Mind, Brain, and the Self
Inspiration
"Logic will take you from A to B, but imagination will take you everywhere"- Albert Einstein.
I often feel that using logic only takes us from one question to the next, yet when we add imagination to the problem, there is more nuance and finesse to the art of questioning. I am a neuroscience and philosophy student, and my goal in life is to understand how the mind substantiates an entity called 'I' which is so surreal and different from anything else in the world. It just so happens that I took some very interesting classes last semester that touched on some of the deepest questions I had. Each class focused on its own curriculum: 1. My philosophy of mind class went over different theories of mentality and theories of consciousness 2. My neuroplasticity class went over current biological and neuroscience research on axon guidance, neural identity, visual pathway, and cortical circuitry 3. My Systems Neuroscience class went over the dynamic, yet topographically specialized, role of the brain and its function in different aspects of life. These three classes gave me the foundation to think deeply about the topic of mentality and self. What follows in this blog is a synthesis of my understanding from these classes. I will mention sources here and there, but this blog isn't meant to be an academic paper. As stated earlier, it is a way for me to structuralize my imagination of the mind and synthesize the information I have learned in my neuroscience studies so far. Is it me who is curious about all this stuff, or is it just the brain arranged in a certain way that disposes me to think about these things? Who knows, but let's find out (maybe?).
Philosophy of Mind- Minding about the mind
Our minds are the biggest black boxes we will ever know. There is so much that happens in our minds that we are unaware of, yet it makes us who we are and facilitates what we do in our lives. It is only natural that we have a branch of philosophy for mind which explores several interesting questions regarding mentality and consciousness. First we have to start by defining the mind, which is the ontological problem: What are mental properties, and how are they different from physical properties? In short, what is the relationship between mind and body? Some would argue the mind is just a folk psychology concept of the brain, and all things are physical in nature. This leads to another problem: Hard problem of consciousness, which states how can physical states create such subjective experiences. Even if we don't completely agree with the mind-brain identity, it still seems intuitive that the mental stuff is somehow connected to the physical stuff in our bodies, so the question becomes: How do physical changes in our bodies cause mental changes in the mind?
Hypothetically, if neuroscientists knew all the physical facts about how the brain and body worked, would they know everything there is to know in the world? If you are dualist, you are likely to argue this is impossible and that there are some things in the world that are non physical hence private to each individual's mind. If you are a functionalist, you are more inclined to argue that irrespective of whether the facts are physical or not, the neuroscientist must know the functional relationship between different nodes of information processing units. If you knew the functions of systems but not the anatomy, you would still have understanding of mentality. If you are an eliminative materialist, you want to say introspection needs to be replaced with a rigorous scientific method of studying the brain and once we know all about the brain we will have an objective understanding of a previously known subjective experience. And finally, if you are a panpsychist, you would say all physical matter has fundamental properties of consciousness so we those physical states are conscious by nature. They are sort of suggesting: the body's intrinsic nature is to facilitate conscious experience so we don't need an extra entity called the mind.
There are much more subtleties to each of these theories, but the idea is each of them is attempting to solve the mind-body problem and somehow addressing the ontological and hard problem of consciousness. There are two other problems that arise as people are studying this: the epistemological and methodological problem of consciousness. First, the epistemological problem asks if we can ever actually know someone else's mind. The word, 'know' is referring to qualia, often defined as what it is like to be something. Thomas Nagel's famous paper, What Is It Like to Be a Bat?, is a phenomenal paper. (no pun intended) Nagel argues that the experience of what it is to be a bat is not accessible with the sensory and neural apparatus us humans have. So then, the question becomes do we have the proper physical apparatus to understand other human's mental states? When we think about what it is like to be someone, do we simply employ our own prejudices about what it is like to be ourselves? We may ask someone what it is like to be them, or to think like them, but most of these things are ineffable, and difficult to share through conversation. This is the epistemological problem, and most scientists tend to ignore it and state 'what it is like to have someone else's mind' is just generalized by logical understanding of natural and social sciences. In other words we just need to know about their biopsychosocial circumstances and we will understand the other person. Is it that simple? Perhaps that is something all of us have to answer for ourselves.
Linked: What Is It Like to Be a Bat?
The other problem is the methodological one- what methods do we use to study the mind? This may be contingent on answering the other problems, yet still it is the most practical one we have so far. Behaviorists and early psychologists would argue that by observing people's behaviors, we can understand their mental patterns. That model has changed recently, and modern psychologists and neuroscientists argue that testing people's neural states (fMRI, PET, EEG scans) alongside their cognitive-behavioral states is a better method. Computational neuroscience has grown tremendously with advent technological innovations and people are trying to use machine learning in tandem with neuroimaging to decode people's thoughts, feelings, and emotions. I am not an expert in this field, but below is a fascinating article about using artificial intelligence and fMRI to convert thoughts into text. Consequently, the next section will give more details on the neural basis of consciousness and its subsequent issues.
Linked: AI makes non-invasive mind-reading possible by turning thoughts into text
Neuroscience of Consciousness- its not all brains
So, let's start with trying to understand how the mind is born from the workings of the brain. But before we look at neuroscience, we have to go back to evolution and molecular genetics. What makes a brain a brain, and not a lung or a kidney? The answer is we have specialized cells called neurons which have an intrinsic property of making connections with other neurons and releasing action potentials as signal messengers. Premature neurons are progenitor cells that differentiate into neurons at the proper time of development based on environmental chemical signaling. Neurons have long reaching axons with growth cones which contain specific receptors that help the neuron locate its connection. As a neuron is randomly elongating its axons, environmental regions release chemicals that serve as attractants or repellents for the outgrowth of the coming neuron. Almost all afferent signals from the body have to cross to the other side of the spinal cord. Similarly, there is abundant cross lateral hemispheric crossing of axons. The natural question is how do these neurons 'know' where to go, and when to cross? The simple answer is they have receptors that bind to specific morphogens that are released only at specific locations. Once bound, that leads to a complicated secondary cascade which eventually changes gene expression and establishes a direction for the neuron. Once the neuron has arrived at its location, it forms a synapse which is nothing but a strong electrochemical connection between two neurons.
Neurotransmitters are chemicals released to excite or inhibit these connections, and they are the major ways of integrated communication between these cells. So neurons are able to find their partners using chemical morphogens, and they are able to communicate with them using neurotransmitters, but what does this have to do with thinking and cognition? So far I have only described the biological behavior of neurons, so how does that translate to more psychological causes? The general idea is by establishing connections, neurons learn to represent incoming information in their own language, call it the language or neurons. Because neurons don't talk, they need another causal mechanism to encode events- hence they use something called a long term potentiation (LTP) for learning and memory. A LTP is simply an increase in post synaptic potentiation due to increased communication between two neurons. In simple words, when neurons start to fire synchronously, their synapses become stronger and it requires lesser neurotransmitters to impact each other. This is also known as sensitization, where due to increased receptors on the postsynaptic neuron, the presynaptic neuron is able to excite its partner very quickly and with minimal chemical signaling. The idea is that all our memories are formed in a network across different neurons ( such as in visual, auditory, tactile) and the consolidation of that memory is related to higher LTP in synapses across those neurons. It just so happens that we have a specific region, namely the hippocampus, that is integral to binding the information from different neurons. But the molecular concept is that neurons build a system in which they excite or inhibit each other and thus change the function of the entire network responsible for a cognitive experience. Networks are established among different regions, and any true experience is never just firing of one brain region or another. Instead all perception emerges from a network of neurons maintaining an electrical signal and then changing the body's physiological processes.
Cognition and perception aren't just neural processes, but rather they are embedded in the entire body. A key structure in the brain, hypothalamus regulates other physiological processes based on the neural connections it has with the rest of the brain. For example, during a stressful event, the hypothalamus will instruct the anterior pituitary glands to release ACTH, a hormone that travels through the blood to the adrenal cortex, where cortisol, a stress steroid, is released. High levels of cortisol can actually target hippocampus receptors and reduce its volume. The hippocampus, a region for memory consolidation, is no longer able to contextualize fear and becomes unable to regulate the emotional response. On the other hand, the amygdala is a region that appraises fearful stimuli and stimulates the hypothalamus to release more stress signals that instruct adrenal medulla cells to secrete epinephrine/ norepinephrine and increase our heart rate and perspiration. I am referring to the brain structures here, but what is actually happening is a specific network of neurons is activated and influenced by the regulatory feedback. Thus, the stress hormones create a vicious cycle of reducing emotional regulation while increasing fear appraisal. My goal in sharing this example is to show that there is a physiological component to emotional and cognitive experience. In most cases, what happens in the body affects the brain's ability in decision making.
Zhang & Wang et al., 2018 International J. Oncology
My ideas here come from a famous theory known as the Somatic Marker Hypothesis by Antonio Damasio. The principal notion here during a subjective or emotional experience, there are somatic markers across the body which are associated with primordial feelings. The intensity and duration of those feelings depends on various factors such as the dosage of the marker or the previous sensitization to the marker. That marker is a physiological index such as heart rate, blood pressure, skin conductance, stress hormones, or glucose levels. The combination of the entire set of physiological processes gives feedback to the brain, specifically the hypothalamus. It is the role of hypothalamus to create drives and motivations to change current physiological state to affect subjective experience. The hypothalamus has connections to emotional and cognitive centers which together create a network to produce a drive. So a set of somatic markers change the neural network activation primed by the hypothalamus and brainstem. The brain stem works in the background to regulate some of the unconscious processes such as respiration rate, digestive processes, and immune functioning. Overall, the somatic marker hypothesis suggests any experience is conscious if and only if it creates a change in homeostasis, which is the equilibrium state of the body. The brainstem is a key region for conscious experience, as shown by Moruzzi and Magoun's 1949 experiments on cats with brain stem stimulations. They found that electrically stimulating the brain stem, specifically a structure called pons, suddenly woke the cats up. EEG scans found that electrical activity went from delta, low frequency, to beta, very high desynchronized frequency upon that stimulation. More recent studies have shown that the brain stem has global connections across the brain, and the global activation is what is responsible for change in consciousness. But consciousness isn't just wakefulness, it also involves attention- the property of incoming information to process the mind and hold it there. Wakefulness certainly seems to be associated with the brain stem, a very primitive yet important structure in the brain, but what about attention?
Linked: Moruzzi and Magoun study
Modern neuroimaging studies have shown a specific structure called the locus coeruleus(LC) to be responsible for attention. I have attached a recent literature review below that implicates further evidence of this region. The idea is that the LC has a lot of norepinephrine releasing neurons. Norepinephrine is a key neurotransmitter for selective attention, and also increases several physiological markers responsible for arousal. Like the brain stem, LC has connections to the prefrontal cortex, amygdala, and hippocampus all of which play a role in regulating attention, and providing emotional and historical context. The PFC, seems to be the one involved in holding information in working memory, on the command of LC connections. Norepinephrine increases LTP at amygdala and hippocampus, thus suggesting a mechanism of learning while paying attention. And finally, it seems LC norepinephrine release suppresses spontaneous activity in sensory cortices, and facilitates executive control using the PFC. Too high levels of norepinephrine can actually damage hippocampus and impair executive control of PFC, so we see a classic Yerkes Dodson inverse U curve. Alertness seems to be most optimal when NE levels are moderate to high, but not very high.
Aston-Jones et al, 1999, Biol. Psychology
To sum up this section for the neuroscience of consciousness, I can say two things: 1. Consciousness can be studied by looking at wakefulness, i.e. what global systems are associated with circadian rhythms and being awake, or it can be studied by awareness/ attention, i.e. networks that allow us to hold information in the mind. 2. Conscious experience isn't limited to one region of the brain, or let alone the central nervous system (brain+ spinal cord). Rather, it is emergent on the interaction of somatic physiological markers and changes in neural networks primed by hypothalamus and brain stem. Ultimately, these two structures alongside the LC, use neurotransmitters and neurohormones to change communication between the brain and body to provide a subjective emotional experience.
So, What is the Self?
Hearne et al. (2016) Nature
Our mental experiences may be purely physical in nature or they may be metaphysically divine, but the real question is what is the relationship between the mind and self. We take our minds to be granted and unconsciously build a personality that we identify as. But if we try to take a step back and ask, who am I, we become dizzy with possibilities. I am going to argue that everything we think we are is simply a process of intracranial network activity. I am not suggesting that we are the brain, but rather we become what the brain does. We cannot identify our deepest memories and feelings with the physical substrate of neurons, but instead we can argue that those physical substrates are in fact the causes of our subjective selves. As the picture to the left suggests, current neuroscience has found several functional brain networks that are responsible for different mental states. For example the salient network is more active when we are attending to a novel event in the moment, while the default mode network is active when we are daydreaming about past events. The idea is that the proportion of blood oxygen level in different networks produces a specific mental state that we become conscious of. But this can only tell us what we do, or what we think we do. What this scientific work doesn't tell is what we are, and why we are what we are based on the physical networks. So this is where we need to look at the entire organism, and its environment outside the brain.
The reason why it is so hard to find a singular thing or network that is associated with the self is because there is no such thing in the first place. I am arguing that the self is an illusion that is born out of different networks (in and outside the brain) performing their own roles in their own ways. The organism as a whole is nothing but a process of different systems functioning based on an evolutionary program that is flexible to ongoing environmental conditions. So there is this pull and push from nature outside and nature inside. And as these internal and external processes are working, an autobiographical self is born.
Here is a simple thought experiment: try to come up with 3 characteristics that best define who you are right now and then who you were 10 years ago. Now, try to see if there is some property or attribute of yourself that remains across the time period. The goal is to find something that surpasses transient periods, and has potential to remain for your whole life.
If you do this sincerely, you find that most things that you think you are only stick around for a couple years before new attributes take over. The quest for an unchanging, static personality comes to an end when we realize that we are nothing but a changing process in connection with our environment. As external things change , internal changes follow, and as internal change occurs, our autobiography moves to a new page in the book of life.
The classic counter argument would be that we choose what environments we want to be in, and therefore we have a sense of free will in the world. But the very notion of motivation is contingent on other social and psychological dispositions. We choose 'this' call it X over 'that' call it Y because X is more compatible with the orderly arrangement of our nervous system. Some people prefer quiet areas while others prefer loud places, and in both cases they train their internal system to get accustomed to that particular environment. Over time, they can very well switch places if their internal system adapts to the opposite conditions.
The classic distinction between self and other arises only when we create boundaries to distinguish transient events and people. But at the macroscopic level, the self is pretty much everything, everywhere, all at once. The universe doesn't have an agenda of what to do, it simply exists for the sake of it. And given that the we as the organism and our nervous systems are part of the universe, we can argue that we also exist just for the sake of existing. The labels of identity we put on ourselves are like the different outfits we try in a clothing store's fitting room. We look around us, choose from the disposed items, try things out, and then after a while move on to new things. Similarly, our personalities are in constant flux, always looking to change when something new comes. Thus the self as an unitary entity is purely an illusion, what is more probable is the self as a process. A process in which things come and go, inputs drive outputs, attributes build on one another and one story leads to the next. Letting go of our 'self' is very difficult because the brain is predisposed to build a self and protect it. What I propose we do instead is spend more time thinking about the bigger world. The more work we do for the world, the more holistic our sense of self becomes. A more holistic and flexible self, paradoxically, gives more authenticity than one that is confined to its selective identity.
Like a plant that grows out of a seed with sunlight and water, our 'selves' grow out of the mind with consistent neural and physiological processing. Neither the mind nor the brain exist as a part but rather as a process of the whole universe.