Neonatal Stepping in Relation to Terrestrial Optic Flow

This experiment examined whether newborn stepping, a primitive form of bipedal locomotion, could be modulated by optical flow. Forty-eight 3-day-old infants were exposed to optical flows that were projected onto a horizontal surface above which the infants were suspended. Significantly more air steps were elicited by exposure to a terrestrial optical flow specifying forward translation than by a rotating optical flow or a static optical pattern. Thus, a rudimentary coupling between optical flow and stepping is present at birth, suggesting a precocious capacity in the newborn to perceive and utilize visual information specifying self-motion. The findings may help the early diagnosis of infants with visual or visual-motor deficits and the development of visually based interventions for disabled infants.     

Why Does Infant Stepping Disappear and Can It Be Stimulated by Optic Flow?

Two independent experiments (n = 22 and n = 22) showed that 2‐month‐old infants displayed significantly more stepping movements when supported upright in the air than when supported with their feet contacting a surface. Air‐ and surface‐stepping kinematics were quite similar (Experiment 2). In addition, when data were collapsed across both experiments, more air steps and more donkey kicks were seen when infants were exposed to optic flows that specified backward compared to forward translation. The findings challenge the currently accepted heavy legs explanation for the disappearance of stepping at 2 months of age and raise new questions about the visual control of stepping.     

Hidden skills: a dynamic systems analysis of treadmill stepping during the first year

When prelocomotor infants are supported on a motorized treadmill, they perform well-coordinated, alternating stepping movements that are kinematically similar to upright bipedal locomotion. This behavior appeared to be a component of independent walking that could not be recognized without the facilitating context of the treadmill. To understand the ontogenetic origins of treadmill stepping and its relation to later locomotion, we conducted a longitudinal study using an experimental strategy explicitly derived from dynamic systems theory. Dynamic systems theory postulates that new forms in behavior emerge from the cooperative interactions of multiple components within a task context. This approach focuses on the transitions, often nonlinear, where one preferred mode of behavior is replaced by a new form. Specific predictions about these transitions help uncover the processes by which development proceeds. Chapters II, III, and IV introduce dynamic principles of pattern formation and their application to development. In our application of these principles, we tested nine normal infants twice each month beginning from month 1 in a task where the treadmill speed was gradually scaled up and in an additional condition where each leg was driven by the treadmill at a different speed. Kinematic variables were derived from computerized movement analysis equipment and videotaped records. We also collected a number of anthropometric measurements, Bayley motor scores, and a behavioral mood scale for each month. Several infants stepped on the treadmill in their first month, but in all infants performance showed a rapidly rising slope from month 3 to month 6. Infants also showed corresponding improvement in adjustments to speed and relative coordination between the legs. In dynamic terminology, we found evidence that alternating stepping on the treadmill became an increasingly stable attractor during the middle months of the first year. Dynamic predictions that transitions would be characterized by increased variability and sensitivity to perturbation were borne out. Identifying the transitions enabled us to suggest a control parameter or variable moving the system into the stable response to the treadmill. This appeared to be the waning of flexor dominance in the legs during posture and movement that allowed the leg to be stretched back on the treadmill and so elicited the bilaterally alternating response. Further studies are needed to test this hypothesis. This dynamic analysis confirmed earlier suggestions that skill in general, and locomotion in particular, develops from the confluence of many participating elements and showed how emergent forms may result from changes in nonspecific components. A dynamic approach may be useful for understanding ontogenetic processes in other domains as well.     

From spontaneous to instrumental behavior: kinematic analysis of movement changes during very early learning

3-month-old infants who can activate a mobile with their spontaneous leg kicks increase their kick rate over baseline. Kinematic analyses of the temporal and topographic characteristics of reinforced leg kicks were compared with those of infants who saw noncontingent mobile movement. In both experimental and control groups, the flexion and extension movement phases of the kick remained remarkably invariant in duration. Pauses between movements varied inversely with rate. Kick amplitude increased with increasing rate except in the extinction phase, where in some infants, kicks became less frequent but more forceful. Movement duration was unaffected by reinforcement condition. By varying amplitude and frequency domains, infants adjusted movement by neuromuscular mechanisms similar to those of mature humans. The experimental imposition of a voluntary component on spontaneous kicking did not alter the modifiability of the movement control parameters.     

Spontaneous Leg Movements of Infants with Down Syndrome and Nondisabled Infants

Infants with Down syndrome (DS) represent a population in which new behaviors are acquired significantly more slowly than in nondisabled infants. We propose that infants' spontaneous movements hold a key to understanding the process of development—of integrating intrinsic dynamics and function. In this investigation, we compared the spontaneous leg movements of 10 infants with DS and 2 groups of nondisabled (ND) infants matched for chronological age and motor age. In contrast to common perceptions, we did not observe a significant difference in the frequency of movements between infants with DS and ND infants. But, infants with DS demonstrated significantly fewer of the most complex patterned leg movements, that is, kicking patterns. Further, the frequency with which both DS and ND infants kicked was significantly correlated with the age at which they began to walk. Biomechanical variables were identified, as well, that related to their emergent movement patterns. These data are consistent with Edelman's proposal that spontaneous movements that occur repeatedly in regions of the organism's functional work space facilitate the development of stable behavioral patterns and emphasize the role of the interaction of multiple subsystems in the emergence of new behaviors.     

Ontogeny of infantile oral reflexes and emerging chewing

The ontogeny of rooting, lip, lateral tongue, mouth opening, biting, and Babkin reflexes and emerging chewing behaviors were observed in 2 normal infants from 1 week to 35 weeks of age. These behaviors were videotaped at 9 monthly test sessions, and their movement patterns analyzed during slow-motion playback. The reflex responses were elicited in both infants through 35 weeks of age. They consisted of those characteristic movements described in the literature plus additional movements that elaborated the characteristic pattern. The complexity of the reflexes and the quality of movement changed with age. Components of chewing, which emerged sequentially from 1 week of age, were cyclical mandibular elevation and depression, lateral tongue movements, transport of the bolus from lateral to medial oral position, mandible retrusion, lateralization and protrusion movements in association with mandibular elevation and depression, increase in speed of rhythmical chewing movements to the mature speed of 1 cycle per second, and mastication. Chewing and oral reflexes contained similar movements but differed in the relative frequency of certain characteristic movements and in the stimulus response relationship.     

Development of the Stretch Reflex in the Newborn: Reciprocal Excitation and Reflex Irradiation

The stretch reflex is a spinal cord pathway between a muscle's stretch receptors and its own motor units. This reflex is thought to play an important role in normal motor function, because it is unique as a monosynaptic pathway, and because its hyperactivity is a hallmark of many motor disorders. We previously reported a difference in the stretch reflexes in healthy newborn infants and nonambulatory individuals with cerebral palsy (CP): these reflexes are characterized by responses from the stretched muscle and from the reciprocal or antagonist muscle. We proposed the existence of a functional spinal cord pathway that connects both agonist and antagonist muscles at a single joint. We hypothesized that this "reciprocal excitation" is a functional pathway of all newborn infants, which during the normal course of development of motor skills in infants is eliminated. If the CNS is damaged at birth, as in CP, the pathway of reciprocal excitation endures and is reinforced. In the current study of newborns, we recorded stretch reflex responses from all major muscle groups of the lower limb. This "irradiation of reflexes" is a normal phenomenon of the newborn CNS. This pathway becomes suppressed during normal maturation and control of coordinated limb movements.     

The Transition to Reaching: Mapping Intention and Intrinsic Dynamics

The onset of directed reaching demarks the emergence of a qualitatively new skill. In this study we asked how intentional reaching arises from infants' ongoing, intrinsic movement dynamics, and how first reaches become successively adapted to the task. We observed 4 infants weekly in a standard reaching task and identified the week of first arm-extended reach, and the 2 weeks before and after onset. The infants first reached at ages ranging from 12 to 22 weeks, and they used different strategies to get the toy. 2 infants, whose spontaneous movements were large and vigorous, damped down their fast, forceful movements. The 2 quieter infants generated faster and more energetic movements to lift their arms. The infants modulated reaches in task-appropriate ways in the weeks following onset. Reaching emerges when infants can intentionally adjust the force and compliance of the arm, often using muscle coactivation. These results suggest that the infant central nervous system does not contain programs that detail hand trajectory, joint coordination, and muscle activation patterns. Rather, these patterns are the consequences of the natural dynamics of the system and the active exploration of the match between those dynamics and the task.     

Neonatal characteristics and mother-infant interaction in two observational situations.

134 mothers and their newborn infants were studied in order to evaluate the realtionship's between neonatal characteristics and mother-infant interaction. The procedure included a newborn assessment with the Brazelton Neonatal Assessment Scale and 2 mother-infant interaction observations, 1 carried out during feeding and the other during a semistructured situation. The results indicated that there were consistent relationships between infant and maternal behavior; more alert and responsive infants had more responsive and sensitive mothers. These consistencies were found for both infants and mothers across the different situations. Both infant and maternal responsiveness to a variey of social stimuli were noted.     

Smooth-pursuit eye movements in the newborn infant.

The capacity of newborn infants to smooth-pursuit eye movements in single-target tracking and in optokinetic nystagmus to a moving striped field was examined utilizing DC electrooculography. Smooth-pursuit movements were observed in all infants who were alert during testing, but they occupied less than 15% of viewing time during single-target tracking. The velocity of smooth-pursuit segments in single-target tracking increased linearly to a target velocity of 19 degrees/sec and deteriorated rapidly at faster speeds. No smooth pursuit occurred above 32 degrees/sec in single-target tracking. By contrast, optokinetic nystagmus was observed at all field velocities to 40 degrees/sec, but the speed of the mean slow component increased linearly to 25 degrees/sec and diminished above that field velocity. Infant optokinetic nystagmus differed strikingly from that of adults in that tonic ocular deviation was in the direction of field movement rather than away from it. This feature of neonatal optokinetic nystagmus is consistent with deficient foveal function and suggests that the relatively poor smooth-pursuit performance of newborns may be related to foveal immaturity.     

Infant visual scanning of two- and three-dimensional forms

2- and 3-dimensional forms affected 4- and 8-week-old infant visual behavior differently, 4-week-old infants fixated a recessed 3-dimensional form more than a 2-dimensional form but did not scan it differently. 8-week-old infants did not look more at 1 stimulus than another but scanned a raised 3-dimensional form differently than a 2-dimensional equivalent. For all stimuli and both age groups, there was a relation between attractiveness of stimuli and how they were scanned; babies who were most attracted to stimuli inspected them with the smallest eye movements.     

Asymmetric action in the human newborn: sex differences in patterns of organization.

We developed a procedure and scale to quantify movement asymmetry in 36 full-term newborns from several normal newborn nurseries (Measure of Behavioral Laterality, MOBL). The majority of newborns had elicited reflexes and spontaneous movements that were stronger and more coordinated on the right than on the left side of the body; there was no asymmetry in the latency, threshold, or habituation of these behaviors. Although asymmetry of different movements was associated if they relied on the same motor pool, there was little association of movement asymmetries among different body regions, indicating that multiple subsystems, rather than a single asymmetric system, controls asymmetric action in the newborn. Finally, there was a sex difference in asymmetry of all 3 distal lower-body elicited reflexes: females were right biased, but the majority of males were left biased. These sex differences are discussed in terms of alternative mechanisms for the development of asymmetric action and the role of newborn reflexes in adult voluntary movement.     

Social interactions of young abused children: approach, avoidance, and aggression.

10 abused toddlers (ages 1-3 years) and 10 matched controls from families experiencing stress were observed during social interactions with caregivers and with peers in their daycare settings. The abused infants more frequently physically assaulted their peers. They "harassed" their caregivers verbally and nonverbally, and they were the only infants who assaulted or threatened to assault them. The abused infants were much less likely than the controls to approach their caregivers in response to friendly overtures; when they did so they were more likely to approach to the side, to the rear, or by turning about and backstepping. In response to friendly overtures the abused infants more frequently avoided peers and caregivers or combined movements of approach with movements of avoidance. A similar behavior pattern has been identified by Main in maternally rejected infants in normal samples.     

Infant Differences in Rate of Visual Encoding

To clarify the basis for infant differences in rate of visual encoding, the eye movements of a sample of 9 12-week-old infants were recorded throughout an encoding experiment. Results showed that the more slowly encoding infants scanned less extensively over the stimulus, often spent extended intervals in the continuous inspection of one part of the figure, and frequently engaged in prolonged fixations. A second experiment provided comparable scanning data from a sample of 9 2-week-old infants. There were significant age differences in the manner of visual scanning, and the scanning style of the more slowly encoding 12-week-old infants proved to be more like that of the younger infants. Possible explanations for both the between-age and within-age differences are proposed.     

Temperament and attachment security in the strange situation: an empirical rapprochement

In response to Frodi and Thompson's recent demonstration that infants classified A1-B2 in the Strange Situation differ significantly in emotional expression from infants classified B3-C2, several longitudinal data sets were examined to determine whether these group differences might be a function of infant temperament. Data from 3 separate samples revealed significant concordance between infant-mother and infant-father Strange Situation classifications when scored in terms of A1-B2 versus B3-C2, but not when scored in terms of the traditional A-B-C system. In addition, in 2 samples on which newborn behavioral data were available, A1-B2 infants displayed more autonomic stability than B3-C2 infants, and in one of the samples the former infants were more alert and positively responsive as newborns (with means in the same direction in Sample 2). Moreover, mothers of A1-B2 infants described their babies as less difficult to care for at 3 months of age. Considered together, these findings suggest that infant temperament affects the manner in which security or insecurity is expressed rather than whether or not the infant develops a secure or insecure attachment. These findings are discussed in terms of their implications for the study of the interactional antecedents and the developmental consequences of attachment security.     

Radial localization of odors by human newborns.

To study sensitivity to radial location of an odor source, 20 human newborns, ranging from 16 to 130 hours of age, were presented with a small amount of ammonium hydroxide. The odor source was placed near the nose slightly to the left or right of midline, with its position randomized over repeated trails. Direction of headturn with respect to the odor location and diffuse motor activity were scored from the videotape recordings of the newborns' behavior. It was found that as a group, the newborns turned away from the odor source more frequently than they turned toward it. The tendency to turn away from the odor was stronger in infants who displayed less motor activity after the response. Newborns also exhibited a right bias in the direction of the head movements. It is concluded that a spatially appropriate avoidance response is present in the neonate and that the newborn is innately sensitive to the radial location of an odor.     

新生儿窒息后头颅CT检查的结果分析

目的:通过CT检查,对新生儿窒息的预后进行更好的评价。方法:选择114例窒息新生儿,其中26例早产儿、88例足月儿进行研究,选择48例无窒息新生儿,其中20例早产儿、28例足月儿进行对照分析。将其分为轻度窒息、重度窒息;根据CT表现,将新生儿缺血缺氧性脑病(HIE)分为轻、中、重度。按照Apgar评分标准进行评分。结果:114例窒息新生儿中,轻度窒息78例,重度窒息36例,颅内出血48例,治愈109例,死亡5例。结论:轻度窒息新生儿发生HIE后,轻、中度较多,而重度窒息后发生HIE的新生儿重度者较多。轻度HIE新生儿,经积极治疗后,预后较好,重度HIE特别是合并颅内出血者预后较差。早产儿的额叶、枕叶低密度改变不能作为新生儿缺血缺氧性脑病的依据,应根据有无窒息史及临床症状和体征来判断。     

Head-mounted eye tracking: a new method to describe infant looking

Despite hundreds of studies describing infants' visual exploration of experimental stimuli, researchers know little about where infants look during everyday interactions. The current study describes the first method for studying visual behavior during natural interactions in mobile infants. Six 14-month-old infants wore a head-mounted eye-tracker that recorded gaze during free play with mothers. Results revealed that infants' visual exploration is opportunistic and depends on the availability of information and the constraints of infants' own bodies. Looks to mothers' faces were rare following infant-directed utterances but more likely if mothers were sitting at infants' eye level. Gaze toward the destination of infants' hand movements was common during manual actions and crawling, but looks toward obstacles during leg movements were less frequent.     

采用微处理器的步进电机控制系统

步进电机是应用于机电一体化控制系统中的一种常用的执行元件.控制系统要求步进电机控制的设计要能更好地服务于整个系统,而微型处理器与微机技术的日渐成熟,其良好的性价比,可更好地服务于步进电机控制系统.根据步进电机的工作原理和其基本的控制方式,通过接口电路,使不同的步进电机在任意通电方式下被有效地控制,利用脉冲分配,实现通电方式,又根据其通电规律,由软件编程列出数据表,微型处理器强大的数据处理功能使编制软件查表法实现对各种步进电机的控制.在此基础上,对采用微处理器控制步进电机方法进行深入探讨,并给出适应多种步进电机运行方式的软件程序.     

Does Infant Carrying Promote Attachment? An Experimental Study of the Effects of Increased Physical Contact on the Development of Attachment

This study was designed to test the hypothesis that increased physical contact, experimentally induced, would promote greater maternal responsiveness and more secure attachment between infant and mother. Low-SES mothers of newborn infants were randomly assigned to an experimental group (n = 23) that received soft baby carriers (more physical contact) or to a control group (n = 26) that received infants seats (less contact). Using a transitional probability analysis of a play session at 31/2 months, it was demonstrated that mothers in the experimental group were more contingently responsive than control mothers to their infants' vocalizations. When the infants were 13 months old, the Ainsworth Strange Situation was administered. Significantly more experimental than control infants were securely attached to their mothers. We infer from these results that for low-income, inner-city mothers, there may be a causal relation between increased physical contact, achieved through early carrying in a soft baby carrier, and subsequent security of attachment between infant and mother.