the characteristically irregular motor activity and exponential rates of divergence of initially similar states of motor activation. Results support the conclusion that irregularity is an intrinsic property of the dynamics of motor activation involving relatively few effective degrees of freedom and raise questions about the advantages or disadvantages of irregularity built into early behavioral organization.

Effects of warmth on newborn rats' motor activity and oral responsiveness to an artificial nipple.

Temperature is a powerful regulator of the behavior and physiology of newborn altricial animals. The effects of warmth on newborn rats' oral responsiveness to suckling stimuli and spontaneous motor activity in a thermoneutral environment were investigated. Newborn rat pups' oral grasp responses to an artificial nipple and overall motor activity were recorded for 18 min. Near-term pups were delivered by cesarean section so that their 1st experiences with suckling stimuli could be observed. Experimental pups were warmed for 15 s every 2 min; control pups were not warmed. Warmed pups grasped the nipple fewer times than the not-warmed pups. However, oral grasp durations became longer for the warmed pups but not for the not-warmed pups. Warmth increased pups' motor activity but only while the heat was applied. Warmth in a thermoneutral environment may promote longer nipple attachment during newborns' early feeding experiences.

Behavioral responses of the chronically instrumented sheep fetus to chemosensory stimuli presented in utero.

Fetal sheep were surgically prepared on Days 113-114 of gestation with an array of chronic instruments for recording electromyographic data (EMG) in oral--facial, axial, and limb muscles and heart rate (FHR). Fetuses also were fitted with an intraoral catheter for infusion of chemosensory fluids (isotonic saline, quinine, colostrum, sucrose) onto the surface of the tongue. Individual subjects received chemosensory infusions on Days 134-137. Fetuses showed consistent oral responses to quinine and milk, but did not respond to isotonic saline or sucrose. Different patterns of motor responses suggest that fetuses discriminated among different concentrations of quinine. The expression of tachycardia to quinine and bradycardia to milk also suggested differential responding to chemosensory fluids that differ in hedonic qualities. Detailed characterization of fetal responses to these stimuli in utero confirm the functionality of the gustatory system in the sheep fetus near term.

Variability in general activity and the expression of complex behavior in the fetal rat (Rattus norvegicus).

Rat fetuses exhibit intrinsic fluctuations in general motor activity and respond to an artificial nipple (AN) with mouthing and oral grasping behavior. The present study examined the relation between the organization of general activity and the expression of these specific responses to an AN on Embryonic Day 21. In Experiment 1, continuous exposure to the AN resulted in nonspecific behavioral activation characterized by an increase in amplitude and high-frequency variability. In Experiment 2, increased amplitude and variability in general activity preceding discrete presentations of the AN resulted in more mouthing and oral grasping responses to the AN. These results suggest that presentation of the AN triggers behavioral reorganization in which the level and variability of overall activity may facilitate expression of well-defined action patterns.

The development of nuchal atonia associated with active (REM) sleep in fetal sheep: presence of recurrent fractal organization.

The behavioral state of active or rapid eye movement sleep (REMS) is dominant during fetal life and may play an important role in brain development. One marker of this state in fetal sheep is neck nuchal muscle atonia (NA). We observed burst within burst NA patterns suggestive of recurrent fractal organization in continuous 13 day in utero recordings of NA during the third trimester. Consistent with fractal renewal processes, the cumulative mean and standard deviation (SD) diverged over this time and the tail of NA distributions fit a stable Lévy law with exponents that remained invariant over the periods of development examined. The Hurst exponent, a measure of self-affine fractals, indicated that long-range correlations among NA intervals were present throughout development. A conserved complex fractal structure is apparent in NA which may help elucidate ambiguities in defining fetal states as well as some unique properties of fetal REMS.

The neural control of cyclic motor activity in the fetal rat (Rattus norvegicus).

The spontaneous behavior of rat fetuses (in a saline bath with fetal-placental-uterine connections intact) was observed directly for 30 minutes on Day 20 of gestation. Rearleg and nonrearleg movements from fetuses with a mid-thoracic spinal cord transection or sham operation were analyzed for cyclic organization. Oscillations in rearleg activity occurred at the same frequency in fetuses with spinal cord transections (0.74 cycle/min) and sham-operated fetuses (0.72 cycle/min). However, oscillations in nonrearleg activity were much slower in the fetuses with spinal cord transections (0.30 vs. 0.77 cycle/min). Other characteristics of the cyclic patterns in motor activity were unaffected. The findings demonstrate 1) the caudal half of the spinal cord can generate cyclic output in the absence of descending input from the brain, 2) there is no single timing center, and 3) rostral sources are slower.

Development of sucking rhythm in preterm infants.

We studied the ontogeny and temporal organization of non-nutritive sucking during active sleep in 6 healthy preterm infants (mean birthweight 1.1 kg (range 0.8-1.3 kg) gestational age 28.6 weeks (range 26-30 w] from 30 to 35 weeks of post-menstrual (PM) age. Recognizable rhythmical sucking bursts were recorded at 28 weeks in one infant and by 31-33 weeks in the others. Results were analyzed for the periods 30-31, 32-33 and 34-35 PM weeks. The number of bursts/min increased with age, while the duration of each burst was stable (mean 4.1 s). The pause between bursts decreased. Sucking pace within bursts increased with age which resulted in an increase in the overall rate of sucking. The coefficient of variation (CV) for intersuck time within bursts and for interburst time was computed to examine the stability of the sucking rhythm. For intersuck time the CV was relatively low and constant across ages. However, for interburst time CV was relatively large across ages. Thus, there appears to be a stability of the intraburst sucking rhythm from 30 weeks of gestation, whereas the interburst rhythm is less regular. This documentation of temporal organization in sucking from 30 weeks is one of the earliest indications of an intrinsic rhythm in human behavior.

Human cyclic motility: fetal-newborn continuities and newborn state differences.

The spontaneous movement of 41 healthy human newborns was analyzed for cyclic patterns during different behavioral states and also compared to similar data obtained during their last few months of gestation. Spectral analysis was used to identify and quantify the motility cycles, except in quiet sleep, for which the instantaneous frequency of the isolated movements was analyzed. Cyclic motility (CM) was common in all states, and measures of its cyclic organization were similar in the non-sleep states in spite of very large differences in the total amount of movement. During active sleep, CM was weaker and less regular than during the non-sleep states, but similar to fetal CM during the last month of gestation. Thus cyclic variation in spontaneous motor activity, a basic feature of fetal behavior, is also a nearly constant feature of newborn spontaneous movement. Fetal CM persists relatively unchanged in the newborn during active sleep, and the cyclic organization of newborn movement is independent of the level of motor output.

Infants of diabetic mothers: late normalization of fetal cyclic motility persists after birth.

The prenatal development of cyclic motility (CM) in the human is disrupted by maternal diabetes, but appears normal by the end of gestation. To determine whether birth and adaptation to postnatal life reveal new or persisting abnormalities in CM, 24 newborn infants of insulin-dependent diabetic mothers (IDMs) and 24 normal newborns were studied for 2-4 hr in a controlled environment. Spectral analysis of spontaneous movement revealed that CM was common in both groups. Measures of its cyclic organization in each state did not differ between IDMs and controls. State differences were the same in the two groups, and replicated the pattern found in a previous study of normal newborns. For IDMs, there were no differences associated with neonatal evidence of increased glucose supply in utero (macrosomia, postnatal hypoglycemia), or with determinations of prenatal maternal hyperglycemia. IDMs had also been studied as fetuses, and the pattern of continuity and change in CM across birth replicated the pattern previously reported for normal fetuses. The results suggest that the development and control of CM is buffered from the prenatal metabolic insults suffered by IDMs, and support speculations that cyclic activation is a general and robust property of the developing motor system in the human.

Oscillation and complexity in early infant behavior.

Cyclic fluctuation is a ubiquitous property of spontaneous motor activity in the human fetus and neonate. Oscillation occurs on the scale of minutes, and irregularity is one of its most characteristic properties. To determine whether cyclic motor activity (CM) persists beyond the neonatal period (1 month after birth), and beyond what has been called the period of the fetus ex utero (2-3 months after birth), 30 infants were studied at monthly intervals from 1 to 4 months after birth during active sleep and awake. Spectral analysis was used to quantify the rate, strength, and irregularity of CM. To examine the characteristic irregularity of awake CM more closely, a nonlinear forecasting technique, developed to study chaotic dynamic in other fields, was used to estimate the predictability of spontaneous movement in a state space reconstructed from the time series. The rate and irregularity of CM during active sleep and awake, and its strength during active sleep, did not change across the first 4 postnatal months. However, there was a pronounced drop in the strength of awake CM from 2 months onward and a concurrent increase in the broad-band power of fluctuations faster than 2 cycles/min. The predictability of awake CM also dropped abruptly between 1 and 2 months, especially for prediction intervals less than 20 sec. The changes at 2 months reflect the introduction of a source of variation with a shorter time constant than fetal-neonatal CM, and which is specific to awake periods. The source of these effects may be moment-to-moment interactions between CM and attention.

Intrinsic temporal patterning in the spontaneous movement of awake neonates.

The temporal organization of spontaneous movement in healthy, awake neonates was studied on the second or third day after birth. Movement was recorded using time lapse photography and quantified as a function of time. Fourier analysis was then used to partition the total variance of each neonate's time-based data into independent components in the frequency domain. Tests on the resulting cumulative variance distributions indicated that the fluctuations in movement over time were not random. Smoothed spectral density functions were then computed to isolate the dominant rhythms. Spectral peaks occurred in the region between .24 and 1.86 cycles per min, indicating the presence of rhythms in general motility with an average frequency (across babies) of .69 cycles per min. These findings are evidence of intrinsic temporal organization at frequencies very different from previously documented rhythms in newborn behavior and physiology.

Cyclic motor activity in the human fetus after midgestation.

The spontaneous movements of human fetuses were studied longitudinally between 21 and 41 weeks of gestation. At each age, spectral analysis of the fluctuations in fetal movement revealed strong cyclic patterns. The frequency of the dominant motor rhythms ranged from .13 to 1.91 cycles per minute. The strength of oscillations between .18 and 1.02 cycles per minute increased slightly with gestation, but the frequency of the dominant motility cycle, the width of the corresponding spectral peak, and the incidence of weaker (usually faster) rhythms did not change. Neuromuscular activity is known to serve important developmental functions in the embryo and fetus. The ubiquity and relative consistency of cyclic motility in the last half of human gestation, and the existence of similar periodicity in other species, suggest that the cyclic activation of developing motor circuits may possess particular adaptive value.

The development of cyclic motility in fetuses of diabetic mothers.

The cyclic organization of spontaneous movement was studied longitudinally in 22 fetuses of diabetic mothers (FDMs) during the third trimester of gestation and quantified with spectral analysis. Cyclic motility at frequencies between .08 and 1.22 cycles/min was found in all fetuses, although it was temporarily absent in 12 of the 22 fetuses at some time between 25 and 38 weeks. While some parameters of cyclic motility changed little, the frequency of the dominant motility cycle doubled from .24 to .48 cycle/min between 28 and 36 weeks, and the relative strength of motility cycles in the band between .18 and 1.02 cycles/min decreased temporarily at 36 weeks. These developmental changes and the common absence of cyclic motility contrast sharply with previous findings in normal fetuses, and (except for its absence) are accounted for by a subgroup of FDMs whose mothers' blood glucose levels were least well controlled during the third trimester of gestation. The presence of cyclic motility in all FDMs provides further evidence that cyclic activation is a basic property of the developing central nervous system in the human, as it appears to be in other vertebrates. However, the differences between FDMs and normal fetuses suggest that the development of cyclic motility is sensitive to disturbances in the fetal metabolic environment.

Event perception by children in the early stages of language production.

The distribution of attention to the actors in a visual event and the influence of linguistic variables on attention were studied. 1-word and 2-word children viewed a filmed event that portrayed a brief agent-action-recipient sequence in the presence of a nonparticipant. The event was accompanied by linguistic input that was general or named an actor. A habituation paradigm was used with a cardiac response measure. Response recovery to brief occlusions of the actors in the test trials indicated the existence of a neutral period before the action began during which attention was evenly distributed across the actors. During and after the action, the agent commanded a priority in the distribution of attention. Naming an actor had a strong directing influence on attention in the neutral period and more limited effects on attention during and after the action. There were no effects of sex or language status.