Attentional dynamics of infant visual foraging.

Young infants actively gather information about their world through visual foraging, but the dynamics of this important behavior is poorly understood, partly because developmental scientists have often equated its essential components, looking and attending. Here we describe a method for simultaneously tracking spatial attention to fixated and nonfixated locations during free looking in 12-week-old infants using steady-state visual evoked potentials (SSVEPs). Using this method, we found that the sequence of locations an infant inspects during free looking reflects a momentary bias away from locations that were recently the target of covert attention, quickly followed by the redirection of attention--in advance of gaze--to the next target of fixation. The result is a pattern of visual foraging that is likely to support efficient exploration of complex environments by facilitating the inspection of new locations in real time.

Empty-headed dynamical model of infant visual foraging.

Visual foraging is one important way that very young infants explore and learn about their environment. We recently showed that a simple stochastic dynamical model acts quantitatively like free-looking 1-month-old infants, even though it does not include any components that directly represent the perceptual-cognitive processes that operate on the input from visual foraging. This suggested that early in development, generic low-level processes like noise and hysteresis in the mechanisms controlling gaze may drive visual foraging behavior and therefore regulate the input to higher-level perceptual-cognitive processes that later come to have more influence on free looking. Here we evaluate the model's ability to behave like 3-month-olds studied under the same experimental conditions as 1-month-olds. The results show that the empty-headed model can also behave like 3-month-old infants, although not as well as 1-month-olds. Its partial success at 3 months suggests that generic low-level processes controlling gaze remain important in visual foraging. Its pattern of failure suggests that by 3 months time-dependent processes like attention have become especially important.

Embodied infant attention.

Does real time coupling between mental and physical activity early in development have functional significance? To address this question, we examined the habituation of visual attention and the subsequent response to change in two groups of 3-month-olds with different patterns of movement-attention coupling. In suppressors, the typical decrease in body movement at the onset of looks persists into the looks. In rebounders, the initial decrease is more transient and movement quickly returns above baseline. Suppressors and rebounders did not differ on measures of looking during habituation, but when the stimulus changed rebounders looked more than suppressors. When it did not change, they looked less. In addition, during habituation rebounders spent more time looking away from the stimulus. Rapid motor reactivation soon after gaze locks onto a target, characteristic of rebounders, may influence visual foraging and the response to change by keeping attention near a threshold of engagement.

Cyclic motor activity in the fetal rat (Rattus norvegicus).

Rat fetuses were observed on Day 20 of gestation using a technique that permits direct observation of fetal behavior. The resulting time series was analyzed to assess cyclic organization in fetal movement. Fetal activity did not occur randomly but showed significant cyclic variation with a mean frequency of 0.61 cycle/min. This finding agrees with studies of human fetuses, which also exhibit short-period cyclicity in motor activity.

The dynamics of attention during free looking.

Simple methods to study attention dynamics in challenging research and practical applications are limited. We explored the utility of examining attention dynamics during free looking with steady-state visual evoked potentials (SSVEPs), which reflect the effects of attention on early sensory processing. This method can be used with participants who cannot follow verbal instructions and patients without voluntary motor control. In our healthy participants, there were robust fluctuations in the strength of SSVEPs driven by the fixated and non-fixated stimuli (rapidly changing pictures of faces) in the seconds leading up to the moment they chose to shift their gaze to the next stimulus sequence. Furthermore, the amplitude of SSVEPs driven by the fixated stimuli predicted subsequent recognition of individual stimuli. The results illustrate how information about the temporal course of attention during free looking can be obtained with simple methods based on the attentional modulation of SSVEPs.

Child care setting affects salivary cortisol and antibody secretion in young children.

Elevated afternoon levels of cortisol have been found repeatedly in children during child care. However, it is unclear whether these elevations have any consequences. Because physiologic stress systems and the immune system are functionally linked, we examined the relationship between salivary cortisol concentration and antibody secretion across the day at home and in child care, and their relationships with parent-reported illnesses. Salivary antibody provides a critical line of defense against pathogens entering via the mouth, but little is known about its diurnal rhythm in young children or the effect of different environmental contexts. Saliva samples were taken at approximately 10:30 a.m., 3:30 p.m. and 8:00 p.m. on two child care and two home days in a sample of 65 3-5-year-old children attending very high quality, full time child care centers. Results indicated that (1) a rising cortisol profile at child care, driven by higher afternoon levels, predicted lower antibody levels on the subsequent weekend, (2) higher cortisol on weekend days was related to greater parent-reported illness, and (3) a declining daily pattern in sIgA was evident on weekend and child care days for older preschoolers, but only on weekend days for younger preschoolers. The results suggest that elevated cortisol in children during child care may be related to both lowered antibody levels and greater illness frequency.

Robust coupling of body movement and gaze in young infants.

In the first few months after birth, rapid bursts of body movement precede and possibly facilitate shifts of gaze during free looking, with potential consequences for perception and cognition. Here we report that the characteristic features of movement-gaze coupling found during free looking are preserved when attention is perturbed by a salient change in the visual environment. Twenty-four 3-month-olds looked at two attractive 3-dimensional objects while body movement and corneal reflections of the objects were recorded. Lateral head movement was measured offline. After approximately 2 s of looking at one stimulus, the nonfixated stimulus either began to rotate back and forth (distracter events) or remained motionless (control events). In distracter events, the motion of the nonfixated stimulus triggered substantial motor quieting, shortened the duration of the look, and shortened the time to reorient gaze compared to control events. Abbreviated motor quieting and small increases in lateral head movement occurred during control events at the same time in the look as the protracted motor quieting and increased head movement in distracter events. Despite these perturbations, the characteristic bursts of body movement that precede shifts of gaze during free looking occurred in both distracter and control events. The results demonstrate the robust nature of early movement-gaze coupling, raise questions about the specific role of attention in the dynamic links between body movement and gaze, and highlight the potential short and long term functional significance of movement-gaze-attention coupling.

Movement-attention coupling in infancy and attention problems in childhood.

Adaptive behavior requires the integration of body movement and attention. Therefore, individual differences in integration of movement and attention during infancy may have significance for development. We contacted families whose 8-year-old children (n=26; 16 females, 10 males; mean age 8 y 2 mo, SD 8 mo) participated in a previous study of movement-attention coupling at 1 or 3 months of age, to assess parent-reported attention or hyperactivity problems using the Child Behavior Checklist and Diagnostic and Statistical Manual of Mental Disorders (4th edn) criteria. Parent-reported attention problems at 8 years of age were associated with less suppression of body movement at onset of looking, and greater rebound of body movement following its initial suppression at 3 months, but not at 1 month. Parent-reported hyperactivity was not related to any of the infant movement-attention measures. Results suggests that the dynamic integration of movement and attention early in life may have functional significance for the development of attention problems in childhood.

Fetal cyclic motor activity in diabetic pregnancies: sensitivity to maternal blood glucose.

Spontaneous fetal movement in the last third of human gestation is dominated by irregular oscillations on a scale of minutes (cyclic motility, CM). The core properties of these oscillations are stable during the third trimester of gestation in normal fetuses, but disrupted by poorly controlled maternal diabetes. Here we investigated whether fetal CM is linked to short-term instabilities in maternal glucose metabolism. The fetuses of 40 mothers with type I (n = 28) or gestational (n = 12) diabetes were studied one to six times between 27 and 40 postmenstrual weeks of gestation. Fetal movement and maternal blood glucose concentration were measured during two separate periods of fetal activity in each session. Fetal CM was quantified with spectral analysis. Early in the third trimester, changes in the rate of oscillation in fetal CM between the two periods of activity were inversely related to changes in maternal blood glucose levels. Fetal CM was unrelated to concurrent maternal blood glucose levels at any point in the third trimester. The pattern of results suggests that disruption of the temporal organization of spontaneous fetal motor activity in pregnancies complicated by maternal diabetes represents an acute response to fluctuations in the metabolic environment rather than an alteration of CM development.

The dynamics of infant visual foraging.

Human infants actively forage for visual information from the moment of birth onward. Although we know a great deal about how stimulus characteristics influence looking behavior in the first few postnatal weeks, we know much less about the intrinsic dynamics of the behavior. Here we show that a simple stochastic dynamical system acts quantitatively like 4-week-old infants on a range of measures if there is hysteresis in the transitions between looking and looking away in the model system. The success of this simple three-parameter model suggests that visual foraging in the first few weeks after birth may be influenced more by noise and hysteresis in underlying neural mechanisms than by how infants process visual information after a look begins.