Neurobiology and Behavior, Week 6

"Depression's Upside" is the title of a New York Times article I just read, which explores the possibility that depression can have a positive effect on mental health.

Andy Thomson and Paul Andrews, the authors of the paper cited, argue that an area of the brain closely associated with depressed people (the left ventrolateral prefrontal cortex, or VLPFC) is also important for our ability to intensely focus our attention on a particular problem or situation. Thus, when depressed people are using their VLPFC, they are also training themselves for more difficult mental tasks.

Thomson, a psychiatrist, seems to value this training above the current medical climate, which seems to favor medicating depression. "As a society, we’ve come to see depression as something that must always be avoided or medicated away," he says in the article.

"We’ve been so eager to remove the stigma from depression that we’ve ended up stigmatizing sadness.”

The article highlights a lot of objections to this argument, including that Thomson and Andrews homogenize depression, which in fact has many different causes and effects; that depression can lead to suicide, which certainly does not help the brain; and that when it is particularly severe, depression can be completely crippling, making any possible benefits seem somewhat remote.

But Thomson responds with a story from his clinical practice about how he treated a depressed woman with medication, only to find that while she was no longer "depressed," per se, the situation in her life that contributed to her depression had not gone away. "The point is the woman was depressed for a reason; her pain was about something," the article states.

I found Thomson's and Andrew's argument compelling, on a personal level at the very least. I've never been severely depressed—I can only speak to my own mild, occasional depression (which, after all, maybe doesn't even count as "depression")—but I've found that lifestyle changes are extremely effective at changing my mood. Often, I'm depressed—or perhaps just "sad" is more accurate—because I've been sitting around and not doing anything. When I get up, get things done, feel accomplished, I feel better. Moreover, when I've had longer periods of (admittedly) non-severe depression, I've come out of them with new insights about my life.

To me, this makes more sense than the immediate move to pathologize all depression and treat it with medication. While, in the end, everything may just come down to chemicals in the brain, there's no denying that life circumstances affect those chemicals. Or, in the language of our class, some aspects of depression may be purely brain-related: outputs with no inputs; others, however, have an identifiable external source.

As Thomsons asks, why do we assume that all sadness is inherently bad? Using medication to maintain some kind of artificial level-ness in mental state seems unhealthy—people get sad, people cheer up. Sometimes, it takes a long time, and in rare cases, it takes more than just time to clear it up, but overall, the fluctuation seems like a natural part of human existence—something to think about, evaluate, and discuss, but not something to medicate out of existence.

I'd appreciate any attempts to more closely tie this issue to the specific terms and ideas we've been discussing.

http://nytimes.com/2010/02/28/magazine/28depression-t.html

I am still stuck on this concept of the "I-function".  I have been trying to better define it for myself and have become satisfied with the following explanation of what the "I-function" entails.  The "I-function" is our sense of what we can do based on the capabilities of our nervous system.  The "I-fuction", I think, is unique to humans in that we may be able to respond physically to certain inputs (i.e. Christopher Reeves and the foot pinch response), but the response is not a part of what we have constructed to be "us" even though we can recognize and acknowledge that there is a visible response or reaction.  In the case of a dog or frog, I would argue that the dog or frog does not realize the unfelt physical response due to a lack of or less developed self awareness.  In class we mentioned that there is a system within the nervous system that allows for the nervous system to look at itself.  We asked, is this the "I-function"?  Maybe. I would argue that only certain species have a nervous system equipped with this internal system that allows for the nervous system to assess itself.  I would argue that this is the difference between a human and a frog (and perhaps a dog).  On the subject of dogs, I have been wondering that if one pulled, pinched,or flicked a paraplegic dogs tail, if it would respond like Christopher Reeves would.  Do you think the dog has the cognitive capability to realize that even though he/she doesn't feel a response that there is still a physical resposne?  I would surmise no and that is how I would differentiate between a human being and a dog. 

I think the transition from the discussion of the I-function to the discussion of neuronal signals is reasonable because of the example of Christopher Reeve. The neuronal signals in Christopher Reeve's body allow his hand to jerk back in response to pain but he has no control or awareness of his ability to move his hand. Therefore, it is essential to understand the I-function before learning about the mechanisms underlying how information is processed by the I-function. Even though Christopher might not be aware that he can move his hand, the neuronal signal that will enable his hand to move still exists. And it's the same signal as the one that makes him think that he can't move his hand.

The transition from the i-function to neuronal signaling seems somewhat unreasonable in that the transition is from a complicated higher function to the basics of how neurons work.　 it would seem more reasonable to transition from the basics to the more complex and demanding.　it would be something like understanding how horses walk before trying to explain how they gallop.　 the study of neurons would show that they all work in the same way.　the next step would be to look at the connections made up into pathways to see if some kind of organization of the neurons explains how higher functions are attained.　 all of this is highly physical.　higher functions may be more than physical?

 This week we talked about action potentials. Action potentials are extremely precise, all-or-nothing signals which are responsible for our neuronal connectivity and on a macroscopic level, our thoughts, feelings, urges, unconscious processings, and ultimately us! It is such a wonder to me how action potentials become animation. Carrie and I were talking earlier today about this, and we stumbled upon some really interesting questions about consciousness. The main question I have is how do our senses combine with everything else with in our brains (feelings, thoughts, unconscious processings, etc.) to yield an experience, a reality. Touching my keyboard, seeing the screen, hearing the keys, thinking a thought, pausing my thoughts as I type them, continuing where I left off, relating to past memories (my conversation with Carrie), acting, thinking, subconsciously thriving...this is my reality right now; how do propagating changes in concentration across a semipermeable membrane generate this WORLD?

My dreams are often hazy, but on rare occasions I have extremely vivid dreams which feel like reality. This must be the brain creating its own outputs, its own action potentials, in lieu of any sensory stimulus. But, what is it exactly that gives a vivid dream its "vivid-ness", its vivid quality, as opposed to duller dreams. What is making our mind and body (I know everyone's had a dream where they felt like they were falling!!!) feel REAL?
...hope this makes sense
 

We were also talking about the nature of these connections. Carrie wrote her first web paper about vegetative states vs. comas, in which levels of consciousness vary. If the connections within the brain regarding consciousness are severed or many are broken, can these connections be rebuilt? If so, are certain levels of consciousness learned as opposed to being innate? How do connections re-establish themselves? How to these connections form to begin with (I picture a little axon creeping along in the brain like a root in soil)? Action potentials allow connections to interact, but do they help form connections? How could the help "form" a connection if there is nothing for them to "form" on? How do connections become learned?
...a summary of this string of questions: What's up with connections?????

 I've learned about electrical and chemical signaling in the brain before-- on more than one occasion, actually. I knew the textbook explanation that I've learned in a series of bio classes... but, as always, Professor Grobstein has changed the way that I understand the intricacies and complexities of life.

Thinking of the electro-chemical gradient along the axon, of the negative/positive charges, as a series of batteries moving across and along the axonal membrane actually made the concept easier for me to grasp. I do have to admit that it took more than a good minute to wrap my mind around it. The idea of the batteries across the membrane and ALONG it, thereby propagating the action potential, made more sense than the idea of chemical and voltage gated channels and pumps... doing things...

Yeah.

I think it’s interesting that we’re jumping from discussing the I-function to discussing the nuts and bolts of neurons and the way they work because it seems like neuronal activity is not controlled by the I-function. For instance, if someone were to ask me to make a specific one of my nerves propagate an action potential, I wouldn’t be able to. If someone were to ask me to wiggle my toes, I’d simply wiggle my toes. I wouldn’t initiate an action potential in the section of my brain devoted to the I-function that would then tell the nerves in my foot to tell the muscles in my toes to contract and relax, producing the behavior known as toe-wiggling. As far as I know, people aren’t capable of directly influencing the most basic behaviors of their nervous systems just by wanting to. I am also of the opinion that the I-function is only a very small portion of the inner workings of the nervous system, and it would seem that all neurons, no matter what their role, behave the same way at the most basic level. So my question is this: are we simply moving from the I-function to neuronal signals because we need to move from a general discussion of nervous system behavior to a technical discussion of nervous system logistics, or is there a specific point to be made about neuronal signals and the I-function specifically? I personally am more interested in how neuronal signals, which (as far as we’ve discussed) all behave similarly, can produce such diverse responses as evidenced by the vast array of different behaviors among individuals of the same and of differing species. This is partially because I find such behavioral diversity fascinating and because I remain skeptical of the necessity of an I-function in explaining behavior. 

            This week during class, it was interesting to find out that all axons contained the same signal. Initially, I was somewhat surprised about this, but when thinking about the axons and signals, it made the most sense that there was only one type of signal. The pathways of the cables are what really differed, so the signals involved in moving one’s eyes and feet were identical. However, the pathways and cables containing the signal were completely different. Also, the concept of time and the nervous system was an interesting topic during class.   At first, the idea of the brief disturbance by the action potential taking milliseconds seemed quite fast to the class. However, when comparing it to the speed that an electrical signal travels at, which was the speed of light, the action potential seemed extremely slow. This brief disturbance that we were talking about happened to be a switch taking place between the positive and negative signs on the axon.  I had never known that an axon was so similar to a battery, until we discussed the diffusion and selectively permeable layer.  In fact, all it took was a selectively permeable membrane and a concentration gradient of the ions to create this battery. Hence, we were able to find out that because there was a lot more potassium inside the battery than outside, the inside of the axon happened to be negative. At first, this may have seemed confusing, but the example using the red and blue particles in a box with a semi-permeable layer and a force acting upon it helped clarify this confusion.   Therefore, when the battery in the axon went from inside negative to inside positive, a gradient was created in which there was more sodium outside the axon than inside.

The transition from the I function to neuronal signals seems like a huge leap for me. Obviously the two are connected, but the I function and other important characteristics of the human brain are removed in my mind from neuronal signals. Neuron firings are like the building blocks to the I function, except that there are many stages before the I function is reached. I think because of these countless steps, it is hard to see how the two interconnect. Despite this difficult transition from something as complicated as defining ourselves to understanding things on a molecular level, there is no other way to make the transition. Individual neuron firings lead to a traveling signal, which leads to an interpretation of that signal and eventually a response. But we have not dealt with complicated responses such as defining the self relating to the response of a stimuli in class. This is difficult because the gap between neuron firing and the I function is so great that it is hard to know where to begin to fill it. That being said, any transition between the two would be difficult. Perhaps it would have made more sense to start on a molecular level and eventually build up to understanding things such as the I function. However, it is also important to intrigue learners with the ideas that they will eventually be able to understand. This allows for a goal at the end of interpreting the complications of the brain on a molecular level. It is also hard to understand the connections between the two because they are so different from each other. We cannot see, feel, or slow down a neuron firing, and yet we constantly think about the identity of ourselves. Something as reachable as the I function is hard to connect with in depth molecular actions.

This week we clarified the idea of the “I-function” a bit in our description of signals and connections. If all signals are the same, then it must be the pathways through which they travel that affect a person’s behavior. So, if those cables that connect the “I-function” to the rest of the brain/nervous system are blocked or disabled, signals generated in the I-function will not be able to reach the rest of the nervous system. In addition, signals from the rest of the nervous system will not be able to use pathways that lead to the I-function. Such is the issue in Christopher Reeve’s case in that “he” was unable to generate outputs because the signals he generated could not reach the rest of the nervous system to, say, move his leg.

This situation is interesting because it demonstrates that one’s mind is not usually separate from one’s brain and that this connection is essential for an individual’s survival. While there are certain behaviors that the I-function does not seem capable of influencing (heart-beat, organ function, blood flow, etc.) it does seem to function as a “box” that creates a representation of the nervous system. It almost allows the nervous system the ability to view itself, its actions, its inabilities. This function is crucial because an ability to look at one’s actions and to be self-aware allows an individual to better adapt to changes in the environment and in oneself. In addition, it further allows ones actions to be a bit less instinctual and more learned (based upon the situation and previous experiences). I am interested in learning more about the idea of self-awareness and its advantages.

 

 Learning about how signals work could definitely help with understanding the whole output without input where a signal could start in an axon without getting a signal from some connected neuron. This could be due to the "battery" movements and with their movements they create a potential that occurs in the axon and then creates an action. This signal would then not be influenced by an input either from another neuron or from an outside stimulus. I'm still wondering if the output signal is random or not since the movements of ions or molecules are random. I know there are the channels and pumps that aid in keeping a gradient so maybe the signals are random because they can be influenced by the pumps. Can't wait to figure an explanation using what we know about signals. 

I do understand signals and how they function with sodium and potassium ions but I am a little confused on our explanation of potentials with batteries. I understand what a battery does but when talking about action potentials I became confused. Could someone maybe explain action potentials more clearly without using batteries?