The effects of head restraint on the sleep architecture of mice

  • Ali Mahboba

Student thesis: Master's Thesis

Abstract

The mouse is a commonly used species for systems neuroscience studies. Particularly, a head restraint has been recently applied by many researchers to allow the use of advanced technologies, such as in vivo electrophysiology, imaging and optogenetics. However, little is known about the effects of head restraint on sleep in the mouse. To address this issue, we compared the sleep architecture between freely behaving mice and mice in head restrained conditions. We surgically implanted cortical electrodes for cortical electroencaphalograms (EEG's) and twisted wire electrodes into the neck muscle of C57BL/6 mice for electromyograms (EMGs). Mice were either restrained or allowed to move freely during recordings. Restrained mice were placed in an open ended cylindrical tube with their heads fully secured and unable to move while freely moving mice were placed in a tethered condition. Recordings lasted for up to five hours and the data from each recording was then analyzed offline on MATLAB. Analysis included determining which state of vigilance the mice were in by scoring individual epochs (each epoch represented a 4s period of the recording) to identify and compare any differences in the properties (duration, frequency, number of episodes and number of transitions between sleep states) of non-rapid eye movement (NREM) and REM sleep between freely moving and restrained mice. We found that restraint had an impact on all stages of sleep. The most apparent effect was the fragmentation of NREM sleep which resulted in a marked increase in the number of NREM episodes in restrained mice. The duration of REM episodes was also significantly reduced in restrained mice. In addition, at least in the current data set we did not observe re-entry of REM sleep in the head restrained mice following REM sleep. In contrast, freely moving mice displayed a more natural cyclic pattern of sleep and were able to re-enter NREM from REM. To further characterize REM sleep, we aimed to monitor pontine (P) waves. Although a bipolar electrode was also implanted into the brainstem to monitor P waves, we were unable to detect P waves throughout the study possibly due to the mislocation of the electrode. This study highlights the importance of the experimental conditions needed to study sleep in mice.The mouse is a commonly used species for systems neuroscience studies. Particularly, a head restraint has been recently applied by many researchers to allow the use of advanced technologies, such as in vivo electrophysiology, imaging and optogenetics. However, little is known about the effects of head restraint on sleep in the mouse. To address this issue, we compared the sleep architecture between freely behaving mice and mice in head restrained conditions. We surgically implanted cortical electrodes for cortical electroencaphalograms (EEG's) and twisted wire electrodes into the neck muscle of C57BL/6 mice for electromyograms (EMGs). Mice were either restrained or allowed to move freely during recordings. Restrained mice were placed in an open ended cylindrical tube with their heads fully secured and unable to move while freely moving mice were placed in a tethered condition. Recordings lasted for up to five hours and the data from each recording was then analyzed offline on MATLAB. Analysis included determining which state of vigilance the mice were in by scoring individual epochs (each epoch represented a 4s period of the recording) to identify and compare any differences in the properties (duration, frequency, number of episodes and number of transitions between sleep states) of non-rapid eye movement (NREM) and REM sleep between freely moving and restrained mice. We found that restraint had an impact on all stages of sleep. The most apparent effect was the fragmentation of NREM sleep which resulted
Date of Award26 May 2017
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorShuzo Sakata (Supervisor) & Christian Wozny (Supervisor)

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