Daniela Corbetta

The developmental origins of bimanual coordination: a dynamic perspective.

Patterns of interlimb coordination associated with infant reaching fluctuate frequently over developmental time. This study investigated whether these fluctuations are related to coordination tendencies. Interlimb patterns were studied in reaching and nonreaching movements in 4 infants, which were followed through their 1st year. Each week, reaching and nonreaching endpoint kinematics were recorded in both arms during multiple 14-s trials. It was found that patterns of interlimb coordination in reaching matched coordination tendencies in nonreaching. Reaching fluctuated between uni- and bimanual periods. During the bimanual periods, nonreaching interlimb activity tended to be synchronous. During the unimanual periods, nonreaching activity revealed no predominant form of interlimb coordination. It is argued that changing coordination tendencies may influence the organization of specific goal-oriented behaviors from early in life.

Motor constraints on the development of perception-action matching in infant reaching

Abstract Previous studies on reaching and grasping have suggested that infants need considerable experience at both seeing and touching in order to develop responses adapted to the environment. Such an account, however, does not reveal how appropriate perception-action matching emerges from these repeated experiences at seeing and touching. The present research addresses this issue by investigating the dynamics of perceiving and acting in 5- to 9-month-old infants as they saw, reached for, touched, and grasped objects of different sizes and texture. To gain insights into the mechanisms of change that underlie pattern formation, we observed infants’ responses as a function of time, as infants reached for and manipulated objects successively. We found that the developmental process by which appropriate perception-action matching emerges is tied to important changes in the motor system. Before 8 months, infants’ reaching responses are constrained by systemic motor tendencies that conflict with the process of perceptual-motor mapping. When these motor tendencies disappear, infants are able to use and integrate visual and haptic information to scale their actions to objects. These results are consistent with a dynamic systems approach, which views behavioral changes and their underlying psychological processes as the product of continuous tensions and interactions between the organism’s own constraints and the characteristics of the task at hand.

Motor memory is a factor in infant perseverative errors

Why do infants make perseverative errors when reaching for two identical targets? From a dynamic systems perspective, perseverative errors emerge from repetitive perceptual–motor activity in novel and/or difficult contexts. To evaluate this account, we studied 9-month-old infants performing two tasks in which they repetitively reached toward either a single target or two identical targets. Results showed that, in the context of the two identical targets, perseverative responses were preceded by the creation of strong memories of previous reach directions and trajectories. In contrast, we found little evidence for convergence on habitual reach trajectories when the infants performed the less taxing single-target task, suggesting that the demands of reaching for two identical targets strongly constrained the reaching behavior. In total, results indicated that memories of prior movements make a critical contribution to performance in the A-not-B task and its variants.

Exploration and selection in the early acquisition of skill.

This chapter describes the development of brain and behavior, a dynamic systems approach to development, behavioral dynamics of learning to reach, and infant reaching and neural dynamics. The developmental process means the complex, contingent, multiply determined web of interactions that leads the organism from a single cell to a toddler who can climb, sing songs, and tease her baby brother. The most serious shortcoming of invoking brain maturation is a disregard for developmental process, either at the neural or at the behavioral level. Infants who are blind from birth are significantly delayed in reaching for objects outside of their close personal space, because without vision they lack the motivation to reach forward and grasp things. They do not have the concept of an object to reach for. New understanding of the mutual influences of brain and behavior, rather than assuming the conventional brain-to-behavior path of causality is important. Data on humans and monkeys depicts that there is a possibility of the involvement of the brain area in finding a successful solution of the Piagetian A-not-B error and various other delayed-response tasks.

A Method for Identifying the Initiation of Reaching Movements in Natural Prehension.

Identifying the start of a movement is critical for calculating variables such as movement duration, movement speed, or trajectory length and straightness. In most experiments, the problem is simplified by giving instructions to the subjects and by constraining the task. This is not possible in populations that are too young or disabled to understand and execute the task as instructed. In this article, a method is presented for reliably identifying the onset of reaches in infants, whose movements are embedded in their ongoing activities. A computer program prompts the user to choose reach initiation on the basis of comparison between hand kinematics and videotaped behavior and to code the reach as emerging from 1 of 4 movement contexts. The method is highly reliable in infants of all ages and captures expected age-related changes in reaching. It is suggested that researchers could use this or a similar method to study movements that are part of natural, ongoing activities in normal and in clinical populations

Object retrieval in the 1st year of life: learning effects of task exposure and box transparency.

Before 12 months of age, infants have difficulties coordinating and sequencing their movements to retrieve an object concealed in a box. This study examined (a) whether young infants can discover effective retrieval solutions and consolidate movement coordination earlier if exposed regularly to such a task and (b) whether different environments, indexed by box transparency, would impact the rate of learning and time of discovery of these solutions. Infants (N=12) were presented with an object retrieval task every week from 6 1/2 months of age until they were able to retrieve the toy from the box using coordinated two-handed patterns for 3 weeks. To reach that criterion, infants tested with an opaque box took 2 1/2 months and infants tested with a semitransparent box took 1 1/2 months. Both groups outperformed age-matched controls who received a one-time exposure to the task. Repeated exposure to the task and vision of the toy significantly enhanced this process of solution discovery.

Infant Eye-tracking in the Context of Goal-Directed Actions.

This paper presents two methods that we applied to our research to record infant gaze in the context of goal-oriented actions using different eye-tracking devices: head-mounted and remote eye-tracking. For each type of eye-tracking system, we discuss their advantages and disadvantages, we describe the particular experimental setups we used to study infant looking and reaching, explain how we were able to use and synchronize these systems with other sources of data collection (video recordings and motion capture) in order to analyze gaze and movements directed toward 3D objects within a common time frame. Finally, for each method, we briefly present some results from our studies to illustrate the different levels of analyses that may be carried out using these different types of eye-tracking devices. These examples aim to highlight some of the novel questions that may be addressed using eye-tracking in the context of goal-directed actions.

Lateral Manual Asymmetries: A Longitudinal Study From Birth to 24 Months

Longitudinal studies tracking the early development of manual asymmetries are fairly rare compared to the large number of studies assessing hand preference in infancy. Moreover, most prior longitudinal studies have performed behavioral observation over relatively short-time spans considering the celerity of early development. This study aims (i) to investigate the direction and consistency of manual lateral asymmetries over a longer period, from birth to 24 months of age, and (ii) to compare individual and group trajectories to better understand discrepancies between prior studies. Nineteen healthy infants were observed eight times in tasks that were adjusted progressively as infants manual skills developed. Results suggested two distinct periods in terms of the direction, strength, and consistency of manual preference. First, infants went through an initial phase characterized by a lack of lateral manual asymmetries. From 9 months of age, however, group analyses revealed an emerging and steadily growing right lateral bias over time, while individual trajectories revealed that the group-level right-bias formed progressively from a background of highly fluctuating and highly variable developmental trajectories.

Infant Motor Development: Implications for Motor Neuroscience

Developmental studies can inform motor neuroscience by describing the initial state of the perception-action system, identifying change and the emergence of new forms, and by determining the processes which engender these changes. We describe a research program studying the limb dynamics of human infants using a combination of kinematics, kinetics, and EMG measures. The dynamics of spontaneous kicking reveal the self-organizing qualities of the neuromotor system. The transition from spontaneous waving to reaching suggests ways by which intention is mapped onto these self-organizing qualities. We conclude with a discussion of developmental processes of skill acquisition.

Brain reorganization as a function of walking experience in 12-month-old infants: implications for the development of manual laterality

Hand preference in infancy is marked by many developmental shifts in hand use and arm coupling as infants reach for and manipulate objects. Research has linked these early shifts in hand use to the emergence of fundamental postural–locomotor milestones. Specifically, it was found that bimanual reaching declines when infants learn to sit; increases if infants begin to scoot in a sitting posture; declines when infants begin to crawl on hands and knees; and increases again when infants start walking upright. Why such pattern fluctuations during periods of postural–locomotor learning? One proposed hypothesis is that arm use practiced for the specific purpose of controlling posture and achieving locomotion transfers to reaching via brain functional reorganization. There has been scientific support for functional cortical reorganization and change in neural connectivity in response to motor practice in adults and animals, and as a function of crawling experience in human infants. In this research, we examined whether changes in neural connectivity also occurred as infants coupled their arms when learning to walk and whether such coupling mapped onto reaching laterality. Electroencephalogram (EEG) coherence data were collected from 43 12-month-old infants with varied levels of walking experience. EEG was recorded during quiet, attentive baseline. Walking proficiency was laboratory assessed and reaching responses were captured using small toys presented at mid-line while infants were sitting. Results revealed greater EEG coherence at homologous prefrontal/central scalp locations for the novice walkers compared to the prewalkers or more experienced walkers. In addition, reaching laterality was low in prewalkers and early walkers but high in experienced walkers. These results are consistent with the interpretation that arm coupling practiced during early walking transferred to reaching via brain functional reorganization, leading to the observed developmental changes in manual laterality.