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THE THRESHOLD AND MENTAL SYSTEMS
It may be well to point out some principles, important in many respects; but which at the present moment are of interest from a psychopathological standpoint.
Living tissue can only be set into activity by stimuli of certain minimal intensity; should the stimulus fall below that minimal intensity, the living protoplasm does not react. This holds true of all cells, from the lowest to the highest,―from the bacterium and infusorium to the highly differentiated cell, such as muscle cell, or neuron. The reaction of the living protoplasm to the stimulus shows the irritability or sensitivity of the cell. This sensitivity has its physiological threshold, so that a stimulus falling below a certain intensity cannot call forth any reaction in the cell. The rise or fall of the threshold would mean an increase or decrease of the minimal intensity of the stimulus requisite to bring about a cellular reaction. By varying the conditions of sensitivity, such as mechanical, thermal, electrical, chemical and nutritional, the physiological threshold can be raised or lowered.
The same holds true of a whole psycho-physiological system,―there is a threshold of sensitivity below which the minimal stimulus cannot fall, the latter does not awaken any reaction in the system. All the senses reveal the presence of such thresholds which are also present in the case of all the higher psycho-physiological systems. If we term the stimulus which can just bring about a reaction in the system the stimulus threshold, we can say that a given system can only be thrown into activity by a stimulus rising in intensity above the stimulus threshold. Intensity of stimulus, then, is an indispensable condition of the functioning of a psycho-physiological system.
In highly differentiated cells, however, it is not only the quantity, or intensity of the stimulus that is to be considered, but also the quality. The visual sense organ is not affected by auditory stimuli nor can the auditory sense organ be affected by visual stimulations. Similarly, in the functioning of the higher psycho-physiological systems the quality of the stimulus should not be overlooked. Systems that remain inactive under one set of stimuli, however intense, will respond to another set of a different quality.
The same holds true of that synthesis of mental systems which we term moment consciousness, and which we shall treat in detail further on. To set the moment into activity, the moment threshold must be passed, and not only the intensity of the stimulations should be taken into consideration, but also the qualitative aspect of the stimuli. Ideas, emotion and feelings which apparently remain dormant at the action of one set of excitations will respond readily to the action of excitations of a different nature. Habits, habitual movements, habitual thought, depend entirely on the qualitative character of the excitations, on the combinations of special objects, circumstances and times. The quality of the stimulus is one of the important factors in the activity of a psychophysiological system, or of a moment consciousness.
Besides those two factors of intensity and quality, another factor, that of inhibition, plays quite a role in the variations of the threshold. We are acquainted with inhibitions in physiology, such, for instance, as the inhibitions exercised by the pneumogastric nerve on the heart, or the arresting of the activity of glands or of the peristalsis by the stimulation of afferent nerves. We know also of central inhibitions, such as fear, distress, pain, acting as so many inhibitions on the peripheral organs and serving to arrest functioning activity. Similarly in mental life, complex as it is, the highly organized psycho-physiological systems, with their concomitant moments consciousness, still fall under the same general physiological laws of inhibition. In the course of associative activity systems become organized into complex groups, into complicated systems or constellations of systems which, to maintain their functioning equilibrium, keep one another in check or under inhibition.
Such a formation of checks and inhibitions is just what takes place in the training and the education of the individual and the race. Every psycho-physiological system or moment entering into relations with other systems and moments is bound in the course of its associative activity to form inhibitions to its function by the direct influence of external or internal excitations. In other words, there is a rise of threshold due to inhibitory associations.
Inhibition and rise of threshold may also result in a different way in the process of association. We may possibly lay it down as a law, which plays no small role in the interaction of systems and moments, that in a series of aggregation of various systems or moments, forming a more complex organized whole, due to association and synthesis of the component systems, having various thresholds, the ones having the higher thresholds will raise the thresholds of the moments having a greater sensitivity. This, however, may be counterbalanced by the lowering of the moment threshold by associations with moments of great sensitivity, that is, with low moment thresholds.
While on the one hand the inhibitions and the consequent rise of threshold go along with the complexity of systemic structure as well as with the increase of associative activity, both in extension and intension, there is at the same time an advantage gained for the system, inasmuch as it really has now more chances to become active, on account of the greater number of systems with which it has become associated. The threshold of the associated system rises, but on the other hand, the chances for activity increase, while the liberation or discharge of energy with the consequent evil effects of extreme fatigue, exhaustion and ill nutrition is checked and guarded against by the inhibitions and the rise of threshold.
What happens now when a psycho-physiological system becomes dissociated? The inhibitions become removed and the threshold falls. The system is no longer checked by inhibitions or by other systems, and hence, with a lowering of the threshold, becomes sensitive, reacting to any slight, passing stimulus, manifesting or liberating all the energy it possesses until fatigue and complete exhaustion set in. From this vantage ground we can understand the fact of the extraordinary energy which the dissociated subconscious systems manifest, so much so that the unusual energy appears almost supernatural, and has on that account been ascribed by the superstitious to diabolical possession.
To quote from a former work of mine: