Do my eyes have anti-shake vision?

05 June 2011

Question

Hi Chris,

I recently bought a mini video camera for my bike trips to and from work. I noticed when i watch the video back that there can be considerable camera shake when i go over bumps, for example,  (I do believe some of the more expensive cameras have anti shake devices) and blurriness when changing direction quickly. In fact i can get a bit queezy looking at the video replay.

So how is it this doesn't happen with the images that are going into my head. I know that the eyes fixing on a given spot might help, but i suspect that my brain brain is doing some pretty sophistcated editing. What's going on; does my brain have anti shake, too? Why doesn't it use anti-shake when i wtch the video back? And might this be to do with the brain predicting images before they actually happen?

All the best, 

Lionel, Spain.

Answer

Chris - You can actually find the answer lurking in your inner ear on each side. It's in a system called your vestibular system and this is your organ of balance. What you have are three tiny semi-circular canals. These are actually smaller than a one penny piece each. They're a tiny canal, they contain fluid and they're orientated at 90 degrees to each other. So you have one which is a hoop going over your head towards the front, one which is at 90 degrees to that so it's going from one ear to the other, and then one like a dinner plate lying flat.

And these three together can detect the movement of the head in any direction and the rate of movement. They send signals via a nerve supply to the brain and they're connected to the nerves that control your eye movements. And so what they do, whenever you move your head in any direction, this movement is picked up by this vestibular system and it then makes your eyes move in completely the opposite direction at the same rate and amount to directly compensate for the movement of your head and this is called the vestibule-ocular reflex and it's the reason that you're going to hold a finger out in front of you, fix it up with your eyes and then shake your head backwards and forwards, and maintain a continuous gaze on your eye without everything looking shaky.

And if something goes wrong with that vestibular system, you do feel very giddy because you've lost your own built-in fuzzy logic.

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