History and Core Concept
The study of higher nervous activity pathology began due to an accidental incident. During a catastrophic flood in Petrograd in 1924, laboratory animals at Ivan Pavlov's institute were subjected to severe emotional stress. After rescue, researchers discovered that the dogs had developed a severe neurotic state. The main manifestation of this disorder was the complete disappearance of all conditioned reflexes that had been painstakingly developed for months prior to the incident. This case became the starting point for targeted experimental modeling of nervous system breakdowns.
Etiology and Pathogenesis of HNA Breakdowns
To induce a neurotic state in laboratory settings, researchers use specific methodologies aimed at depleting the resources of the nervous system. There are four main pathways for neurosis formation:
- Overstrain of the excitatory process. Occurs when an animal is presented with extremely strong conditioned stimuli. As a result, a breakdown occurs, and protective inhibition begins to prevail in the cerebral cortex. Clinically, this manifests as drowsiness and the extinction of reflexes. Animals with a weak constitution ("melancholics") fall into the risk group.
- Overstrain of the inhibitory process. Develops when an animal is required to perform overly fine differentiations (distinguishing very similar stimuli) or when the time between the conditioned signal and reinforcement is excessively prolonged. A breakdown toward pathological excitation occurs: inter-signal reactions and continuous salivation appear. Animals of the strong unbalanced type ("cholerics") are most vulnerable to this mechanism.
- "Clash" («sshika») of nervous processes. A specific term introduced by Ivan Pavlov. It denotes a pathogenic situation where there is a sharp, almost instantaneous transition from excitation to inhibition or vice versa.
- Destruction of the dynamic stereotype. A profound neurotic state is triggered by a sudden and drastic disruption of the habitual system of behavioral reactions.
Clinical Picture and Phase Phenomena
Experimental neuroses are not limited to the loss of reflexes alone; they are systemic disorders affecting the entire organism. Characteristic signs are divided into three groups:
1. Violation of the law of strength Normally, a strong stimulus elicits a strong response, and a weak stimulus elicits a weak response. During neurosis, pathological phase phenomena develop:
- Equalization phase: reflex responses to strong and weak stimuli become absolutely identical.
- Paradoxical phase: reversal of reactions occurs. Positive signals begin to cause inhibition, while inhibitory stimuli provoke a positive conditioned reflex response.
- Inhibitory phase: complete areflexia sets in (disappearance of all responses).
2. Behavioral changes Animals actively resist being brought into the experimental room. Inappropriate motor activity, constant vocalization (howling, whining), and a sharp increase in fussiness with inter-signal reactions are observed.
3. Autonomic symptoms Nervous breakdown inevitably impacts somatic health. Cardiovascular manifestations include increased blood pressure, extrasystoles, and dyspnea. The skin and coat suffer: the fur becomes dull and falls out, and long-healing trophic ulcers may appear. Often, these changes are functional in nature and regress after the cessation of the stressor. However, in severe breakdowns, special medical treatment is required to restore functions.