Neurobiology and Behavior, Week 10

 The experiment with the sea slug’s behavior choice (to withdraw its mouth or not) is interesting in that it shows how corollary discharge signals can influence what the nervous system does in response to input signals. For the sea slug, the input was banging on its mouth, and the output was retraction of the mouth. However, retraction does not occur if the nervous system is inhibited by the corollary discharge signals from the CPG that is used to grind its teeth. If this occurs, the mouth will stay out. Given this scenario, it is possible to account for aspects of choice using corollary discharge signals and CPG’s. However, I am not convinced that this is adequate enough to characterize what we mean by choice in human beings. It seems like there is much more involved than an inhibitory effect when we choose. For instance, when we are deciding what kind of car to buy, there are a lot of factors to consider: how safe is it? Is it fuel-efficient? Do I want a car that is fuel-efficient? Is it aesthetically pleasing? How much can I sell it for later? These are just some of the questions one might ask. If the sea slug module is correct, then where is the inhibitory factor in this decision? And what about those decisions that we make in a split-second, the ones that most people refer to as instinct? Humans make instinctual choices all the time, and they occur so fast that if there is indeed an inhibitory factor, it must occur at top speed. Right now, I seem to be having a hard time understanding how behavioral choice in humans can be explained in this manner.

On a different note, I had never considered the idea of set points and negative feedback loops in the nervous system or how much of our daily patterns are influenced by these. But this makes so much sense to me now, especially in terms of how the body reacts to disruptions/perturbations to its normal pattern of functioning. Our body’s response to fever is a great example of this: the body has a set point for temperature, but in the presence of an infection, this set point is increased to fight the infection. Although our bodies are warm/hot, we shiver because our body temperature is now below the new set point and it is trying to reach it. Our nervous system is acting in such a way as to adjust to the changing internal environment. This process however, is not in the realm of what the I-function can do. Going back to choice, there are choices that can be made in the absence of the I-function (i.e. maybe instincts), but there are also instances in which the I-function is necessary for explaining human behavior and choice. Maybe further exploration into the involvement of the I-function in choices outside of biological processes would help explain what we refer to as human choice, those decisions that are made every day that do not concern the functioning of our bodies. 

When we were talking about pain on Tuesday, and the fact that the child only cries after it has been pointed out to it that there is injury, I was not very convinced that the child did not experience some element of pain prior to the acknowledgment of injury.  I was thinking that if I sliced my finger open, I would totally feel it regardless of whether or not I actually saw the open wound occur and I would feel it regardless of whether or not someone pointed it out to me.  Well, I was proven wrong.  I went to the Gunks this weekend to do some bouldering.  I was working out this problem - one of two boulder projects I have.  The move requires holding on with both hands to a sharp edge, fully extending both arms, placing the right foot on a small foot hold and smearing the left foot on some slippery slab and then throwing the left arm up to this hold.  Well, I was doing this over and over again, sometimes sticking it, and during one of my successful attempts I tried to throw my right hand to match up to my left.  I got it, then fell, but I was quite pleased with myself.  I went to get some more chalk and then noticed my right hand was covered in blood.  Apparently, the sharp edge had caused a flapper - a piece of skin had been torn off my one of my fingers.  I thought it was weird I did not even feel it, then suddenly my finger hurt.  It is interesting that I did not feel pain until the blood and the concerned look on my friends' faces suggested to me that I should feel pain.  Further, at the end of the day, I noticed additional scrapes, bruises, blisters covering my body that caused me no pain what-so-ever during the day because I was so focused on my two projects that pain was unfelt or unobserved.  I think that is interesting.  Perhaps we can shut off pain with sharp focus or perhaps we are adjusting our nervous system's response to pain in order to stick all these ridiculous boulder moves.  However, there is a point where pain is obvious.  You break a limb, sprain something, etc. pain usually follows instantaneously.  Seems like maybe there is a set point for pain.

So, we have been speaking a lot about CPGs and movement.  We acknolwedged that CPGs may be tuned and adjusted both physically and mentally.  Well, I worked very hard to physically tweak my CPGs yesterday in my attempt to send a boulder problem, and it just did not happen.  It could be another I-function interference or perhaps more modification needs to occur.  I have a mental score of the moves I need to stick in order to send this boulder problem and I have been playing them in my head since yesterday.  I am wondering if this mental recall will assist me in anyway when I get back to the project this weekend. This is my test for the week - to see if I can mentally tweak my CPGs. 

After our class, I'm interested in how the set points are set and adjusted. It makes sense to me that we have some kind of a set point for body weight, body temperature, etc - it's probably just one of the mechanisms for our physiological regulation. What I'm curious about, however, is how do our bodies decide the proper set point? I'm pretty sure there is a strong influence by genetics, but that doesn't explain how our bodies sometimes alter the set point drastically. Is there a specific location in our brain that controls the set point? Hypothalamus seems to be capable of controling body weight by regulating some important hormones, but still, to what stimuli does it react and change the set point? Also, for people with severe obesity, do their set points work properly? Is their obesity a result of a wrongly set set point, or of a set point failure, or maybe both?
Another thing I'm very interested in is the bird songs we discussed in class. As Professor Grobtein said, depending on the species, birds from sister species may or may not be able to distinguish the song patterns between two closely related taxa if they have no previous exposure to them. It really intrigues me because it reminds me of the paper I did on the greenish warbler ring species last semester. (A brief but very useful introduction: http://www.zoology.ubc.ca/~irwin/GreenishWarblers.html).  Since there are interbreeding zones between neighboring subspecies, it must also react to songs from its most closely related subspecies, so I wonder how do these birds learn their own subspecies' song. Or maybe those birds in interbreeding zones just randomly learn one of the two existing patterns?

 I've been thinking about the subject of internal calibration processes and how birds have a genetic template for the songs that their species sing. A bird song is a type of reafferent loop where the bird needs to try out the song multiple times before it is able to perfect it. This is the same for human talking and other output patterns. 

How does this relate to other pattern generators? When a piano prodigy sits down to play, they don't have to practice a piece they have heard before they can just play it. Is there something special about their learning process that they don't have to make a loop out of it, rather they can just get it on the first try? 

Another point to bring up: I wanted to to clarify a question I had on the difference between neurotransmitters and hormones. Since both are chemical signals that are released in the brain and trigger some sort of response, I wasn't sure why they were classified as different things. After talking to Professor Grobstein and reading a bit about them, I think I can see the difference. A lot of it actually has to do with how they were researched. While neurotransmitters were associated with the nervous system, hormones were researched by scientists examining the endocrine system. Also, neurotransmitters are normally associated with signals that stay relatively local in the brain while hormones are known to travel great distances throughout the body. Still, these differences seem slight to me. It's interesting to think that if these chemical substances had been studied together, more similarities would have been made between the two and they could possibly have been grouped together. 

Last Thursday, we dicussed the matter of set point in different, everyday examples. I have heard of body weight having a set point in the past, but I never understood it. Even now, I'm still a little confused by it. If we eat less or exercise more, our weight will definitely go down. In contrast, I doubt eating a significant amount of bad food choices would allow you to remain at your set point. So is a set point the tendency for a weight to hover near that certain number? Maybe it is easier to adjust the body weight towards the set point, rather than away from it? Because it is certainly not a distinct number that we are tied to. Besides pregnancy, what else adjusts this set point? Do we have any control over adjusting it? I have heard the term 'set point' used only when referring to weight, but I had not heard it used in other examples discussed in class, such as shivering with a fever. This occurs because the body is trying to raise the temperature to the newly established set point. Did a virus or bacteria cause this set point adjustment? How do set points change? Furthermore, how are set points determined? What makes one person have a higher set point for weight than another? I'm assuming it's genetic, but what specifically? How does something that's genetic change due to other influences, such as pregnancy? This idea of not having control over something as close to you as your own weight is intimidating, and not greatly believed in our society full of advertisments of lowering your body weight.

Our conversation about the ineffectiveness of dieting raised some questions for me, mostly chemical.  A UCLA study exposed the following findings on dieting after noticing the strange trend that existing research rarely followed up on dieters beyond six months:

" 'We found that the average percentage of people who gained back more weight than they lost on diets was 41% (...) In each of the studies, a third to two-thirds of the subjects gained back more weight than they lost.'

Does this mean that most of the people in the studies actually lost weight and kept it off? No, Mann says.

'This is actually bleaker than it seems -- even though most people would find that 41% number to be pretty depressing," she says. 'We have strong reasons to feel that this number underrepresents the true number of participants who gained back more weight than they lost.""

This seems to be a mostly chemical phenomenon.  According to LiveScience, we're "stuck with" the amount of fat cells in our bodies by the time we're 20 years old, and that number is largely due to our childhood exercise and diet routines.  But maybe there's hope; because there's a function in the body that generates new fat cells when one dies, if scientists can figure out a way to cease this turnover, we could actually "reduce fat-cell number in adults."   

I am curious to learn more about the details of the nausea reaction we discussed in class this week. As we talked about on Tuesday, when you’re driving the car, the nervous system is producing corollary discharge signals that set up the expectations. Furthermore, the less disagreement between the signals, the less likely you are to get sick. This seems logical to me; our body wants an agreement between the internal signals of our nervous system (the corollary discharge) and the external sensory inputs. When they do not align, it is very interesting that the body reacts by inducing a feeling of discomfort. If it’s really bad, we even expel the contents of our stomach, perhaps eliminating a toxin we may have ingested. What a brilliant evolutionary acquisition. But we also talked about how it is a failed adaptive process. I wonder if there is any way to alter how the nervous system constantly adjusts its expectation. If the adjustment is successful, we don’t get sick (and vice versa). Well how does the nervous system adjust its expectations? Do all adjustments occur with the same frequency and rate? When someone gets their “sea legs,” does that mean that they have gotten very adept at making these adjustments or rather is it that they don’t adjust at all and have started to suppress the mechanism that checks expectations against sensory input?

So if this whole thing is going on constantly, why is it that we evolved to do this process largely without involvement of the i-function? In other words, why is it that the i-function plays such a removed role in this complicated and constant event? I suppose this is just one of many events that occur constantly without our conscious consent. But can we override this? As in, if we tried to take a deliberate stance against getting seasick (and tried to consciously accept the disagreement between corollary discharge signals and sensory input), could we successfully suppress the impending seasickness? I don’t think so…at least I’ve never seen anyone succeed at this route.

Also, I’m interested to learn more about the setpoints that our nervous system creates. I am writing about firewalking for my web paper, and it appears that setpoints are the key “trick” to walking on fire.
 

            I have a few questions about the process of learning species-specific communication (i.e. language in humans, songs in birds). We agreed that a young member of the species can tune out other sounds, only paying attention to the sounds of its species. That would enable it to successfully learn the language or the song or whatever it may be. However, at least in birds, this doesn't always happen: (http://www.allaboutbirds.org/netcommunity/faq). Birds occasionally learn the songs of different species, or they somehow manage to create a new song by incorporating pieces of their species’ song and another’s. Obviously, not every bird gets confused and learns a different species’ song, but every bird is exposed to other bird songs everyday. So, what's wrong with these birds? Why do some birds get confused? Is there something wrong with the way they are interpreting information? And if birds are able to get confused about which song that they are supposed to sing, is it possible for humans to get confused about which animal they are supposed to mimic?  

 When talking about the weight set point I thought about my dad who stayed the same weight from 18 until a few years ago and since then has gained some weight. But it seemed that he gained weight more because he was not moving around as much as he did while with the forest service. I see that the nervous system has something to do with weight but also the environment or activity of a person. So I am glad that we are now including the external input since it does not always seem that your behavior is only due to the nervous system. With paralysis after a stroke, although the I-function is not able to create an action due to the lack of connection although it seems since a person can still move their arm when a ball is thrown at them that the central pattern generator is still active and can be activated in order to protect the body. As if even though you’re not aware of the paralyzed part of your body it is still aware of your surroundings and keeps its function in keeping the body aware of dangers or other stimuli. What about a person in a coma, they still have their CPG's intact, but I don't think they respond to a ball being thrown at them. Are their CPG's damaged or latent due to the nervous system shutting down portions in order to extend energy to places in the body that need it? Do they still have an I-function? I guess I would say that they still have the nerves that form the I-function but that the function is dormant. I guess I'm just thinking about all the connections and keep wondering about what occurs when one of the connections, CPG's, I-function, corollary discharge is not functioning properly. With paralysis the I-function has no effect but the CPG's are still able to respond, while in a coma the I-function doesn't seem to be working or CPG's but maybe corollary discharge is still telling neurons what's going on in the body, keeping it aware of the outside although I'm not completely sure.