A mechanism of nervous system functions capable to have evolved: by generating an inducible variant of inter-cellular fusion

A realistic hope has been that from ontogeny, it may become possible to understand the steps of evolutionary changes that may assist in understanding the mechanism of nervous system functions. However, explaining how first-person internal sensations are formed in the nervous system makes this approach very difficult. In this context, if it becomes possible to derive an operational principle by using constraints from observations at different levels, then it will enable examining whether it is possible to arrive at its specific circuit features from single neuronal cells using simple steps of introducing variations and selection. In this context, semblance hypothesis is examined. Inter-neuronal inter-spine interaction leading to the formation of inter-postsynaptic functional LINK (IPL) is necessary for generating units of internal sensations and their computation. The results show its suitability as an evolved mechanism. Significant neuronal and spine loss during ontogeny indicate that following these events, IPLs resulted from the selection of a suitable variation. This can only be achieved through transient inter-neuronal inter-spine fusion, which leads to inducible molecular changes for keeping the spines separate by arresting fusion at the stage of hemifusion. The importance of sustaining this one-time induced IPL mechanism for retaining cognitive functions throughout life is discussed.