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The brain as interconnected boxes: autonomy, distributed signals, and an "I-function"

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. You're welcome to post here any thoughts that have arisen during the course this week (and to respond to thoughts others have posted).

Some issues worth thinking about this week is thinking about the nervous system in terms of interconnected boxes that can generate signals on their own, input and output as distributed signals, and the existence of an "I-function". Are these good summaries of observations? stories? What observations do they not incorporate? What new questions do they raise?

Molly Pieri's picture

Autistic brains....

It's interesting you bring up autism- one symptom/aspect/condition (?) commonly seen in many autistic children is that their brains grow to adult size any where from 8 to 10 years early ( “When Autistic Kids Grow Up” By Barbara Kantrowitz and Julie Scelfo, Newsweek; 27 November, 2006; Pg 46. I can't find it on the internet, but I know they have it in Magill at Haverford, possibly at BMC as well?)- I don't know much about human neuro-development, but I would imagine that growing to full size approximately a decade prematurely would cause disturbances in the connections made in the developing parts of the brain...

-Molly.

Lyndsey C's picture

autistic brains

yay im so glad other people are interested in autistic brains. i wrote my first webpaper on that subject so be sure to check back if you wanna learn about some of the current theories behind what causes the disorder and what the autistic brain looks like!
eambash's picture

Humans as social, emotional memory tracts

I anticipate some more satisfactory ideas (or questions, or failures) tomorrow morning, but I've been thinking about the role of the neocortex and decided to throw out a few thoughts.

One small idea: mammals are warm-blooded, so they may have a greater need to be aware of their own bodily systems. If the neocortex receives signals from the thalamus (as Margaux said), the reception of those signals may ensure that the brain sends out signals to other bodily organs, thereby carrying out essential processes like generating heat or cooling the body down. The neocortex could be kind of like a conductor, ensuring that one small box in the brain gets its message out to the rest of the brain and then the body.

What's really getting to me: in the previous comment, Nana brought up the idea of "intelligence" as a possible, but scientifically problematic, result of the neocortex. While her anteater example confuses me, it also gives me food for thought. What if "intelligence" doesn't just mean physical agility or sensory processing but relates more to self-consciousness? Awareness of the self seems to me like something humans may possess more of than other animals, even though others clearly have some level of it too.

In thinking about the child-rearing example mentioned in another comment, I'm also starting to think that a complex web of social behavior might be a result of the neocortex. Maybe that is like a kind of awareness of species -- or awareness of the self as one among many? as a human? as a function of society? Although it is difficult to separate humans from other mammals, the idea that all mammals do a certain amount of teaching and babysitting, even though some mammals end up as solitary creatures, does seem to suggest that the neocortex causes some sort of instinct to form a community, to ensure the success of procreation, to pass on behaviors not just through genes but also through parenting.

Another idea that isn't fully formed: why do humans have so much of the spongy stuff? Tuesday's class made me think that most of the stuff we see from the outside, when looking at a brain, is white matter -- tracts, paths, connections. Thinking back on things I've learned from PBS, the Discovery Channel, and high school, I also know that the human brain constantly forms new passageways as we learn new things or change our behavior. (To use the lingo I've learned from class, our neurons are always rearranging.) Most of the brain -- or at least the white stuff? -- isn't even in use, at least not until our neurons carve our new connections. What are those new connections? Are they skills, calculations, friends, memories?

Lots of other creatures can recognize things or relations, like their young or their nests, but does that mean they remember when they befriended their egg-layers? I'm not sure. I do know that humans, as they grow, learn not only to be aware of their current environment, their status in relation to the outside world, and many of the stimuli they're receiving, but also to compare the current moment to past moments, to associate themselves and their identity with other people, to study their inner states and thoughts, and to perceive or infer emotions and thoughts in others. Maybe the number of available white folds in the neocortex -- the density of its connections -- determines how much of that awareness or ability a mammal can develop, regardless of the overall size of the neocortex or the brain.

Jen Benson's picture

evolution of the cortex in mammals

Reading your response made me wonder how recently human primates have evolved to have such a large and complex neocortex...I didn't find an answer to this question (and would love if somebody could contribute information about it) but I found an interesting article talking about some of the unique properties and functions of the neocortex in mammals.

When brains expand: Mind and the evolution of cortex.

Kirkcaldie,-Matthew-T.-K; Kitchener,-Peter-D
Acta-Neuropsychiatrica. Vol 19(3) Jun 2007, 139-148.

I couldn't get the full text but part of the abstract is interesting:

"the mammalian neocortex is unique: its relationship to the rest of the nervous system is unusually plastic, allowing great changes in cortical organization to occur in relatively short periods of evolution. The fact that even advanced abilities like self-recognition have arisen in species from different mammalian orders suggests that expansion of the neocortex quite naturally generates new levels of cognitive sophistication. Our cognitive and behavioural sophistication may, therefore, be attributable to these intrinsic mechanisms' ability to generate complex interarchies when the neocortex reaches a sufficient size."

Thus one additional part of the picture is the ability of the mammalian neocortext to evolve quickly, likely leading to greater cognitive sophistication.

I also found another article attesting to a tie between neocortical functions and socioemotional capacities of humans and other primates for such things as communication of emotions to others and within groups, complex facial communication, empathy, and self-conscious emotions. These functions allow such species to respond adaptively to their social environments and ensure their reproductive survival.

TI: Emotional communication in primates: Implications for neurobiology. AU: Parr,-Lisa-A; Waller,-Bridget-M; Fugate,-Jennifer SO: Current-Opinion-in-Neurobiology. Vol 15(6) Dec 2005, 716-720.

(I saved it in Haverford storage in a folder called "neurobiology and behavior")

The article cites a theory by Dunbar positing "a relationship between large brain size and complex societies among Homonoids." Thus several people in the forum were possibly correct in attributing many evolved social abilities to the neocortex according to the theory (such as increased ability to cultivate large numbers of personal relationships as facilitated by better cognitive processing speed and memory for social information).

 

Interestingly, none of this evidence presents information about neocortical functions that exist only in humans. If anyone has anything to say about that I'd be really interested to hear it.

nasabere's picture

Neocortex, intelligence, and the like...

Yea, I'm at loss. I agree with Molly in that I am having a hard time finding traits that are entirely unique to mammals...

With respect to evolution, the neocortex is the newest part of the cerebral cortex and is said to be "involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, concious thought and, in humans, language." (http://en.wikipedia.org/wiki/Neocortex)

"In the more primitive section of the brain, behaviours and actions for the survival of the individual and preservation of species are generated. These include the mechanism of aggressive defence, sex, social hierarchy and defending one’s territories."
http://www.selfgrowth.com/articles/Transcending_the_Primitive_Brain.html

The above would hold that nonmammals possess these charteristics and not concious thought, "intelligence", and language which are associated with the neocortex.

Other ideas regarding the neocortex implicate it in learning processes and voluntary action.

These definitions make me a bit uncomfortable. Where is the data to back this up? How can we really say that if neocortex=conciousness, for example, then non-mammals lack conciousness? What is conciousness anyway and how do you measure it? I can't help but think that such definitions come out of our own arrogance and necessity to validate our "inherent superioirity" as mammals, and furthermore as humans. I'm really curious to know how all of the aforementioned parameters were measured...

Now about intelligence: there is a long-standing belief that the growth of the neocortex is responsible for the evolution of "intelligence;" thus, it would hold that mammals would be inherently more "intelligent" than so called "lower organisms." Furthermore, this would also support the notion that a larger neocortex=more intelligent. Contrary to this, anteaters have a larger neocortex than do humans, yet many are reluctant to claim superior "intelligence" in anteaters. This in addition to many other anomalies in the Animal Kingdom hint that neocortex size is an unsatisfactory indicator of "intelligence."

So, I'm not quite sure where this leads me...but here is a starting place. More to come. ..

Mahvish Qureshi's picture

inputs and outputs

Looking further into the question, of how there can be an input with out a resulting output, I found myself looking at the more biological aspect behind the nervous system. I think that such an occurance can occur if the input does not generate enough of a stimulus to result in an action potential, that goes above a threshold value. For an output to be generated, there has to be a strong enough action potential. So there may be an input that isnt strong enough to cause a reaction/output. Otherwise an organism would constently be reacting, and having an output for every small input that occurs.

Looking at the same question in a different manner, explaining the presence of an output with out an input, is still unclear to me, unless the inputs are so insignificant, that we do not realize them, or the inputs could be internalized and something that we can not obviously recognize as an input.

Caitlin Jeschke's picture

Inputs and Outputs

"So there may be an input that isnt strong enough to cause a reaction/output. Otherwise an organism would constently be reacting, and having an output for every small input that occurs."

     When you think about it though, this is exactly what occurs in the body.  In our last class, Prof. Grobstein described an input or perception as a pattern of activity in sensory neurons, and an output or reaction as a pattern of activity in motor neurons.  Unless a person is completely isolated from all possible stimuli, sensory neurons will experience some kind of activity, even if the person is unaware of it.  For example, our bodies are constantly sensing the temperature of the room that we are in, and regulating internal temperature accordingly, even if we "think" that we have adjusted to the room, and ceased to be aware of how warm/cold it is. 

     Another thing that comes to mind is the phenomenon of "spinal shock" that came up during the paralysis discussion.  As I understand it, spinal shock is the period of time following the severing of the spinal chord during which it adjusts to a LACK of signals from the upper portions of the nervous system.  Such a severe reaction to a disruption of signals (signals that the person was probably "unaware" of) shows that it is quite possible for nervous system activity to go unnoticed by the person, or organism, in whom the signals are being transmitted.

Margaux Kearney's picture

Neocortex in mammals

After class on Thursday, Pr.Grobstein left us in suspense as to why mammals have a neocortex and amphibians/reptiles etc don't. After researching a bit on the function of the neocortex, I found something on www.brainconnection.com that I found very interesting. Catching prey requires highly tuned sensory and motor systems. The neocortex is made up of both primary sensory areas that receive input from the thalamus and primary motor areas. Mammals with a larger neocortex therefore have an advantage. Maybe the neocortex plays a role in catching prey? Just a guess....I know I have to be wrong at least one time per posting! 

heather's picture

hmm

that's an interesting thought.

a reptilian behavioral phenomenon to consider when thinking about your theory is that snakes know to swallow their prey head-first. to me this implies a high level of sensory perception - to be able to recognize anatomical structure....

i need to do more research on that, but i just thought i'd share.

cheers!

Paul Grobstein's picture

frogs catch prey pretty well, lack neocortex

You get credit this week. See Directed Movement in the Frog: Motor Choice, Spatial Representation, Free Will? (Grobstein P., 1992, In: Neurobiology of Motor Programme Selection: New Approaches to Mechanisms of Behavioral Choice. Kien, J., McCrohan, C., Winlow, B., eds., Pergamon Press, pp 251-279)
Margaux Kearney's picture

Interconnected boxes

From our many discussions in class and over the forum, we have discussed the idea of inputs and outputs entering and leaving the brain. In some cases inputs can enter the brain, but no output can be generated and vice versa. However, I am having a hard time grasping the concept of the nervous system in terms of interconnected boxes that can generate signals on their own. How can the nervous system react without an input? Are there factors as humans that we cannot perceive? Like someone mentioned in class, dogs have a level of hearing that surpasses humans. Often they react to stimuli that humans are often unaware of. Could previous experiences integrate themselves in the brain and cause "inputs" later on in life?  Is it gene related? Is there a biological clock that generates an output every so often?  

Nelly Khaselev's picture

I totally agree with you

I totally agree with you Margaux. I cannot grasp the idea of our nervous system being able to produce an output without an input. I would like to add though; maybe we should revise our model of the nervous system that would specify inputs as ones that we as human could detect. Then again would unconscious inputs and out puts be included in this new revised model/theory of our nervous system? If no, then we have a problem again. Of course this is all under the assumption that for outputs to occur there needs to be a reason. If we seperate the two words "reason" and "input" maybe then we could better grasp an understand of the ability of the nervous system to create outputs on its own. Most observations of outputs have cause/reason coinciding with inputs, when the NS produces an output on its own there is no input but there must still be a cause/reason...its just from within. Atleast I think...

The experiment on the leech and its nervous system at first had me stumped! The first thing that came to my mind is that there needs to be some kind of control mechanism to the nervous system. Otherwise, we could be twitching whenever the NS felt like it. Now I feel like the nervous system has a mind of its own. Hey! maybe its the mind that controls the nervous system! ....or not? Who knows? Perhaps a spirit/soul/mind whatever you want to call it is controlling the nervous system so it seems that outputs can occur with no inputs. Although, I am a big skeptic about the idea of a mind...

Penn Tong's picture

Brainless

I had the exact same thought about the leech's NS Nelly. I thought that the reason for the "twitching" of the NS was because that was the natural state of its NS and that it needed some sort of inhibitor/regulator (ie the brain) to control these spasms. I mean it is very possible. Look at people who have epilepsy. They have these uncontrollable spasms. Although it's not the same because in this situation we have our brain connected to our NS, we still consider this as a brain disease. So there must be something going on up there (or lack of).

Paul Grobstein's picture

Neocortex?

Whoops, sorry, got this forum up too late. For some relevant thoughts about one box, the neocortex, see Lyndsey C and Molly Pieri.