Mark S. Blumberg, PhD
During REM sleep, every skeletal muscle in the body twitches, causing jerky movements of arms and legs, fingers and toes, and even eyes. These movements are particularly prominent during the perinatal period when REM sleep predominates. Because twitches, for millennia, have been interpreted as by-products of dreams, there has been little motivation to investigate them in human infants. To fill this gap, we recently conducted a study of twitching across the first postnatal year, documenting its quantity and patterning across the body. The results demonstrate that twitching, as in other developing mammals, is abundant in human infants and is expressed deferentially across the body as new motor skills develop. These findings complement recent research in infant rodents that has fundamentally altered our conception of the neural causes and functional consequences of this behavior. Specifically, sensory feedback from twitching limbs is a powerful source of brain activation during early development. Moreover, sensory feedback from twitches is processed very differently from sensory feedback from wake movements, a surprising finding that may hold the key to understanding the contributions of twitching to activity-dependent development of the sensorimotor system. 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.
Mark Blumberg is F. Wendell Miller Distinguished Professor and chair of the Department of Psychological and Brain Sciences at The University of Iowa. He is also a member of the Iowa Neuroscience Institute and the Department of Biology. Over the course of his career, he has investigated and written about a variety of topics including sleep, temperature regulation, evolution, and the origins of instinct. As a developmental behavioral neuroscientist, he aims to reveal the processes that guide behavioral and brain development in young animals. Most recently, he has focused on the development of sleep in perinatal rats and mice—and now humans—with the overarching goal of understanding why mammals sleep so much when they are young. Related to this work, he seeks to understand how spontaneous motor activity during sleep contributes to sensorimotor integration and the development of topographic maps. He has supplemented his more traditional scholarship with the writing of several books of popular science, including Freaks of Nature: What Anomalies Tell Us about Development and Evolution (Oxford University Press, 2009). In 2010 he co-edited The Oxford Handbook of Developmental Behavioral Neuroscience and in 2016 he co-edited a special collection of essays entitled How We Develop for WIREs Cognitive Science.