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Neurobiology and Behavior, Week 7

Paul Grobstein's picture

Welcome to the on-line forum associated with the Biology 202 at Bryn Mawr College. Its a way to keep conversations going between course meetings, and to do so in a way that makes our conversations available to other who may in turn have interesting thoughts to contribute to them. Leave whatever thoughts in progress you think might be useful to others, see what other people are thinking, and add thoughts that that in turn generates in you.

As always, you're free to write about whatever thoughts you add this week. But if you need something to get you started, what further insights into both the nervous system and behavior come from understanding the chemical aspects of synaptic transmission, chemosensitivity in general? inhibitions?  And the pattern generating capabilities of neuronal networks?   

nafisam's picture

I was intrigued by the

I was intrigued by the notion of a chicken running with its head cut off. When you cut a chicken's head off, you are essentially turning its inhibitory signaling off. It is interesting to think of this in the context of human beings. It it seems that we are continually being inhibited from certain actions. Perhaps this is one reason we don't reveal all our thoughts at once, and we take the time to select what information we reveal, or do not reveal. It is interesting to think about how much of our behavior/thoughts are inhibited on a daily basis. How does the nervous system choose what is inhibited at different times during our lifetime? Does the reafferent loop account for all of this behavior?
mmg's picture

Creating the world

Having read the article on anosognosia I was taken aback by the evidence mounting to the control the brain has on how we perceive our experiences. Also, the way we go about trying to rationalise such discrepancies is noteworthy. (The 2 out of 3 ladies that insisted even healthy persons were paralysed) Is it the brain making up such explanations for factual and supposed inaccuracies, or is it the ‘I function’ doing so? How much outside information can be ‘warped’ by the brain without our knowledge?  
Leah Bonnell's picture

the nba and the flute

The NYT article about the NBA made me think of my experiences as a flutist. I can remember one audition in particular where I was nervous and couldn't really focus. To deal with my nervousness, I ended playing the piece without really thinking about it; I was pretty much on automatic. That audition ended up being by most successful. I think basketball players also get it this automatic mode during games, where brain can react to surroundings and coordinate the body, but at the same time the players don't really feel like they're thinking. A few of the NBA players also found they were most successful when they were not thinking too much. I find it interesting that not thinking can somehow make you a better player. I guess awareness can be a distraction. 


fquadri's picture

Week 7

Do reafferent loops prove a part of Dickinson's claim that nearly everything is a contruct of the brain?  That our behavior is a construct of the brain? It certainly proves that brain= behavior in the sense that the brain uses its outputs as inputs and recycles signals in order to generate behavior. Reafferent loops, as well as a large percentage of interneurons in the brain, almost make me think that the brain doesn't need to rely much on environment for inputs (except maybe for the very first input from the environment that can spark an action potential). So is our interpretation of the world more dependent on our behavior and actons than the actual environment itself? 

bpyenson's picture

Are we ever dealing with the same machine?

We learned from the classes a couple of weeks ago that the brain acts very much like a computer, transferring inputs into outputs like a mathematical function.  Even when discussing reafference loops, we still viewed the brain in a machine-like manner.

In this given reflexive machine model, it might seem that the machine is relatively static: a particular input creates a particular output consistently.  The machine, though, seems to be in flux constantly since the inputs do generate seemingly unpredicted outputs, as well as creating spontaneous inputs within the system.

Given these understandings of the brain and reflexive nervous system, can we effectively separate inputs that come from the environment from the seemingly 'spontaneous' or genetic inputs that emerge from within the system without any apparent origin.  In particular, can we ever say that there are 'genetic' portions of the nervous system, or is at least somewhat involved with the environment.  Is it possible though that a signal could be entirely 'environmental' in origin and lack any genetic component? 


Certainly with my thesis research on environmental sex determination, there seems to be a heavy environmental component, but I'm not yet audacious enough to say that the environmental components are entirely separated from the genetic components.

hlee01's picture

In reading the news article

In reading the news article on New York Times about these NBA players who perform their best when they are playing "unconsciously", I began to wonder if there is any difference in chemoreceptors (knowing that chemoreceptors influence behavior which may result in good performances in NBA players) when we do things "unconsciously" vs. "consciously".
jwiltsee's picture

New Discovery

I was watching BBC World news while I was in Rome this past week and one of the highlights was that researchers had a break through in neuro science where they were finally able to figure out a person's thoughts by looking at images of their brain function/behavior.  Does anyone have more information or any ideas/thoughts on how this is able to occur?
Sarah Tabi's picture

Chemosensitivity and behavior

If humans in general have exactly the same chemoreceptors and if chemoreceptors influence our behavior, then what aspect of that concept makes us different. Theoretically, our bodies have the same reflexes to external stimuli (i.e. if something is hot, we pull away), so how does that connect to our behavior being unique. Does chemosensitivity contribute to each human's individuality at all?
aybala50's picture


The latest discussions we've been having in class makes me wonder how 'psychology' fits into the scheme of neuron's etc. I know that psychology has a lot to do with how the physical body works, but at the same time, a person's psychology almost feels like it should be about 'the soul'. I guess I'm still confused as to how the idea of a soul fit's in with everything and if it can in any way be separated from the activities of the brain. 
redmink's picture


I think reafferent loop is a mechanism that has been evolved in such a way to fisrt, minimize the energy/time of finding inputs from environment, and second, reinforce our brain of the pattern of our behavior (making even closer connection between brain and behavior). 

The loop draws a parallel to the following analogy: in mathematics, the shortest line that can be drawn from the two points, A and B, is a straight line between them.  This simple analogy exemplifies the first point which is the loop minimizes the energy/time of finding inputs from environment. 

The second point can be further expanded.  Reafferent loop forms reinforces one's identity and pattern through recycling the information originated from oneself within one's neural system.  For example, a person can observe one's health over long periods of time and figure out which food they need to eat and which they should avoid.  They tend to study their life-rhythms throughout their life.  This self-feedback or control is i think the result of evolution, indicative of more efficient and better neural pattern with minimum energy for maximum adaptation.

Adam Zakheim's picture


It seems correct to say that the “Reafferent loop forms reinforces one's identity and pattern through recycling the information originated from oneself within one's neural system.” This sense of a reinforced identity and behavior honed through a recurring motor symphony made me think about obesity. In the United States, over 72 million adults (34%) are obese. There are a lot of different theories that describe the causes of obesity, but the prevalent belief is that the problem is largely psychological, a matter of will power. In such cases, where someone is suffering from a purely psychological condition, is the reafferent loop to blame? Since this loop is responsible for coordinating and, in the absence of inputs, generating outputs, it seems to be responsible for our habits and predispositions. These patterns, as we discussed, are generated through improvisation, or are pre-programmed responses. With this model, how does one explain obesity?
ddl's picture

The Reafferent Loop

     The reafferent loop is a pretty amazing component of the human nervous system.  To be able to sense one’s own outputs and have such perception generate newly modified and ‘improved’ inputs is a very necessary and often overlooked aspect of our everyday lives. 

     Our discussion in class about a person reaching for something in the dark was very useful in elucidating the role of the reafferent loop for me.  By reaching for something that we can’t see and not finding or touching it, we talked about how the reafferent loop may play a role in being able to signal back to our nervous system, thereby generating an input which says that the desired item is not in the place that we have already checked.  Thus, this function facilitates additional, future searches for the same object in that it can effectively prevent us from checking the same area twice and allows us to eliminate places in which we have already directed outputs to explore.

      From this example, I began to wonder if it was at all possible that this reafferent loop was malfunctioning or compromised in people who have been diagnosed with severe amnesia or short term memory loss.  In cases where people do not remember whether or not they locked their door, turned off a light, remembered a person’s name, etc. (even after multiple attempts or interactions), is this loop simply not producing inputs which can be successfully redirected to their nervous system (in order to be used to influence that person’s related future nervous system outputs)?  Or is the problem that that person cannot retain the inputs that have been generated by this loop’s ability to sense nervous system outputs?

Lisa B.'s picture

Week 7

For me the underlying question of our discussion has to do with personal identity. Is behavior only composed of the nervous system? According to the Scottish philosopher David Hume (1711-1776), "we are nothing but a bundle or collection of different sensations, succeeding one another with inconceivable rapidity." Furthermore, the British neurologist Oliver Sacks wrote that there are two fates of human perception, the ‘Freudian fate' or the ‘Humean' fate (The Man Who Mistook His Wife for a Hat 124).  Some humans have a Humean, as opposed to a Freudian fate, if neuronal activity overpowers identity. In Chapter 14, "The Possessed," Sacks wrote that the Freudian fate compelled his patient diagnosed with Tourette's syndrome to survive. Sacks wrote that the will to survive as a unique inalienable individual was stronger than disease. I agree with Sacks that humans survive to become an individual and that we are more than a bundle of nerves. 
jlustick's picture

Some questions

One question that was posed in class on Thursday that I continue to wonder about is whether emotions are outputs. If I feel sad, is that an output of or input to my nervous system, or both? How is the reafferent loop related to emotions?

On a completely different note, I am curious as to whether the idea of a "motor symphony" be extended a bit...In class, we talked about how a motor symphony allows us to perform everyday actions like picking up a coffee mug or opening a door handle. Are motor symphonies also related to thoughts/patterns of thinking? Does thinking have a "motor" component? Do people tend to think/process and analyze information in specific ways based on stored motor scores? Is education in any way responsible for helping us form "scores"?

kenglander's picture

emotions and outputs

I don't think emotions can be considered forms of input nor do I think that they are physical outputs. Under certain conditions-- what we might label fear or anxiety, for example-- there may be particular trends in the flux of hormones in the nervous system (particularly the brain), but they do not necessarily translate into the same actions for all individuals. For example, if someone sees and hears a large dog barking he might experience a sense of panic. While some people may run from the dog, others might freeze, while others may not be scared of or intimidated by the dog at all. In addition, the argument for attributing actions to particular emotions is circular; the statement seems to be: "I ran because I was scared. You know I was scared because you saw me run." In other words, I don't think it makes sense to say that a particular emotion is the cause or root of one's behavior. Rather, it might make more sense to say that a person who heard a dog barking was scared and ran.
BMCsoccer01's picture

The Human Mind & Body: Capable of Anything

In reading the most recent blog posts, I think that Brie raises a very valid point. Being a psych major myself, I have before thought about the possiblity that we are born with far greater capabilities than we actually use in our daily lives, and thus throughout the span of our entire lives. Knowing that human development is one of the longest developmental periods among animals, we can recognize that human beings are extremely vulnerable to external factors from birth. Doesn't this in fact acknoweldege that human beings are one of the most adaptable beings that have the ability to recognize a barrage of stimuli if given the chance? Knowing that infants are capable of mimicing & in time, learning, all of the different languages of the world, I believe that we are susceptible to & thus capable of utlizing many different stimuli.

For example, I firmly believe that if an infant was born in a cave and lived in darkness a considerable amount of his/her life that this individual would have far better night vision (& maybe vision for that matter), in comparison to an ordinary human being. Is this really that far-reaching? There are stories of children being born blind that have a much better sensation for when an individual enters a room or can decipher emotion just from speaking without any image of facial expression. Overall, one could state that they can "sense" the presence & behavior of human life better than an individual with sight. 

In conclusion, I do believe that human beings are capable of having nervous systems that are far more "in-touch" with a vast variety of stimuli, however, without being exposed to this stimuli, our capability of mastering the inputs and outputs from our external environment is lost. Furthermore, I think we should take this topic one step further and ask ourselves: what do we believe the human mind & body is incapable of, if given exposure & time to learn?     

jrlewis's picture

neurobiology and stories

Taking a break from this course has caused me to reflect on what I have learned this semester, so far.  I’m finding it challenging to organize all of the information on the nervous system.  At the lowest level are the neurons, input/output boxes based on chemosensitivity, inhibitions, and synaptic transmission.  At the next level, are neural networks, patterns of activity, and explanation of how we walk on our own feet.  The following level is the differentiation between the I-function and the unconscious or the part of ourselves we know and the part that is cannot be observed by us. 

What I am curious about, is how the I-function and unconscious interact to create stories?  By stories, I mean not only the tales we tell one another, but tacit understandings, private summaries of observations.  Sometimes stories are buried so deep, the person doesn’t even have complete conscious access.  Yet stories are omnipotent, capable of influencing conscious and unconscious behavior alike.   Both logical rational decisions and emotional intuitive acts are guided by stories.  So if brain=behavior, where does the storyteller reside? 

ilja's picture

The reafferent loop that we

The reafferent loop that we discussed last class seemed very logical and illogical at the same time.Although the output from our own body seems very important in determining our next steps in our behavior it seems difficult to know what percentage of our inputs can be based off of our outputs. How can we account for the environment in these calculations? Even if we know that there are many systems (photoreceptors etc.) that are regulating the outputs of our body and then become inputs in return this seems to be applying mostly to internal balances and actions. How about events in a persons environment that is not connected to internal regulations? How can we determine what is part of the reafferent loop and what is not?
Bo-Rin Kim's picture

As with any other behavior

As with any other behavior or output we produce, it is hard to trace the exact processes the reafferent loop goes through and what parts of our nervous system or additional external inputs are involved. However, I think having the concept of a reafferent loop is necessary to understand how many of our behaviors/thoughts/outputs interact with and influence each other. This concept helps us to see the complexity of our nervous system and how it is not just a one-way output producing system. One reason why humans are complex because we can think of something (which is an output) and this thought will go back and influence our subsequent behavior as an input. This looping around of signals improves the efficiency (and possibly the speed) of our nervous system as we don't have to find a new input signal for all of our actions (the reafferent loop is basically how our nervous system recycles the signals it produces). We don't have to wait for some external input to motivate us to do something when we can produce internal thoughts that can motivate us. Similar to how our biological systems have positive/negative feedback systems to help maintain/inhibit certain bodily processes, our nervous system has a similar maintainence system with the physical and mental outputs it produces. So while there are many questions still surrounding the details of how the reafferent loop, I think it is a helpful concept that answers other questions about how the nervous system functions and that allows us to better see the complexity of the nervous system.
eglaser's picture

phantom limb

As we discussed inhibitions and intuition in class I began to think about something called phantom limb sensation and how it could be applied to what were learning. The studydiscussed in this article from Scientific American used physical therapy to help reduce the pain in the lost limb. The article determined that, "...people with pathological pain have distorted maps of the body, or a generalized disinhibition of parts of the brain (reduction of the normal inhibitory control that keeps brain activations in check)."

What makes this find really interesting is that the researchers found that  visualizing the body/ the amputated limb alone can help drastically reduce the phantom limb sensation. "Simply thinking about body parts activates their virtual counterpart—one can’t feel one’s body without using neurons that represent it. Honing in on a particular body part requires inhibitory processes, the loss of which might underpin the extravagant activation patterns that were observed in the pre-training scans."
Phantom limb sensation highlights the importanceof inhibition and intuition in our nervous system.

Paul Grobstein's picture

basketball and the I-function

Crystal Leonard's picture

constant movement

The discussion on the idea that the nervous system can create motor symphonies without the use of reafferent loops or external stimuli got me thinking about some of the little everyday movements of different people. Many people seem to be constantly making small, unconscious movements for no particular reason. Very few people every actually stay still. For example, I know a guy whose legs are always moving. Whenever he is sitting or laying down he unconsciously starts jiggling his legs. No external stimuli cause this behavior, and usually he doesn't even realize he's doing it until someone brings it up. Also, whenever I'm sitting I start wiggling my toes. These movements seem to serve no purpose and occur without thinking. Perhaps these are examples of a combination of pre-existing motor scores that the nervous system contains and specific neurons that are continuously permeable to some degree to sodium ions.
Sam Beebout's picture

body language

I was wondering about the same types of movements along with things like breathing or blinking, all of those movements that are necessary and we don't usually think about. I had a nerdy memory from high school biology when we learned about how the digestive system works and it similar to the way the worm moved because its all about a wave of movement and pressure causing contractions of muscles down the line.

I am wondering whether our body language, and facial responses, are a "symphony" already programmed in because so much of it is unconscious. I know that there are some facial emotions that are "universal". At the same time thinking about emotions and body language confuses our discussion last class because although we may all have the some of the same indicators of how we are feeling, the level of emotional response and the triggers for these responses vary so much from person to person. Personalities are different, cultures are different, etc. 

I'm not sure if reafferant loops apply to body language and facial emotions because these types of responses are something we are often not trying to control and something we are also not always in control of, unlike reaching out for a cup on the table or playing the piano. Although its not the same thing, metaphorically emotions are more like a wave, an uncontrollable momentum that fuels itself rather than our more controlled movements. 

Brie Stark's picture

While I understand that

While I understand that neurobiology and psychology at two separate entities, I keep coming back to psychology in reference to several topics we've discussed this week.  Namely, we discussed if, at one point, we as humans possessed "all stimuli."  While it was ruled out in class if we did, at one point, possess "all stimuli," I still find an argument in favor of the fact that we may have.  In terms of language recognition as an infant, psychologists believe that we can understand/parse/hear every phoneme in every language of the world.  Over time, at about six months, we have heard our own native language so much that we begin to lose the ability to separate certain tones that once sounded different to us.  For example, Japanese children forget that there was once a difference between the "r" and "l" sound because there is no audible difference in spoken Japanese.  However, at one point, researchers proved that they could tell a difference between these two phonemes.

So still I wonder, could we have had, at one point, the ability to perceive all stimuli in the world?  However, having been raised as a human and in the social constructs of humanity, we lost several aspects of 'sensing' that didn't seem particularly useful to us?  It seems probable, if looked at with the above conditions in mind.

BeccaB-C's picture

I agree, to a point, that

I agree, to a point, that there may be evidence to suggest that we were capable of recieving and processing far more stimuli as infants than we do as adults and even as young children. The period of plasticity is really interesting and the particular example of receptors of certain phonemes exist before we reach the critical language period, but atrophy when that part of neuroplasticity ends is a great one. Further, many studies have beenconducted that show evidence for quite a bit of neural plasticity in adults, though not with the same level of permanence. For example, adults were taught how to juggle and with this procedural knowledge, higher density of neurons were observed in certain brain regions. This increased density, however, atrophied after the skill was lost.

I would be interested to explore the consistency with which this pattern exists. What is the threshold of "currency of skill-knowledge"/"skill loss" at which point neurons begin to atrophy? Is this controlled to any degree among humans?