The sixth sense: Your place in space

In addition to the familiar five senses—touch, sight, smell, hearing and taste—scientists know of a sixth sense called proprioception. It's the sense of your body being in space that allows you to touch your nose even with eyes closed.

LSI Research Assistant Professor Shawn Xu and his colleagues discovered that the "sixth sense" is present in the model organism C. elegans, a 1-millimeter nematode, and have been using worms to study proprioception, which also informs balance and how to put one foot in front of the other to walk without looking at your feet.

They also recently have discovered neurons that possibly regulate stretch receptors, which tell the body how to move. For patients with Parkinson's disease these stretch receptors are thought to be involved in the loss of movement control, so finding a neuron that can tweak these signals could be a step toward developing new Parkinson's treatments.

Xu focuses his research on a super family of critical, but poorly understood, calcium-permeable ion channels, the TRP channels. Using C. elegans he found a communication channel between neuron and muscle, TRP-4, which plays a role in movement. Xu's research shows that TRP-4 acts in a neuron called DVA that regulates how sensory-motor function is put together to produce movement. It controls locomotion, providing a unique mechanism whereby a single neuron can fine-tune motor activity.

"We are really studying neuronal signaling and the movement behavior," Xu says. "There are many channels and they are the same in worms and humans."

The paper "A C. elegans stretch receptor neuron revealed by a mechanosensitive TRP channel homologue," by Wu, Wei Li, Zhaoyang Feng, Paul Sternberg, was published in the journal Nature March 29.

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