fb0m+@andrew.cmu.edu (Franklin Boyle) (04/11/91)
Replies to the following message I posted about a week and a half ago are listed below (there were very few -- only two different references -- and I have not had time to check the literature in the meantime to add to this. However, as I do, if I run across other sources I will post them on the net. Note: I have not had a chance yet to check the two references below. Thanks to those who replied). >Does anyone know a good reference(s) for answering questions >about neural connectivity in the brain (as opposed to what people >model), e.g. How many axon terminals are there per neuron on average? >How many different dendritic trees do these synapse to on average? >How far laterally do these connections range? What is the >nature and number of dentritic-dendritic connections in >interneurons? in output neurons? Are there significant connectivity >differences in different layers of the cortex? etc... >I'm particularly interested in any recent publications which give >numbers or reasonable approximations as opposed to just saying >"many" or "far reaching" etc. >Thanks, >Frank Boyle --------------------------------------------------------------------- (1) The best book I have found is _The Synaptic Organization of the Brain, Third Edition_, 1990, Oxford, edited by Gordon M. Shepherd. It has many references to "theoretical studies of computational neuronal models and neural networks." For example, table 1.1 shows how various biophysical mechanisms can be used to produce logical gates (or, and, etc), negative feedback, etc. It discusses in detail the different types on connectivity in the various parts of the brain, discusses distances, and so forth. ----- The Synaptic Organization of the Brain, 3rd ed., 1990. Oxford Press. Ed. Gordon Shepherd. This volume is organized by brain region and has pointers to the primary literature. It is intended in part to answer just such questions. -------------------- (2) Unfortunately, there are very few data in the primary literature addressing the above questions. The primary reason is the extreme difficulty and often imposibility of doing the necessary experiment. Few *want* to do the experiments. (It can take a few years to reconstruct a single pyramidal neuron with its dendrites and synaptic input using serial sections. After all of the work one still does not know where the synapses originated from!) Having said that, there is one neuroscientist that I know of that has made a career of this tedious, but important, work. Ed White has brought a lot of his data together into a book called: Cortical Circuits: Synaptic Organization of the Cerebral Cortex: Structure, Function, and Theory. (1989) Edward L. White. Birkhauser. Otherwise, what data there are on the subject are scattered about in the primary literature. -------------------- -Frank Boyle