(I’ll tart this up with some clip art after while. Enjoy it while it lasts; in business school they threatened to take my clip art away from me.)
The brain is kind of complicated, but I think it helps to have some basic concepts in mind as we look at the relationship between the brain, the mind, and spirituality. I will start the discussion by looking at some general principles of brain organization. Then we will talk in more detail about Memory, emotion, and how the brain handles visual information.
There are a couple of different ways of looking at how the brain works. Easiest way is to back out a bit and see how the brain is generally organized before you start drilling down into the details.
Even then you have a couple of options. If you’re a schoolteacher, you might be most interested in the right-to-left organization of the brain, since reading and writing are usually in the left hemisphere, and some of the mechanisms that govern attention are in the right.
There is also an front-back organization, where the back half of the brain tends to draw you toward interesting things in the environment, and the front tends to… look! ↓↓↓
For the purposes of this discussion — as we are trying to understand how brain function, the mind, and spirituality are connected — I feel it’s better to think of the brain’s bottom-to-top organization.
By “top” I am referring to structures that are on the surface, or cortex of the brain. These structures are specialized, lateralized, evolutionarily recent, and tend to manage concept formation and species-specific activities like speech and tool use.
Higher cortical functions include:
- Cognition. In other words, thinking. The work the brain does. Math, reading, figuring out a map. Naming an object that is in sight. Things like that.
- Working the hands, recognizing that the human hand is pretty special. Fine manipulation. Feeling shapes and textured.
- Executive function. Making a plan. Initiating action when the time is right, and inhibiting behavior when it isn’t.
By “bottom,” I am referring to structures that are deep, midline, primitive, and evolutionarily ancient. These sub-cortical structures tend to manage gross movements such as muscle tone, posture and balance. They are responsible for the so-called “vegetative functions” such as breathing, alertness, regulation of hunger and thirst.
I think it’s helpful to think of human behavior as something that originates deep down inside the brain, and percolates up to the surface. The behavior we can observe in others, then, is the end result of multiple layers of refinement.
You might think I have that backwards. The brain-box is higher than the body, so it stands to reason that information flows down, right? That’s true, but if you look inside the skull, it’s like an old-fashioned coffee percolator, where water has to go up before it drips back down. In the brain, information flows up for processing. At each level of processing, signals are then sent to the spinal cord, which integrates the information and passes the result to the muscles. Thinking is bottom-up.
Consider movement, for example. The most basic and primitive functions responsible for movement include:
Arousal. Don’t get too excited; this is neurologist-speak for wakefulness, more or less. Specifically, it refers to the extent to which the brain is prepared for action, and that action might include thought or movement. Arousal is not a switch; it’s a continuum. You can be minimally or highly aroused. This comes straight from the brainstem, which is at the bottom of the brain bucket.
Autonomic function. This regulates things like blood pressure, heart rate, and respiratory rate that prepares the body for movement. This comes from the brainstem and hypothalamus, which are deep in the center of the brain.
Release of cortical inhibition. The sophisticated surface structures that form the final common pathway for behavior are, by default, switched off. Certain deep structures control that switch.
There might be an intermediate level of processing that stores motor programs, or “engrams.” Engrams (using the term very generously) might, in theory, consist of simple oscillations, simple proto-movements that can be stitched together to form complex movements, or complex movements stored in motor memory. The simple engrams aren’t usually visible in healthy humans, but we see some evidence of these things in various disease states. I am of the opinion that certain repetitive movement disorders, such as tremors or tics, represent simple engrams that have somehow found their way to the surface.
You probably prefer the term “muscle memory” to “motor memory,” which is fine. We are talking about the same thing, and we both know those memories are actually stored in the brain rather than the muscle.
At the highest level of processing – the cerebral cortex – the final touches are added. Fine finger movements are added to upper arm movements and gross, subconscious contractions of spinal posture muscles. Sensory feedback is integrated into movement. The executive part of the brain regulates precisely when the movement occurs, in light of what the plan is, and how the plan is working out. Memory is brought into the mix.
Emotion works the same way. Arousal and autonomic functions are involved. Mid-level structures in the so-called “limbic system” are responsible for the basic building blocks of emotion. The amygdala codes rage and fear (and at that level of processing, there’s not much difference between the two). The system that codes pleasure is complicated; one part you might have heard of is the so-called “reward center” in the nucleus accumbens.
Like thought and motor activity, emotions travel upwards to access higher brain functions, where they are refined and integrated with memory. And, like movement systems, emotion signals are sent to the body, to affect the muscles that control facial expression and body language, autonomic functions like the heart rate and blood pressure, and glandular functions like sweating or crying.
Thinking, emoting, and moving are very similar. They are processed along parallel pathways, and sometimes these pathways converge on the same structure. A disease of one of those structures can cause both a movement disorder, and a thought disorder.
Consider Tourette syndrome, for example. Tourette’s is a disease of a mid-level structure called the basal ganglia. You could think of it as a disorder of the brain’s “off-switch,” where the switch gets stuck in the on position. This allows motor engrams to work their way to the surface. We call these surface behaviors “tics.”
We tend to think of tics as simple involuntary movements, like the twitching of the eye. The movements we see in Tourette’s are considerably more complicated, and there is an ambiguity as to whether or not they are voluntary. The patient is quite certain these movements are not voluntary. An observer is not always quite so sure. Although the movements generally don’t seem to serve any specific purpose, they look like the sort of things a person might do on purpose, for example to draw attention to himself. This is more than a little frustrating to the patient, as you can imagine.
At the same time, these patients sometimes complain of thought intrusions; in other words, thoughts that find their way into their consciousness, that they perceive don’t belong there. This has the potential to make Tourette syndrome sound a bit like obsessive-compulsive disorder. The key feature of OCD is the obsessional thinking, where the patient perceives that his thoughts are intrusive, and not under his control. The compulsive movements we see in OCD, unlike Tourette’s, seem voluntary; and the patient will take responsibility for them. In other words, he will claim to be doing these things – the hair-plucking, the compulsive hand-washing – on purpose.
We tend, then, to think of Tourette’s as a neurological disorder, and OCD as a psychiatric disorder. But I wonder. The very first Tourette patient I ever took care of was dual-diagnosis; he was also diagnosed with OCD. I’m not at all sure he had two separate diseases.
As I’ve said, I don’t see a bright line between neurology and psychology. It’s a continuum. Brain structure and brain function are related, and that’s true even for very sophisticated functions, like thinking.