The Neurosciences of Religion: Meditation, Entheogens, Mysticism
How the Neurosciences Explain Religion or Not
In the last lecture1, we learned how humans evolved as hunter-gatherers and how our genetic, mental, and behavioral nature was conditioned by and for this kind of life, even as we now live in a very different environment of our techno-cultural creation. We considered how evolution had shaped our predispositions for religion and what functions and dysfunctions religion might have played in our species’ history. We were introduced to the idea that the human mind was modular, that there were instinctive dispositions that then developed in conjunction with social and environmental factors into various inference systems in our brains. Religion, we were told, could be understood as a potent combination of these different inference systems in our evolved brains – agency detection, ontological categories, intuitive physics, intuitive psychology, pollution-contagion templates, memory-recall patterns, and so forth, all assembled and accessed as independent mental modules (Boyer 2001).
In this lecture, we are going to examine the human brain directly to see how the cognitive neurosciences try to understand and explain religious and spiritual experiences. And we note first that there has been a tremendous amount of new research and new insights into the working of the human brain in the last few decades. Powerful new tools also allow us to examine the function of healthy human brains and these tools have recently been used to study the brain functions of Buddhist monks, Catholic nuns, Pentecostals speaking in tongues, and others.
Inside the Brain
Now if you look inside the human brain, you do not actually see these mental modules previously referred to. There is no piece of the brain that one could label the “agency detection module” or the “pollution-contagion module”. In dissecting a human cadaver, we first see large-scale structures. On the outside is the cerebral cortex, or neocortex, including areas labeled the Frontal Lobe, the Parietal Lobe, the Occipital Lobe, and the Temporal Lobe, and of course, these are divided into two hemispheres, right and left, with a broad band of nerve fibers know as the Corpus Callosum connecting the two halves. If we peal away the neocortex, we discover the mesocortex and subcortical structures in the limbic system, including the Thalamus, the Amygdala, the Hippocampus, and the Cerebellum, all connected to the brain stem and the spinal cord. This much you probably already know. Images of the human brain have become iconic in our 21st century culture.
A lot of what we know about the specialized functions of different areas of the brain comes from observing survivors of traumatic brain injuries or stroke victims. In both cases neuroscientists correlate the destruction of certain brain regions due to hemorrhaging or injury with the loss of particular mental functions, for instance the loss of motor-control, speech, or even particular parts of speech or sets of word concepts, the latter known as Aphasia.
Curiously, memory seems to be distributed throughout the brain and is not located in any particular region. I recall a colleague at Oxford University, who I visited in the hospital shortly after he had had a stroke. He could point to Paris or London on a map, but he could not say the word “Paris” or “London”. Nor could he speak the names of any number of other common items and places, though he certainly knew what they were and could directly point to any of them. When I said “wallet,” he reach into his back pocket, pull out the wallet, he just could not himself say the word “wallet”. Our brains are strange, indeed, though we take them for granted until something goes wrong. Fortunately, my friend was able to fully recover his speech, but did so by training new regions of the brain to compensate for the loss of the one region destroyed by the stroke. This is an example of another curious characteristic of the brain called neuro-plasticity.
When we examine brains under powerful microscopes we see that the brain is made up of neurons, lots and lots of neurons. There are different types of neurons in the brain, and throughout our central nervous system in the rest of the body, but they all share a basic structure. The cell body contains the nucleus and organelle. Extending out from the cell body are lots of dendrite “trees” and axon “arms”. These connect to other neurons. This maze of connections end in synapses, linking each neurons with hundreds or thousands of other neurons. The neurons fire electrical charges in the form of chemical ions, which are mediated by a variety of neurochemicals that are produced endogenously by the brain. The chemicals produced and present in different areas of the brain are very important.
There are a lot of neurons in the human brain, estimated at 1011 (one hundred billion). Now each neuron has on average about 7*103 (seven thousand) synaptic connections. A three-year old child has about 1016 synapses (10 quadrillion), but this happily decreases with age to a more manageable number between 1015 to 5*1015 synapses (1 to 5 quadrillion).
Here are a few comparisons to help you remember these big numbers. The number of neurons in your brain is approximately the same as the number of stars in our Milky Way galaxy, which turns out to be conveniently also the number of galaxies in the observable universe, i.e., one hundred billion. Or if you prefer, there are more neurons in your brain than the number of hamburgers served by McDonalds (before they stopped counting).
And it takes a lot of hamburgers, or other food, to keep our neurons firing. The 1.5 kilograms of your brain, give or take, represents only 2 percent of your body weight and yet it consumes 15 percent of your cardiac output, 20 percent of your body oxygen, and about 25 percent of your body’s glucose consumption. Just sitting around the brain needs about 0.1 calories per minute. With intellectual activity this can increase to as high as 1.5 calories per minute. From a biophysical and evolutionary point of view, the human brain is an expensive item. In birth, it is difficult to pass through the female pelvis, too often resulting in the death of the infant or the mother. In life, it requires a lot of extra food and care.
The brain is best understood as a kind of Rube Goldberg machine. Rube Goldberg (1883-1970) was an American cartoonist who was famous for depicting complex devices that performed simple tasks in convoluted ways. One such cartoon depicts a man eating his soup. The spoon is attached to a string which flips a cracker to a Parrot which then activates water pouring into bucket which pulls a string which activates a lighter which launches a rocket attached to a knife which cuts a string that turns on a clock with a pendulum which swings back and forth moving a napkin that now wipes clean the soup-eating man’s mustache. The entire contraption is worn on the head of the mustached man as a kind of hat. Our brains are like this Rube Goldberg machine, except that the complex machine is worn inside our heads instead of outside. Neuroscientists today are developing algorithmic flow charts that map out neural processes. Something simple like engaging in meditation sets off an impossibly complex series of actions, reactions, and feedback loops (Newberg 2006). Thankfully, we do not need to be the least bit aware of any of these processes to have wonderfully functional brains allowing us to mindlessly perform lots of simple and complex mental activities everyday. It is worth stopping a moment, however, to reflect that the most complicate object in the known universe is sitting right here between our ears.
Read the whole article -- there's much more to be digested.
No comments:
Post a Comment