Neurobiology and Behavior, Week 9

I’ve been wondering how and why songs can get stuck in your head. This seems to happen to me frequently. Sometimes the song is one I’ve heard recently, so it makes sense that I’m thinking about it. Other times, it’s a song I haven’t heard (or I haven’t been aware of hearing) in a long time. Does it make sense to think about songs that are stuck in someone’s head as a repeating pattern of signals that may or may not have an input trigger? It’s interesting that sometimes it’s just the tune that gets stuck, other times it’s the sound of a specific recording of a song, or a specific person’s voice singing it. I suppose this makes sense after talking about how inputs can be complex and induce behaviors and responses that are even more complex. I wonder what it is about having a song stuck in your head that makes you want (or NEED) to hum it or sing it. I also wonder why the (usually successful) cure for a song that’s stuck in your head is to listen to that song. What does that do to alter the pattern in the brain enough to break the loop? 

Are there other, similar phenomena in the nervous system? I never really think of having a sight or a smell or a feeling or a flavor stuck in my head. Scent memory (a specific scent reviving a memory out of context) is somewhat similar, except that phenomenon is generally associated with a scent input. Recurring dreams might also be similar, except I don’t usually think recurring dreams run on a loop incessantly throughout the night. 

The concept of the phantom limb is fascinating but incomplete. The experiment “The Mirror Cure for Phantom Pain,” only looked at 3 groups: mirror movements, covered mirror movements and imagined movements. The conclusion from this particular experiment is that patients that watched the reflected image of their intact foot in a mirror while they moved reported a decreased in pain in their amputated leg. My question is why didn’t they put in a group for people who wore prosthetic limbs or those who have 2 amputated legs? If the results were that using mirror movements helped, wouldn’t the concept of knowing you have a prosthetic attached have the same affect? As for those who have 2 amputated legs, how would you categorize them in terms of this experiment?The idea of corollary discharge can be applied here too. If corollary discharge means a mechanism in the brain that allows one to distinguish between self-generated and external stimuli and perceptions, could it be possible that a patient just perceive they have a limb or self-generating the pain?

Another thought that I had on corollary discharge is when children pick which hand will be their dominant hand. As in many Asian cultures, the right hand is the preferred hand of choice and grandparents or parents sometimes uses force to establish the dominant hand. But, if you place the a utensil or pencil in front of the child, it will choose which hand it would like to use by itself without any external stimuli. Its an innate ability just like walking, eating and breathing.  

I found the discussion about the phantom limb syndrome and mirror box treatment very interesting. I have seen this in the show House, MD awhile ago and thought it was interesting. Of course, I didn’t know anything about corollary discharge and wasn’t even sure if it was made up thing for the show, or well known and recognized treatment. I also thought the pain and why the treatment works is are all because of “psychological” effect. In other words, it’s all in your head (not the head with nervous system, neurons, etc, but head as “mind”). Learning about corollary discharge taught me that the problem with phantom limb syndrome is not because one “believes” something, therefore it happens even though it’s not really there, but there really is brain chemistry that explains why brain acts that way. I don’t know what I’m saying makes sense for others, but it is kind of legitimating the syndrome.

With phantom limb syndrome and mirror box treatment, corollary discharge is used to “fool” the brain to think of the hand in the mirror as real arm and because it’s working fine, it shouldn’t hurt, therefore it doesn’t hurt. In contrast, the car sickness example used corollary discharge to correctly put the vision in accordance with the movement, therefore does not feel sick in the moving car. If I understood correctly, these two examples showed how one idea can be used in opposite ways to get rid of problems. Clever!  

http://www.youtube.com/watch?v=MEDUrEh7hSU&feature=related

This is pretty cool - didn't know that newborns also have the ability to float on their backs.

I think it is amazing that we are born with the innate ability to perform certain tasks and activities due to the presence of central pattern generators.  A question that comes to mind, and that we touched on during class, is to what extent the environment impacts these central pattern generators.  Specifically, I am interested in what causes CPGs to fade.  Can they ever fade?  Can they disappear completely?  Is it possible that they are still completely in tact in the nervous system, but have faded in the I-function, the part of the nervous system that you designate you.  Or maybe they have not faded in the I-function particularly, but the corollary discharge, the reporting mechanism for that particular activity or task, has faded.  We discussed that newborns have the ability to swim which is why it is recommended to parents to start swimming lessons with their kids very early on.  Yet, many parents wait until 2 or 3 or even later to put their kids in the water and at this point, the kid has lost the CPGs necessary to hold their breath under water and blow out.  Perhaps though, the child has not lost the ability, it is merely being blocked or overpowered by other CPGs corresponding to fear and anxiety.  Or they have faded just because the child has not used them; however, in the case of the baby bird experiment, the baby bird had not used its wings, yet the instant the jacket was removed the bird had total knowledge of how to fly.  Why does the young child not have total knowledge of how to swim when the CPGs necessary for swimming were present at birth?  It is clear that the environment must play some sort of role as we determined.  When I was learning how to swim I was terrified of the water.  My Mom would tell me put your face in the water and I would totally freak out.  I refused and every time I tried I was convinced I would drown even if I was in only three feet of water.  Then, one day, my Mom was completely fed up with my refusal and complaints to get in the water so she picked me up and threw me in the deep end.  I was shocked and pissed off, but I swam to the surface and to the side of the pool with no problem. That's how I learned to swim and that's how my CPGs for swimming were quickly rekindled and reactivated.  I remember getting to the edge of the pool and crying because I thought what she did was cruel, but I was also thinking, now that wasn't so bad.  It makes you wonder what other CPGs we have that our minds are continually blocking due to emotions and environmental factors.  Climbing, for example, is always blowing my mind.  I know that my body has all the necessary tools to land certain moves, but doing that move at 3,000+ feet can throw one off.  I remember this one mantel I was trying push up over and I kept falling and falling and the rope kept rubbing up on the edge of the mantel.  I knew the rope would be okay from a logical point of view, but the fact that I was hanging off a rock 2000 feet above the ground with a belayer 70 feet above me that couldn't see me freaked me out to the point where I became frozen and forgot everything.  I think becoming scared and hesitant impedes the functioning of certain CPGs.  Eventually I had to get over it and just do it.  I had to just detach myself and my fears from the situation - kind of like detaching the I-function because it was the I-function that was screwing up the corollary discharges I needed to coordinate that movement to power myself over the rock.  I guess this suggests that your experience of things is a function of not only sensory input and CPGs, but also your own state of mind.  I think that your state of mind can cloud your ability to activate certain CPGs.  Now, I understand why some climbers prefer a beer or two before they power up a rock...  

To generate a central pattern the behavior patterned has to occur or at the very least as if it had occurred.  Repeating the behavior strengthens retention of the pattern.  Neurons carry out the behavior and the sequential activation of the neurons is retained as the pattern.  Central Pattern Generation is not exclusive to actually carrying out the behavior.  The neurons which would have carried out a behavior can be patterned even if they do not carry out the behavior so long as they and the pattern are identified.  This may relate to musicians preparing music to be performed when they study the music to be performed without actually performing the music in order to prepare themselves to play a composition.  Central Pattern Generations appear to be coordinated by corollary discharges. 

 I found our discussion on motion sickness and corollary discharge rather interesting because I have always wondered why some people get motion sickness and others don't.  Are the nervous systems of some people just better at realizing that even though the person is not moving, the car is?  My mom does not get motion sickness at all, she can be crocheting or reading a fine print book in the car and be perfectly fine.  My brother, on the other hand, cannot read or do anything else in the car other than sleep.  So does this mean my mom's nervous system is better at blocking out the unexpected signals received while sitting in a car?  Does that make her nervous system faulty? Since our bodies rely on pain to tell us something is wrong, would not having motion sickness mean that even when what the nervous system expects and the actual signals received do not match, the body can accept that?

Corollary discharge signals can also be applied to watching movies in IMAX/3D.  I saw a move in IMAX/3D this weekend and it definitely got me thinking about the actual signals we receive versus what is actually there.  So even though the movie was technically in 2D, due to visual effects, the images virtually came to life.  What I found interesting was that when an object was being thrown at a character, most people in the audience ducked.  It is instinctual to avoid objects that are coming at your head, but we were all sitting in a movie theater, we all knew that the screen could not actually harm us, and yet most of us still flinched.  I have a friend that cannot even watch movies in 3D because she gets headaches from it.  I guess watching 3D movies can be interpreted as a type of motion sickness because our nervous system is expecting a movie on a large screen but in 2D while the actual signals being interpreted are of 3D figures coming out of the screen.  

An interesting article on Phantom limb for anyone who's interested: http://www.scientificamerican.com/article.cfm?id=phantom-limb-cure-retrain-brain

Corollary discharge helps explain why neurons are connected in such complex patterns and how their communication creates behavior that is not exactly the same each time. If central pattern generators didn’t communicate with one another, they wouldn’t be all that useful, because they wouldn’t be able to adapt to changing circumstances. It also brings “thinking” into the equation, since internal actions affect outputs through corollary discharge. This leaves me wondering why some behaviors involve a connection to the I-Function and others don’t.  How does the I-Function seem to “get in the way” of patterns to which it isn’t connected, like riding a bicycle? How easy (or difficult) is to create new lines of communication between patterns? How do patterns and the lines of communication between them actually form?

On Tuesday we talked about the fact that everyone has difference experiences based on the same input signals, and that any single experience can never be the same for two people. In my opinion this gives more evidence for the idea that every one inhabits there our reality, their our universe, but that those realities must be similar to some degree, since it’s not the inputs that are different, just the internal signals that we use to interpret them. It’s sort of a frightening thought, that we (humans in general) don’t really have a common reference point of experience. No one will really ever understand what another person is experiencing, especially in terms of emotion. I suppose that’s why it’s so difficult to predict what any one person will do when presented with a difficult situation. On another note, if these internal signals were connected to the I-Function, would it then be possible to consciously change what we perceive as reality to some degree? We can change the input we are receiving, but maybe we can change how we experience it, effectively changing our reality and not anyone else’s.

I think that corollary discharge and central pattern generation help us make sense of behavior in terms of neurons. Corollary discharge and central pattern generation make it easier for me to understand how we perform common daily activities so easily and effortlessly. I found our class discussion about phantom limb syndrome very interesting. It does make sense that the central pattern generator for a limb remains even after a limb has been amputated. If phantom limb is due to the non-correspondence between sensory input and corollary discharge, is there any way to stop or decrease the pain? After a substantial amount of time, will the limb’s central pattern generator stop working due to disuse?   I also found our discussion about motion sickness very interesting. I have noticed that I get car sick when I am in the backseat of a car but never when I am driving.  This also makes sense in the terms that is due to the non-correspondence between sensory input and corollary discharge

 Corollary discharge has helped me better understand vision and hallucinations. In my first web paper a Revision of Vision, I wrote about vision as a function of the brain, that what we see has to do with what neurons are active (whether due to outside stimuli or processes within the brain). However, I had no background to say what specifically would cause the brain to activate its own neurons. This week we learned that CPGs interact across the NS with sensory input, influencing how that input is interpreted. The brain's own "outputs" altering how our sensory inputs are translated supports my claims, that what we see has just as much to do with what our eyes tell us (sensory input) as what our brains tell us (CPGs/corollary discharge). Corollary discharge helps us make sense of behavior in terms of the neurons because it shows how connected all the neurons are to each other; they can "check" each other. 

             I think that corollary discharge has helped me understand a lot of natural phenomena. For example, I get carsick rather easily, especially on the blue bus, and my friend has always told me that I should look out the window when I get carsick.  Whenever I do, I start to feel better. I now recognize that my body happens to be very sensitive to conflicting signals. My inner ear is telling me that I’m moving, but when I’m reading or even just looking at the head in front of me, my eye’s sensory neurons are telling me that I’m not moving.  When I look out the window, however, I see movement, and so the conflict goes away.

            Corollary discharge also helps me make sense of why the mirror treatment works on people with phantom limb syndrome. If someone’s eyes see that there is no limb moving, even when that person thinks that he or she is moving it, then that person’s body will come to realize that there is no limb to move and the pain that that person feels will decrease. This makes me wonder about how much pain a person with a prosthetic limb would feel. If the sensory neurons see that there is a limb, does that information trick the brain into thinking that there is a limb? And if it does, would this decrease pain because it would cause the brain to think that the signals for movement are successfully getting through?