title: Self-generated movements with "unexpected" sensory consequences.
abstract: The nervous systems of diverse species, including worms and humans, possess mechanisms for distinguishing between sensations arising from self-generated (i.e., expected) movements from those arising from other-generated (i.e., unexpected) movements [1-3]. To make this critical distinction, animals generate copies, or corollary discharges, of motor commands [4, 5]. Corollary discharge facilitates the selective gating of reafferent signals arising from self-generated movements, thereby enhancing detection of novel stimuli [6-10]. However, for a developing nervous system, such sensory gating would be counterproductive if it impedes transmission of the very activity upon which activity-dependent mechanisms depend [11]. In infant rats during active (or REM) sleep--a behavioral state that predominates in early infancy [12-16]--neural circuits within the brainstem [17, 18] trigger hundreds of thousands of myoclonic twitches each day [19]. The putative contribution of these self-generated movements to the activity-dependent development of the sensorimotor system is supported by the observation that reafference from twitching limbs reliably and substantially triggers brain activity [20-23]. In contrast, under identical testing conditions, even the most vigorous wake movements reliably fail to trigger reafferent brain activity [21-23]. One hypothesis that accounts for this paradox is that twitches, uniquely among self-generated movements, lack corollary discharge [23]. Here, we test this hypothesis in newborn rats by manipulating the degree to which self-generated movements are expected and, therefore, their presumed recruitment of corollary discharge. We show that twitches, although self-generated, are processed as if they are unexpected.
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, IA 52242, USA; Delta Center, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Tiriac
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Del Rio-Bermudez
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, IA 52242, USA; Delta Center, University of Iowa, Iowa City, IA 52242, USA; Department of Biology, University of Iowa, Iowa City, IA 52242, USA. Electronic address: mark-blumberg@uiowa.edu.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Blumberg
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement; D011434:Proprioception; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D012895:Sleep, REM