The Essential Instability of Systems with Threshold, and some Possible Applications to Psychiatry

Publisher Summary The widespread occurrence of threshold in the nervous system, and the importance of threshold in the details of neuronic activity, has been well known. Any large system that uses threshold as the criterion for whether transmission is to occur at each node is fundamentally unstable in its density of active points. Any increase in density, by increasing the chance that other stimuli will be successfully transmitted, tends to cause yet further increases in density. Calculation of the exact effects confirms the expectation. Were the threshold fixed, and were the conditions as assumed, any network using threshold would be erratic in action, tending continually to run away either to complete inactivity or to maximal activity. Since many processes in the nervous system are not normally seen to exhibit such runaways, there must be some factors opposing the primary instability. One is described briefly, showing that stabilization of a thresholded network is not difficult. The application of these facts to various symptoms seen in psychiatry is considered briefly.