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Desert Diary
Biology/The Eyes Have It


We're slowly realizing that the universe we perceive is quite different from the real thing. Light frequencies are turned into nerve impulses which our brain interprets as light and color. Pulses of greater and lesser density of air—sound waves—are turned into nerve impulses that our brain interprets as sound; yet other nerve impulses are felt as pain.

Some of us have been subjected to this knowledge often enough that we tend to think that all of stimuli processing occurs within the brain. However, this is not entirely true. The eye, for example, does a considerable amount of manipulation before the nerve impulses are sent to the brain. Thus the frog's eye is hypersensitive to such moving objects as flies, resulting in a barrage of nerve impulses to the brain, while the immobile is pretty much ignored. And ourselves? Look to where our mountains meet the sky; a nice, crisp demarcation between the two—thanks to our eye construction that emphasizes borders. The brain really doesn't have to have a formal vote on things like this—after all, the eyes clearly have it.
pen and ink

Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.

Franklin Mts. from the east.

The Franklin Mountains from the east. Where mountain meets sky is emphasized by mechanisms of the eye. Photograph by A.H. Harris.