When most people think of a sixth sense they think of supernatural abilities of the mind. The real sixth sense is proprioception, which is not the ability to see dead people, but rather the ability to have a special awareness of the body without the use of sight. A new study published in The New England Journal of Medicine in October of 2016 could explain how some people are naturally more coordinated than others and a certain gene may play a key role. The gene was
identified when two patients who lacked proprioception had their genomes sequenced; a catastrophic mutation in PIEZO2 was found in both. PIEZO2 has been shown to contribute to the ability to perform coordinated movements and to sense physical touch.This novel finding could give insight into how people are able to combine many modes of input into two of our main senses: touch and proprioception.
Previous inquiry into the PIEZO2 gene showed that if the gene was absent in mice it would always cause death. It was thought that this would also be the case in humans, but the two patients observed in the study compensated for loss of gene function by using other sensory modes of input. The patients not only lost their sense of proprioception, but also exhibited skeletal issues with their hips, fingers, and feet bending at unusual angles. In addition,they had scoliosis, a condition marked by an unnatural curvature of the spine. A series of tests were performed on the patients to see just what sensory inputs were affected by loss of PIEZO2. In these tests, patients were blindfolded and asked to do simple tasks like walking and indicating whether or not they could feel the up and down motion of their joints. Proprioception ensures that proper movement occurs when a person cannot see where their body is. Since the patients lost PIEZO2 function, they stumbled and fell as they walked, and were clueless as to whether
their limbs were moving up or down. When the blindfolds were removed they could use their sight to compensate. It remains to be seen what role PIEZO2 has in the patients’ skeletal deformities. One thought is that proprioception might be necessary for the body to hold its joints in proper orientations for skeletal development.
This new insight is a big step in understanding how proprioception works, and provides a baseline for further research. The research highlights how the body can even make up for catastrophic loss of one mode of input with other modes of input. PIEZO2 might even give insight into factors that determine how athletic or clumsy an individual is.