Mark Blumberg, PhD, University of Iowa, presents "Developing the sensorimotor system in our sleep".
How are the "rudimentary" movements of fetuses and infants transformed into the coordinated, flexible, and adaptive movements of adults? Some believe that adult behaviors are built from "motor primitives," endowed units of behavior, hardwired in the central nervous system, that arise fully formed without the need for experience. In contrast, an increasing number of developmental scientists and roboticists are emphasizing how infants discover how their bodies are built. Not surprisingly, this process of discovery has been presumed to occur only when infants are awake, reflecting the common wisdom that sleep is a period of sensory isolation and behavioral stillness. But this is far from the truth. Instead, during active (or REM) sleep, every skeletal muscle in the body twitches, causing jerky movements of arms and legs, fingers and toes, eyes, and (in rodents) whiskers. These movements are particularly prominent during the perinatal period when active sleep predominates. Although considered for millennia to be by-products of dreams (think dogs "chasing rabbits"), research in infant rodents over the past decade has fundamentally altered our conception of the neural causes and functional consequences of this behavior. Indeed, sensory feedback from twitching limbs is a powerful source of brain activation in developing animals. Moreover, recent work from my lab shows that twitches are uniquely different from wake movements with regard to how they are processed by the sensorimotor system, a surprising finding that may hold the key to understanding the role of twitching in driving activity-dependent development of the sensorimotor system. All together, this work has implications for our understanding of typical and atypical development, for recovery of function after injury or disease, and for detecting neurodevelopmental disorders earlier than is currently possible using standard clinical assessments.
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