week 5 - Neurobiology and Behavior

I was thinking a lot about neurons and action potentials, and how there must be more going on in neurons than just the propogation of action potentials leading to the eventual release of neurotransmitters. Here's my thinking: in order to generate an action potential in a neuron, you need to depolarize (make the inside of the cell more positive) it. An action potential is only generated if you break through a certain threshold potential of that cell. After you break this threshold, you create an action potential no matter what, and you get the same response every time even if you continue to increase the amount you deploarize the cell. My question is this: if a neuron has the ability to release more than one kind of neurotransmitter, what signal determines what kind of neurotransmitter is released? The only signaling device I've learned about is the action potential, but clearly the neuron must be getting other kinds of signals to tell it what kind of message to spread across the synapse to the next neuron. Does anyone know what other signals neurons receive/transmit?

I am writing my web paper on the holographic theory of the brain, and as I read these posts on phantom limbs I can't help but relate it to the Holographic model. Basically, in a holographic model of the universe, which is more in the realm of physics than biology, the universe is full of waves which are interpreted by our senses into visible, smellable, hearable things. These waves bounce off of and mix with each other and create interference patterns. A hologram is produced by the interference patterns of light waves reflecting off of an image. One of the distinctive qualities of a hologram is that every bit of the hologram contains an image of the whole, so if you cut a tiny piece of holographic film off of the original, you will be able to see what the original image was in its entirety. According to the model, memories are dispersed across the brain in this way, as are some learned behaviors. I wonder if phantom limb pain can be explained by saying that the memory of that limb is still in existence throughout the brain, that the waves that made up the limb are somehow still imprinted in the person and therefore reacting to the external environment.

I wrote my paper on aphasia, a language disorder caused by the brain.  Individuals with aphasia have trouble with verbal and written language sometimes being unable to understand other or make understandable sentences and statements themselves.  One type of aphasia occurs in the Wernicke's area in the temporal lobe.  In Wernicke's aphasia individuals can form fluent sentences however they do not make sense and they sometimes use neologisms, or made up words.  Because these individuals cannot understand what other people are saying to them they do not understand that they are talking in gibberish and making up sentences that are unclear.  I think that this may be similar to the afferent loop.  These individuals create an output but because there is no input (they do not understand verb language) they never realize what they are saying.

In class on Thursday we discussed the reafferent loop of the nervous system, where an input causes an output, then this new output triggers and a new input and so on. For example it is easier to walk forwards rather than backwards in part due to the fact that you can see where you are going. As you step, your brain visually registers what just happened and where your limbs are. You are able keep stepping and keep moving with ease thanks to visual confirmation and the reafferent loop. In class we discussed the reafferent loop with respect to the physical control of over our bodies, such as lifting a leg or moving an arm. I am interested in how the reafferent loop affects internal processes of the brain like learning. Can the reafferent loop explain why some people are visual learners? If a mathematical concept is sketched out in a diagram and then explained to me, I am much more likely to understand the problem then if the professor merely reads it out loud. The diagram offers a visual confirmation of what I am learning. Is this the same as watching your leg move or seeing the angle of your arm to confirm where it is in space?

A recent New York Times essay (2/20/2007) by Daniel Goleman entitled "Flame First, Think Later: New Clues to E-mail Misbehavior" details a rather common and growing social faux pas which virtually all of us are guilty of committing from time to time. Classified under the umbrella of the developing field known as social neuroscience, this phenomenon is called flaming, or more technically "online disinhibition effect," which refers to one's increasingly unrestrained behavior in an online environment, such as e-mail and Instant Messaging.

Goleman reports that an article found in the CyberPsychology & Behavior journal cites multiple potential dynamics at play here, including "the anonymity of a Web pseudonym, invisibility to others, the time lag between sending an e-mail message and getting feedback, the exaggerated sense of self from being alone, and the lack of any online authority figure."

Biologically speaking, our social behavior is moderated by the circuitry concentrated on the orbitofrontal cortex, which serves as our primary foundation for empathy and ensures that we appropriately interact with others based on certain signals and cues, like facial expressions and various forms of body language. If we lack the opportunity to interact face-to-face, then we consequently lack the ability to read these key cues and react suitably.

This rather novel way of looking at the brain (that is, from a social perspective) raises several interesting issues involving attitudes toward (abnormal) human behavior and such behavior's causes and methods of treatment. Furthermore, we are compelled to question the value of new technologies. Are these tools really making communication easier? Or are they just creating more harm than good?

(reposted in case people are interested in this article- this was posted a bit late) found an interesting article concerning the prefrontal cortex and abstract thought:     http://web.mit.edu/newsoffice/2001/abstractthought.html                                                                                                                                                                                                                                                                     The article describes a 2001 study performed at MIT concerning pattern recognition and abstract thought. The study, in which monkeys apply rules about ‘same’ and ‘different’ images, shows that the prefrontal cortex works on the abstract assignment rather than simply recalling the pictures. In other words, the prefrontal cortex is involved in figuring out the rules of the “same/different” activity, rather than the simple performance of the activity. What is innovative about this approach to brain research is that it deals with abstract patterning and recognition, whereas traditional studies have focused on structures responsible for performing specific tasks, such as moving muscles or image recognition                                                                                                                                                                  The Study:                                                                                                                                                                Over a period of nine months, the researchers trained a group of monkeys to identify whether hundreds of different pictures were the same or different images. By recording signals from neurons in the prefrontal cortex of the monkeys as they performed cognitive processes, the scientists monitored the regions associated with “holding information in mind”, a requisite ability for information processing and thinking.                                                                                                                                                                                                                                                                                                                                                      The monkeys were trained to pull a joystick if a picture was the same as the one shown before. At other times, the monkeys were required to pull the lever to identify different images. The monkeys could apply the rule to pictures they had never seen before, showing that they were dealing with abstractions. By the end of the nine month period, the monkeys were able to respond instantly to the rule and were right more than 85 percent of the time.                                                                                                                                                                                                                                                                                                                 In studies of monkeys and humans with damage to the prefrontal cortex, researchers have found many of the same cognitive problems seen in schizophrenic patients. Among them is what is widely believed to be a disorder of working memory, which allows you to keep several pieces of information in mind simultaneously.  Abnormal functioning of the prefrontal cortex is implicated in schizophrenia, attention deficit disorder, obsessive-compulsive disorder and other diseases.                                                                                                                                                                                                                                                                              Why This Should Be interesting To Us:                                                                                                                                                                                                                                                                                                                                          The aim of this study is to gain some insight into what we’ve been referring to in class as the “I function” (the article uses the phrase “executive or cognitive control”). What this study suggests is that, although we know very little about abstract thought and its analogues, the responsible neurons are physiologically situated in the prefrontal cortex.  Although there are significant limitations to animal experimentation, and the specific physiological analogues associated with abstract thought remain unmapped, the investigative process is itself immeasurably valuable. If all of human experience is wrapped up in the phenommenon we call 'abstract thought', then potentially have much to gain from further research on the prefrontal cortex.

I have taken a recent interest in brain scanners such as MRI scans, and fMRI scans. An fMRI (Functional Magnetic Resonance Imaging) is a technique that enables researchers to create maps of the brain's networks in action as thoughts, sensations, memories, and motor commands are processed. This "brain mapping" is achieved by setting up an advanced MRI scanner in a special way so that the increased blood flow to the activated areas of the brain shows up on Functional MRI scans. With this type of technique we can map the areas of the brain that become active whenever we perform our self proclaimed "motor symphonies". However, because an fMRI requires a scanner and stillness, it would be the mental thought of moving. An fMRI can show activity in the mind when giving an inner monologue. In an experiment, a subject would be given a task, such as thinking of a room with an obstacle course. They would be asked to mentally move themselves through the course by thinking of how each movement would propell them forwards through the track. In this way, we could track whether certain actions they must perform requires a greater amount of activity in the brain or if it is something that has already been pre-programmed.

Taking into account this idea of a “motor symphony,” I wonder how the analogy would pertain to the creative brain – if it would be heightened at all, more apparent perhaps? Now that we know an action = motor symphony (as a contained movement), how does this reafferent loop work? I understand that the basic break-down of said symphony is motor neurons all doing different things at different times in a coordinated fashion, but where does the loop come into play? Does it record the movement? Does it conduct the movement? If I’m not mistaken, an element of input alteration is introduced, is it not? Any thoughts? I’m intrigued but very confused as to how to finish the metaphor!

Additionally, beyond the semantics of the symphony, I wonder if creative thought – as in “inspiration” (in dance, theater) – has any pre-programmed movements just as reaching for an object is imbedded in our nervous systems. Since it was stated that the ability to walk in humans does not depend on experience, what do we make of this notion of creative movement? Are prolific choreographers and actors simply recycling pre-existing functions of the nervous system but presenting them in new ways? Where does dance/movement even come from? What makes humans go beyond basic “pre-programmed” motions and make them into an art form? I’m trying to account for this notion that mostly everything we do in a day has been written into some inner code – that even with our eyes closed (like in the example of reaching for a cup of coffee) we would still be able to function and it wouldn’t be solely due to our experience. It is this idea of a pre-written score that really throws me for a loop – how many are there and how would we even know where to find them?

I’ve been thinking a fair bit about these excitatory and inhibitory synaptic potentials and I find them quite interesting. An action potential is either excitatory or inhibitory, and for it to move from neuron to neuron there are conditions that need to be met. Action potentials are summed in the cell body of a neuron and if they have a strong enough intensity and/or frequency to bring the membrane potential above the threshold then an action potential is created. I guess that seems simple enough, to say that the system works in this way. But the problem is that it’s not always that simple. Yes, in the best-case scenario, everything works right and there are excitatory and inhibitory action potentials that work in harmony and everyone lives happily ever after.

So then, let’s talk about epilepsy. In the New York Times Science Times this week there was an article called, Battling Epilepsy, and Its Stigma which I found to be very interesting and very pertinent to our discussion this week. The article profiled a family in Pennsylvania whose 12-year old daughter, Nora has intractable epilepsy (this is a type of epilepsy that cannot be controlled with medication). Reading this article and watching the video stimulated questions but also promoted concerns about the way we think about neurological disorders.

Epilepsy is a neurological disease and affects almost three million Americans, half are children. Epileptic seizures can be thought of as there is either too much excitation in the brain or not enough inhibition. Huh. I found this description interestingly vague; it basically seems like we are covering the bases here with that definition. Isn’t that the reason that all behavior occurs: there is either not enough inhibition or too much excitation? Yet, Dr. Devnisky, the director of the epilepsy center at NYU is quoted as saying, “epilepsy just needs to be recognized as another neurological disorder.” (Granted, I am somewhat taking this comment out of context, but it still frustrates me.) True, epilepsy is just another neurological disorder, but just a neurological disorder?!? If Emily Dickinson is right, then just doesn’t cut it. There is so much about the brain, its support systems and what it controls.

Behavior, specifically looking at epilepsy isn’t just about excitation or inhibition, because then what causes you to snap out of it? In the case of Nora, I begin to wonder what else is going on. I think that Nora’s case is a prime example that there are other things going on in the system. Nora is now 12, but until recently had been seizure free for three years. She was able to stop having seizures because here parents put her on the ketogenic diet (this is a diet which induces a constant state of ketosis by feeding a diet rich in fat. Note that ketosis is an extremely severe condition and in diabetics can be fatal.). What is it about the ketogenic diet that worked so well, and not just for Nora, but for 50% of the people tested in the Johns Hopkins study? This diet stopped working for Nora recently and her parents blame it on her “growing up” and the “flow of hormones.” Again, I am unsatisfied by the answer (because it’s so vague), but also because it further illustrates the fact that behavior is under complex control systems, and it is not simply excitatory and inhibitory synaptic potentials.

But what about medication? The medication/treatment strategies are equally frustrating. There are lots of different epilepsy medications which do fundamentally different things, and when you are diagnosed with epilepsy they play guess-and-check until they find a medication that works for you. Yet, there are still 30% of epileptics who cannot control their seizures with medication. I want to first know if these medications are tailored to certain triggers (such as if you have too much excitation in your brain X chemical gets released) or if they are targeting something else.

I think epilepsy points further exemplifies the complexities that are responsible for behavior and also the minute amount of understanding we have of them. We know that these excitatory and inhibitory synaptic potentials exist and work most of the time, but they don’t work the same way or right in anyone. There are still more questions out there about behavior and how everything works together (or for that matter, doesn’t).