C. elegans

[Gary Cottrell]

>I just read that all 329 (?) neurons in C. elegans, the nematode worm,
>have been mapped.
>Has anyone ever simulated this network?
> If it didn't work,
>that might indicate that the idealized neuron
>(sum-unit-cum-squashing-function) in use now is too simple.

It is clear that this version of the neuron is too simple.

One of the most common oscillators in neurobiology is the
mutually inhibitory pair of neurons. This can't be done
with the standard pdp units. You can do it if you have
delay or post-inhibitory rebound. Delay can come about through
modeling membrane currents more closely.

Another aspect of real circuits not addressed by pdp units is
electrotonic connections.

Fu-Sheng Tsung, Al Selverston, Peter Rowat & I have simulated a 13
unit network in the lobster (the gastric mill of the stomatogastric
ganglion), and found pdp units do well at fitting the behavior, but
poorly at generalizing to what happens when a cell is removed from the
circuit. Peter & Fu-Sheng have developed more realistic models based
on differential equations and difference equations that do a better
job, although this is still ongoing research.

For copies of Peter's paper, write peter at crayfish.ucsd.edu. It will be
coming out in Network.

Fu-sheng's algorithm is in the connectionist summer school proceedings.

gary cottrell