gib65

Aux contraire, this site says otherwise: http://dericbownds.net/bom99/Ch12/Ch12.html Scroll down to figure 12-6 where it says: "One model for how different aspects of a conscious experience may be bound together. Two systems linking thalamus and cortex are proposed. The first (dashed lines) is a series of closed oscillating loops between specific sensory or motor nuclei of the thalamus and the regions of cortex to which they report via layer 4 of the cortex. Within each modality (visual, auditory, somatosensory, and so on), the firing of cells reflecting the relevant percept are coordinated. Each of these is then bound or recruited into a larger unison by a second, more global assembly of loops between the thalamus and layer 1 of the cortex (solid lines). These sweep as waves of activity from the front to the back of the cortex, as indicated by the arrow at the top, starting every 12.5 millisecond. Each of the waves has a frequency of about 40 hertz, corresponding to bursts of action potentials occurring every 25 millisecond. Each of the sweeps that start every 12.5 millisecond corresponds to one "quantum" of conscious experience."

I should hope you know that you're in grade school. I'd hate to be an eighth grader stressing over a university exam I mistakenly think I'm supposed to be cramming for.

Yes, and this is actually what caused my confusion in the first place But it's all clear now, thanks to your answers. I appreciate the help.

I heard a theory one time that when the brain is in a dream state, it fires signals back to the primary sensory areas. That is, the normal path signals take when they are processed in the primary sensory areas and go to higher processing areas is reversed. Therefore, you get a truly vivid experience that can be as wild and random as your imagination will allow, because, really, it is literally coming from your imagination. Is there any truth to this?

I'm confused. I've heard two theories of color perception at the level of the retina, and to me they seem to contradict each other. On the one hand, I've heard that the retina has 3 cone receptors that are most sensitive to 3 different ranges of light frequency (namely, red, green, and blue), and on the other hand, I've heard that the retina has mechanisms that respond to opponencies (red-green, blue-yellow, and black-white). I'm guessing that the latter, known as the color-opponency system, works on a different level than the cones' trichromatic system. Is this true? If so, where and how is the color-opponency system integerated in relation to the trichromatic system of cones? If not, these two systems seem mutually exclusive, so how are they reconciled? Also, how exactly does the color-opponency system work? That is, what is its function? Does it prevent opposites from being seen at the same time? Is that why we can't see red and green at the same time, but we can see red and yellow (which would be orange)?

That sounds pretty plausible, YT2095. Snail's hypothesis could also be plausible if he could back up his statement:

What are any of you talking about?

I was just thinking about how our heart never stops beating and our lungs never stop breathing. They have to keep it up for the entirety of our lives. That's a long time for muscles to keep working without a moment's break. How do they not get exhausted?

That's right. And as a matter of fact, if you take the French words for the week days and the English for the weekends, you can pretty much match the days with the planets: Sunday -> Sun Lundi (French for Monday) -> Lune (French for moon) * Mardi (French for Tuesday) -> Mars Mercredi (French for Wednesday) -> Mercury Jeudi (French for Thursday) -> Jupiter Vendredi (French for Friday) -> Venus Saturday -> Saturn * I guess Monday works too ('Moon' and 'Mon').

I wouldn't say that so soon. I think this thread is a great idea. It might be starting off slow, but I can see it gaining momentum.

OK, so I'm picturing this. On the evening before Sumeria was erected, there was simply a gathering of tribes. In one of these tribes, someone came up to the group and said: "You know, guys, I've got an idea. Now, it may sound a little crazy, and I don't know if it will work, but hear me out..." and he begins his rant of building an entire civilization with all the common faculties of science, politics, arts, entertainment, etc. Finally, he concludes: "Now I know it sounds like hard work, but if we put enough effort into it, and we start ASAP, I figure we could be finished by, oh, tomorrow morning sometime."

I guess this falls under the category of philosophy so I'm posting it here (sorry to the mods if this is inappropriate). I had a thought the other day: During our dreams, we can perceive ourselves in situations that are bizzare and fantastic yet think nothing of it. I once had a dream that there was a camel in my living room and I shrugged my shoulders about it as though that was normal. The brain must release some kind of chemical when we're sleeping that subdues the parts of our brains associated with shock and surprise so that they are inactive. If this is so, it means that our brains are capable of being in a state in which they can witness amazing and extraordinary things and not recognize that they are indeed amazing and extraordinary. If this is so, what if dreams were not the only time the brain could be in this state. What if amazing and extraordinary things were happening all around us all the time, and the brain naturally blocks them out. What if we are constantly in the midst of natural laws being violated but our brain are in such a state that they brush them off without realizing what we just saw? This is just something to think about. I don't really believe in this, but it is interesting to contemplate anyway. What do others think?

What part of the brain corresponds to our ability to laugh?

Oh, yes, I wasn't thinking about this. My mistake.

Gravity doesn't have a velocity. If anything, it would have an acceleration, but even this is only in a manner of speaking. It makes more sense to ask what's the velocity of an object falling in a gravitational field after a certain amount of time after being dropped from rest. And then you'd have to specify what the force of that gravitational field is (the Earth's gravity is more powerful than the moon's). Of course it is, but only semantically. Physically, light is a collection of photons, particles of electromagnetic energy. Darkness is only the absence of such particles, therefore darkness is not a thing that's there. Light travelling through air or water travels slower than through a vacuum. As far as I know the speed of light is pretty much constant in a vacuum though (300,000 km/s if I'm not mistaken). However, I remember reading that some studies have shown that this speed limit was faster at the beginning of our universe. Anyone want to back me up on this?

I was thinking about this the other day and I wonder what other people think. So far, the only life we've encountered is that which is based on DNA. But DNA is just a melocular structure. Why could there not be other molecular structures, similar in complexity and reproductability, that end up supporting macroscopic structures that exhibit complex and intellegent interactions with their environment such that they mimic life as we know it? These molecular structures need not be possible here on Earth, but supposing they could form on other planets with a completely different environment (which might not be habitable by DNA based lifeforms), such planets could host "life" and we wouldn't even know to look for it there. What do others think?

I remember reading somewhere (in a few introductory university course text books, I believe) that science is founded on 5 principles, or "pillars", as I'm calling them. I can't remember what they are though. Here's my guess: 1) empiricism 2) determinism 3) repeatability 4) testability 5) parsimony Am I missing anything? What about reductionism? What about explainability?

Now I've got a related question: What about the perception of curves? Are their neurons specializing in this? Do signals have to pass through the line detectors before being perceived as curves, or do we perceive curves independently from lines?

Essentially, the problem comes down to this: r represents the distance between the 2 objects from their centers of mass. Since all applicable objects are, in practice, made of matter, their volumes will always be greater than a singularity, and therefore they will "hit" each other before their centers of mass coincide, thereby putting a lower limit on how small r can become and thus how great the force of gravity can be. I think this is what the other posters were saying, not in so many words.

No need. I understand. Thanks.

So each retinal point gets its own fully set of line-orientation neurons in the occipital lobe. Am I interpreting you correctly?

While we're on the topic, does anyone know if marijuana causes permanent brain damage? I've read some studies that say pot's been shown to hinder short-term memories in heavy users, but it did not say what "heavy users" meant or what "hinder" meant. How frquently does a heavy user smoke and for how many years before effects on memory are noticed? Does a hindered memory mean permanently damaged memory or just not performing as well as it could be during and around the time of getting high?

I'm reading a paper that talks about the anatomy of our visual system. It says that there are neurons in the occipital lobe corresponding to our perception of orientation of lines. That is, when we see a series of points in a continuous straight line, these cells become active, and moreover there is a range of cell "columns", each corresponding to a particular orientation of lines. My question is this: when each point on our retina sends information to the occipital lobe, do they each get their own full set of line-orientation neurons, or is there only one set of line-orientation neurons in the brain that each point sends its information to?

Ah, so in other words, the red, green, and blue channels in the occipital lobe are responsible for relaying information from the different color receptors in the eyes, but not necessarily for perceiving color per se. I'd still like to know more about this. Are there any websites that go into detail about specific centers in the brain that seem to be associated with perceptions of specific colors?