I used to get the willies when I caught sight of myself in a full-length mirror. I could identify my left arm and leg as parts of me, but my right limbs seemed somehow disconnected. I could not move them as easily as I could move my left arm and leg.

I would turn my eyes away when I passed plate glass windows, too.

But you would see a normal foot. And you would be right. My foot is a part of me. I can walk. I can dance. My foot is there. I just don’t always own it.

That’s right, I don’t always own my foot. It’s because I’m a Chiarian, a person whose cerebellum has slipped down into the spinal column a little bit.

If you pack an extra scoop into an ice cream cone, you’ll get the idea. The bottom scoop oozes into the tip of the cone. The slippage doesn’t affect the ice-cream. For the cerebellum, however, it’s another matter.

Our cerebellums keep track of every part of us, thanks to special body sensors called proprioceptors. They get their name from the Latin word for ownership: proprius. If you appropriate something, you make it your own. If you have full proprioception, you can make your body your own.

These receptors report the tension in every tendon, the angle of every joint, the flexing of every muscle. These receptors report the pressure on our spinal columns, our ankles and the soles of our feet when we stand. And these proprioceptors can detect a single hair moving.

Infants pick up the difference between “me” and “not me” very early. It’s “me” if I can see it and touch it and sense it from inside. It’s “not me” if I can only see it and touch it and taste it and smell it. It’s “not me” if I can’t sense it from inside.

We say that mature people are in “full possession” of themselves.

My Chiarian cerebellum can’t pick up messages from certain parts of my body, especially from my right foot. My eyes tell me that it’s there. My fingers tell me that it’s there. But my proprioceptors don’t confirm what my other senses tell me. That’s why I used to get the willies when I stood in front of a full-length mirror.

But I regain possession of my foot when I go dancing.

Why? As I move, the volume from my proprioceptors pumps up. More signals reach my cerebellum.

As I move in ways that I’ve practiced hundreds of times, my brain stem and spinal column take over from my cerebellum so it doesn’t have to work so hard.