Twitching in Sensorimotor Development from Sleeping Rats to Robots

Abstract

It is still not known how the “rudimentary” movements of fetuses and infants are transformed into the coordinated, flexible, and adaptive movements of adults. In addressing this important issue, we consider a behavior that has been perennially viewed as a functionless by-product of a dreaming brain: the jerky limb movements called myoclonic twitches. Recent work has identified the neural mechanisms that produce twitching as well as those that convey sensory feedback from twitching limbs to the spinal cord and brain. In turn, these mechanistic insights have helped inspire new ideas about the functional roles that twitching might play in the self-organization of spinal and supraspinal sensorimotor circuits. Striking support for these ideas is coming from the field of developmental robotics: When twitches are mimicked in robot models of the musculoskeletal system, basic neural circuitry self-organizes. Mutually inspired biological and synthetic approaches promise not only to produce better robots, but also to solve fundamental problems concerning the developmental origins of sensorimotor maps in the spinal cord and brain.

Sleep and Development in Genetically Tractable Model Organisms

“…These results support the notion that REM sleep in early life could be crucial for normal brain patterning, although nonspecific or non-sleep-dependent effects of the lesion are difficult to rule out. In line with these findings, REM sleep deprivation in adolescent mice delays the critical period of visual cortical development, suggesting REM sleep disturbances somehow impinge upon brain maturation (Shaffery et al 2002;Blumberg et al 2013). Compelling evidence for an active role of sleep in brain sensorimotor development has also come from rodent pups.…”

“…There are many arguments in support of the universality of sleep, but conservation of ontogenetic sleep changes with an active role in the developing nervous system is emerging as one of the strongest (Roffwarg et al 1966;Jouvet-Mounier et al 1970;McGinty et al 1977;Shaw et al 2000;Kirov and Moyanova 2002;Raizen et al 2008;Hasan et al 2012;Todd et al 2012;Sorribes 2013;Kayser et al 2014). The observation that sleep amount is highest during developmental periods across species has led to extensive and ongoing explorations of the ontogenetic hypothesis, suggesting that sleep promotes normal brain development by providing necessary endogenous activity (Roffwarg et al 1966;Jouvet-Mounier et al 1970;Oksenberg et al 1996;Shaffery et al 1999;Frank 2011;Blumberg et al 2013;Kayser et al 2014;Tononi and Cirelli 2014). The selfevident fact that all nervous systems originate from a single cell can be viewed as a truly universal constraint imposed by the very nature of development.…”

“…Like human infants, rat pups spend a large amount of time in REM/active sleep, characterized by muscle atonia with sudden bursts of muscle twitches and resultant limb jerks. Blumberg et al (2013) have shown that this twitching is highly structured and that sleep-dependent twitches may provide a source of patterned neural activity with a role in sensory map development. Whether sleep disruptions during specific developmental times permanently disturb map establishment remains unknown.…”

“…Similar trends, where the amount of total sleep, or vertebrate REM sleep, is highest early in development, have been observed in mammals, fish, birds, insects, and nematodes (Jouvet-Mounier et al 1970;McGinty et al 1977;Szymczak 1987;Shaw et al 2000;Kirov and Moyanova 2002;Paredes et al 2006;Raizen et al 2008;Hasan et al 2012;Todd et al 2012;Sorribes 2013). These findings led to the hypothesis that during early life, REM sleep and invertebrate sleep may play an important role in the development of the nervous system, by establishing a period of globally heightened plasticity and/ or providing endogenous, specialized activity in certain neural circuits (O'Donovan 1999;Blumberg 2008, 2010;Blumberg et al 2013;Corner 2013). Such specialized activity could, for instance, promote appropriate neurodevelopment through feedback by coupling function (such as recurring limb movement) to the refinement of neural connections.…”

Movement characterisation with accelerometry for improved paediatric sleep assessment

“…Error 2. conventional summaries of movement persist throughout sleep literature, despite evidence of movement characteristics specific to certain sleep stages [22], di↵erences in muscle activation e↵ort between sleep and wake [23], and di↵erences in movement coherence [18]. Considering that literature highlights these di↵erences between movements during sleep and wake, there are likely technically di↵erentiable characteristics.…”