The development of reaching behavior in low-risk preterm infants

This longitudinal study investigated the development of reaching behavior in the seated position in preterm infants at the ages of 5–7 months by analyzing kinematic variables (straightness and adjustment indexes, movement unit, mean and final velocities). The correlation between kinematic variables and grasping was verified. The participants were nine low-risk preterm infants with no cerebral lesions. Ten fullterm infants served as control. In both groups, kinematic variables remained unchanged over age, except for the adjustment index, which was higher at 6 months in the preterm group. Successful grasping increased in both groups over age and it was shown to be negatively correlated with mean velocity in the preterm infants. At the ages of 6 and 7 months, preterms showed lower mean and final velocities and higher adjustment index when compared with fullterms. The relative constancy in the kinematic variables suggests that, after having explored the action possibilities during the acquisition phase, the infants selected an adaptative pattern to perform the reaching movements. Slower movements and greater adjustments may be functional strategies of preterms to achieve successful grasps.     

Proximal and distal adjustments of reaching behavior in preterm infants

The authors aimed to investigate proximal and distal adjustments of reaching behavior and grasping in 5-, 6-, and 7-month-old preterm infants. Nine low-risk preterm and 10 full-term infants participated. Both groups showed the predominance of unimanual reaching, an age-related increase in the frequency of vertical-oriented and open hand movement, and also an increase in successful grasping from 6 to 7 months. The frequency of open hand was higher in the preterm group at 6 months. Intrinsic restrictions imposed by prematurity did not seem to have impaired reaching performance of preterm infants throughout the months of age.     

Effects of physiologic jaundice on behavioral function in low-risk preterm infants

This study is aimed at assessing untoward effects of physiologic jaundice on apparently well babies 1 month after jaundice was cleared. Two measures of neonatal physiologic jaundice were correlated with 15 behavioral measures, taken from 37 low-risk Black preterm infants tested at expected date of birth. The behavioral measures evaluated visual function, motor function, affect, and central nervous system integrity. Higher bilirubin values were associated with poorer visual function, quicker cessation of distress in response to social intervention, and longer periods of active sleep. The pattern of the results was similar when the effects of health risks other than jaundice were statistically controlled. The results support the hypothesis that even physiologic jaundice is associated with individual differences in the behavioral outcome of preterm infants.     

Potential underlying mechanisms for greater weight gain in massaged preterm infants

In this paper, potential underlying mechanisms for massage therapy effects on preterm infant weight gain are reviewed. Path analyses are presented suggesting that: (1) increased vagal activity was associated with (2) increased gastric motility, which, in turn, was related to (3) greater weight gain; and (4) increased IGF-1 was related to greater weight gain. The change in vagal activity during the massage explained 49% of the variance in the change in gastric activity. And, the change in vagal activity during the massage explained 62% of the variance in the change in insulin. That the change in gastric activity was not related to the change in insulin suggests two parallel pathways via which massage therapy leads to increased weight gain: (1) insulin release via the celiac branch of the vagus; and (2) increased gastric activity via the gastric branch of the vagus.     

Affective behavior and weight changes among hospitalized failure-to-thrive infants

The affective behavior and weight change of 12 nonorganic failure-to-thrive, 12 organic failure-to-thrive, and 12 control infants (M age = 8 months) were compared across their hospitalization. Infant affect was evaluated at approximately the beginning, middle, and endpoints of hospitalization using the Behavioral Assessment Scale. Among the failure-to-thrive infants, positive responses to stimulation at the initial assessment were related to weight loss across the course of hospitalization, while positive responses to the same stimulation at the middle assessment were related to weight gain. These unexpected results coupled with the finding that 70% of the failure-to-thrive infants gained weight and 30% lost weight across hospitalization led to a comparison between infants who gained and infants who lost weight. An increase in positive affect across hospitalization occurred only for the infants who gained weight. Paradoxically, the losers may have experienced hospital stimulation as less adequate than maternal stimulation, while the gainers may have experienced hospital stimulation as more adequate than home stimulation.     

Global influences on the development of spatial and object perceptual categorization abilities: Evidence from preterm infants

Influences on the development of perceptual categorization were examined by comparing the performance of three groups of infants on spatial and object categorization tasks. The groups consisted of 1) fullterm infants tested at 3 to 4 months of age, 2) healthy preterm infants tested 3 to 4 months from birth (postnatals), and 3) healthy preterm infants tested 3 to 4 months from their due date (postterms). Four experiments showed that fullterms and postterms outperformed postnatals on a spatial categorization task (i.e., ‘above’ vs. ‘below’, and that fullterms outperformed both postnatals and postterms on object categorization tasks (i.e., dogs vs. cats, and cats vs. birds). These results suggest that maturation may be the predominant influence on the early development of the ability to form categorical representations of spatial information, while preterm birth may exert a limiting influence on the development of object categorization abilities.     

Moderate versus light pressure massage therapy leads to greater weight gain in preterm infants

Sixty-eight preterm infants (M GA = 30 weeks) were randomly assigned to a moderate or to a light pressure massage therapy group to receive 15 massages three times per day for 5 days. Behavior state, stress behaviors and heart rate were recorded for 15 min before and during the first 15-min therapy session. Weight gain was recorded over the 5-day therapy period. The moderate versus light pressure massage group gained significantly more weight per day. During the behavior observations the moderate versus light pressure massage group showed significantly lower increases from the pre-session to the session recording on: (1) active sleep; (2) fussing; (3) crying; (4) movement; and (5) stress behavior (hiccupping). They also showed a smaller decrease in deep sleep, a greater decrease in heart rate and a greater increase in vagal tone. Thus, the moderate pressure massage therapy group appeared to be more relaxed and less aroused than the light pressure massage group which may have contributed to the greater weight gain of the moderate pressure massage therapy group.     

A study of reaching actions in walking infants

Acquiring motor skills transforms the perceptual and cognitive world of infants and expands their exploratory engagement with objects. This study investigated how reaching is integrated with walking among infant walkers (n = 23, 14.5–15.5 months). In a walk-to-reach paradigm, diverse object retrieval strategies were observed. All infants were willing to use their upper and lower bodies in concert, and the timing of this coordination reflected features of their environment. Infants with an older walking age (months since walking onset) retrieved items more rapidly and exploited their non-reaching hand more effectively during object retrieval than did same-age infants with a younger walking age. This suggests that the actions of the upper- and lower-body are flexibly integrated and that this integration may change across development. Mechanisms that shape sophisticated upper-body use during upright object retrieval are discussed. Infants flexibly integrate emerging motor skills in the service of object retrieval in ways not previously documented.     

Individual differences in ERP measures of executive function in early childhood: Relation to low-risk preterm birth and parent-reported behavior

Although behavioral studies have demonstrated that executive function (EF) develops rapidly during early childhood, few studies have investigated neural systems supporting EF during the preschool years. These systems are sensitive to variations in children’s early life experiences, including preterm birth. The current study collected behavioral and event related potential (ERP) data during an EF task (directional Stroop) in a sample of 150 full-term and low-risk preterm children aged 4-years. Children’s IQ and processing speed (WPPSI-III), and parent report of EF (BRIEF-P), were also measured. Forty-nine children born full-term and 43 low-risk preterm children provided useable ERP data. Similar to prior studies with adults and older children, preschool-aged children showed modulation of ERP components (N2, P3) by cognitive conflict. Effects of trial type were also present for early attentional components (N1 and P2). Exploratory analyses demonstrated that ERP measures of EF were correlated with individual differences in cognitive and behavioral functioning in both full-term and low-risk preterm populations. Future research investigating the neural correlates of early measures of EF in low-risk preterm children and other at-risk groups is warranted to better understand how trajectories of EF development are altered in the first years of life.     

Visual control of reaching and grasping in infants.

The role of visual input during reaching and grasping was evaluated. Groups of infants (5, 7, and 9 months old) and adults reached for an illuminated object that sometimes darkened during the reach. Behavioral and kinematic measures were assessed during transport and grasp. Both infants and adults could complete a reach and grasp to a darkened object. However, vision was used during the reach when the object remained visible. Infants contacted the object more often when it remained visible, though they had longer durations and more movement units. In contrast, adults reached faster and more precisely during transport and grasp when the object remained visible. Thus, continuous sight of the object was not necessary, but when it was available, infants used it for contacting the object whereas adults used it to reach and grasp more efficiently.     

Evidence of motor planning in infant reaching behavior

When adults reach for an object, kinematic measures of their approach movement are affected by what they intend to do after grasping it. We examined whether such future intended actions would be reflected in the approach-to-grasp phase of infant reaching. Twenty-one 10-month-old infants were encouraged to either throw a ball into a tub or fit it down a tube. Kinematic measures of the approach phase of the reach toward the ball were obtained using a motion analysis system. Infants, like adults, reached for the ball faster if they were going to subsequently throw it as opposed to using it in the precision action. The perceptual aspects of the ball were the same and cannot account for these kinematic differences. Infants appear to be planning both segments of their actions in advance. Our findings provide evidence for a level of sophistication in infant motor planning not reported before.     

The nature of environmental influences on weight and obesity: a behavior genetic analysis.

The nature of environmental influences on individual differences in weight and obesity is presently unclear. To resolve this issue, behavior genetic studies are reviewed for their relevance to environmental influences on weight and obesity. Results are consistent in suggesting that environmental experiences are important for weight and obesity, although they account for much less variation than do the effects of genes. Furthermore, only environmental experiences that are not shared among family members appear to be important. In contrast, experiences that are shared among family members appear largely irrelevant in determining individual differences in weight and obesity. These conclusions are consistent with a growing body of evidence on the relative unimportance of such shared experiences for many psychological characteristics.     

Anticipatory reaching of seven- to eleven-month-old infants in occlusion situations

The present study examined 7- to 11-month-old infants’ anticipatory and reactive reaching for temporarily occluded objects. Infants were presented with laterally approaching objects that moved at different velocities (10, 20, and 40 cm/s) in different occlusion situations (no-, 20 cm-, and 40 cm-occlusion), resulting in occlusion durations ranging between 0 and 4 s. Results show that except for object velocity and occlusion distance, occlusion duration was a critical constraint for infants’ reaching behaviors. We found that the older infants reached more often, but that an increase in occlusion duration resulted in a decline in reaching frequency that was similar across age groups. Anticipatory reaching declined with increasing occlusion duration, but the adverse effects for longer occlusion durations diminished with age. It is concluded that with increasing age infants are able to retain and use information to guide reaching movements over longer periods of non-visibility, providing support for the graded representation hypothesis (Jonsson &; von Hofsten, 2003) and the two-visual systems model (Milner &; Goodale, 1995).     

Linked proximal and distal changes in the reaching behavior of 5- to 12-month-old human infants grasping objects of different sizes

This study evaluates age-related proximal and distal changes in reaching organization for objects of different sizes. To this end, eight objects ranging from 2 to 9 cm diam. were presented to 23 infants ages 5 to 12 months. Proximal control was determined by the relative frequencies of bimanual reaching for large and small objects. Distal control was assessed by hand opening and orientation with respect to an object, and by the proportion of the object being included within hand opening at touch. Five-month-old infants tended to reach bimanually regardless of object size. Starting at 7 to 8 months, infants tended to reach for large objects bimanually more often than for small ones. Only at 11 to 12 months did reaching closely reflect the object’s diameter. The frequency of thumb-index finger angle opening during the approach phase also increased after 7 to 8 months of age, as well as the adjustment of the angle to the object diameter and the proportion of the object within hand opening at touch. Proximal and distal changes appeared coupled at 5 to 6 months, when the few subjects showing evidence of some proximal adjustments to object size were also those who exhibited some distal adjustments. After they started to appear, however, proximal and distal adjustments seemed to be independent, as revealed by the lack of correlation of proximal and distal changes between 7 and 12 months.     

Factors associated with the socioemotional development of preterm infants

Preterm birth is a risk factor for problems in interactions with others. We compared the difference in socioemotional development between hospital discharge and at six months of corrected age of infants born ≤32 weeks and assessed the impact of maternal and infantile factors on socioemotional development rate within a 6 month’s period. Mother-child dyads (n = 144) were assessed by the Mother-Baby Observation Protocol 0–6 months through a video microanalysis. Multivariate model was built. Neonatal, maternal and child factors were associated with interactive gaze, initiate contact, responsiveness, infantile vocalization, and thus contributed to the socioemocional development of preterm infants with their mothers.     

Corrected and uncorrected Bayley scores: Longitudinal developmental patterns in low and high birth weight preterm infants

In this study, we longitudinally investigated developmental changes in very low birth weight (VLBW, less than 1500 gms), in higher birth weight (HBW, 1500–2000 gms) preterm, and in full-term (FT) infants. We also investigated changes in their caretaking home environment. The subjects were 20 VLBW, 39 HBW, and 24 FT infants who participated in an intervention study. Blind independent assessments were performed at 4, 8, 12, and 16 months corrected age using the Bayley mental and motor scales, both corrected for prematurity and uncorrected, the Infant and Toddler temperament questionnaires, and the Caldwell Home Observation for Measurement of the Environment inventory (HOME). The VLBW infants obtained the lowest mental (77) and motor (77) uncorrected scores, which were significantly different from the mental and motor scores of the HBW (94 and 89, respectively) and of the FT (115 and 109, respectively) infants. Mental and motor uncorrected scores were significantly lower at 4 months than at 8, 12, and 16 months. By 12 months, the uncorrected scores of the HBW infants no longer differed from the FT ones, and by 16 months only the difference between the FT and the VLBW was significant. The corrected mental and motor scores yielded no significant group or age differences. Post hoc analysis of an interaction in the motor scores yielded significantly higher scores for the FT than for the VLBW group at the last assessment. Overall, the VLBW infants were more passive and less intense than were either HBW or FT infants. In general, the home environment of the VLBW infants was significantly less stimulating and responsive than was the home environment of the FT and HBW infants. These results are discussed in terms of vulnerability of the VLBW preterm infants to developmental deficits and the difficulties their parents experience in their caretaking role.     

Attachment representations in mothers of preterm infants

The aim of the study was to assess attachment representations in mothers of preterm infants using the Working Model of Child Interview (WMCI) at the 12 months of the infant's corrected age. In addition, the relation between WMCI representation categories and the Edinburgh Postnatal Depression Scale score at 6 months of the infant's corrected age was studied. There were 38 mothers of preterm infants (<1500 g or <32 gestational weeks) and 45 mothers of full-term infants. The results showed no differences between the study groups in the distribution of the three main representation categories (balanced, disengaged and distorted). However, there were qualitative differences in representations between the groups. Furthermore, maternal depression symptoms were associated with distorted representation category. We suggest that despite the qualitative differences in the mothers’ representations, mothers of preterm infants are as likely to form balanced attachments with their infants as mothers of full-term infants.     

Conservation of weight in infants

Conversation of weight can be defined as the ability to affirm that the weight of an object remains invariant during the transformations of the form of the object. It is known to be achieved at a conceptual level at about 9 years of age. The behavior of infants seems to indicate that between 6 and 18 months of age they develop a sensorimotor form of conversation.