Constancy of neurons, precision of connectivity patterns and specificity as a product of neuron differentiation in invertebrates

Abstract

There is a level of explanation of behaviour in terms of neurons at which the primary interest lies in which nerve cell one is talking about. This is the level of the actual circuit diagram. Most of "Interneurons" was written before the concept was clear but connectivity pattern was defined in the glossary as "the actual complete anatomical pattern of connexions between identified neurons" (Horridge, 1968). Subsequently the paper on accuracy of patterns of connexions began with the words "At one level of analysis the action of any small region of the nervous system is the result of a connectivity pattern" (Horridge and Meinertzhagen, 1970). The implication is that the connectivity pattern is the actual wiring diagram at a definite place and that each neuron can be individually recognized. The emphasis is upon the actual anatomical description rather than the idealized diagram in which individual neurons or particular locations are not distinguished at cell level. Conceptually we are far from the inferred idealized black box system derived from physiological pathways of excitation.