area of the physical brain is damaged with an associated specific psychological disruption. Once the neuropsychologist has gathered a wealth of such examples, then psychological functions like language (which is often disrupted after brain injury) can be divided into various subsystems or “modules” operating in different areas of the brain, each of which can be differentially affected.
The upshot of this methodological enterprise is that scientists are now able to speculate about normal brain function and to link localized physical brain mechanisms with aspects of the mind. This is quite an achievement, resulting directly from the prevailing localization paradigm governing a major part of neuropsychology. It is therefore not unusual to come across references to the mapping of the human brain whereby different areas are associated with different psychological functions.
Bearing this in mind, it is clear that we could examine the entheogenic experience in a similar way. That is, by looking at the specific changes to consciousness arising from the presence of specific substances in the brain, we should be able to theorize about how normal consciousness arises. In other words, just as we can analyze abnormal language production and then speculate about how the language system works in normal people, so too can we analyze altered states of consciousness and speculate about the nature of normal consciousness. At any rate, by examining chemical changes associated with changes in consciousness, we ought definitely to come to some understanding about the nature of mind stuff and the ways it is possible to modify mind stuff through chemistry. On the face of it at least, this area of study promises a wealth of relevant psychological data with which to understand the elusive nature of mind.
Despite this reasoning, scientists, as should be clear by now, have unfortunately been hindered from investigating the psychedelic experience, and it is only in the last few decades that they have been permitted to resume studies in this fascinating domain. And yet enough information on the psychedelic experience has been generated with which to construct a user-friendly theory of consciousness. Most of this information I have outlined in previous chapters, in particular, information on the fundamental type of global change in consciousness caused by psilocybin. If we add relevant information regarding the physical details of psilocybin, we shall be able to reach some sort of sound theoretical conclusion about the nature of consciousness. Regardless of any legal issues, this mode of inquiry promises to be most fruitful. In fact it is rather apt that a mysterious phenomenon like consciousness should require such radical means with which to pry open its nature.
Introducing the Neuronal Brain
As mentioned, the brain consists of individual information-processing nerve cells, or neurons. It is estimated that the human brain contains up to one hundred billion of them. This is an astronomical number pretty much impossible to conceive. Regardless, these billions of neurons are the essential “wetware” of the brain, and massed together with other cells that provide support and energy, they form the spongy gray matter residing within our skulls. We should also consider that each of these billions of neurons forms interconnections with thousands or even tens of thousands of other neurons. We will learn more about this a bit later on.
Although the evidence is overwhelming, it still seems extraordinary that this convoluted blob of porridge-like neuronal stuff within our skulls is bound up with the elaborate properties of the human mind. Although one might have reservations in associating a spongy, wet blob with consciousness, the association is indisputable. Scramble someone’s brain either through a severe blow to the head or through some other trauma, and that person’s consciousness similarly becomes scrambled. Or, electrically excite the brain of a patient undergoing brain surgery who is under the effects of only a local anesthetic, and the electrical stimulation evokes definite and often vivid lifelike experiences. And, of course, certain chemical substances introduced into the brain serve to alter consciousness.
Hence, it is overwhelmingly apparent that the human mind with all its attendant beliefs, ideas, neuroses, fears, hopes, dreams, goals, and aspirations is intimately bound with the unsightly wet-blob brain inside our crania. Indeed, what distinguishes
So what is the neuron exactly and how does it come to be involved not only in your reading of these words, but in the psilocybin experience? What is it exactly that these billions of units do?
Naturally Neat Neurons
Structurally, the neuron has four main components: dendrites; the soma (no relation to Wasson’s Soma!), or cell body; the axon; and terminal fibers. This may sound somewhat complicated, but the basic principles involved are easily understandable and are essential knowledge to anyone interested in how the brain does its thing.
Imagine a big tree suspended in midair. The bottom of this tree has a dense network of roots, which are attached to a bulbous lower trunk. Above this fat lower trunk is a long, thin upper trunk that ends with a wispy network of branches. In this picturesque analogy of the neuron (which will be worth bearing in mind for the discussions to come when we try to imagine psilocybin’s journey within the brain), the roots of the tree are the dendrites, the bulbous lower trunk is the soma, the long upper trunk is the axon, and the topmost branches are the terminal fibers. This is the essential structure of an archetypal neuron with its four distinct components, and all of the brain’s neurons are basically made in this way. Neurons are akin to microscopic protoplasmic trees.
The dendrites are the root structures of the neuron, which serve to receive information in the form of signals, or impulses, from other neurons. In our analogy, the root network of the suspended tree receives signals from the branches of other trees suspended below it. These neuronal signals travel to the soma (lower trunk), where they are integrated. The singular result of this integration is then passed on to the axon (upper trunk), which in turn passes on the information to the terminal fibers (branches).
Already we can see that neurons transmit informational impulses in an orderly and well-defined manner; that is, informational signals progress or flow through the neuronal architecture in one direction only. But what exactly are these signals? Because neurons are living tissue, they operate by making use of their inherent electrochemical property, which is to say that their particular chemical molecular structure allows electrical potentials to be generated. The neuron has been constructed by Nature in such a way that it can either fire or not fire, depending on its input from other neurons. Firing here means that the neuron sends forth an electrochemical impulse (a rapidly traveling wave of electrical excitation) down its axon to its terminal fibers, at which point the impulse can be transmitted to other neurons.
This then is the way that neurons process information. The information they carry is
The purpose of the soma is to integrate all the incoming signals from its dendrites (signals that come from other neurons) and then yield a subsequent impulse down its axon—or not, as the case may be. The concept of threshold is therefore crucial here. For simplicity’s sake, if there are a certain number of impulses received by the soma from other neurons, then the firing threshold will be met and an impulse will be passed on down the axon. Conversely, if the particular threshold is not met, there will be no impulse sent down the axon.
Don’t relax yet, for there is one more important fact to consider. Neurons can be excitatory or inhibitory. If the neuron is excitatory, then if it fires, as its name suggests, its impulse will be one that tends to cause excitation in other neurons with which it connects. In other words its impulse will add to the chances of the next neuron in
