Properties of nervous processes
The basis of I.P. Pavlov's classical typology is the assessment of the fundamental characteristics of excitation and inhibition processes. Three key parameters are distinguished, the combination of which determines individual behavioral traits:
- Strength. Determines the functional limit of nerve cells. When this limit is exceeded, protective pessimal inhibition develops. According to this criterion, the nervous system is divided into strong and weak.
- Balance. Characterizes the balance between excitation and inhibition processes, as well as the ability of the nervous system to switch adequately between them without leaning heavily to either side.
- Mobility. Reflects the speed of alternation of nervous processes in response to environmental changes. The property opposite to mobility is inertness.
Classification of HNA types in animals (temperaments)
I.P. Pavlov established a direct physiological link between the properties of nervous processes and the ancient classification of temperaments proposed by Hippocrates (which was originally based on the predominance of body fluids). Using dogs as an example, the following types were identified:
- Sanguine: possesses a strong, balanced, and mobile nervous system.
- Choleric: distinguished by a strong yet unbalanced organization with a pronounced predominance of excitation processes.
- Phlegmatic: characterized by strong and balanced processes, which are nevertheless inert (low mobility).
- Melancholic: a representative of the weak type. Due to rapid cellular exhaustion, other parameters (balance and mobility) cannot be clearly differentiated in such subjects.
Specifics of human HNA: signaling systems
Unlike animals, humans possess two signaling systems, which creates an additional level of HNA typology.
The first signaling system is responsible for the direct perception of physical characteristics of stimuli (light, sound, smells). It is common to both humans and animals. The second signaling system operates exclusively with words, which I.P. Pavlov called the «signal of signals». This is the basis of human speech activity.
Depending on which system dominates, people are divided into three specific categories:
- Artistic type: the first signaling system predominates. People of this type tend toward an emotional and figurative perception of the world.
- Thinking type: the second signaling system dominates. Characterized by a pronounced inclination toward analysis and abstract thinking.
- Mixed type: both systems are in physiological equilibrium. This is the most common variant.
Systemic organization of behavior
Traditional neurology relies predominantly on the reflex principle, classifying pathologies through the balance of excitation and inhibition. However, the theory of functional systems suggests evaluating brain lesions through the prism of the stages of a goal-directed behavioral act.
Key stages of systemic organization include:
- Afferent synthesis.
- Decision making.
- Formation of the action result acceptor (anticipatory apparatus).
- Efferent synthesis.
- Direct action.
- Achievement and evaluation of the result.
Individual variations in the formation of these stages are observed in every subject. Moreover, situational variability exists: the efficiency of components varies in the same person depending on the context. Understanding this architecture opens new paths in topical diagnosis and allows tailoring therapy to correct specific impaired stages rather than acting on the brain in a generalized manner.
Briefly: answers to topical questions
What specific components are included in the afferent synthesis stage of a functional system?
The afferent synthesis stage of a functional system includes four components that ensure the integration of various types of excitations:
- Dominant motivation—the leading energetic component, the dominant need determining the goal of behavior; built on the basis of various metabolic needs.
- Situational afferentation—information about the external environment and the conditions in which the body is located; continuously enters the CNS via exteroceptors.
- Memory—a component of afferent synthesis; includes genetic and individually acquired memory, utilizes past experience associated with the satisfaction of this motivation.
- Trigger afferentation—a specific trigger stimulus, the permissive component of the afferent synthesis stage, which unlocks pre-trigger integration and launches the behavioral response at a given moment.
What types of conditioned (internal) inhibition exist in higher nervous activity?
The sources explicitly describe the following forms of internal inhibition:
- Extinction inhibition—associated with the withdrawal of reinforcement: the absence of food during previously established conditioned reflexes leads to a breakdown of extinction inhibition.
- Differentiation inhibition—associated with the development of fine and complex differentiations; complex differentiations cause a breakdown of differentiation inhibition.
- Active cortical inhibition—its breakdown is caused by delayed reinforcement, i.e., increasing the interval between the conditioned signal and food presentation.
- «Sleepy» inhibition—deepened, generalized internal inhibition spreading to both hemispheres and adjacent subcortical structures.
To memorize the association between temperaments and Pavlov's properties of nervous processes: the acronym SBM (Strong, Balanced, Mobile) describes the Sanguine type. If mobility is replaced by inertness in a strong and balanced type, it is the Phlegmatic type. If balance is removed, it is the Choleric type. And the weak type is always the same—the Melancholic type.
Class and exam questions
What is pessimal inhibition?
This is a protective mechanism of nerve cells that occurs when their functional limit is reached. It is directly related to such a fundamental property of nervous processes as strength.
How does the second signaling system differ from the first?
The first system responds to physical properties of stimuli (sound, light) and is present in both animals and humans. The second is inherent only to humans and is associated with verbal influences (speech).
What is an action result acceptor?
This is the stage of systemic organization of behavior responsible for anticipating the required result even before the action itself is performed.
What else to study on this topic
- Mechanisms of afferent synthesis in the formation of a behavioral act
- The role of the action result acceptor in evaluating behavioral success
- The impact of situational variability on human performance efficiency
- Information properties of functional systems in modern concepts of HNA
- Principles of psychopharmacological correction of specific stages of the systemic organization of behavior
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