The Sixth Sense: Proprioception in Elderly Adults

 

Perception of the world around us is modulated by the five senses: taste, touch, smell, hearing, and vision. But being able to perceive the world is not the only thing we need to operate within it; we also must be able to perceive ourselves, our bodies, in relation to everything else. This is called proprioception, and it sometimes referred to as the sixth sense (Jahn & Krewer, 2020). Proprioception, also known as kinesthesia, is the body’s awareness of where its different parts are without looking. It also allows us to know what kinds of forces are acting on our body parts. Things like the ability to hold something with the proper force, know that your elbow is bent at a certain angle, or know that your hand is raised above your head even with your eyes closed are functions of proprioception.

                In the study, “Effects of Noise Electrical Stimulation on Proprioception, Force Control, and Corticomuscular Functional Connectivity,” Vincent Chen and colleagues assessed the impact of subthreshold electrical stimulation on proprioception and force control tasks. Subsensory level noise stimulation is stimulation, which is not detected by the brain. It does, however, enhance the sensitivity of which ever extremity it is applied to. In this study, researchers applied the noise stimulation, in the form of vibrations and electrical stimulation, to the participants’ forearms during two experiments. All participants were healthy young adults. The first experiment was testing the “immediate effects of the noise stimulation of force and joint angle proprioceptive senses” while the second experiment tested the “effects of 30-minute continuous noise stimulation on grip force control and corticomuscular connectivity” (Chou et al., 2023). They found that with optimal intensity of the noise stimulation, participants made significantly fewer force errors and joint position errors, which suggests that electrical noise stimulation improves proprioceptive senses.

                Studies have shown disorders of proprioception can be developmental, happening early in childhood and continuing into adolescence, or they can be due to a traumatic injury. Proprioception can also decline with age. The loss of proprioceptive senses with age is associated with impaired balance and higher probability of falls. “Improved proprioceptive function by application of subsensory electrical noise: Effects of aging and task-demand” is a similar study to the one previously mentioned. However, this study compared older adults to younger adults and applied the noise stimulation to the legs while participants performed a detection task. Participants had their foot on a platform which moved to change the angle of their ankle. They were told to press a button when they detected a change in their ankle’s angle, they did this with and without the noise stimulation. Then, they repeated this while the participants had their eyes closed and again with the room moving. These experimental conditions allowed for isolated testing of proprioception as it impair the other senses. They found that participants performed better on the tasks during the noise stimulation condition and that the older adults tended to benefit more than the young adults (Toledo et al., 2017).

                While these two experiments focused on different extremities, their results both suggest a potential treatment for proprioceptive sense disorders. Not just a treatment, but a minimally invasive treatment, a device which could be worn during tasks involving proprioception and apply noise stimulation. This could potentially help elderly people gain independence and a better quality of life. Moreover, this could be used in hospitals for fall risk patients and assisted living communities which would greatly benefit patients and staff alike.

References:

Chou, L.-W., Hou, S.-L., Lee, H.-M., Fregni, F., Yen, A., Chen, V., Wei, S.-H., & Kao, C.-L. (2023). Effects of Noise Electrical Stimulation on Proprioception, Force Control, and Corticomuscular Functional Connectivity. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 31, 2518–2524. https://doi.org/10.1109/TNSRE.2023.3277752

Jahn, K., & Krewer, C. (2020). [Proprioception—The Sixth Sense And Its Disorders]. Deutsche Medizinische Wochenschrift (1946), 145(25), 1855–1860. https://doi.org/10.1055/a-1220-4840

Toledo, D. R., Barela, J. A., & Kohn, A. F. (2017). Improved proprioceptive function by application of subsensory electrical noise: Effects of aging and task-demand. Neuroscience, 358, 103–114. https://doi.org/10.1016/j.neuroscience.2017.06.045