The scientists found that even though the two sets of images were presented to the eye almost on top of each other, they were processed by different places in the brain: the face images by a particular region on the surface of the temporal lobe that is known to specialize in face recognition, and the house images by a neighboring but separate group of neurons specializing in place recognition.

  Most importantly, Desimone and Baldauf found that the neurons in the two regions behaved differently. When the subjects were told to concentrate on the faces but to disregard the houses, the neurons in the face location fired in synchrony, like a group of people singing in unison, while the neurons in the house location fired like a group of people singing out of synch, each beginning at a random part of the song. And when the subjects concentrated on houses and disregarded the faces, the reverse happened. Furthermore, another part of the brain called the inferior frontal junction, a marble-sized region in the frontal lobe, seemed to orchestrate the chorus of the synchronized neurons, since it fired slightly ahead of them. Evidently, what we perceive as “paying attention” to something originates, at the cellular level, in the synchronized firing of a group of neurons, whose rhythmic electrical activity rises above the background chatter of the vast neuronal crowd. Or, as Desimone once put it, “This synchronized chanting allows the relevant information to be ‘heard’ more efficiently by other brain regions.”

  A connection between attention and neuronal synchrony was first hypothesized by Ernst Niebur and Christof Koch twenty years ago. Desimone was one of the first scientists to prove it for particular cases, in 2001. A pioneer in the field, he is quick to mention other leaders, such as John Reynolds of the Salk Institute, who uses a combination of physics, neurophysiology, and computational neural modeling to study how simultaneous objects in the visual field, such as separate highlighted areas in an illuminated grid, compete with one another for attention. Meanwhile, Sabine Kastner of Princeton has recently begun comparing humans with monkeys in their attention to visual tasks; and Columbia’s Michael Goldberg has recently shown that, in the process of attention, a particular area of the brain called the lateral parietal area “sums up” visual signals and cognitive signals. In this growing field of neuroscience, Desimone has trained over thirty-five people himself.

  I asked Desimone how the conductor of the neuronal chorus, in this case the inferior frontal junction, would know that a particular stimulus should be attended to. In his experiment, the subjects were told to focus their attention on either faces or houses, but what about an unexpected stimulus—say a charging lion or the sudden entrance of a potential romantic partner? “We don’t understand the answer to that yet,” said Desimone. And how do a bunch of random voices come into synchrony? Can they do so merely by exchanging notes with one another, or do they need an outside director? At the second question, Desimone broke out in a boyish grin and took six small metronomes from his briefcase. He placed them side by side on a wooden board, balanced on two empty lemon soda cans. Then he set the metronomes ticking, out of synch with one another. After a couple of minutes, they were all ticking in synchrony. They had communicated with one another and come into synch solely through the vibrations of the board, without any outside agency. Neurons, of course, use a different method of communication with one another: passing chemical messengers between the hundreds of root-like filaments radiating from each neuron. Desimone’s pendulums suggest that some neurons could come into synch on their own, without a conductor. But the question of which neuronal processes are self-organizing and which require a higher-level cognitive director isn’t yet understood.

  As my visit came to an end, I asked Desimone about the seemingly strange experience of “consciousness,” to me the most profound and troubling aspect of human existence. How does a gooey mass of blood, bones, and gelatinous tissue become a sentient being? How does it become aware of itself as a thing separate from its surroundings? How does it develop a self, an ego, an “I”? Without hesitation, Desimone replied that the mystery of consciousness was overrated. “As we learn more about the detailed mechanisms in the brain,” he said, “the question of ‘What is consciousness?’ will fade away into irrelevancy and abstraction.” As Desimone sees it, consciousness is just a vague word for the mental experience of attending, which we are slowly dissecting in terms of the electrical and chemical activity of individual neurons. He threw out an analogy. Consider a careening automobile. A person might ask: Where inside that thing is its motion? But he would no longer ask that particular question after he understood the engine of the car, the manner in which gasoline is ignited by sparkplugs, the movement of cylinders and gears.

  I am a scientist and a materialist myself, but I left Desimone’s office feeling somehow bereft. Although I cannot say exactly why, I do not want my thoughts, my emotions, and my sense of self reduced to the electrical tinglings of neurons.

  I prefer that at least some parts of my being remain in the shadows of mystery.

  Immortality

  Early August. I am lying in a hammock and musing on mortality. A hundred years from now, I’ll be gone, but many of these spruce and cedars will still be here. The wind going through them will still sound like a distant waterfall. The curve of the land will be the same as it is now. The paths that I wander may still be here, although probably covered with new vegetation. The rocks and ledges on the shore will be here, including a particular ledge I’m quite fond of, shaped like the knuckled back of a large animal. Sometimes, I sit on that ledge and wonder if it will remember me. Even my house might still be here, or at least the concrete posts of its footing, crumbling in the salt air. But eventually, of course, even this land will shift and change and dissolve. Nothing persists in the material world. All of it changes and passes away.

  That said, I think that the distinction between life and death may be overrated. I have come to believe that death occurs gradually, through the diminishing of consciousness.

  Let me explain. According to the scientific view, we are made of material atoms, and nothing but material atoms. To be precise, the average human being consists of about 7 × 1027 atoms (seven thousand trillion trillion atoms)—65% oxygen, 18% carbon, 10% hydrogen, 3% nitrogen, 1.4% calcium, 1.1% phosphorous, and a smattering of 54 other chemical elements. The totality of our tissues and muscles and organs is composed of these atoms. And, according to the scientific view, there is nothing else. To an alien intelligence, each of us human beings would appear to be an assemblage of atoms, humming with our various electrical and chemical energies. To be sure, it is a special assemblage. A rock does not behave like a person. But the mental sensations we experience as consciousness and thought, according to science, are purely material consequences of the purely material electrical and chemical interactions between neurons, which in turn are simply assemblages of atoms. And when we die, this special assemblage disassembles. The atoms remain, only scattered about.

  Particularly special in these considerations is the brain. In the view of science, the brain is where our self-awareness originates, our memories are stored, our elusive ego and “I-ness” are formed. Neuroscientists like Robert Desimone of MIT have studied the brain in great detail. Much is known. Much remains unknown. But the materiality of the organ is not in doubt. There is good evidence that the processing and storage of information is done by the brain cells called neurons. There are about a hundred billion neurons in the average human brain, and each neuron is connected by long filaments to between a thousand and ten thousand other neurons. The electrical and chemical components of these neurons are largely understood.

  Despite the known material nature of the brain, the sensation of consciousness—of ego, of “I-ness”—is so powerful and compelling, so fundamental to our being and yet so difficult to describe, that we endow ourselves and other human beings with a mystical quality, some magnificent and nonmaterial essence that blooms far larger than any collection of atoms. To some, that mystical thing is the soul. To some it is the Self. To others, it is consciousness.

  The soul, as commonly understood, we cannot discuss scientifically. Not so with consciousness, and the closely related Self. Isn’t the experience of consciousness and Self an illusion caused by those trillions of neuronal connections and electrical and chemical flows? If you don’t like the word illusion, then you can stick with the sensation itself. You can say that what we call the Self is a name we give to the mental sensation of certain electrical and chemical flows in our neurons. That sensation is rooted in the material brain. And I do not mean to diminish the brain in any way by affirming its materiality. The human brain is capable of all of the wondrous feats of imagination and self-reflection and thought that we ascribe to our highest existence. But I do claim that it’s all atoms and molecules. If the alien intelligence examined a human being in detail, he/she/it would see fluids flowing, sodium and potassium gates opening and closing as electricity races through nerve cells, acetylcholine molecules migrating between synapses. But he/she/it would not find a Self. The Self and consciousness, I think, are names we give to the sensations produced by all of those electrical and chemical flows.

  If someone began disassembling my brain one neuron at a time, depending on where the process began I might first lose a few motor skills, then some memories, then perhaps the ability to find particular words to make sentences, the ability to recognize faces, the ability to know where I was. During this slow taking apart of my brain, I would become more and more disoriented. Everything I associate with my ego and Self would gradually dissolve away into a bog of confusion and minimal existence. The doctors in their blue and green scrub suits could drop the removed neurons, one by one, into a metal bowl. Each a tiny gray gelatinous blob. Stringy with the axons and dendrites. Soft, so you would not hear the little thuds as each plopped in the bowl.

  Likewise, the same doctors in their blue and green scrub suits could create consciousness by building a brain from scratch, one neuron at a time, delicately arranging the connections between neurons. The doctors might connect some of the neurons to a device that monitored their combined electrical activity. Neuron by neuron, connection by connection. At first, there would be simply noise. But at some point, presumably, a change would occur, a coherent signal, perhaps Desimone’s synchronous hum, that would translate, roughly, into “Yikes, something is messing with me.”

  If we conceive of death as nothingness, we cannot imagine it. But if we conceive of death as the complete loss of consciousness, a view supported by the understanding of the body as an arrangement of material atoms, then we approach death in gradual stages as consciousness fades and dissolves. The distinction between life and death would no longer be an all-or-nothing proposition.

  The neuroscientist Antonio Damasio has defined different levels of consciousness. The lowest level, which he calls the “protoself,” is related to an organism’s ability to carry out the most basic processes of life, but nothing else. An amoeba has a protoself. I would not associate this level of existence with consciousness. Almost certainly, thought and self-awareness require a minimum number of neurons, well beyond the stuff of an amoeba. Next comes “core consciousness.” It is self-awareness and the ability to think and reason in the present moment, but without memories extending earlier than a few minutes into the past. Such an organism, far above an amoeba, might be able to have an understanding of the world around it and its place in that world, but it would exist only in the present. People with certain brain disorders have only core consciousness. They cannot form new memories that last more than a few minutes. They cannot remember what happened to them in the past, except for isolated periods. For the most part, they cannot recall past personal relationships or the people they loved and who loved them. They cannot make plans for the future. They are trapped in the moment.

  The highest level of consciousness is “extended consciousness,” which all healthy human beings possess. Here, we can remember most of our past life as well as function completely in the present. We can remember our view of the world based on past experiences, we can remember our value system as grounded in those experiences, we can remember what we like and don’t like, places we’ve been and people we’ve met. Self-identity, as most psychologists understand it, probably requires extended consciousness, that is, long-term memory. These are complex issues, not fully understood.

  The slow dismantling of a human brain, whether by my imaginary doctors in their scrub suits or by the deterioration of the brain in neural disease, might proceed from extended consciousness to core consciousness to the protoself. Or perhaps it might proceed in a less orderly manner, by removing chunks of extended consciousness and core consciousness here and there until nothing is left but the protoself. However it proceeds, one begins with full consciousness and ends with an amoeba-like existence, alive only by the biologists’ formal definition of the word. One begins with a full life and ends with death, or the equivalent of death. And this process can happen gradually, so that there may be some awareness of the increasing loss of awareness.

  Personal accounts of early dementia provide the best knowledge we have of approaching death in this manner. In the early stages of dementia, enough of the mind remains to understand and articulate what is happening. In later stages, the reporter has slipped and disappeared into the abyss of confusion. Somewhere in that intermediate nether zone, the sense of self dissolves and is gone. It’s a grim subject.

  Some of my own loved ones have gone through various forms of dementia. Many of us will not suffer this depressing approach to death, and I prefer not to think of it myself. But consciousness and its loss are part of my musings today on the boundary between life and death. For a person who does not believe in the afterlife, consciousness is the subject of interest. For a materialist, death is the name that we give to a collection of atoms that once had the special arrangement of a functioning neuronal network and now no longer does so.

  From a scientific point of view, I cannot believe anything other than what I have laid out above. But I am not satisfied with that picture, just as I was not satisfied with Desimone’s explanation of consciousness. In my mind, I can still see my mother dancing to the bossa nova as she often did, giving her hips a jaunty shake with the beat. I still can hear my father tell his Cooshmaker joke—“It went coosh, and I can have another one up in fifteen minutes.” I often wonder: Where are they now, my deceased mother and father? I know the materialist explanation, but that does nothing to relieve my longing for them, or the impossible truth that they do not exist.

  I have a confession to make. Despite my belief that I am only a collection of atoms, that my awareness is passing away neuron by neuron, I am content with the illusion of consciousness. I’ll take it. And I find a pleasure in knowing that a hundred years from now, even a thousand years from now, some of my atoms will remain in this place where I now lie in my hammock. Those atoms will not know where they came from, but they will have been mine. Some of them will once have been part of the memory of my mother dancing the bossa nova. Some will once have been part of the memory of the vinegary smell of my first apartment. Some will once have been part of my hand. If I could label each of my atoms at this moment, imprint each with my Social Security number, someone could follow them for the next thousand years as they floated in air, mixed with the soil, became parts of particular plants and trees, dissolved in the ocean and then floated again to the air. Some will undoubtedly become parts of other people, particular people. Some will become parts of other lives, other memories. That might be a kind of immortality.

  The Ghost House of My Childhood

  The distant Earth bristles with tiny imitations of houses and roads as I slide through the air in the silver ghost, a miracle of science. Now that my second parent has passed away, all things seem strange. Am I awake or asleep? I am flying back to Memphis, the place of my childhood, to settle the last of my father’s affairs and to see one final time the house where we all lived.

  I sit at a table at Panera Bread. After lunch, I will get into my rented car and drive out to West Cherry Circle. I was hoping my brothers would join me on this trip to our family home, but they don’t want to see it again. We sold the house months ago. I look out a window toward Poplar Avenue and remember the diner that once stood across the street, the Ohman House, where my friends and I used to go late at night, after high school dances and parties, to eat hamburgers smothered with onions, hash brown potatoes, and black bottom pie.

  It’s time. I get into the rented car. When I last visited the house, two years ago, my father was waiting to greet me. He sat in the den in his wheelchair, wearing a warm sweater even in April and soft bedroom slippers, an open book on his lap.

  I turn onto West Cherry Circle, drive past familiar houses. Flowers are blooming, it’s spring. But something is wrong. The house isn’t here. There’s a hole in space where the house used to be. Slowly, I inch up the driveway and park the car. Something is terribly wrong. I feel as if I’m not in my body any longer. My body is a distant, cold moon. There was a two-story house here, with pink brick walls and a porch with white posts and dormer windows. I can see right through the empty air to bushes and trees on the other side. And on the ground where the house was, new grass. Not a single brick or splinter or piece of debris.

  Slowly, I get out of my car, a knot forming in my gut, somebody’s gut, and I walk around the patch of grass where the house used to be. The space is too small. I stare at the driveway, follow it with my eyes as it winds down to the street, curves by the towering magnolia around which my brothers and I once chased one another with a gushing garden hose. I stare at the neighboring houses, the fence at the back of the lot, thinking that somehow I’ve made a mistake.

 

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