Leigh F. Bacher

The Integration of Body Movement and Attention in Young Infants

The normal development of adaptive behavior in humans depends on the integration of visual attention and body movement, yet little is known about the initial state of movement-attention coupling at the beginning of postnatal life. We studied 1- and 3-month-old infants during extended periods of visual exploration and found that spontaneous shifts of gaze are preceded by rapid changes in general body movement. The results reveal a tight link between motor activation and overt attention on a time scale of seconds or less. This link undergoes substantial developmental change in the first few weeks after birth. During that time, phasic motor activation may play a key role in visual exploration by helping to unlock gaze when the environment is unchanging.

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.

Sensitivity of the rate of spontaneous eye blinking to type of stimuli in young infants.

Although progress has been made toward understanding the mechanisms of spontaneous eye blinking (SB), few reports focus on the ontogeny of SB. The purpose of the present work was to investigate SB in infants by attempting to manipulate SB and examine potential correlates of SB. Fifty-two infants were observed in a quiet baseline condition then presented with either moving stimuli or a social stimulus. SB, eye movement, body movement and various background variables were measured. Results demonstrate that SB can be manipulated and that SB rate is differentially sensitive to the type of stimulus presented. Eye and body movements did not systematically relate to the rate of SB. Implications for mechanisms of SB regulation are discussed.

Contractile activity of the uterus prior to labor alters the temporal organization of spontaneous motor activity in the fetal sheep

Contractile activity of the uterus before the onset of labor (uterine contractures) has been described in a number of species and provides a powerful source of repeated stimulation for the fetus throughout much of gestation. To understand how fetal behavior responds to this dynamic aspect of the intrauterine environment, we investigated the effects of uterine contractures on the temporal organization of spontaneous motor activity in the fetal sheep during the last fifth of gestation. Eleven fetuses were instrumented on 113-116 days of gestation (dGA). Electromyogram (EMG) activity was recorded from flexor and extensor muscles in the fetal forelimbs and hindlimbs, and from the uterus. Pooled limb EMG activity from 2300 hr to 0700 hr on 118, 125, 132, and 139 dGA before, during, and after uterine contractures was spectral analyzed to detect and quantify the cyclic organization in fetal motor activity. There was strong evidence of cyclic organization in fetal motor activity (CM) at each gestational age, similar to what has been described in the fetal rat and human. There was no evidence of developmental changes in the baseline spectral measures of CM. The most prominent feature of the response of CM to uterine contractures was a transient decrease in irregularity at 118-132 dGA. The strength of CM increased during contractures at 125 and 132 dGA, and a slight acceleration of CM during contractures was detected at 118 and 139 dGA. The results demonstrate that the stimulation associated with contractures influences an important source of complexity in early behavioral organization. The results are consistent with speculation by others that uterine contractures might induce transient cerebral hypoxemia in the fetus, and suggest that conditions established in the first few minutes of sustained uterine activity constitute the effective perturbation of CM.

Development and manipulation of spontaneous eye blinking in the first year: Relationships to context and positive affect

The present study explored the development of spontaneous eye blinking (SEB) and its relationship to approach-inhibition behavior during the second half of the first year. The dopaminergic regulation of SEB in adult primates provides an empirical basis for studying blinking in infants, and dopamines role in infant temperament provides justification for examining approach-inhibition specifically. A longitudinal design with an experimental manipulation was used to examine developmental change in the rate of SEB. Healthy, full-term infants (N = 74) were observed at 4 and 12 months. Blinking rate was observed during a quiet baseline and a randomly assigned stimulus condition. Then, approach-inhibition responses were examined as stimulus objects were presented. Experimental conditions altered blink rate at both ages, but the effects varied by age and stimulus type. At 12 months, individual differences in SEB were associated with positive affect during the approach-inhibition task. The divergent effects for the cognitive and social conditions suggest that the mechanisms regulating blink rate have distinct relationships to these behavioral domains and that these undergo changes during the first year.

Intraindividual and Interindividual Differences in Spontaneous Eye Blinking: Relationships to Working Memory Performance and Frontal EEG Asymmetry

The rate and timing of spontaneous eye blinking (SB) may be used to explore mechanisms of cognitive activity in infancy. In particular, SB rate is believed to reflect some dimensions of dopamine function; therefore, we hypothesized that SB rate would relate to working memory performance and to frontal electroencephalogram (EEG) asymmetry. Forty, 10-mo-old infants completed an A-not-B task while SB and EEG were measured throughout. We found that SB rate varied across phases of the task, variability in SB rate was positively related to working memory performance, and frontal EEG asymmetry was related to individual differences in the rate of SB. Results provide indirect, but convergent support for the hypothesis that SB rate reflects dopamine function early in human development. As such, these results have implications for understanding the tonic and phasic effects of dopamine on cognitive activity early in human development.

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 pups intrinsic oscillations in motor activity may regulate the expression of discrete responses to cues important for the initiation of suckling.

Developmental psychobiology: a look back on 30 years.

Developmental Psychobiology publishes papers from the disciplines of psychology, biology, neuroscience, and medicine that contribute to an understanding of behavioral development. Research focuses on development in the embryo/fetus, neonate, juvenile, and adult as well as multidisciplinary research that relates behavioral development to anatomy, physiology, biochemistry, genetics, and evolution. The journal represents a broad phylogenetic perspective on behavioral development by including studies on invertebrates, fish, birds, non-human primates, and humans. This paper presents an analysis of empirical articles published since its first issue in 1968. This analysis covers number of authors, sex of first author; evidence of grant support, and participation of investigators from outside the US. Additionally, the analysis includes the topic of research, level of analysis, and subject of experimental study. Over its 32-year history, Developmental Psychobiology has published papers on a wide range of topics representing a broad phylogenetic perspective with a continued focus on behavioral investigation. This analysis revealed trends such as an increase in the number of studies at a physiology/anatomy level, an increase in studies with human subjects, and increases in contributions from investigators outside of the United States as well as women.