Random Thoughts on Mysterious Brain

I am always wondering about two mysteries: the immense universe in the external world and the complex brain inside our own body. The universe is massive. It is hard to imagine its size for us earthling creatures. Hubble space telescope once took a picture of deep space; each tiny pale dot on the picture is a whole galaxy. To imagine the size of universe, we have to go through a series of scale-ups; at each scale, we see a new structure: earth, solar system, Milky Way, and galaxy.

Brain and mind are mysterious in a different way: it is small in size, but the few pounds of mass control our behavior, produce rich experience like mind, emotion, and free will, and create wonders like culture and science. In the popular Disney movie, Shrek said: “Ogres are like onions”, “because they both have layers”. There are indeed multiple layers in Shrek: He looks ugly and scary from appearance; he is cranky, bad-tempered, and selfish, but he is also gentle, warm, and courageous. A person, like Shrek, has similar complex behavior. I am sure even ourselves are often puzzled by our own behavior. To uncover secrets of our mind and behavior, we can follow Shrek’s onion metaphor and take a layered approach. Just like peeling an onion or looking at the universe at a particular scale of distance, we can take a certain perspective, decompose it, and study factors and their interactions.

This idea is what I learned from [1]. It uses a multi-layer and inter-discipline approach to understand brain and human behavior. The layers are classified based on time scale: when behavior occurs, what has caused it one second before, second to minute before, hours to days before, days to months before, … all the way to centuries and millennia before. At each time scale, behavior is explained in a particular conceptual framework. By narrowing down to a particular time scale, it reduces the number of factors and highlights the most important factor for each time scale.

The First Time Scale: Neurons and Brain Activity

At the first time scale, neurons and brain activities determine behavior in seconds. Any action is commanded by neural signals. The brain function can be classified into three layers:

An ancient part of brain mediates automatic, regulatory functions, such as body temperature, blood glucose level, etc.
A more recently evolved region, limbic system, regulates emotions.
The most recently evolved layer, frontal cortex, has advanced functions such as cognition, memory, sensory, and abstraction.

This brain function division helps to study brain activities, but there is considerable overlap and interaction between layers. For example, the hypothalamus, a limbic structure, is the interface between layers 1) and 2), the core regulatory and emotional parts of the brain. On the one hand, an emotional response can change bodily functions; on the other hand, the state of the body can feed back to the brain and influence behavior.

Seconds to Minutes: Perception and Subliminal Cuing

What caused the activities in the brain and neurons? They are caused mostly likely by perceptions in the environment seconds to minutes before. Our brain continuously processes sensory data from environment such as sound, vision. Even though we don’t notice sensory data consciously, it can still influence our behavior seconds to minutes after. This is called the subliminal and unconscious cuing.

Although we know behaviors are easily influenced by sensory and environment factors, we tend to attribute others’ unpleasant behavior to traits and become irritated. In contrast, if we act inappropriately ourselves, we tend to find excuses. For example, if a driver cuts in the line, we may consider him/her a careless driver. But if we are late for an appointment and cut in the line, we consider ourselves as in a hurry and are perfectly justified for it.

Hours to Days: The Effect of Hormones

If we trace back to hours to days before, the effect of hormones come into play. Hormone is a chemical messenger released in various glands. All glands are controlled by the pituitary, a master gland which is in turn controlled by the hypothalamus in the limbic system. Once hormones are secreted, they can influence any cell throughout the body that possesses receptors for them. The effects of hormones can last from hours to days, which include changing protein activities, turning genes on or off, and altering cell metabolism such as cell growth, division, or death. The hypothalamus in the brain’s limbic system regulates the secretion of hormones.

For example, glucocorticoids are secreted from adrenals when stress is detected by brain and can activate the “fight or flight” response, such as increase heart rate and blood pressure, mobilize energy into circulation from storage sites in the body, postpone growth and tissue repair. Moderate stress can enhance brain functions such as cognition and sensory acuity; it can also enhance dopamine release, the neurotransmitter for reward in the brain. We love moderate stress and look for opportunities to obtain it such as a roller coaster ride, an expedition into the unknown, challenges in sports and daily work. However, prolonged stress can disrupt cognition, impulse control, emotional regulation, and decision making.

Days to Months: Brain Plasticity and Learning

At the next time scale, from days to months before, brain plasticity takes effect. This is about how the brain changes itself and accomplishes learning. These time scale levels can go back further to development periods in adolescence, childhood, and fetus. All previous layers are personal related factors that affect individual behavior. If we bring time scale further back and look at human behavior as groups and races, our behavior are results of genetic, social, and cultural factors and evolutions.

The Mystery of Free Will

Now, if our behavior is determined at various layers by neural, perceptional, biological, developmental, evolutional, and social factors, do we have free will at all? This is a difficult question and there is no definitive answer. We know there is no homunculus (little people) in our brain making decisions. When we are asked to take responsibility for our action, when people are punished for their misconduct, how can it be justified if the action is caused by a neural activity, an elevated stress hormone level, or a traumatic experience in childhood? Apparently our belief system and social rules fall apart if free will is abandoned. It is a mystery where the feeling of self and free will come from.

Physics and Understanding

Compared with physics, where great progress has been made in last century, the mysteries of free will and brain remain as philosophical discussions. Physics laws are written in math equations. Some laws of physics not only explain and predict experimental results but also introduce paradigm shift of world views. For example, special and general relativity redefines space, time, gravity, mass, and energy; quantum mechanics re-defines what we can observe at atomic level and describes a probabilistic worldview inside atoms. Many of these results are counter-intuitive and against our daily experience. Without discovery of the physics laws, we will never think of time slows down when traveling at high speed; nor will we think of entangled atomic particles can influence each other instantaneously. The physics laws can predict these phenomena but we cannot understand why the world behaves this way. Richard Feynman once said the accuracy of quantum mechanics matches with experiment so well; it is like if we were to measure the distance between earth and moon, the theory can tell if we measured from a person’s head or toe.

Maybe we are not supposed to understand the results in physics or inside our brain. If evolution theory is correct (highly probable), we are just a gene-carrying vehicles, evolved to fit the environment and pass on genes most effectively. It is great we humans have big brains and developed culture and science. Keep in mind brain was selected by evolution for our survival so that our genes can be passed on. It is natural that we couldn’t understand universe, atoms, and other big questions. It is not natural that brain can develop math and science. Fortunately and surprisingly, physics laws follow math equations. Math becomes the tool of our cognition to overcome the limitation of our experiences; math allows us to take a glimpse of the blueprint of the universe. But it is just a glimpse. We can calculate but cannot comprehend the result. On this regard, I think understanding is a feeling based on the similarity with past experiences or gene programmed neural patterns. Phenomena predicted by physics laws are nothing like past experiences or neural patterns and therefore we don’t feel familiar or understand it.

Can Brain Understand Brain?

Back to the mysterious brain: We are trying to use brain to understand brain. Have we reached the cognitive limit that nature has given us? Is brain able to understand brain? Books like [1] explain the neural and biological mechanism of brain at various levels, but mind and free will are about the collective function of multiple layers and billions of neurons. To study mind and free will at neuron layer is like to study viscosity at water molecular layer. We will need another tool to make the jump between layers. I think that tool is likely related to the new science of complex systems. For example, Stephen Wolfram (student of Richard Feynman and creator of the software of Mathematics) describes the strange behavior of cellular automaton: Complex patterns can emerge from simple rules [2].

Brain can be considered as the central information processing and decision system. Every layer of a time scale has its information carriers or medium. For example, excited neurons release neurotransmitters to excite other neurons; hormones circulate in the body and modifies protein and gene activities. The information processing and transmission mechanism turns brain into a complex network. Mind and free will are emergent features of this complex network. When future computers are powerful enough to model the whole brain (or whole body with external sensory inputs) as a complex network, maybe we can simulate the emergence of mind and free will from neural activities. However, even if this simulation comes true, I think we will be in the same dilemma as in physics: we can calculate mind and free will, but cannot understand it.

Reference

[1] Behave: The Biology of Humans at our Best and Worst. Robert M. Sapolsky, New York: The Penguin Press, 2017.

[2] A New Kind of Science. Stephen Wolfram, Champaign: Wolfram Media, Inc., 2002.

Random Thoughts on Mysterious Brain