cvl@athena.mit.edu (Craig V Lewis) (05/03/91)
Somebody inquired about inherited mouse memory. I believe Sci. Am. had an article some years ago on inherited memory in some low invertebrate (tapeworm or similar) organism (the concept of memory in a species with rudimentory CNS is questionable). Since my first pt. indicates a high degree of unfamiliarity with invert. zoo., I'll raise another question. Does anyone know of a good invertebrate zoology course either in a summer program or in the Boston area? I'm in Biological Oceanography if that helps slant the replies. Please reply by e-mail to cvl@athena.mit.edu. Craig Lewis, Woods Hole Oceanographic Institution
winalski@psw.enet.dec.com (Paul S. Winalski) (05/03/91)
In article <1991May2.181440.14045@athena.mit.edu>, cvl@athena.mit.edu (Craig V Lewis) writes: |> |>Somebody inquired about inherited mouse memory. I believe Sci. Am. had an |>article some years ago on inherited memory in some low invertebrate (tapeworm |>or similar) organism (the concept of memory in a species with rudimentory CNS |>is questionable). I think you're referring to the studies on RNA memory inheritance in flatworms. There was an experiment years back where flatworms were tought to run a maze. The educated flatworms were gound up and fed to a group of flatworms that did not know how to run the maze. These uneducated flatworms subsequently made fewer mistakes running the maze than could be explained by statistical chance. The conclusion was that RNA in the educated flatworms encoded the memory of how to run the maze and that this was incorporated in the memory of the flatworms that ingested this RNA. This concept of RNA inheritance of memory has been widely adopted by science fiction authors (e.g., Frank Herber's DUNE books). I think later Biological research has invalidated these studies. --PSW
doug@eris.berkeley.edu (Doug Merritt) (05/05/91)
In article <1991May3.162715.21825@hollie.rdg.dec.com> winalski@psw.enet.dec.com (Paul S. Winalski) writes: > The educated flatworms were gound up and fed to a group >of flatworms that did not know how to run the maze. [...] >I think later Biological research has invalidated these studies. Right. This, the discrediting of Penfield's interpretation of his experiments with electrical stimulation of the brain, and the discrediting of the "you only use 10% of all the parts of your brain", are probably the three most important debunkings of things that "everyone knows" about the brain. (I've heard third hand reports of some paper that claims that that it takes 50 to 100 years for scientific research, or its debunking, to become common cultural knowledge --- things that "everyone knows", not just scholars. Things are probably not quite this simple, but it's probably true that it will take a very long time until these three things cease to be things that "everyone knows".) >This concept of RNA inheritance of memory has been widely adopted by >science fiction authors (e.g., Frank Herber's DUNE books). Bad example. Dune assumed no such thing. It did assume a mystical transference of memory from one generation to the next (apparently to/from females only), and (arguably) tied this to some sort of inherited cellular memory, but RNA was not mentioned, the tie between neural memory and reproductive system was never explained, and the emphasis was 100% on mysticism, not any assumption of a scientifically explicable mechanism. Dune is primarily sociological science fiction; it makes little or no pretense of being "hard" science fiction. Doug -- -- Doug Merritt doug@eris.berkeley.edu (ucbvax!eris!doug) or uunet.uu.net!crossck!dougm
gb661@leah.albany.edu (BROADWELL GEORGE AARON) (05/07/91)
In article <1991May4.190132.22684@agate.berkeley.edu> doug@eris.berkeley.edu (Doug Merritt) writes: >Right. This, the discrediting of Penfield's interpretation of his >experiments with electrical stimulation of the brain, and the discrediting >of the "you only use 10% of all the parts of your brain", are probably the ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >three most important debunkings of things that "everyone knows" about the >brain. Could you fill in a non-biologist on how this was debunked? Students frequently mention this to me, and all I can say is that it doesn't seem the least bit likely on evolutionary terms.
rowe@pender.ee.upenn.edu (Mickey Rowe) (05/07/91)
In article <1991May6.221144.13332@sarah.albany.edu> gb661@leah.albany.edu (BROADWELL GEORGE AARON) writes: >In article <1991May4.190132.22684@agate.berkeley.edu> > doug@eris.berkeley.edu (Doug Merritt) writes: > >>the discrediting >>of the "you only use 10% of all the parts of your brain", are probably the > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > >Could you fill in a non-biologist on how this was debunked? Students >frequently mention this to me, and all I can say is that it doesn't >seem the least bit likely on evolutionary terms. I don't think that it's ever been actually debunked, per se, because I don't think that it was ever considered to be an established fact. (If someone knows of a reference where this might have come from, I'd be very pleased to find it.) When this topic has come up in conversations I've heard people speculate that the notion arose from a few different possible sources. First, some think that it came from the fact that early experiments found only limited areas of cortex that lead to motor output (i.e. you stimulate that area and a part of the body moves), or other obvious functions. Wilder Penfield (mentioned earlier by Doug Merritt) labelled most areas "association areas" as a wastebasket for things that he didn't understand. Perhaps it was thought that these areas of indeterminate function were in some sense "non-essential" (Penfield would likely have contributed to this misperception, because his arrogance would have lead him to believe that if he didn't understand it it had to be inconsequential). This is of course flawed by the fact that those "non-essential" areas are not necessarily "unused". Others have claimed that the idea comes from hydrocephalic patients whose brains were compressed agains their skulls. Ordinarily, cerebrospinal fluid is created in the ventricles (large fluid-filled cavities inside the brain) and is shunted down towards the spinal cord and up around the outer surface of the brain where it is taken back into the circulatory system. In part of its journey the fluid travels through a thin canal that sometimes becomes blocked. When this happens, the pressure built up by the fluid that is continuously created in the ventricles causes the ventricles to swell. This causes a compression of the overlying cerebral structures. In one severe case, a woman in Britain had her ventricles swell to the point that they nearly filled her skull so that her brain was compressed into a thin layer at the periphery. Since her brain (excluding the venticles, of course) now occupied a much smaller volume, people have claimed that that's all of the volume that you need (this woman scored around average on IQ tests, and to the best of my recollection had no noticeable effects that could be attributed to the compression of her brain). This is flawed by the fact that these patients are not without some x% of their brains; they just have their full brains compressed (granted some tissue is probably destroyed, but you certainly can't get that number by comparing volumes...). Still others have claimed that the figure came from lesion studies. That is if you find people with a portion of their brain damaged, and if there is no apparent affect of that damage, then that area is unimportant. I have little doubt that if you made a composite patient with damage to all areas that were determined to be "unimportant" in this way you could arive at that 90% figure. However, if you had a person with all of those areas damaged in reality, I suspect you'd find some deficits (understatement). Furthermore, the fact that we can't measure a deficit does not mean that the person was not using that part of their brain before it was damaged. One of the hallmarks of biological systems in general, and nervous systems in particular is redundancy. Individual neurons take part in a variety of tasks, and most tasks are performed by a variety of neurons. If some neurons are lost, you will usually have others that can perform the tasks that those lost neurons ordinarily performed. An inability to find a deficit after such a lesion may be due to the fact that other neurons perform the deceased neurons tasks just as well, or that we just don't know how to measure a deficit in the area in question. On the positive side... Your brain is the most energy intensive organ in your body. Fully half of your serum glucose is burned in your head. Since your entire brain makes up only about 2% of your body by weight (you might want to check me on that... I think that's right, but I'm not too certain) it seems silly to suggest that only 10% of that 2% is actually using half of your energy. Also, PET studies using 2-deoxyglucose (the proteins that transport glucose into cells will confuse 2-DG for glucose, but the proteins that normally break down glucose will not, so 2-DG builds up in cells that are metabolically active) do not find regions of the brain that are "inactive". There are variations in the level of activity, but no silent areas. EEG studies yield similar results--that the pattern of activity may change drastically from moment to moment, but that there is no time when an area is completely silent. I think that blankets the topic fairly well, though I'm sure I've left out some things I could have included. In any case, I hope that this was intelligible to biologists and non-biologists alike. Mickey Rowe (rowe@pender.ee.upenn.edu)