Introduction

People with anxiety and post-traumatic stress disorder commonly have sleep disturbances. This is a problem as it has been shown that people who get poor sleep can have a risk factor in the development for the demark fearful and traumatic memories (Spoormaker, 2008). Healthy sleep helps in the formation of extinction memories. However, people with anxiety and post-traumatic stress disorder have their fear extinction impaired because of poor sleep (Fritz et al., 2021). This is where the 129S1/SVLMJ or S1 mouse strain comes into play. The goal of this paper was to investigate if this specific type of mouse strain had shown altered sleep at a reference line which could make them susceptible towards maladaptive fear processing compared to a common mouse strain C57BL/6 or BL6. In order to do this, they do a surgical procedure to have electrodes and EEG electrodes around the brain (Fritz et al., 2021). Then using a program called MATLAB they analyzed sleep spinal detection, non-rapid eye movement sleep and rapid eye movement, sleep period and awake states. Their primary findings was that S1 had sleep patterns of hyper insomnia during the dark period. During the time that they were awake they had a tough time not falling asleep (Fritz et al., 2021). Whereas with the light the S1 mice had shown that they had increased latency when entering sleep and an increased percentage of waking up during rapid eye movement sleep. For the future this specific type of strain in mice could be used for investigating sleep biomarkers in anxiety and post-traumatic stress disorders (Fritz et al., 2021). As well as finding more treatment strategies for people who have sleep disturbances because of anxiety and PTSD. 

For anxiety and PTSD there is a risk in development when experiencing poor sleep because it can interfere with the emotional memory processing (Spoormaker, 2008). Fear extinction is a decline in condition fear responses following exposure to a feared condition stimulus (Meyers, 2006). It is an important mechanism that unlearns these fear responses (Fritz et al., 2021). This is impaired usually with people that have anxiety or trauma related disorders as they have problems with sleeping (Fritz et al., 2021). Sleep is crucial to emotional coping. Having healthy sleep patterns helps the amygdala activation linked to the expression of fear learning during a delayed extinction (Phelps, 2004). People who have anxiety related disorders have a very common complaint where they have disrupted sleep (Baglioni, 2016). There has been studies done that show people who do have these types of disorders have shown a cycle of hyper insomnia and insomnia. These two cycles makes it harder for an individual to have a better emotional coping mechanism to deal with their anxiety or PTSD (Koffle, 2019). 

Methods

In order to test the hypothesis, they did a surgical procedure in the frontal lobe to put four epidural electrodes inserted and two electroencephalography electrodes, EEG. An EEG is used to record electrical activity on the scalp (Šušmáková, 2004). In order to record sleep spinal detection, awake periods, sleep periods, non-rapid eye movement sleep, and rapid eye movement sleep. Recording session lasted 23 hours where light hours lasted 12 hours and during dark hours lasted 11 hours (Fritz et al., 2021). However, for the actual room with the mice the lights would automatically turn on at 10 a.m. and would stay on for 12 hours and then turn off for 12 hours. There were approximately 15 mice tested, seven of the BL6 mice and eight of the S1 mice (Fritz et al., 2021).

Results

Their results had found that in the S1 mouse strain they had found increased amount of spindles during the dark period and reduced spindle density during the light period. As well as S1 mice had shown patterns of both hypersomnia and insomnia (Fritz et al., 2021). During the dark period they had sessions where they were awake and found difficulty to go to sleep (Fritz et al., 2021). In the light dark cycle, the S1 mice had showed increased periods where they're asleep and difficulty trying to stay awake during the daytime (Fritz et al., 2021). During the dark period they are shown that they had a higher percentage of waking up during rapid eye-movement sleep compared to the BL6 mice. These correlate with humans who have anxiety or posttraumatic stress disorder as in some patients they have cycles of hyper insomnia and insomnia. While during hyper insomnia there have been reports of being sleepy during the daytime and anxiety of having to do stuff during the day (Capaldi, 2011). Then for insomnia a lot of humans had reported that they had a hard time falling asleep (Ohayon, 2000). As well as for people with PTSD they would have increased awakenings during the rapid eye movement sleep because of nightmares (Kabayashi, 2007). Although S1 mice are not able to determine if waking up during rapid eye-movement sleep could represent nightmare. In the S1 mouse strain they had found increased number of spindles during the dark period and reduce spindle density during the light period (Fritz et al., 2021).

Discussion

The significance of the sleep and wake behaviors of the S1 mouse model shows similarities between sleep disturbances in anxiety and PTSD patients (Fritz et al., 2021). Using this information, the strain of mice can be used to better understand why people with anxiety and trauma related disorders have these types of cycles with poor sleep quality. As well as can help find treatment strategies for people who do have these types of sleep patterns. There is a lot of potential with this particular strain of mice now that there is a clear similarity in sleep patterns with people who have anxiety and PTSD.

[+] References

[+] Other Work By Olivia Molano