PubMed · 4697594
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R Engeseth, T O Endsjo. 1973-03-20. [Infant control in practice].. https://pubmed.ncbi.nlm.nih.gov/4697594/
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OBJECTIVE: To evaluate whether sleeping in the supine position resulted in changes in gross or fine motor developmental milestones observed at routinely scheduled well-child checkups at 4 or 6 months of age. DESIGN: A retrospective chart review. SETTING: One private pediatric practice involving 2 full-time and 2 part-time board-eligible or board-certified pediatricians. SUBJECTS: The study included 343 full-term infants whose weights were appropriate or large for gestational age, had no history of hospitalization other than for normal newborn care, and were examined in the office for their 4-month well-child checkup within 2 weeks of being 4 months old. METHODS: The Denver Developmental Screening Test-Revised was administrated at the 4- and 6-month well-child checkups. The primary sleep positions of the infants were determined by telephone survey, office interview, or letter after the 6-month checkup was completed. Background data collected from the mother for each mother-infant pair included maternal age at the time of birth, parity, and marital status, Medicaid status and ethnicity of the infant, and whether the infant was breast-fed. RESULTS: Infants who slept in the side or supine position were less likely to roll over at the 4-month checkup than infants who slept primarily in the prone position (P < .001). No significant differences were found when comparison by maternal age, parity, or marital status, Medicaid status or ethnicity of the infant, or the use of breast-feeding were considered. Other motor milestones screened did not show statistically significant changes. CONCLUSIONS: Sleep position significantly influences the age of achieving the gross motor developmental milestone of rolling over; infants who sleep in the side or supine position roll over later than infants who sleep in the prone position.
There has been recent interest in the idea that principles governing learning in connectionist networks can form the basis for an alternative understanding of developmental processes (Elman, Bates, Karmiloff-Smith, Johnson, Parisi, & Plunkett, 1996). The present paper can be viewed as a case example of the usefulness (and limitations) of connectionist modeling for the study of infant cognition. Specifically, the paper reports on a series of connectionist models designed to analyze the factors responsible for the emergence of global-level and basic-level category representations in young infants. The models (1) simulated the formation of global-level and basic-level representations, (2) revealed a global-to-basic order of category emergence, (3) uncovered the formation of two distinct global-level representations-an initial "self-organizing" perceptual global level and a subsequently "trained" arbitrary (i.e., nonperceptual) global level, and (4) displayed a gradual transition from perceptual global-level to perceptual basic-level representation with increasing exposure to training stimuli. Hypotheses for empirical investigations of category development in infants that follow from the modeling efforts are discussed.
Nine young infants were followed longitudinally from 4 to 15 months of age. They performed multi-joint reaching movements to a stationary target presented at shoulder height. Time-position data of the hand, shoulder, and elbow were collected using an optoelectronic measurement system. In addition, we recorded electromyographic activity (EMG) from arm extensors and flexors. This paper documents how control problems of proximal torque generation may account for the segmented hand paths seen during early reaching. Our analysis revealed the following results: first, muscular impulse (integral of torque) increased significantly between the ages of 20 (reaching onset) and 64 weeks. That is, as infants got older they produced higher levels of mean muscular flexor torque during reaching. Data were normalized by body weight and movement time, so differences are not explained by anthropometric changes or systematic variations in movement time. Second, while adults produced solely flexor muscle torque to accomplish the task, infants generated flexor and extensor muscle torque at shoulder and elbow throughout a reach. At reaching onset more than half of the trials revealed this latter kinetic profile. Its frequency declined systematically as infants got older. Third, we examined the pattern of muscle coordination in those trials that exhibited elbow extensor muscle torque. We found that during elbow extension coactivation of flexor and extensor muscles was the predominant pattern in 67% of the trials. This pattern was notably absent in comparable adult reaching movements. Fourth, fluctuations in force generation, as measured by the rate of change of total torque (NET) and muscular torque (MUS), were more frequent in early reaching (20-28 weeks) than in the older cohort (52-64 weeks), indicating that muscular torque production became increasingly smoother and task-efficient. Our data demonstrate that young infants have problems in generating smooth profiles of proximal joint torques. One possible reason for this imprecision in infant force control is their inexperience in predicting the magnitude and direction of external forces. That infants learned to consider external forces is documented by their increasing reliance on these forces when performing voluntary elbow extensions. The patterns of muscle coordination underlying active elbow extensions were basically the same as during the prereaching phase, indicating that the formation of functional synergies is based on a basal repertoire of innervation patterns already observable in very early, spontaneous movements.