carolf@sco.COM (Carol Freinkel) (03/07/89)
In article <11945@swan.ulowell.edu> sbrunnoc@hawk.ulowell.edu (Sean Brunnock) writes: >the human brain is pretty much uniform. This >fact becomes dramatically obvious in the cases of people who have >had accidents resulting in the damage of sections of the brain. >If the damaged section performed a specialized function, then >for awhile, the person will not be able to perform that action. >After some time, the rest of the brain is able to assimilate >the functions performed by the damaged section and the person >is able to function normally again. This is only partially true. There are many areas of the brain which cannot be replaced if damaged. If the vision-processing region at the back of the brain is removed, the person will be blind. Also, if both sides of the hippocampus are removed, the person will not be able to retain long-term memory anymore. (This operation was performed only once. When the damage this causes was realized, it was never done again. I read about this case in a neurobiology class. This man lives in a perpetual present. If you were to visit him, leave the room, and walk back in, he wouldn't know you.) And the human brain is definitely *not* uniform. There is an elaborate architecture on both the macroscopic and microscopic level. The list of names which describes these structures is frighteningly long. There are many areas of the brain which are mostly inflexible. On the other hand, it is true that people can sustain large amounts of damage to the frontal lobes with (apparently) minimal effects. Also, some children born with brains compressed/damaged from hydrocephaly (water on the brain) are quite intelligent. When damage occurs at a younger age, adapation is more likely to occur. Generally speaking, animals with larger brains have more flexibility. If the eye of a newt is rotated, the newt will perpetually move its head up to reach food which is below it and vice versa. When this experiment was done on kittens, the kittens eventually adapted to the change and were able to move appropriately. With some animals, the circuitry is essentially "hard-wired." (As one anatomy professor put it, there might as well be pulleys and levers in there.) Creatures with more complex nervous systems have more flexibility and possibility of "reprogramming." Carol Freinkel carolf@sco.COM ...!uunet!sco!carolf
johne@astroatc.UUCP (Jonathan Eckrich) (03/15/89)
(Sean Brunnock) writes: >>the human brain is pretty much uniform. This (Carol Freinkel) replies: >This is only partially true. There are many areas of the brain >which cannot be replaced if damaged. If the vision-processing >region at the back of the brain is removed, the person will be >blind. I recently read an article (Sorry, but I cannot recall the name) that discussed operations performed on infant ferrets. The optic nerves were rerouted to what should be the part of the brain that handles hearing. As the baby ferrets grew and experienced their environment, they developed essentially normal sight - I don't know the quality of the surgeon's work in reattaching the optic nerves to the auditory section of the brain. This suggests to me that certain parts of the brain are uniform at birth, but as experiences accumulate, new synaptic connections are made, and that these parts of the brain become specialized by virtue of the unique processing that they must learn. -- Jon Eckrich (rutgers, ames)!uwvax!astroatc!johne nicmad!astroatc!johne
sheinberg-david@CS.YALE.EDU (David Sheinberg) (03/15/89)
In article <1595@astroatc.UUCP> johne@astroatc.UUCP (Jonathan Eckrich) writes: >... >I recently read an article (Sorry, but I cannot recall the name) that >discussed operations performed on infant ferrets. The optic nerves were >rerouted to what should be the part of the brain that handles hearing. The article you're referring to is called "Experimentally Induced Visual Projections in Auditory Thalamus and Cortex" by Mriganka Sur, et al. It's published in the December 9, 1988 _Science_ (vol 242) pp. 1437-1441. It certainly raises some fascinating philosophical questions. David Sheinberg sheinb@yale-zoo-suned.arpa
vickroy@mis.ucsf.edu (Chip Vick Roy) (03/16/89)
In article <1595@astroatc.UUCP> johne@astroatc.UUCP (Jonathan Eckrich) writes: > >I recently read an article (Sorry, but I cannot recall the name) that >discussed operations performed on infant ferrets. The optic nerves were >rerouted to what should be the part of the brain that handles hearing. > The article you refer to is: "Experimentally Induced Visual Projections into Auditory Thalamus and Cortex", by Mriganka Sur, Preston E. Garraghty and Anna W. Roe, Science v242, Dec 9, 1988, p1437-41. This is a marvelous study which demonstrates significant plasticity of the developing nervous system, even across different sensory modalities.
brp@sim.uucp (bruce raoul parnas) (03/16/89)
In article <1595@astroatc.UUCP> johne@astroatc.UUCP (Jonathan Eckrich) writes: >I recently read an article (Sorry, but I cannot recall the name) that >discussed operations performed on infant ferrets. The optic nerves were >rerouted to what should be the part of the brain that handles hearing. I have heard of this article. does anyone out there have a reference for it? bruce brp@sim
bph@buengc.BU.EDU (Blair P. Houghton) (03/17/89)
In article <53646@yale-celray.yale.UUCP> sheinberg-david@CS.YALE.EDU (David Sheinberg) writes: > >The article you're referring to is called "Experimentally Induced Visual >Projections in Auditory Thalamus and Cortex" by Mriganka Sur, et al. It's >published in the December 9, 1988 _Science_ (vol 242) pp. 1437-1441. It >certainly raises some fascinating philosophical questions. Only if you have some unfounded, preconceived notion of the purpose of the things, such as this one, for which the first understanding is now being discovered. I.e., the scientific questions it raises are much more fascinating than the philosophical questions it renders moot. --Blair