Date of Degree
PhD (Doctor of Philosophy)
Blumberg, Mark S.
First Committee Member
Freeman, John H.
Second Committee Member
Voss, Michelle W.
Third Committee Member
LaLumiere, Ryan T.
Fourth Committee Member
Tranel, Daniel T.
Nervous systems distinguish between self- and other-generated movements by monitoring discrepancies between planned and performed actions. To do so, when motor systems transmit motor commands to muscles, they simultaneously transmit motor copies, or corollary discharges, to sensory areas. There, corollary discharge signals are compared to sensory feedback arising from movements (reafference), which can result in gating of expected feedback. Curiously, in infant rats, twitches—which are self-generated movements produced exclusively and abundantly during active sleep (AS)—differ from wake-movements in that they trigger robust neural activity. Accordingly, we hypothesized that the gating actions of corollary discharge that predict wake reafference are suspended during twitching. In this dissertation, we first demonstrate that twitches, but not wake movements, robustly activate sensorimotor cortex as they do other brain areas. Next, we demonstrate that wake movements can activate the sensorimotor cortex under conditions involving presumed discrepancies between corollary discharge and reafference signals. Lastly, we reveal a neural mechanism in the brainstem that inhibits reafference, but only during wakefulness; this inhibitory mechanism is suppressed during active sleep. All together, our findings provide the first demonstration of a state-dependent neural comparator of planned and performed actions, one that permits the transmission of sensory feedback from self-generated twitches to the developing nervous system.
It is easier for someone to tickle you than it is for you to tickle yourself. This is because tickling entails some level of surprise, and you can’t surprise yourself. Therefore, your brain must have a mechanism that suppresses the sensations arising from self-tickling. This type of suppression lies at the heart of our ability to distinguish between the sensations that arise from our self-produced movements from those that arise from other-produced movements. Interestingly, whereas self-generated movements produced during wake are accompanied by this type of suppression, self-generated movements produced during active sleep (i.e., twitches) are not. Twitches are a predominant behavior of early development and are exhibited by all mammals. Yet, despite their predominance, the neural mechanisms that permit twitches to bypass sensory suppression are unknown. In this dissertation, we show that twitches, but not wake movements, robustly activate the brain. Moreover, we describe one neural mechanism that leads to the selective inhibition of wake-related activity, and show that this mechanism is located early in the pathway of sensory processing. Taken together, the results presented here demonstrate that twitches, despite being self-generated, are processed by the brain as if they are not. This novel aspect of twitching supports the view that twitching, by robustly activating the infant’s sensorimotor system, contributes to its development.
corollary discharge, development, reafference, REM sleep, sensorimotor, twitch
viii, 81 pages
Includes bibliographical references (pages 75-81).
Copyright © 2016 Alexandre Tiriac
Tiriac, Alexandre. "State-dependent processing of reafference arising from self-generated movements in infant rats." PhD (Doctor of Philosophy) thesis, University of Iowa, 2016.