The HumanNervous System

Let’s talk about science and the appropriate level of explanation for our behavior and for consciousness. How do we know things about ourselves and our world? Neuroscience looks for the neural underpinnings that correlate with consciousness, states of consciousness, and subjective experience. It looks for the biological substrate of our phenomenology, our lived experience. Brain activity can be measured and imaged in vivid detail during mental tasks and in different states of consciousness. Is this brain activity consciousness? Or is it the result of consciousness? How is it related to behavior? The science of consciousness needs to explain the physical relationship between the mind and body.

Let’s back up and define consciousness. Consciousness is the experience of having individual sensations, feelings, and awareness. It is important to note that sensations, feelings, and awareness do not require consciousness. Consciousness is the integration of those sensations, with directed attention, emotion, memory, and other cognitive processes, including language. I am defining consciousness as an emergent property of the neural processing occurring during that integration. I’m also going to show you, hopefully, how an emergent property can direct and be responsible for our behavior.

Emergent properties have been evoked in biology, chemistry, physics, psychology, sociology, and economics, to list a few. Neuroscience, which is an amalgamation of sciences, including biology, chemistry, and medicine, is also on that list. Not everyone agrees, if you can imagine that. From what I have learned about how the brain produces thought and behavior, I am happily surprised that anybody could ever agree with anyone else about anything. We will get to that shortly.

Can the mind or consciousness be understood from exclusively looking at the brain, or at even higher resolutions, individual neurons? Or we can zoom even closer and talk about the flow of sodium and potassium ions across protein membranes, or down to the subatomic level of quarks, fermions, and bosons. I don’t think higher resolutions help us understand behavior, consciousness, or the mind. It is difficult to let go of reductionism in science as it has been very useful, and reductionist accounts of consciousness can be found in the literature. These accounts, in my opinion, cannot capture the richness of human thought and behavior, and discount the potential for the mind as an active agent.

Sometimes, the closer you look, the less you see.

Zoom in onto a cell with a microscope, or zoom in on a cluster of stars, and you gain resolution, but you lose information density, you water down the data. The microscopic world and the heavens are not uniform, there is not the same amount or type of stuff wherever you look. There is a mind-numbing amount of space between things, the closer we look. You gain information about what you are zoomed in on, but that sample of information cannot tell you the whole story. The sample (one level of resolution) is not representative of the population of stuff it was taken from (a lower level of resolution).

Scientists have known this for hundreds of years and direct their observations (higher resolution samples) based on hypotheses that are most often deduced from theories. Science does not randomly search for information. For the detective, same. You figure out where to look though deduction. But the closer you look, the less you see, especially if your hypotheses, deductions, or theoretical model were flawed.

That’s not really what I want to talk about, but it leads us up to it. When you gain resolution, you lose power (data, information) to explain the original perspective. If you want to explain consciousness, you lose power focusing on cells. The property of the whole is more than the sum of a closeup of its parts. We need to pull the focus back and look at patterns of activation across networks in the brain, for example the ventral and dorsal attentional networks that span across brain regions. That may not be the right resolution either, but it seems to me to be moving in the right direction.

The hard part is to explain how that emergent property of consciousness can be a cause of our behavior. One solution is to say that consciousness is an add on, and an emergent property cannot cause our behavior, it is not a cause of neuronal firing. This view of emergent consciousness likens our phenomenology, our subjective experience, to a running narrative. Consciousness is just us silently talking to ourselves. This is likely to be true in most cases of thinking and conscious behavior. I for one am not ready to give up on the causal nature of consciousness, but I must admit that much of our behavior does not require thought. As A. E. Housman says, “A moment’s thought would have shown him, but a moment is a long time and thought is a painful process.”

Part of the painful process is defining an emergent property. This is an unfortunate use of language. A property is a characteristic of something, and that something comes into being, it emerges. What is the it that emerges? Birds flocking behavior is an example of an emergent behavior. There can be emergent situations. These things, let’s call them things for now, come into being from the interaction of independent parts. Birds flying. Systems interacting. These things have characteristics that the individual parts don’t have and are difficult to see until they manifest. When you point at that flock of birds, you are pointing at the emergent thing, not the individual birds.

Alternatively, consciousness can be considered an emergent cognitive workbench. This internal space is the result of neural processing across a wide range of brain areas and functions, including the lobes of the hemispheres, the deep brain structures, and higher integrations of neural processing in areas of the brain called association cortex. This mental and physical space is for evaluating various potentially conflicting behavioral responses, choosing one, and directing behavior. Consciousness, from this perspective is adaptive. That doesn’t necessarily mean that it evolved for this purpose. It does mean it can direct your behavior.

Let’s look at what we know about consciousness and how we know that. Then we can look specifically at the sense of sight. Vision will provide a familiar example of our personal phenomenology and how it directs our behavior, both consciously and unconsciously. Learning more about our sensory apparatus can move us forward in understanding how consciousness affects our behavior.

In neuroscience, one way we learn about consciousness and how the brain is involved in behavior is from injuries that disrupt that consciousness and behavior. A concussive blow to the head results in altered consciousness, or unconsciousness. Multiple blows can cause chronic traumatic encephalitis (CTE) which can drastically affect consciousness, personality, and behavior. Strokes and tumors of the cortex, the thalamus, and the brainstem can result in unconsciousness and coma – a prolonged and severe unconsciousness. Damage to the spinal cord does not affect consciousness in this way. Consciousness seems to be in the central nervous system, and specifically inside the skull. Drugs that affect the central nervous system inside the skull alter our consciousness. Anesthesiologists expertly create, administer, and monitor the effects of drug cocktails that squelch some aspects of consciousness while leaving other aspects intact.

A problem with these types of clinical data is trying to determine how the intact system works based on observations of the impaired system. If damage to the motor cortex results in paralysis, we can infer that the motor cortex functions to move the body. We can’t infer how input from the premotor cortex, the supplemental motor cortex, from the basal ganglia, and from the thalamus influences this function. They show us perturbations in the system and give us important knowledge for developing therapeutic interventions, but don’t give us the type of information we need about the working and waking system. Again, they are at the wrong resolution.

How do we study the phenomenology, the conscious experience of other animals? We can observe them in their environments, and with carefully planned observations, try and infer their subjective experience. We have learned about imprinting in birds, communication in bees, and the social interactions of various primates, giving us glimpses into their internal lives. Animal cognition and experience has been assessed in more controlled environments as well. For example, color vision has been studied in a variety of animals including dogs, shrimp, and bees. These animals have different types of color receptors in their retinas, for example, three in humans, two in dogs, four in bees, and shrimp can have up to twelve. These animals also react differently based on colors in their environment. An animal’s color perception can be deduced from looking both at the protein structures of their color photoreceptors, and from behavioral data. Animals have been taught aspects of human languages, giving us some insight into their mental experience, and the opportunity to ask them what they think and feel. Still, we are inferring what the animal sees, experiences, thinks.

An often-cited discussion of these points can be found in Thomas Negal’s paper, What It’s Like To Be A Bat, in Philosophical Review in 1974. His argument is that an animal’s conscious experience cannot be understood though conventional reductive science, meaning biological explanations. He is not saying that the mind is not physical, or that consciousness does not arise from physical processes. Of course, they do. For him, and others, the mind cannot be explained by looking closely at the brain. The level of resolution is wrong. His points are not without significant criticisms, but they do bring up an important theme: How do we confirm the existence of mental states in others? We directly experience our own consciousness but have no direct access to the mind of others. The problem is not do other animals have minds, the problem is do other people?

Why would we think that others are conscious? What would be the advantage of inferring mental states to others? Psychologists call our attribution of mental states to others Theory of Mind. We develop an ability to attribute mental states to others that are different than our mental states. We learn, as we age, that other people have different perspectives, feelings, and opinions than ours. As we learn the nature of those differences, and similarities, we begin to better understand others’ intentions. We can better predict and explain someone’s behavior from those attributions. Our theories of the minds of others drive our social interactions and give us fuel for our sympathy for others. Psychological science longitudinally and cross-culturally studies the development of Theory of Mind and contributes to our quest and understanding of the ghost in the machine.

We have the scientific precedent and methodology to study consciousness, and we are developing a language to understand how emergent properties can direct our behavior. We know that the primary motor cortex tells lower motor neurons in the spinal cord to produce movement. We know that we plan that movement in the premotor cortex, just rostral (toward the nose) of the primary motor cortex. We know this from clinical data collected on damaged brains. We know that other motor modules and networks are involved. We don’t have a good explanation for what kicks it all off. The environment alone is an inadequate explanation. Genetics alone is inadequate. Their interaction of environment and genetics through epigenetics and learning is also an incomplete explanation. We need to pull back our resolution and look at how large neural networks interact, and how these systems interact with environmental and social systems. A good place to start is with our visual system, and how it connects with other sensory and motor systems to produce our subjective and internal experience of sight. That will be the subject of the next blog.