Population calcium imaging of spontaneous respiratory and novel motor activity in the facial nucleus and ventral brainstem in newborn mice

The human brain is by far the most complex organ inside the human body. Despite all that is currently known, the inner workings of the brain are still unclear and new mysteries are discovered all the time. One example of this is motor activity. It is widely known that groups of neurons located largely in the brain stem work together to produce certain movements in the body. Within these groups is a particular subset known as the facial nuclei, responsible for muscular movement in the face. The facial nucleus is known to be active in many orofacial and auricular behaviors. Additionally, it is a part of the motor program that maintains upper airway patency during breathing, swallowing and chewing. However, the role of neurons and the facial nucleus is not the real mystery; instead, what is being slowly unraveled within the academic community is the role of premotor neurons and different motor subnuclei in brain function. Little is known about this particular field and there is an overall lack of research focused on determining to what extent subnuclei are involved in processes such as breathing.

Understanding this process was the main goal of the study conducted by Persson and Rekling from the Copenhagen University – Panum Institute. By using nerve recordings, whole-cell patch clamps, and calcium (Ca2⁺) imaging, these researchers were able to test the spontaneous spatiotemporal activity patterns in the upper brainstem. To obtain these measurements, state-of-the-art testing materials such as Fluo-8 AM were used. This fluorescent calcium indicator is such a widely used tool largely because of its reliability and intensity. By being at least two, and in some cases four, times brighter than previous indicators, researchers are able to clearly and accurately track calcium flux, which leads to more definitive results and reliable claims.

Ultimately, this study found that the dorsal and lateral facial subnuclei show particularly strong respiratory activity and that there is a novel bilateral activity pattern in the ventromedial brainstem, which included strong activity in the medial facial subnucleus and motor output on facial and cervical nerves. These results are significant because they show that there is yet another motor behavior controlled by ventrally-located brainstem circuits. However, the implications of this study go further since the results obtained help to shed further light on the inner workings of the brain as it relates to certain behaviors such as motor activity. Understanding the complex and layered relationships amongst neurons is essential for understanding brain function and for further therapeutic research. The robustness of Fluo-8 AM readings provide the researcher with a key advantage at the hour of obtaining readings. Since it is not temperature dependent and can be easily loaded, there is a high level of confidence that the sample will not be tampered with and that the readings given are accurate. Having this kind of confidence in results is what allows researchers to solve mysteries and then focus themselves on understanding more complex puzzles related to how the human body works.

References

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1. Persson, Karin, and Jens C. Rekling. "Population calcium imaging of spontaneous respiratory and novel motor activity in the facial nucleus and ventral brainstem in newborn mice." The Journal of physiology 589.10 (2011): 2543-2558.