Path: utzoo!utgpu!attcan!uunet!husc6!mailrus!ncar!noao!asuvax!enuxha!rao From: rao@enuxha.eas.asu.edu (Arun Rao) Newsgroups: comp.ai.neural-nets Subject: Neuron Resolution Summary: A potentially useful reference. Message-ID: <183@enuxha.eas.asu.edu> Date: 10 Nov 88 15:28:28 GMT Organization: Arizona State Univ, Tempe Lines: 99 Here's the only useful reply I received to my posting (actually, I received two from Chris Lishka, and this is his second). I got the book he talks about from the library. It is authoritative (Kuffler was apparently a leading light in experimental neurophysiology) and has a textbook flavor to it. It gets into more detail than I need, but is definitely readable. However, there is no mention of the kind of information I was looking for. The trouble seems to be that engineers need information that neurophysiologists never think of obtaining. Another useful book on the human visual system is "The Eye and the Brain" (title ?) by David Hubel. It is the most readable book on the subject that I have yet encountered. Hope you find this useful. - Arun Rao ARPA: rao@enuxha.asu.edu or rao%enuxha.asu.edu@relay.cs.net. BITNET: agaxr@asuacvax.bitnet. P.S.: Chris Lishka's e-mail address is lishka%uwslh@cs.wisc.edu. ___________________________________________________________________ Subject: Re: Synaptic Strengths and Other Neurobiological Issues Thanks a lot for the reply. You're welcome! I was thinking after I made the posting yesterday, and I realized that what I really need for the kind of studies I'm making is the variance in synaptic strength, rather than in firing rate. Conventional neural-net wisdom suggests that a neuron's output is binary - i.e. it either fires or doesn't fire. One is not supposed to have to worry at all about firing rates. The most important lesson I learned in the Neurobiology classes which I took was that the "conventional neural-net wisdom" that most AI researchers keep is not very relevant to real nervous systems. There are too many important differences, and the AI models are still much too different from the Neurobiological models to be effectively related. My semester project for a graduate level AI course was to try and find a fairly close tie between AI and Neurobiology. I succeeded in finding interesting correlations in Associative Memory theories, but I was also very disappointed to find so little in common between Connectionism/Neural-Nets and Neurobiology besides the very thin correlation between Connectionist neurons and real neurons. I get the feeling that the measurement of synaptic strength is probably a considerably more difficult task - have people done it at all ? I'd appreciate any comments that you may have. In the meantime, I'll look into the kind of references you suggest. Oh yeah! This area is a big area in terms of research! Realize that the synaptic strength typically depends on the types of Neurotransmitters that travel across the synapses. One fairly standard fact that aids this research is that neurons almost always release only *one* type of Neurotransmitter (also called an NT). However, many different terminals (each possibly containing a different NT) can synapse at the same point on the same dendrite, so there can be very interesting combinational effects. Furthermore, different neurons will react differently to incoming NT's! Not too mention the role of Calcium channels in regulating the release of NT's. Firing rate also figures into this as well. Synaptic strength is a real complex area! As for references, *the* introductory textbook which is highly regarded here at the UW is: _From_Neuron_to_Brain_ by S. Kuffler, J. Nichols, and A. R. Martin Published by Sinauer Associates, Inc. (1984) This is a textbook intended for biologists, so if you are not up on biology, it may take a while to get through these chapters (don't worry, my background is light on biology too!). A quick browse through the chapters yields the following ones which relate to synapses: Chap. Six: Control of Membrane Permeability Chap. Eight: Active Transport of Ions ** Chap. Nine: Synaptic Transmission ** Chap. Ten: Release of Chemical Transmitters ** Chap. Eleven: Microphysiology of Chemical Transmission Chap. Twelve: The Search for Chemical Transmitters ** Chap. Sixteen: Transformation of Information by Synaptic Action in Individual Neurons The starred chapters (**'s) are likely to be very relevant. Realize that this is over 1/3'd of the book, so you can see that Synaptic Transmission is a hot area! There are certainly other books. One which I do not own and cannot remember the name of was a huge, comprehensive book covering the entire range of Neurobiology, with beautiful illustrations. I would search the nearest medical library for more information (we are blessed here with having a wonderful medical lib.). Also, if you can reach some Professors in Neurobiolgy, they should certainly be able to help you. I am but an undergrad! .oO Chris Oo.