0193 Moving While Sleeping: On the Paradoxical Co-occurrence of Muscle Atonia and Twitching

Abstract

Abstract Introduction During active (or REM) sleep, discreet, jerky movements called myoclonic twitches occur against a background of muscle atonia. The neural mechanisms that allow these two seemingly contradictory phenomena to co-occur remain unclear. One view holds that twitches are produced when a large descending motor signal overpowers the inhibition on spinal motor neurons. An alternative view is that atonia and twitching are coordinated by the same brainstem structures that produce and regulate active sleep. One such structure is the sublaterodorsal tegmental nucleus (SLD), which plays a key role in adult rats to the production of atonia, but whose contribution to twitching has not been examined. Here, we investigated the relationship of SLD neurons to atonia and twitching during a period in early development when twitching is abundant. Methods We recorded extracellular neural activity from the SLD in 8 12-day-old (P12) head-fixed rats as they cycled freely between sleep and wake. To assess the relationship between twitches and neural activity, we also recorded limb movements using high-speed video. Results Consistent with the adult literature, the majority of SLD neurons (35/56) were significantly more active during periods of sleep-related atonia. Interestingly, a subgroup of neurons (n=15) was inhibited at the onset of a burst of twitches, whereas another subgroup of neurons (n=26) was excited around the onset of a burst of twitches. Thus, together, the activity of 41 of 56 SLD neurons was modulated by twitches. Conclusion These results demonstrate that the activity of SLD neurons is associated with both atonia and twitching. This finding suggests that these two early-developing components of active sleep are coordinated within the brainstem. These initial findings open new avenues for further research into the neural mechanisms that coordinate the co-occurrence of twitching and atonia during active sleep. Support (If Any) This research was supported by R37-HD081168 awarded to M.S.B.