[
Japanese Worm Meeting,
2002]
The synaptic connectivity of C. elegans is well known from observations of the somatic system by White et al. and those of the pharyngeal system by Albertson et al. So far, three databases were constructed for computational usage by Achacoso et al. and Durbin, and recently in WormBase. However, they lack some data such as those in tables of White's paper and those in figures of Albertson's book. Our database (K. Oshio, S. Morita, Y. Osana and K. Oka: Technical Report of CCEP, Keio Future No.1, 1998) includes all data described in White's paper and Albertson's book. Unfortunately, some mistakes were found in the database through private communications with John White who is the author of White's paper and with the users of the database. Thus we have been proceeding with the revision to make it perfect one. We are planning to complete the revision in September 2002. The database should be worthwhile not only for neurophysiological studies, but also for post-genomic interests mediating genomes and behavior.
[
East Asia Worm Meeting,
2004]
The anatomical data of synaptic connectivity of C. elegans has been degitized for research with computers. The set of files are entitled 'The database of Synaptic Connectivity of C. elegans for Computaiton' and electronicaly delivered to request. The data files describe all items involved in the paper of Albertson and Thomson (1976) and that of White et al. (1986). The policy we empolyed on creating the data base was that diagrams and tables in the original paper can be reconstructed uniquely up to topology from the degitized data. Since our database is equivalent to the anatomical data, quality of the latter can be investigated on analysing the former by computer. It has been found that the anatomical data is almost perfectly self-contained except a few inconsistent descriptions such that the neuron class PDE sends 61 synapses to the class DVA while the latter receives only 36 synapses from the former. This is an exceptionally extreme case of inconsistency and number of erroneously described synaptic contacts are several hundred among eight thousand contacts. In addition, it has been found that several inconsistent description can be corrected from consideration of topological nature of processes in a three dimensional space, which is also suggested by the database.
[
International Worm Meeting,
2003]
The ultimate goal of the present work is to determine pathways of neuronal signal from sensory neurons to motoneurons in occasion of native responses of C. elegans. The fundamental hypothesis is that the pathways consists of highly multiple synaptic connection among interneurons. The McCulloch-Pitts equation is employed to find out sequence of much synaptic connection from each sensory neuron. Although the McCulloch-Pitts equation cannot be used for simulation of propagation of neuronal signal without knowledge about physical parameters within it, it is useful for the present purpose. The point of the algorithm is ; (i) threshold of menbrain potential is replaced by an integer s which is independent of the neuron and (ii) the coupling coefficient between a pair of neurons is replaced with number of synapses between them. When a sensory neuron is always excited, a stationary distribution of excited neurons is realized. Excited neurons in the stationary state are connected to the sensory neuron by pathways which consist of synaptic connection of multiplicity larger than s. A neuron, which is connected with more than one excited neurons, is also excited when the sum of multiplicity of joined synapses are larger than s. A plan of the neuronal circuit is constructed from neurons, which are excited for s more than six, and synapses connecting them. Interneurons are classified into three groups. Three elementary motions of the worm are defined in terms of motoneurons which are simultaneously excited and its behavior in occasion of native responses is combination of such elementary motions. The number of synapses have been counted using the database constructed by our research group. It is translation from the sketch of neurons published by White et al.. into a digital form.