Are You Conscious, and Can You Prove It?* (Expanded)
To the never-ending battles between science versus creationism, unidentified flying objects, extrasensory perception, ectoplasm, and the like, we now have to add the perpetual battle over human stem cell research. Where should the line be drawn? I have received a personal communication that spermatozoa are human, or at least half human, and should therefore be treated, as such, with appropriate respect. This notion has, understandably, been a source of great embarrassment to certain males of the population. Along the same vein, there is a hue and cry about how, each month, when an egg doesn't get fertilized, there is the potential loss of a life.
Where to draw the line? One can get stem cells from embryos, or less flexible “stem” cells from infants or adults. In the present essay it is argued that there is a simple and non-controversial test: If the cell is conscious, or part of a conscious ensemble, such as a brain cell, it is human and must not be tampered with. This should be non-controversial because, after hundreds of papers written on the subject, including many books, nobody can explain consciousness. It is easy enough to define consciousness – “The state of having an awareness of one’s own existence, sensations, and thoughts, and of one’s environment” – but this does not explain why we have an “awareness of being.” One of the purposes of this essay is to give a minuscule review of what we know about consciousness.
I am under no illusion that bioethicists will pay the slightest attention
to consciousness as a dividing line between stem cell experiments and a scientifically-based
taboo, but one cannot legislate-away stem cell (and cloning) research, because
anybody with a microscope and steady hand can get into the business. Eventually,
perhaps many years from now, even the bootleggers working in their basements,
and who sell body parts, will stop at conscious brain tissue.
About half of the literature on consciousness does explain it with various references to some kind of deity and/or paranormal extra-sensory perception, but these pseudoscientific arguments cannot survive the test of time. The scientific literature reveals that the brain contains very approximately 75 compartments, and we have made tremendous strides in discovering the type of data that each compartment handles (such as visual, auditory, muscle coordination, and so forth).
The “easy” part of consciousness research is to discover how the brain functions ,,,,,. This is “easy” in the sense that, after we completely know the circuitry of the brain, and every signal that accompanies every sensory input and every “thought” and every motor output, we can never answer the basic question: “Is the red that you see the same as the red that I see?”
Nevertheless, let’s take a short excursion into solving the “easy” problems. First, determine the function of each volume of the brain; second, trace the neuronal circuits; third, represent the neuronal circuits in the form of a circuit diagram; fourth, achieve maximum simplification by summarizing the above via a block diagram. Each of these aspects of brain research is illustrated, below, by means of a pertinent diagram.
First, Fig. 1 (Figs. 1 to 6 are taken from ) depicts an approximate cross
section of the human brain. Seventeen of the most important regions, plus
the spinal cord, are labeled, but an anatomy book will show that names have
been assigned to many additional volumes of the brain.
Fig. 1- Approximate cross-section of the human brain, with some regions in dashed lines for the sake of clarity. Seventeen of the most important regions are labeled, plus the spinal cord.
Second, the tracing of neuronal circuits is illustrated, in Fig. 2, for the
cerebellar cortex. (This is the outside layer of the cerebellum of Fig. 1.)
At first glance this seems to be a “hopeless mess,” but with a reasonable
amount of patience (and a magnifying glass, perhaps) one can extract the
main features of the cerebellar cortex. But the hardest part is yet to surface
– one must determine whether each junction is excitatory (E) or inhibitory
2- A three-dimensional view of the cerebellar cortex as provided by three
mutually perpendicular cuts. Parallel to the front cut we have dendrites
of the Purkinje, basket, and stellate cells. The following are mutually perpendicular:
(1)Purkinje cell dendrites; (2)parallel fibers; and (3)basket and stellate
cell axons. The Golgi cell dendrites have a cylindrical architecture, like
a conventional tree. .
Third, having deciphered each portion of the neuronal circuit, and the E and I of every junction, one can draw an electrical schematic, as shown in Fig. 3. Here, also, the hardest part is yet to surface – because the brain is three-dimensional, one must draw a three-dimensional network. (This is reminiscent of the DNA models that gave birth to three-dimensional laboratory and teaching accessories.)
Fig. 3- Hypothetical model of the basic neural network of the cerebellar cortex. It is useless to analyze this circuit as shown, however, because the cerebellum must be analyzed as a three-dimensional network.
Fourth, on an even higher intellectual level that is not concerned with the three-dimensional aspects of a network, are the block diagrams of Figs. 4 and 5. These are highly conjectural summaries of brain activity. Figure 4 shows the mechanisms of memory while Fig. 5 is an even more ambitious depiction of a simple brain that can read and write.
Fig. 4- Hypothetical block diagram that attempts to summarize the mechanisms of memory.
Fig. 5- Hypothetical block diagram of a relatively simple brain that can read and tell us what it is reading in the upper half of the diagram; listen to a conversation and write down what it hears in the lower half.
Before you dismiss Figs. 4 and 5 as worthless conjecture, however, you should
try to answer the following question: Which portions of the block diagram
are inside, and part of, the consciousness “platform”? In other words, what
portions can be deleted (or surgically removed), which will remove sensory
inputs and motor outputs, while still leaving the patient “fully conscious”?
One can gain considerable insight into this from the many people, each day,
who are partially disabled by a stroke.
One must be careful here with definitions. If you are UN-conscious, it may be perfectly ethical for one of those biopsy-wielding monsters to sneak up on you and extract a few stem cells. In my own case, after 10 minutes into any lecture that I ever attended, I lost an awareness of being, and became a candidate for stem-cell research (or, hopefully, cloning).
But there is a greater danger here. Just as we cannot explain consciousness, you cannot prove that you are conscious! The proof of that statement is simple: Suppose that we build a machine (or a computer program, at least) that has a brain. It includes a random-noise generator so that, via serendipity, when a “viable” set of signals comes along, the brain says something that is creative and that makes sense. For example, toss 10 coins into the air; on average, on one out of 1024 throws, all of the coins will land heads up. This is also how it is with human creativity. Because of the random signal generator, the computer brain is unpredictable; it does not, of course, have “free will.” It goes without saying that it has a memory, and stores (learns) all of those nuggets of creativity. The point that I am getting at is this: Ask the brain if it has a consciousness: If it says “Yes, I am conscious,” you say that it is lying because it is only a computer program. But exactly the same argument applies to you, dear reader. I ask you if you are conscious: If you say “No,” you get a biopsy zap; if you say “Yes,” I say “How do I know that you are not lying?”
There certainly is a contradiction here. How can one determine if a volume of tissue is conscious or unconscious? Generation of a particular pattern of chemical or electrical activity does not guarantee consciousness. A minimum requirement for consciousness, however, is that the cell, or group of cells, be part of a "brain." They can be in the form of a clever computer program, or a robot that occasionally says something noteworthy, or even an awake human. But problems remain because the definition of consciousness is rather vague.
The Animal Kingdom emerged, approximately, one billion years ago. Animals move about from place to place in search of food, to escape from predators, find a mate, and so forth. Movement requires a nervous system, and the integration of movement requires a brain. It is appropriate to ask, then, do insects have a consciousness, an awareness of being? If a bee sees a red flower, is it the same red that I see? Is pain the same to a bee, or to you and me? Because these questions can never be answered, it appears that consciousness will forever be beyond the reach of the human brain.
It doesn’t take much to give an impression of intelligent behavior (and I am not thinking of the U.S. members of Congress here): Get a microscope and look at a drop of muddy water taken from a bowl that holds plant stems. You will see a myriad of tiny cells scurrying about exactly like office workers, during lunch time, in Times Square. None of them have a nervous system, of course; they are merely responding to chemical signals (like office workers during lunch time!).
But let’s not muddy the water with talk about paramecia and insects; let’s stick to humans. At what point in embryonic development does consciousness begin? As directed by its DNA molecule, given the proper raw materials, the fertilized egg starts to synthesize amino acids and proteins. At first, it starts to grow by dividing repeatedly in two: 1, 2, 4, 8, … cells. Eventually, a “neural plate” forms, cells proliferate in localized regions, the immature neurons migrate to their final residences , they aggregate and differentiate to form the various parts of the brain, they mature and form connections with other neurons. Starting with almost nothing, with a few simple building blocks, a brain is thus created. Somewhere along the way, probably after birth when a certain minimum number of connections have been completed, the human infant becomes aware that it exists. Eventually, it learns that it has a unique identity, and it acquires an illusion of free will.
There is no “threshold of consciousness.” Scalp electrodes show that electroencephalographic (EEG) signal spectra gradually change from the prenatal period to the beginning of adulthood.
Consciousness resides in a Consciousness Platform (CP) upon which sensory inputs, "thought" signal patterns, and outputs (such as motor commands) interact. The CP is reserved for a select few of the body’s nerve signals. We are not aware of the goings-on in the involuntary, visceral, autonomic nervous systems (housekeeping chores for the most part, such as digestion and heart beat). These modalities would only distract the conscious brain; it has to concentrate on one situation at a time (hence the obvious “discovery” that driving, while paying attention to a cell phone, can be dangerous). A myriad number of experiments are performed on the visual, auditory, and other sensory systems of an intact animal while it is unconscious -- that is, the nerve discharges in its CP have been immobilized via anesthesia. And vice versa: the human experience is that an awake CP gets a blank visual input if, for example, you close your eyes.
Sometimes, in patients desperately ill with recurrent epileptic seizures, the commissure is cut surgically in order to open the feedback path that is responsible for the oscillations. This is known as “split brain” surgery. Actually, it is not possible to completely split the brain because one would have to cut through vital neurons in the central structures Aside from benefit to the patient, the split brain is interesting because it is possible for an experimenter to feed conflicting information into each hemisphere. Normally, each hemisphere knows what information the other is receiving because of the commissure fibers (although there is a great deal of duplication, the two hemispheres are far from identical). In the case of a split-brain patient who is receiving conflicting signals, the dominant hemisphere “decides” that its information is the true state of affairs, and it suppresses the recessive hemisphere. (If a person is right-handed, the left hemisphere is dominant in most of the dual-choice situations, and vice versa.)
Another problem is that consciousness is fragile. Here is an amazing, painless
experiment that you can do to yourself in a few minutes: Borrow a dime and,
on a sheet of white paper, use it to draw two circles around 2 ¼-inch
(5.8 cm) apart. In one circle draw a +, in the other an x, as in Fig. 6.
Then stare at the two circles, but let your gaze look beyond so that the
two circles coincide. Almost immediately, you will lose the +, or the x,
or bits and pieces of the + and x. In this binocular rivalry, the visual
system cannot tolerate conflicting information, so it deletes the input of
an entire eye before it reaches your CP!
Fig. 6- Visual stimulus
used to demonstrate the “blocking out of reality.” Stare at the two circles,
but let your gaze look beyond so that the two circles coincide. Almost immediately
you will lose the +, or the x, or bits and pieces of the + and x. This is
an example of binocular rivalry.
To conclude: The debate over human stem cell research is tied in with a creationist
philosophy which says that a group of human cells has a soul; it will never
end. From a scientific point of view, however, even brain tissue regenerates,
and one can "pick a brain" to get stem cells. Nevertheless, in this essay,
it is suggested that the line should be drawn at tissue that is conscious,
defined as best we can, with all of its pitfalls and problems.
 Stevan Harnad, “No Easy Way Out,” The Sciences, Spring 2001.
*Published in a shorter version in IEEE Engineering in Medicine and Biology Magazine, July/Aug 2002.