Neurobiology and Behavior, Week 4

I have a hard time grappling with the idea that Newton is wrong. Though I'm no physicist, I can't help  this loyal feeling to Newton and his law - that a body in motion remains in motion (&a body in rest remains in rest) unless acted on by an outside force.

In class, the example of thermal motion was brought up. If an object - the table - feels cold/warm, is there a force causing the object to be at a certain temperature?

I was always taught that an object is composed of particles - molecules that are tightly packed together.  These molecules are in constant motion and held together by a variety of forces. Chemistry teaches us that certain molecules/atoms have charges, dipole moments, van der Waals forces, etc that keep solids/liquids/objects together.  Isn't temperature the amount of heat released by reactions between these forces, reactions that are dictated by these very forces?

Maybe if we redefine "force," this law could hold true in the context of this class and in Neurobiology. We said in class that the brain can just generate thoughts without any force causing this response.  I'm assuming that this statement refers to the process of generating new thoughts, something that existed from nothing, etc.

But I have to disagree. I think our thoughts are generated because of stimuli. We think because our minds are stimulated, in one way or another. This can be a thought that comes as a response to a given environment. Or a thought that comes as a response to a posed question, reading, argument, etc.  Thoughts originate from somewhere because of something.  Even our most esoteric, seemingly random thoughts have origins - according to psychology and Freud.

Maybe I'm too firm of a believer of causality.

Like Lauren, I was very suspicious of a narrow definition of an input as something generated outside the nervous system.   Although I understand that most input into the brain comes from outside the nervous system, I am skeptical of a definition of input that excludes input from one part of the brain to another part of the brain especially since the various parts of the brain are massively interconnected.  I also am skeptical as to how activities such as stomach growling, seizures, dreams, etc., which are considered to be “pure outputs” - outputs without inputs.   Although not directly generated by outside events – inputs, there is still an out of body event that indirectly contributes to the generation of these “pure outputs.” For instance, a stomach growl may be triggered by absence of food and dreams are influenced by what happened outside the nervous system sometimes in the distant past.  Therefore, I think one or both of the terms, input and/or output, should be broadened to somehow include what are considered “in body effects,” outputs that are produced by inputs from the body.”

The human brain is an example of a non-traditional stimulus/response system.  It does not always require external inputs to generate outputs. This allows for creativity and advantageous adaptations.   For example, when Galileo was reaching the end of his life, he lamented that his world was getting smaller because he was diminished to his shrinking five senses. Nevertheless he could reflect and powerfully express his situation.  Another example is Beethoven.  At a young age, he went deaf, but could generate powerful sensory outputs - some of the world’s greatest music!

 After our conversation last week, I feel like I have a better understanding of inputs and outputs, of interactions between neurons, of interactions between the environment and the nervous system. However, I am still interested in how these interactions come into being. We talked about neurons that connect the outside world to the nervous system, neurons that connect the nervous system to the outside world, and neurons that connect to other neurons. We talked about how there are orders of magnitude more neurons in one person’s nervous system than there are people on the planet and how the vast majority of those neurons connect to other neurons. I doubt that this was always the case. I wonder which of the three types of connections the original ones were. That is, can a nervous system be simplified so much that it only has one or two types of connections and still be a nervous system? Did all of the types of connections exist in the original, ancestral nervous system, or are some of them derived? Is the ability of the human nervous system to generate outputs without inputs common to all nervous systems, or is that, too, a derived trait? My question from the other week still remains: which came first, inputs or outputs?

Ok, so last week when I tried to come up with my own examples to understand how outputs can happen without inputs, I did think about autism and other cognitive disorders, but I wasn’t really sure if I could say those outputs are without inputs, or even what are the inputs in those examples. But now that it is clarified that the inputs are stimuli outside of the nervous system, it makes more sense. Yes, outputs can happen without inputs. This is what makes us to say, “we can think in our own”, whereas computers or robots cannot (at least, so far, they can’t). Between people, on the other hand, it’s the assembly that makes each individual different, from the same ‘contents’. As it seems like most people were, I was also surprised to learn that 99.9999% of neurons are interneurons. A question I have about this is that is outside world demanding very little or is it capable of affecting out brain with very little amount of neurons. All these topics brought me to think about nature vs. nurture, which has been a question I had for long time. I have believed that both have effect on humans, although nature seems to have greater effect. I feel like this talk about large portion of neurons being interneurons and how the structure makes each individual different support my argument, nature has bigger role in human development. Or maybe, these topics are not appropriate to apply to nature vs. nurture issue?

I was talking to a friend about the ouput without an input phenomenon and she suggested I check out this New York Times post, Patient Voices: Tourette's Syndrome: www.nytimes.com/interactive/2010/02/11/health/healthguide/TE_tourettes.html.  She thought that this post suggested that Tourette's Syndrome, a disease characterized by involuntary movements and vocalizations (outputs), did have associated inputs.  For example, one individual commented that specific people and locations prompted particular inappropraite tics or outbursts.  He said that when he encountered certain races he felt the urge to vocalize racial slurs.  Further, he felt the urge to say degrading things to his girlfriends such as "you're fat".  Also, in public locations he would shout "bomb" or something else he knew would elicit a startled response.  This would suggest that the environment, particular locations and people, provide particular inputs that generate related (and unfortunately oftentimes inappropriate) outputs.  Sometimes, however, it is a fortunate output.  One patient spoke of how acting and performing caused the involuntary movements to stop.  I have witnessed this.  I knew a guy who twitched uncontrollably and then he would sit at a piano bench, start playing, and then the tics would instanteously stop.  How is music, an input, inteferring with the neuronal connections?  It must be interferring with something, with some input.  Additionally, another Tourette's Syndrome patient expressed that stress and excitement definitely factored into the prevalence and severity of the tics.  However, despite these environmental factors, there are clearly still outputs that cannot be accounted for or that do not have an associated identified input.  We do not yet know from where these outputs stem, but I think it completely probable to say that perhaps there are inputs engendering these responses that we have not been able to pinpoint.  We learned in class that our nervous system is comprised of 99.999999% interneurons.  This is amazing and daunting because think of the limitless amount of things these interneurons are doing.  I think it is entirely possible that in the case of Tourette's Syndrome and other disorders of the nervous system, we have yet to discover the inputs that cause these oftentimes visible and mysterious behaviors.  Why did I just blink, or wiggle my toes, or bite my lip?  I have no idea.  Maybe environmental factors or restlessness or boredom.  Something though, I think, elicted that response whether I know what that something is or not.  The featured Tourette's patients do not fully know where their responses are coming from either.  Many experience frustruation with the lack of control or lack of free will.  Some admitted that they did have control over urges, but that to supress these urges caused physical pain and mental anguish.  I also found it interesting that obsessive compulsive disorder is a common partner with Tourette's syndrome.  It almost seems like compensation for the fact that since they have no control over parts of themselves, they try to control other situations.  Is Tourette's syndrome the input for the obsessive compulsive output?  Further, a point of interest was the fact that two twins had the disorder - one experienced tics that diminished with age, while the other experienced an increase in the severity of tics.  Does this suggest environmental inputs?  Lastly, one patient said that the one thing that helped the tics was marijuana.  I find this interesting.  Marijuana must be targetting or reacting with something to generate the improvement.  What is the something? I think it is just easier to say that there are outputs without inputs because we really have no way (at least now and i doubt if ever) of accounting for all the possible inputs.  By the way, have we even defined inputs?  I think in some cases it might be hard to differentiate between output and input and I think at some point it is just easier to say it must be a more circular network.  Right now our model seems pretty linear and I would argue that the whole call and response or response without a call models we have been working with are much too simple.  Yet, I am sure further discussion will produce a new, less wrong, model.  

       In evaluating our evolving view of the nervous system, I imagine that there are several major benefits of a system that can generate outputs without the need for inputs. I am specifically approaching this issue with an evolutionary perspective. Firstly, I would think that the need for internal generation of stimuli is critical to maintaining a daily rhythm. Suppose, for example, that our nervous system only reacted when prompted with an input. If we were sleeping in a dark silent cave, could we sleep indefinitely until awoken by some stimulus (a bear entering the cave, or someone attacking us)? Clearly we cannot sleep indefinitely, and this daily cycle must be tied to internal stimuli. Devoid of any external stimuli, we still wake up (albeit after perhaps more sleep than we might normally get). These rhythms—Circadian rhythms—keep us functioning even without external stimuli. (Check out this cartoon). This cyclic rhythm presents evolutionary benefits in that we can meet our body’s needs in a timely and efficient manner. What if we had no idea when we would be hungry or tired? It would be impossible to plan anything. If you just became overwhelmingly hungry at random times that were not governed by some internal stimuli, it would be very difficult to survive as a hunter/gatherer (or pretty much anyone for that matter, aside from perhaps someone who lives in a supermarket).

       So what other benefits does this “spontaneously generating” nervous system present? It offers us the ability to adapt to new situations and environments. If we could only output based on input, we would be greatly troubled by a new situation. If an input came along that was totally foreign to us, what would we do? While some pathways of response are heavily-traveled highways of the nervous system, (eg- the fight or flight mechanism, or rest and digest), we will certainly be presented with new challenges and the outputs they will demand.

       One other evolutionary benefit would be that it allows us to avoid predation that might normally capitalize on routine. Consider the case of an unlucky mouse who was born with a very primitive nervous system. Whenever cheese was dropped on the floor, he immediately (and always) responded by running out to get the cheese. Furthermore, assume he only ran out of his hole when the cheese was dropped. A cat might notice this pattern and capitalize on his prey’s primitive ability to process inputs and outputs. The next time the cheese dropped on the ground, that cat might be waiting for the mouse. My point is that our ability to generate internal stimuli and operate in a non-prescribed manner is a critical element of defense from predators.

Though the idea that the nervous system generates outputs without inputs seemed strange at first, it actually made a lot of sense to me once I thought about it.  Many of the behaviors that puzzle us, including many of the things that we define as mental illness, like depression, schizophrenia, OCD, mania, and panic attacks, can't be explained by a traditional stimulus/response explanation of the nervous system. They happen without any external cause, and the pharmacological treatments we have for them are based on changes within in the nervous system.

The fact that the nervous system can generate outputs without inputs from the surrounding environment is interesting from an evolutionary perspective. The nervous system is capable of changing how it reacts, because any one output is not linked to a specific action. As result it can adapt to a new environment more quickly and easily than a system that is based on linked inputs and outputs. It also introduces an element of the unexpected, because outputs that occur without inputs cannot be reliably predicted. Variation drives evolution, so in evolutionary terms the nervous system is highly valuable. It also begs the question of how such a system evolved. What was the starting point for outputs without inputs? Did it start as a stimulus/response system? Or as something else entirely?

At first, I was also confused about how the brain could generate outputs without inputs; however, I found the example with the thermal motion to be helpful. Initially, I had believed that a cause is needed for an effect, but since particles (in the table) can move with absolutely no outside force to cause this to happen, there must be other instances as well which result from no cause. Because there is now an example to illustrate that an effect can occur without a cause, the brain must also be able to do the same, especially since the brain is capable of so much.  Also, in class I found it interesting when we said that about 20% of our neurons are motor neurons.  This is because when I think of neurons, I automatically assume their function is primarily movement. Basically, when I found out that 99.99…% of neurons are interneurons, it was very surprising.   This brings up the idea that even though we actually assume the nervous system mostly deals with the outside world, it is quite the opposite. We have a lot more going on inside of the body than we think. 

While most of our discussion revolved around outputs and inputs and neural circuits, the very light neural anatomy that we did go into inspired me to look into basic neuron anatomy even more.  I found this neuron anatomy website  which I thought was particularly good at presenting neuron structure and basic function. What is amazing to me is not this notion of a generation of outputs with any input, but the fact that the cells in our body have the ability to do exactly that.  We see how outputs are generated without any inputs in every day life whether it be through dreams, desires, wants, creative thoughts, or through experiences or encounters with epilepsy or autism.
 

But what it comes down to is the basic anatomy or our brains and nervous systems. The overall structure and function of the neuron is basically the same across the human race.  Impulses, inputs, and outputs are the result of electrochemical gradients, sodium and calcium channels, and much more. Although scientists study neurons and how they function at the biochemical level, we still have been unable to build a neuron artificially.  We attempt to build robots and computer systems that function parallel to our own brain, but none have come close. None of these systems have had a mind of their own – they can’t produce outputs without any inputs.  And the way I see it, it is all because they don’t have the same building blocks that comprise our brains and nervous systems. It just gets me how we take these things called neurons for granted at times. Sometimes we just don’t realize how these neurons. so intricately architectured that we can’t even fully conceive how they work and function, allow us to do so much.

 

Even though I was slightly suspicious of our discussion of outputs being generated without the influence of inputs, I think one main point in class greatly cleared up my confusion. An input is defined as a stimuli OUTSIDE of the nervous system. Thus the many instances I was thinking of contradicting the 'output without input' statement were cleared up. A significant amount of our behavior can have stimuli within the nervous system, and yet these do not count as external stimuli. Therefore if a stimuli was generated within the nervous system, any action in response would be deemed an output without an input. Also, the many examples given in class showed that there really are many everyday examples supporting this statement that hadn't previously crossed my mind. Such examples of radioactive decay, seizures, and other topics discussed allowed me to realize that maybe our interactions in the world aren't as clear-cut as they are imagined in the introductory science levels of education. After Tuesday's class, I am much more open to the initially contradictory ideas that our behavior is not necessarily always linked to an input. The advantages of this are endless, but in short, the main point is that the body can act with a sort of 'free-will' without stimuli. While not all outputs without inputs are beneficial to the organism, a body that requires less input for everyday needs is much more independent.

As mentioned in previous posts, the percentage of interneurons compared to sensory and motor neurons is overwhelming. However, I don't think that necessarily supports the idea that the majority of our behavior is directly due to interneuron interactions. One sensory neuron can pick up on a signal, sending it through countless interneurons before it reaches a motor neuron. Less neurons are required for interacting with the outer world than forming the connections between the two. Also, I feel like one sensory neuron can trigger many other interneurons, suggesting a much greater need of interneurons as well. Although I don't have enough background to make any of these claims, we must remember that other factors can take away from this effect.

After reading Michelle and Emily's comments about outputs with no physical stimuli and interneurons, a few things started to click.  During class we used Autism and seizure disorders as examples of outputs without inputs.  By creating outputs without inputs, it makes sense that seizures and autistic characteristics come from confusion within the interneurons, almost as if there was a traffic jam or a glitch in the system.  Further, if 99.99999% of our neurons are interneurons, it would explain how easy it would be for these problems to occur (with so many interneurons for them to occur at)  and therefore validate how prevalent these disorders are in society.  

As far as interneurons go, it seems to make sense to me why we would need 99.9999% of our neurons to be interneurons.  I can't even begin to imagine the complexity of regulating the entire human body.  From helping the body talk to itself about regulating temperature, blood pressure, breathing and heart rate, the demand on interneurons seems infinite.  If the job of these interneurons is to communicate with each other to achieve homeostasis, then I can justify how our communication with the external world demands only 0.000001% of our neurons.