SPONTANEOUS MOTOR ACTIVITY OF DEVELOPING HUMAN INFANTS

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The present research program has shown that spontaneous motor activity in the fetus and young infant has a strong cyclic organization with irregular periods ranging from 1-4 min. The long-term goals of the research program have been to understand the development of CM, its underlying mechanism, and its functional significance for the fetus and infant. Five studies are proposed to investigate the mechanism of CM and its functional consequences. The specific aims of the studies are to investigate: (M1) The Unperturbed Dynamics of CM. The properties of possible CM attractors will be estimated during undisturbed awake periods at 1 and 3 months using new techniques in experimental nonlinear dynamics. Based on preliminary findings, the study is expected to reveal low dimensional chaotic dynamics in the mechanism responsible for CM, which would suggest a unified explanation of the sustained but irregular fluctuations in motor activity; (M2) The Strength and Extent of CM Attractors. The response of awake CM to perturbation will be examined at 1 an 3 months. The strength and extent of CM attractors will be estimated by analyzing the evolution of perturbed trajectories in reconstructed CM state space. The results are expected to yield more detailed information about the dynamic stability of the CM mechanism, the existence of qualitatively different modes of CM organization, and variation in sensitivity across CM state space. (F1) CM and the Spatial Distribution of Visual Attention. The coupling of CM and attention to elements in a static visual environment will be analyzed during ad libitum looking at 1 and 3 months. Attentional disengagement from stimuli is expected to be associated with specific phases of CM, based on preliminary data. The longer term distribution of attention to stimuli is expected to be linked to CM strength and unpredictability, based on functional theories of attention and chaos; (F2) CM and the Modulation of Response to a Stimulus. Shifting of overt visual attention to a new stimulus will be examined at 1 and 3 months. Attentional disengagement and re-orienting are expected to depend on the phase of CM at stimulus onset, which will be varied systematically based on the findings of Study F1. The data will yield detailed information about how the interruptibility of attention in a changing environment is influenced by CM; (F3) CM and the Habituation of Visual Attention. Unperturbed CM and the habituation of visual attention will be examined at 3 months. During habituation, fixation duration is expected to fluctuate partly in relation to the changing phase of CM. Spontaneous recovery to an unchanged stimulus, and failure to recover to a stimulus change, are expected to be related to the phase of CM when the posthabituation trials begin. Spectral and dynamic properties of unperturbed CM may also explain some of the variance in standard measures of habituation/recovery. More generally, there are several reasons to study CM. (1) As a robust property of early neurobehavioral organization, it is likely to be an important factor in adaptive interactions with the environment. (2) The mechanism responsible for the complex fluctuations of activity in CM may be a very common one, so that understanding it would have broader significance. (3) CM provides an opportunity to test the utility of dynamical systems theory in explaining behavioral organization, currently a topic of great interest. (4) CM is an aspect of behavioral organization which can be studied with precision during early development when the organism and its effective environment are both changing rapidly.