Entry

Il s'agit de prouver que les phénomènes du développement n existent pas seulement dans l'état embryonnaire, mais qu'ils se poursuivent dans l'état adulte.

CLAUDE BERNARD

The beauty of fieldwork is its unpredictability. What one will discover, if anything at all, cannot be known in advance. The challenge is to submit to the outside, to become part of a foreign milieu, to drown in it — and to stay alert to the unforeseen story that is gradually emerging.

The unforeseen story that has been emerging in the course of my fieldwork among Parisian neurobiologists, that intrigued me and involved me and carried me away in unexpected directions, was the story of what I came to call plastic reason — the story of the sometimes intensely contested effort by people such as Brigitte Lesaffre and Alain Prochiantz to prove that was a "silent embryogenesis" keeps the adult human brain plastic. In this introduction I trace how I became a part of this story, this effort, and to provide a first sketch of what is at stake in it.

UNFORESEEN

I had never planned to do work on the brain, let alone its retained embryogenetic plasticity. When I arrived in Paris in early 2002, I wanted to study French biology. To be more precise, I had prepared to inquire into the belated emergence of French — as compared to American or British — biotechnology. Why was there this delay in France? I had wondered whether it had something to do with the late and controversial French institutionalization of molecular cell biology. Could it be that the belated emergence of biotechnology was a reflection of the predominance, in France, of a different, a nonmolecular biology? Different not just in its conception of the living but also in its practice?

In addition, I hoped to explore the relationship between two things often said to have no relationship at all: life and science. "Science," Max Weber famously quoted Tolstoy in the early twentieth century, "is meaningless because it gives no answer to our question, the only question important for us: What shall we do? How shall we live?" What, I wondered, is the relationship between life and science a century later? How is life lived where life itself, in the form of biotechnology, has become the object of scientific knowledge and intervention? How do organisms living their life relate to new knowledge about living organisms?

Once I arrived in France, however, things developed in unforeseen ways. Gaining access to biotechnology centers turned out to be arduous and slow. Weeks passed, and I made little progress in securing a site for my research. But while my frustration with biotechnology labs grew, an unexpected opportunity opened up. I was offered the chance to work in the laboratory of Alain Prochiantz, located at the École Normale Supérieure (ENS) and concerned with the evolution and development of the nervous system.

In conversations with Alain, I learned that he had a plan. "Until September," he explained, "you will work in the lab and learn how to practice at the bench. From October onward, you will then participate in a DEA, a yearlong program in neuropharmacology, and conduct your own research under my supervision." I could thus gain a practical and conceptual understanding of neurobiology, he went on, and that would allow me, perhaps, to do better anthropological research. Was I interested?

I was overwhelmed by this unexpected opportunity — and felt ambivalent about it. Not only was I unsure if I actually wanted to learn how to dissect and experiment on brains, but more important, my visits to the lab made clear that the work of Prochiantz's group did not speak to the curiosity I had so carefully fostered. I wanted to learn about biology, about biotechnology, and about life and science in France. What would I do in a developmental neurobiology lab? I had never read any article, let alone any book, about the brain. I knew nothing about neuroscience.

If, despite my severe concerns, I soon began working in Alain's lab, it was because I quickly became enamored of the intensity that radiated from it — by the movement that seemed to grip everyone who came near it. I could not make sense of this movement, of this intensity, but it intrigued and engaged me, and it carried me further and further away from the questions I had set out to study.

I began, if still hesitantly, to do fieldwork in neurobiology.

AN UNLIKELY STORY

The lab was located on the seventh floor of the nine-story Science Building of the ENS, in the Rue d'Ulm, in the Fifth Arrondissement of Paris. I began working in the lab in March 2002, and my first few months were dominated by practice. I learned how to dissect brains; how to distinguish shapes of neurons taken from diverse brain parts; how to grow neurons in cultures and how to feed them, infect them, and crash them with a centrifuge. In parallel, I began to make sense of the movement that had attracted me to the lab in the first place. Gradually, I could reconstruct the following, somewhat unlikely story.

In the late 1980s, Alain began experimenting with homeotic genes. At that time homeotic genes — and the proteins they code for, homeoproteins — were known to coordinate the formation of the basic body structure in animal development. Alain's idée fixe was that homeoproteins, transcription factors that regulate which part of DNA is activated and when, might also be involved in the cellular formation of the central nervous system. Perhaps homeoproteins determine whether a cell becomes part of the gut or of the brain? Perhaps they even coordinate whether a cell becomes a hippocampal, rather than, say, a striatal, neuron?

In experiments Alain Prochiantz conducted with Alain Joliot, a graduate student who had become a senior researcher in his unit by the time of my fieldwork, he made three observations: that homeoproteins, at least in vitro, appear to slide between cells; that this sliding seems to cause a powerful morphogenetic outgrowth even in already differentiated neurons; and that homeoproteins are found not only in the embryonic but also in the adult human brain.

To Prochiantz and Joliot these observations were exhilarating. Quickly they went public and informed their peers that they might have identified a not yet known developmental mechanism — the cell-to-cell migration of homeoproteins — that is active not just in the developing but also in the adult brain, where it appeared to engender embryogenetic-like processes.

Perhaps, they speculated, drunk by the possibilities opened up by their experiment, the adult human brain is the locus of a "silent embryogenesis."

To their colleagues, both suggestions were absurd. First, at the time, it was held that cells are strictly autonomous, that each cell acts according...