Eyes on the Brain

A neurobiologist explores the amazing capacity of the brain to rewire itself at any age

Seeing and Knowing

Can we see what we don't understand?


A few weeks ago, I took the students in my introductory biology class on a field trip around the Mount Holyoke campus. As we approached the lake, I stopped and asked the students if they saw any new plants. "Do you mean those flowers?" one student asked pointing to a stand of late-blooming asters. When I shook my head no, another student pointed to some ferns.

"Not those either," I said. "Keep looking." Several of the students moved down to the very edge of the water but found nothing out of the ordinary. Finally, after some hints from me, one students asked,

"Do you mean those green stems over there?"

Those green stems were horsetails, and that's what I wanted the students to see. I explained to them that horsetails were an ancient kind of non-flowering plant that dominated the forests 500 million years ago. As we continued our walk, students kept pointing out the horsetails. Earlier, these plants had been invisible, but now they kept popping into focus.

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This week, my students will spend their time looking through the microscope at plant leaves. Leaves may be thin but they have an ordered three-dimensional structure. From past years, I know what will happen. I'll have the students peel off the outer covering of a leaf and then look at their sample under the microscope. When I ask them what they see, they will say something like "I see a lot of green." Nothing will make sense to them. Then we will examine plastic, three dimensional models of leaves as well as prepared slides where the different internal leaf structures are stained different colors. When the students return to their original leaf sample, it will no longer look like a sea of green. They will be able to see the whole intricate arrangement - the way the outer cells fit together like a jigsaw puzzle, the arrangement of the inner cells, and the internal air spaces and surface pores that allow for exchange of carbon dioxide and oxygen. As the lab period draws to a close, the students will be satisfied but tired, and I will be thrilled. Oh - most of the students will forget the details of leaf structure in a few months time. What excites me is how, in a matter of hours, they can see so much than a jumble of green. The information coming from their eyes does not change, but they will be able to recognize and assign meaning to what they see. As I ponder horsetails and leaf structure, I wonder if any of us can see things we cannot interpret and understand.

Susan R. Barry, Ph.D., is a professor of neurobiology in the Department of Biological Sciences at Mount Holyoke College and the author of Fixing My Gaze (June, 2009).

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