Shufflebrain

by Paul Pietsch

  This is a dissection of a tiger salamander larve whose brain had been amputated forward of the medulla and replaced by the entire brain--including the medulla--of a smaller, marble salamander larva. The donor brain is the deep gray structure between the specimen's eyes; the host's medulla is the large whitish trough behind the donor medulla. The behavior of these animals was identical to that of the controls in all discernible respects.

  Even after the tiger-marble series of experiments, I still clung feebly to the hope of impugning hologramic theory by means of some ingenious anatomical transformation. I formulated this last-ditch working hypothesis: Assume, I said to myself, that the medulla is the seat of feeding programs. Suppose, furthermore, that the brain anterior to the medulla merely gives the animal consciousness and nothing else. Obviously an unconscious animal can't carry out an attack. Perhaps all a transplant did, then, was to awaken the creature and allow feeding programs in its medulla to come into play. Clearly, I needed another experiment. I had to eliminate feeding memories from the graft but at the same time revive the host. And so I turned to the frog.

  Now the adult leopard frog is a notorious carnivore. Yet as a young tadpole it is a vegetarian. When the tadpole bothers a tubifex at all, it is only to suck algae and fungi from the worm's wriggling flanks.

  I called the first member of this new series Punky. Punky the tadamander! He had the body of a salamander (Amblystoma punctatum), but the brain in front of his medulla had come into this world in the head of a Rana pipiens.

  ***

  The most obvious question about Punky was whether or not a frog's brain would even connect, anatomically, with a salamander's medulla. But this question had to wait. To answer it for certain, I would have to kill Punky. Meanwhile, it was only my hunch that his new brain would reinstate overt behavior. If he ever came around, I'd actually have to observe him--with my own eyes--eat a worm in order to vindicate my hypothesis.

  By seventeen days after surgery, Punky had fully regained his ability to stand and swim. Within a few days after that, he had become the liveliest animal in my colony. (Tadpoles are more active than salamanders.) He was blind, but his sonar and sense of touch were in splendid working order. When I dropped a pebble into his bowl, the "clink" would alert him and bring him swimming over immediately. And so would a newly presented tubifex worm.

  But the worm was completely safe. Punky would inspect the squirming crimson thread for perhaps a minute or two. Then he would execute a crisp about-face! and swim away. And this continued for the next 68 days, while I virtually camped at the edge of his dish. A conscious, alert and responsive little fellow he remained throughout. But not once during that time did Punky even hint at an attack, despite the fact that a fresh worm was always available for the taking. Worms were now objects of lively curiosity, not of furious assault. If feeding programs existed in Punky's medulla, their presence would have to be accepted on the strength of divine revelation, not experimental fact. My last-ditch hypothesis failed the pragmatic test of truth: it didn't work.

  I had performed an even dozen tadamander operations. None of the tadamanders fed, but eight must be discounted because, although they lived for months, they never regained consciousness. I also introduced a number of control operations into the study. In one control series, I evaluated variables of surgery by transplanting the same regions of the brain I had transplanted to produce the tadamander, but with salamanders as donors, instead of tadpoles. These animals regained typical salamander feeding behavior in less than three weeks. What about the possibility that tadpole tissue had some general inhibitory effect on salamander feeding? I controlled this by transplanting various tadpole tissues (brain or muscle or diced tadpole) to salamanders' tail fins or abdominal cavities. These salamanders exhibited no changes in feeding habits. But perhaps frog-brain tissue had an active inhibitory influence on salamander feeding behavior. To test this, I transplanted portions of tadpole brain in place of the salamander's cerebral hemispheres, leaving the rest of the host's brain intact. These animals ate the worms, right out of surgery. Because tadamanders would not eat spontaneously, I had to force-feed each one, which became a major undertaking. Twice a week, I lightly anesthetized each tadamander and inserted fresh salamander muscle into its stomach. Of course, I also had to control the feeding procedure. What if the meal satiated the animal or the anesthetic dulled its appetite? I anesthetized and force-fed normal animals, but neither the anesthetic nor the meal affected their appetites.

  The extra work had made Punky the tadamander's season a long one. And I might have terminated the experiment much sooner if I had not grown fond of him.

  One morning, I arrived in the lab to find all the active tadamanders except Punky displaying signs of something I had dreaded from the outset--transplant rejection! Fortunately, Punky was still healthy. But I doubted that he would last very long. And I could not risk losing the critical anatomical data inside his cranium.

  I stained alternate slides of Punky's tissues in two different ways. One procedure, a widely used all-purpose method known as hematoxylin and eosin, enabled me to judge the overall health of the tissue at the time of preservation. The other method, called Bodian's protargol stain, involved depositing silver salts on very fine nerve fibers, fibers that otherwise do not show up under the microscope. Bodian's stain is tricky. And the moment the technician handed me the slides, I selected one at random merely to check quality. But that very slide had the answer I sought. A cablework of delicate nerve fibers connected the tadpole brain to the salamander medulla. It is irrational, I confess, but I date my belief in hologramic theory from that first look at Punky's brain.

  Here is a low-power photomicrograph (40 X on the microscope) of Punky the Tadamander:

  ***

  Here is a picture of Punky's frog brain cells and, immediately below it, cells from his salamander medulla. To the trained eye, the two sets are as different from each other as a cow and a horse.

  More Punky, but this time the neural cablework passing between his frog brain and salamander medulla:

  The larger oval and round entities are various nuclei. Many of the smaller, grain-like bodies are known as lipofucsin granules; they are indications in general (including human brains) of the onset of degeneration and, I subsequently found, herald brain-graft rejection in this kind of preparation. Not only did Punky's slides tell me that his transplant had established neurological connections with the host parts; they also indicated that I preserved him just in the nick of time. He would have died in a day or so. In fact, if I'd waited just 24 hours more, the nerve fibers might have degenerated beyond microscopic identification.

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  Internet contact:pietsch@indiana.edu

  chapter six

  The Hologramic Deck

  IN FORMAL TERMS, Punky was just a control. Indeed, in a technical paper I eventually delivered on shufflebrain at the Anatomy Meetings, he became a nameless item in a table of data, a slide on a screen, and a dependent clause of passive-voice prose. But Punky had made my structuralist partisanship vulnerable to the overwhelming case my own data had produced in support of hologramic theory. He had humbled me, Punky had. My narrow notions no longer seemed appropriate to the situation. I think I had begun to appreciate for the first time what science might be but seldom is in our day: the privilege of seeing Nature's secrets unfold, rather than an exercise in who's right and who's wrong.

  Yet my ego was not anchored to hologramic theory. It was not my theory. I would remain aware of this fact at all times, as a hedge against new prejudice that might seep in and occupy the void left by removal of the old one. Yes, I believed hologramic theory, in my guts, but I believed it as I do the theory of evolution and the laws of thermodynamics: not as icon; not as an oath I couldn't disclaim if Nature should reveal something better.

  Before Punky, I'd sought only to refute hologramic theory. Afterward, I began to look at the theory as a whole. And the range of its implications set my im
agination on fire.

  I soon began to realize how lucky I was that the salamander's feeding behavior had obeyed Lashley's dictum so well. For hologramic theory must also take into account what multiple holograms exhibit. From our imaginary experiments in chapter 4, we learned that, by shading, we can keep some codes out of certain parts of the photographic plate; we also learned that we can construct a multiple hologramic system without having every code exist in every single part; but no a priori mandate in hologramic theory rules out the possibilities multiple and asymmetric distribution in any given brain. What might I be writing now, had feeding programs been confined, say, to the salamander's left cerebral hemisphere? Equipotentiality is something we can know only after the fact.

  What principles do account for the survival of feeding after shufflebrain? How can we explain the retention of the salamander's mental codes despite its scrambled neuroanatomy? There are two major explanations. The most obvious one is that various pieces of brain must have housed whole codes. Let's call this the wholeness principle. The second explanation, a much less obvious one, is that each piece of brain must have made its own independent contribution to the animal's behavior. We'll call this the independence principle. If codes had been partially represented in a piece of brain, or if pieces mutually depended on each other to construct meaningful sequences, I could never have swapped, flipped, rotated, deleted, reversed, or added parts of the brain--all parts!--without jumbling feeding behavior.

  The imaginary experiments we performed earlier with transparent sheets illustrate the wholeness principle rather well. It is not difficult to appreciate that if feeding codes had been spread out like ANATOMY, my operations would have had a different meaning.

  The independence principle seemed much more subtle and warranted further investigation. Besides, the independence principle predicted that I should be able to transplant new thoughts into a brain. The new codes ought become integral parts of the host's mental mix and add new features to the animal's behavior.

  Punky's behavior certainly suggested the independence principle, but only indirectly. Demonstrating it required two active minds. Punky only had his donor's. But, critical to future experimentation, he did show that a salamander's behavior can display totally foreign phase codes.

  ***

  Before I describe the actual experiments, let's look at the independence principle by way of another imaginary experiment. This time, instead of transparent sheets let's imagine a deck of cards. Let's begin with a conventional nonhologramic message, using a single card as a set for storing one letter. The meaning of our message--let's use DOG--depends on the relationship between our cards: where each lies in relationship to the others when the deck is at rest, or when a card turns up during the deal. If we shuffle the deck, we obviously run the risk of scrambling the meaning of our message. DOG might become GOD, for instance. Just as with our message, ANATOMY, on the transparent sheets, the message in our conventional deck is made up of inter-dependent elements.

  The hologramic deck of cards is far different. Here each card contains a whole message. And if the same message is on each card, just as the same feeding message is in each part of the salamander brain, then shuffling will not alter the deal.

  But each card is an independent carrier of our hologramic code. What's to stop us from slipping in cards with new codes? Certainly not the codes per se. Cards are independent. Therefore, old and new codes can coexist in the same deck without distorting each other's meanings. And nothing in the information itself would prevent us from constructing a compound hologramic deck, or mind, if hologramic theory really does work. The big "if" is the readout: What happens in reconstruction? Which independent codes activate and drive an animal's behavior?

  ***

  In the bleak Michigan January of 1969, in anticipation of tests of the independence principle, I began a series of preliminary experiments to find out how well a salamander larva would tolerate the brains of guppies. I had not yet begun worrying about the behavioral side of the study--which fishy traits to look for in the hosts, in other words. My major concern was tissue rejection. How long would I have postoperatively before the salamander's immunological defenders ruined my experiments?

  Under the dissection microscope, a person can actually see through the transparent tissue of the larva's dorsal fin. I decided, therefore, to place the heart of a guppy into a tunnel in the gelatinous connective tissue of the fin. The guppy's heart would continue beating for a while I was pretty sure, and I could take its pulse, visually, until rejection caused it to stop. While I was at it, and for control purposes, I also transplanted guppy flank muscle or liver to other salamanders' fins or abdominal cavities. And during one operating session, I decided to see what would happen if I actually replaced a salamander's cerebrum with that of a guppy. I called the animal in this experiment Buster.

  As I said, my attention focused on the operative side of the upcoming study. I had not yet done any really hard thinking about behavior. And what Buster was about to show me was the result not of my scientific prowess but of a series of lucky accidents.

  In those days, I had a light-tight inner sanctum specially built within my main laboratory. Equipped with a heavy-duty air conditioner, double doors and insulated walls, it could serve as a temperature-regulated darkroom (where I sometimes coated radioactive slides with photographic emulsions). I designed the inner sanctum to provide a cool environment, 15-16 degrees centigrade, so as to approximate the temperature of the woods at the time the species of salamanders I usually work with are young feeding larvae. This procedure seems to prevent premature metamorphosis. In addition, cool temperatures retard the growth of a troublesome fungus; and the inner sanctum turned out to be an excellent post-operative recovery room. As the animals grow a little older, they seem to tolerate higher temperatures more readily. At any rate, I always maintained my stock animals in the inner sanctum. I conducted my operations there, and it was where my stereoscopic dissecting microscope was located. The inner sanctum was too small to accommodate all my animals, and I had gotten into the practice of keeping most experimental subjects out in the main lab, where the temperature was 20-21 degrees centigrade. Because the dissecting microscope was in the small room, I took animals there if I had to inspect them under magnification. This was necessary in order to monitor pulse of transplanted guppy hearts. The temperature changes had not affected the outcome of my experiments. But as a precaution, I brought all animals of a group--controls and experimentals--into the cool room together, whether or not they had to be examined. I also made it a practice to feed the animals immediately after my daily inspection of a group, before returning them to the main lab.

  Since Buster was a member of a guppy-heart group, he went into the cool room daily. He had taken surgery well, had righted himself on the following day (usual with injury confined to the cerebrum, which his was), and had fed normally from the moment he could walk. One afternoon, three weeks after Buster's operation, I had just finished taking pulses and was rinsing off some juicy-looking tubifex worms in a jet of spring water when I was startled by the building fire alarm. Now the decibel level of that siren left only two choices: go mad or immediately cover your ears with both hands and flee outdoors! I put down the tubifex and fled.

  When the drill was over, it was almost quitting time. The siren had interrupted my ritual, and I had completely forgotten Buster and company, unfed in the cool inner sanctum. As a matter of fact, it was not until the following day, when I took out my liverwurst sandwich, that I remembered my hungry little pals on the other side of the bulkhead opposite my desk. I stuffed the sandwich back into the bag and went in to make amends.

  As I was stacking the salamander dishes on the tray for transfer back into the main lab, I noticed that Buster had not taken his worm. This was impossible! My first thoughts were profanities against the bureaucrat who'd mashed the fire-alarm siren button. Maybe the noise had affected my animals! All the other animals had already devoured th
eir worms. I checked the stock animals, and their appetites were fine, too. But Buster wasn't taking. Yet he was frisky enough and looked very healthy.

  Now I had a suspicion. I ran into the main lab, filled two beakers with spring water from a carboy, and transferred six feisty-looking stock guppies into each beaker. One group I set beside the fish tank to fast overnight, at 20 degrees centigrade. The second group I chilled to 15 degrees centigrade by swirling the exterior of the beaker in cracked ice. When the thermometer hit the fifteen-degree mark, I transferred these guppies into the cool room and set them down next to Buster.

  I allowed the guppies to acclimate for about an hour, using this time to check the feeding responses of the stock salamanders and the recipients of guppy hearts and then to wolf down my stale lunch. Finally it was time to check the chilled guppies.

  I placed each guppy in a dish by itself. Then I dropped in a worm for each. The fish swam over at once (they're much quicker than salamanders) and inspected the worm. But, like Buster, the fish would not attack.

  ***

  There was nothing unusual about a tropical fish refusing to eat live meat at cool temperatures. Their digestive enzymes become inefficient in the cold. Had my guppies' ancestors back in Trinidad ignored sudden drops in temperature and gone on eating worms they couldn't digest, the species would have vanished via natural selection, eons before my experiments with Buster's brains. The salamander, on the other hand, in a cool pond in early spring or late fall, can't afford to pass up a meal. General considerations notwithstanding, I held off on any conclusions, because I did not know the particulars--the details necessary to make this story ring crystal true. I decided to leave Buster and the guppies in the cool environment overnight. And I placed one fresh worm in each dish.