Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!ernie.Berkeley.EDU!jwl From: jwl@ernie.Berkeley.EDU (James Wilbur Lewis) Newsgroups: comp.ai.neural-nets Subject: Re: temporal domain in vision Keywords: multiplex filter model Message-ID: <26187@ucbvax.BERKELEY.EDU> Date: 22 Sep 88 01:42:30 GMT References: <233@uceng.UC.EDU> <724@cseg.uucp> Sender: usenet@ucbvax.BERKELEY.EDU Reply-To: jwl@ernie.Berkeley.EDU.UUCP (James Wilbur Lewis) Organization: University of California, Berkeley Lines: 35 In article <724@cseg.uucp> lag@cseg.uucp (L. Adrian Griffis) writes: >In article <233@uceng.UC.EDU>, dmocsny@uceng.UC.EDU (daniel mocsny) writes: >> In Science News, vol. 134, July 23, 1988, C. Vaughan reports on the >> work of B. Richmond of NIMH and L. Optican of the National Eye >> Institute on their multiplex filter model for encoding data on >> neural spike trains. The article implies that real neurons multiplex >> lots of data onto their spike trains, much more than the simple >> analog voltage in most neurocomputer models. > >My understanding is that neurons in the eye depart from a number of >general rules that neurons seem to follow elsewhere in the nervous system. I think Richmond and Optican were studying cortical neurons. Retinal neurons encode information mainly by graded potentials, not spike trains....another significant difference between retinal architecture and most of the rest of the CNS. I was somewhat baffled by the Science News article, too. For example, it was noted that the information in the spike trains might be a result of the cable properties of the axons involved, not necessarily encoding any "real" information, but this possibility was dismissed with a few handwaves. Another disturbing loose end was the lack of discussion about how this information might be propogated across synapses. Considering that it generally takes input from several other neurons to trigger a neural firing, and that the integration time necessary would tend to smear out any such fine-tuned temporal information, I don't see how it could be. It's an interesting result, but I think they may have jumped the gun with the conclusion they drew from it. -- Jim Lewis U.C. Berkeley