Neurobiology and Behavior, Week 7

Neuronal signals make all behavior possible. These signals are the links between the brain and behavior. These signals are also diverse and versatile. In class we have discussed the possibility that the signals are all the same and the reason there is such a variation in behaviors, or outputs, is due to the diversity of areas in which the signal occurs. For example, when someone touches their hand to a hot surface, a signal alerts their brain that its hand is in trouble. But before that signal can be interpreted and responded to by the brain, another (similar) signal inspires the reflexive behavior of the hand in response to the heat. The signal was the same in both cases, but they engendered different responses because of the location of the electrochemical impulse.

This could be related to people experiencing phantom limb syndrome. In phantom limb syndrome, people feel pain in the limb that has been lost. This is because the area of the motor cortex that is responsible for the movement of the missing limb has been taken over to control another region of the body. Thus, the people still experience sensation, usually pain, in the missing limb because those same neurons are firing. The signal is the same, but the region of the body being "controlled" is different. This produces feelings of pain in the missing limb instead of movement in the limb that is still attached. This explains how the same signal can be responsible for the multitude of functions that humans have to accomplish every day to survive.

In a little blurb from the NY Times blog called "Brain Science vs. Criminal Law," the author asks readers, "Advances in neuroscience put it increasingly in conflict with criminal law: If all our mental states can ultimately be reduced to neurophysiological conditions, and there is really no such thing as free will, how can people be held accountable for crimes?" (http://ideas.blogs.nytimes.com/2010/03/04/brain-science-vs-criminal-law/?pagemode=print&scp=6&sq=neuro&st=cse)

While asking these kinds of questions seems like a radical departure from traditional thought about law and culpability, it's true that the law has integrated certain "scientific" factors into our understanding and ruling of justice. Neurobiologically, we've come about as far as it gets since the U.S. Constitution was written, and the author of the NY Times blurb seems to think that the brain=behavior philosophy undermines the applicability of a vocabulary that includes words like "liberty" and "freedom." If we do not possess the liberty and freedom of traditional notions of free will and active choice, do we need to reevaluate the bend of our legal terminology and criteria?

When neuroscientists obtain a role in the ruling of justice, the court is transformed and the subtleties of cases can be deepened. For example, a greater understanding of a "psychopathic" brain may transform the assignment of guilt (a term whose usefulness could disappear in a world of self-less behavior, as proposed by the NY Times blurb) in certain court cases. In observing a psychopathic murderer, neuroscientist Kent Kiehl says to the jury, “'There are abnormalities in his brain function.'" Psychopaths make choices, he acknowledged, but “those choices are not necessarily informed by emotion in the same way ours are."

(http://www.miller-mccune.com/legal-affairs/a-mind-of-crime-8440/)

I think I'd like to know more about the physical processes that occur when decisions are made, so that I can more deeply understand the interplay between physiological occurrences and human agency. The idea of randomness of choice vaguely proposed by the NY Times blurb seemed unsatisfactory and lacking depth. I'm not particularly attached to any cohesive notion of my own self-hood, or of my absolute agency in my engagements, but I find it hard to believe that there is no character to the randomness, or no pattern in the chance of choice that unifies the actions of an individual in such a way that a legal system based on justice, freedom, liberty, and guilt would cease to retain its functionality.

Over the break, I read Shades of Grey, a new novel by Jasper Fforde.  I may expand on this post later and write a full commentary about this book, but for now I’ll stick to its relevance to our discussions.  The book begins with a quote from Alfred North Whitehead: “There is no light or colour as a fact in external nature.  There is merely motion of material…. When the light enters your eyes and falls on the retina, there is motion of material.  Then your nerves are affected and your brain is affected, and again this is merely motion of material.… The mind in apprehending experiences sensations which, properly speaking, are qualities of the mind alone.” I was struck by how this sounds a lot like what we’ve been talking about in class.  On a basic level, neuronal function is quite simple, but humans are capable of experiencing a vast array of senses, emotions, memories, etc.  But there is still much we can’t and don’t experience. In the world of this book, set in an indefinite post-apocalyptic future, class structure is determined by the amount of color an individual is able to perceive. Those who can see purple are the heads of society, those who can see yellow or green are lower down the ladder, those who can see red are lower still, but those who can see no color (only shades of grey) are at the bottom.  There also exists, in this world, artificial color that can be seen by anyone.  Color is also used medicinally and as weapons: by looking at a sample of the right hue, a person can be cured of illness, be made blissfully ecstatic, fall unconscious, or simply drop dead. The book also suggests that color perception is heritable (a Red and a Blue could have a child that is Purple) but not fixed generation to generation (over time, families that once had strong color perception can become Grey, and a Grey family could gain color vision without outside influence).

            While it may seem silly to us, this use of color isn’t as fictional as it might seem. Colors are known to affect people’s moods. Color perception can vary tremendously between individuals. It is not so far-fetched to think that this kind of world could be possible, since color is a construct of our minds and as such its perception could be used, abused and changed. All it would take to make a population of humans with limited and variable color vision would be heritable differences in color receptors and a government-controlled method of testing for said differences.  Similarly, it is possible that rewiring the nervous system (or in fact learning more about the nervous system as it is now) could make possible the kind of dramatic responses to color that are seen in the book.  If everything is a result of “motion of material” virtually anything is possible. 

 After class on Thursday, I feel as though we have many of the tools that are needed to make sense of the human brain and human behavior. We know how action potentials are generated (either within neurons or by events outside the nervous system) and how they propagate. We also have an understanding of how signals interact with each other and how neurons communicate with each other. At the end of class we used the analogy of a computer to describe neurons: they take in a lot of information, they integrate the information, and then release the information, and this whole process is constantly altered by its own activity. However, we said that the brain is not a computer, because it is changed by the past. This means that learning and memory are a fundamental part of activating this entire system. Given this notion of how the brain functions, I feel we still need more tools to evaluate the human brain, and thus human behavior. I’m sure we all know that learning how to ride a bike requires a lot of practice. But once we get it, we can do it all the time and it becomes almost second nature. I wonder how we get to this place. Is it all muscle memory? And what about the other activities, such as sports and hobbies, we all enjoy? Certainly that can’t all be the result of muscle memory. So what else is going on in the brain when we learn to do these things? Memory also seems to be pretty complicated. We can’t remember the first few years of our lives, but we definitely had learning experiences then. And why do certain parts of the past get fuzzy after some time has passed? Why can’t we remember everything with a high degree of accuracy? This inability to remember everything may be due in part to information overload that would occur if this were possible. But what is going on in the brain with the things we do remember with such clarity? I wonder if the neuronal connections involved with memory degrade over time or if there is some other mechanism at work. In sum, I guess I feel as though we still have a ways to go in understanding the human brain, but I think with our understanding of action potentials we have a great base from which to move forward. 

At the end of class on Thursday we discussed the notion that synaptic activity varies with time. The amount of neurotransmitter released and the number of receptors for that chemical all may change with repeated use (or disuse).  I was intrigued by this because of its parallel to drug use and withdrawal. For example, when caffeine is consumed and present in the brain, it binds to the receptor for the neurotransmitter adenosine, which serves to regulate blood pressure among other things. An increase in the amount of caffeine one consumes (the amount of this chemical that is consistently present in the brain) is then related to an increase in the amount of adenosine receptors present. This is known as tolerance. If a person were to stop consuming caffeine for a prolonged period of time, the receptors would initially still be present and a larger amount of adenosine than usual would bind to these receptors. Thus, caffeine withdrawal effects (headache, nausea) are in fact caused by the binding of adenosine to these receptors in the absence of caffeine.

I wonder whether other chemicals, such as the endorphins released after long, uninterrupted workouts, have the same effect as caffeine in creating more receptors in the brain. Endorphins resemble opiates in their ability to block pain and cause one to feel well and happy. Should it be expected than an individual who exercises everyday has a greater number of receptors for endorphins than a person who rarely exercises? Are they happier? What would happen to that individual if they stopped exercising suddenly for a prolonged period of time? Can these individuals experience withdrawals from strenuous exercise (pain, depression)? Would some other chemicals begin to bind to the numerous receptors causing other symptoms? Or, perhaps the amount of endorphins produced is small and the effects are fleeting (limited to a short period of time after exercise). Perhaps a lack of exercise would cause no observable detriment in one's behavior.

 

          We are unaware, i.e. unconscious of many things our body is doing. Our brain is the main control system; however, many of the actions it directs especially those that allow our body to care for itself take place below the level of consciousness. The basic units of our nervous system including our brain are neurons which transmit signals as action potentials. I was astounded to learn that action potentials were similar to electrical currents produced by a battery. How a mechanism seemingly so simple can manage complex actions as much as maintaining the body is amazing, and even more amazing are conscious actions which we control and are aware of and conscious actions which have no physical manifestation such as doing multiplication in our head. Even considering that our brain has billions of neurons and that there are all kinds of different neuron shapes which suggest specialization and that the neurons are organized into functional units seems that there must be more than the physical brain to explain higher functions. Many animals have better senses than we have, and the basic organization of their brains seems to be similar to ours. Few animals have larger brains than we do and yet they do not seem capable of higher functions. What is it besides the brain made up on neurons that transmit action potentials that is needed? What makes a brain a mind?

            We might make better sense of human behavior/experience by exploring more irregular situations like that of Christopher Reeves.   We cannot create these situations because that would be unethical, i.e. directly harming someone, but accidents do happen and we might learn from them.

            An interesting topic that we talked about during class dealt with proteins and that one cannot detect anything without having proteins that produce the permeability changes. Basically, we detect certain things in the world by seeing, hearing, smelling, or touching because we have proteins that produce the appropriate permeability changes. This brings up a point that humans cannot detect everything in the world because we do not have the necessary proteins and permeability changes.   It would be very interesting to learn more about some of the things the nervous system can’t detect because of the lack of proteins that change permeability.  There can be so much going on and taking place in a room that we would be never know about.  For example, it’s amusing to think about how a radio is capable of detecting the noises in the electromagnetic field, yet humans are completely unaware of them.   It is also quite remarkable that the nervous system is able to respond and deal with the enormous amount of information that it is able to detect. It is important to note that what a human is aware of is not the same as the information the nervous system is getting.  Also, the nervous system isn’t even able to detect everything that is going on around us, yet it is still being bombarded with bundles of information.   

Another interesting idea I was not that aware of was the fact that signals didn’t leave a cable. For some reason, I had always imagined one signal moving through various connected cables; however, signals end in the cables and do not exit it. This lead to the idea that our neurons were extremely advanced and somewhat like a computer. Despite getting about 1,000 signals, neurons are still able to make their own signals based on the numerous signals they receive.   

 Like everyone else I've been wondering about the other senses that we do not have and so cannot experience or senses that we have but are not aware of. I was thinking about how the senses that we are aware of can be manipulated. Like when you're a child or even when you're in the womb and you here your mother's voice and "know" that this is your mother since you can recognize the sound without being aware of it. Then as you grow you pick up new sounds, give them names, and those are what makes up of your experience. I read in a book that in order to have a memory of something you have to make a name for it or have a word that you can connect your feelings and other senses to, like what you saw and smelled and heard. By placing a name or word to an experience does that muddle with what you actually experienced. When you have a feeling that you can't describe and you keep trying to find words for it but can't. I guess you then just say it was a feeling and that is the word you connect many of your unknown experiences with. Although with so many different experiences being placed with one word your memory can definitely get very confusing or place two things together that are related but did not happen at the same time. I wonder if because when you're born and the first couple of years you haven't placed words with experiences yet or really understand words is why you don't have memories from those years and you have to rely on your parents for some details. We learn with words, seems to be a good summary. For example, a parent is cooking and their toddler is in the kitchen, in order to make sure they don't burn themselves the mother will say "hot" and show a gesture of pulling their hand away from the stove so the toddler understand the word hot and will make the same gesture and then understand that feeling. Then it's pain that makes it so the toddler doesn't continue to touch very hot stuff. It's interesting how much language and words are critical to our way to life in learning and communicating, etc. 

From neuronal signals, we have learned that neurons are computers because they take in information, integrate and process the information and then passes on more information.  Therefore, the brain is made up of all these "computers" which dictate our behavior.  The term "computer" sounds very mechanical which makes me think that anyone with a mental disorder can be taken to a mechanic and be fixed immediately.  While we have learned the general basis of neuronal signals, I can't seem to tie it to behavior and the brain.  I feel that behaviors are subject to interpretation and everyone's brain interprets situations differently so how can we possibly have a reference point to start learning the connection between signals and behavior? We also discussed that more than half our synapses are inhibitory which leads me to believe that our "default" mode is to be expressing ourselves at all times.  So is it due to our inhibitory synapses, that we are able to contain our emotions or thoughts sometimes?  

            What we have learned is how the brain creates action potentials and how those action potentials travel along a neuron and eventually produce a response. We’ve also learned how signals are transferred from one neuron to another. We still have a lot to explore, however. One thing that merits further exploration is what neurons (as in what type of sensory neurons) receive specific signals from the outside world. Personally, I would like to see how these receptors are a part of or contribute to the “other senses:” the senses beyond the five that we are familiar with. I think that I understand the “big five” senses well. We have optical receptors in our eyes, mechanical ones in our ears, and other specific receptors in our body that help us smell, taste, and feel. These I understand, but I don't quite yet understand how the other senses would work. For example, how does the “perception of hormones” sense work? I know that it must-since women’s periods sync and insect males can (seemingly) innately sense a female’s hormones, but I don’t quite understand how these signals are received. Is there something on the inside or the outside of the body that just picks the signals up? I guess this could happen, but it’s hard for me to conceptualize. What I’m wondering is the following: what makes us so sure that our ability to detect hormones is not somehow a part of one of the “big five” senses? We may be able to smell hormones, or to see the affects that they have on someone, without fully realizing that that’s what we are detecting.  I have read studies in which men had to choose pictures of women that they deemed the most attractive, and more often than not, these women were in the middle of their menstrual cycles. These men were nowhere near these women and could not pick up their hormone signals as a result; however, they still thought that the menstruating ones were more attractive. Rather than detecting hormones, they saw the affects of them and became aroused that way.

            I also wonder if our sense of smell might help us to detect hormones. Sometimes, when we are attracted to someone, they seem to “have a nice smell.” And even if we are not aware of the smell consciously, I don’t think that this would mean that it isn’t there. We aren’t aware of everything that touches us, for example. In fact, I think that if we were aware of all of it we would go crazy; however, I don't think that this means that the feeling isn’t there; there just isn’t an awareness of it. Therefore, I think that the sense of smell can detect hormones. I think that our ability to detect hormones is something that may be able to be explained by the five senses, or maybe a combination of the senses.  I’m not trying to say that a separate sense for hormones doesn’t have the possibility of existing, but I won't be convinced that it exists until we discover how humans and other animals pick up on hormone signaling.