This article reviews the literature on infant reaching, from past to present, to recount how our understanding of the emergence and development of this early goal-directed behavior has changed over the decades. We show that the still widely-accepted view, which considers the emergence and development of infant reaching as occurring primarily under the control of vision, is no longer sustainable. Increasing evidence suggests that the developmental origins of infant reaching is embodied. We discuss the implications of this alternative view for the development of eye-hand coordination and we propose a new scenario stressing the importance of the infant body-centered sensorimotor experiences in the months prior to the emergence of reaching as a possible critical step for the formation of eye-hand coordination.
Daniela Corbetta, Rebecca F. Wiener, Sabrina L. Thurman, and Emalie McMahon
Scott W. Ducharme and Richard E.A. van Emmerik
In human locomotion, the magnitude of gait variability is a strong predictor of fall risk and frailty due to aging and disease. Beyond variability magnitude, the past two decades have provided emerging alternative methodologies for studying biological variability. Specifically, coordination variability has been found to be critically important within a healthy, adaptive system. While many activities aim to minimize end-point variability, greater coordination variability indicates a more flexible system, and is greater in experts compared to novices, or healthy compared to diseased individuals. Finally, variability structure (i.e., fractal dynamics) may describe the overall adaptive capacity of the locomotor system. We provide empirical support that fractal dynamics are associated with step length symmetry during challenging split-belt treadmill walking. Individuals whose fractal scaling approached 1/f fractal scaling during constrained walking also exhibited the best gait adaptability performance. Importantly, this relation between fractality and gait adaptability was not observed in unperturbed preferred speed walking.
Ryota Nishiyori and Beverly D. Ulrich
Our goal for this paper is to address changes in motor patterns that occur early in life. To do this, we begin by sharing first a brief set of exemplar patterns of movement that emerge prenatally and during the first year postnatally. We couch these descriptions in the hypotheses proposed to explain what has been observed, and emphasize, as well, the context in which they appear. We follow with some experimental studies developmental scientists have used to test these explanations. Subsequently, we address the brain-behavior collaboration that unfolds and supports skill acquisition across early development. We provide data to show that recent advances in brain-imaging technology enable researchers to monitor cortical activity as infants explore and learn functional skills in real time and over developmental time. This opens a new frontier to the scientific study of the early development of neuromotor control and can enhance both our basic science knowledge and our efforts to optimize positive clinical outcomes.
Karl M. Newell
Howard N. Zelaznik
Over the past 18 years, Zelaznik and colleagues have promoted what is known as the event-emergent timing distinction. According to this framework, control of timing can be based upon a neurological clock-like process or upon an emergent process. I review the highlights of this research program that supports this distinction, then describe a new line of research that examines whether timing is a goal of the task or a consequence of other movement constraints. These results highlight the importance of goals in the control of timing.
Hendrik Reimann, Tyler Fettrow, and John J. Jeka
The neural control of balance during locomotion is currently not well understood, even in the light of considerable advances in research on balance during standing. In this paper, we lay out the control problem for this task and present a list of different strategies available to the central nervous system to solve this problem. We discuss the biomechanics of the walking body, using a simplified model that iteratively gains degrees of freedom and complexity. Each addition allows for different control strategies, which we introduce in turn: foot placement shift, ankle strategy, hip strategy, and push-off modulation. The dynamics of the biomechanical system are discussed using the phase space representation, which allows illustrating the mechanical effect of the different control mechanisms. This also enables us to demonstrate the effects of common general stability strategies, such as increasing step width and cadence.
The last decade has witnessed an increase in the number of moderate to large-scale nonpharmacologic stroke recovery trials. While a majority, having tested the superiority of a particular evidence-based intervention, returned negative findings, the rehabilitation research community has gained an important perspective for future efforts. We offer our interpretation first, on why most of the past decade’s trials failed in the sense of not supporting the primary superiority hypothesis, and, second, we provide our perspective on how to solve this problem and thereby inform the next generation of neurorehabilitation clinical trials. The first large-scale randomized controlled trial (RCT) ever conducted in neurorehabilitation was the Extremity Constraint Induced Movement Therapy Evaluation (EXCITE) trial. The majority of stroke recovery trials that followed were based on a prevailing, but as yet immature science of brain-behavior mechanisms for recovery and limited practical know-how about how to select the most meaningful outcomes. The research community had been seduced by a set of preclinical studies, ignited by the 1990’s revolution in neuroscience and an oversimplified premise that high doses of task-oriented training was the most important ingredient to foster recovery. Here, we highlight recent qualitative and quantitative evidence, both mechanistic and theory-driven, that integrates crucial social and personal factors to inform a more mature science better suited for the next generation of recovery-supportive rehabilitation clinical trials.
3 WINS Fitness is a student-delivered free exercise program for the community delivered in public parks. We believe this program, which operates without external funding and has been sustained for 6 years, is one significant solution to reducing the level of physical inactivity in the United States. The operative 3 WINS in our program are participant health, community health, and student professional development. The primary focus has been underserved communities, and our current eight programs in Los Angeles, serve over 300 participants regularly. Three challenges to the program are student empowerment, faculty understanding and involvement, and establishing the relationship between university and parks, which represent a vital partnership. However, the accomplishment of undergraduate students having such a dynamic impact on public health underscores the need for encouraging this sustainable and innovative strategy to increase the physical activity levels of communities across America.