Theories of Localization of Internal Inhibition
In normal physiology, there are several approaches to explaining where exactly the process of blocking a conditioned reflex arises and develops. Historically, the first was I.P. Pavlov's theory. According to this classical concept, internal inhibition originates and proceeds directly within brain structures, specifically in the cortical cells that serve as the functional representation of specific conditioned stimuli.
However, accumulated modern data have significantly expanded and refined this understanding. In particular, researchers have focused closely on the behavior of various components of a complex reflex response: autonomic, secretory, somatic, and motor. It was found that during the active inhibition of a specific response (for example, when conditioned salivation ceases), the autonomic components of the response do not disappear. Instrumentation continues to clearly record concomitant changes in the animal's heart rate and respiration rate.
The Phenomenon of Schizokinesis
The situation described above, where one part of a complex reflex response is inhibited while another continues to function, has received a special term in physiology — schizokinesis. Literally, this concept translates as "response splitting".
The presence of the schizokinesis phenomenon allowed physiologists to draw a crucial theoretical conclusion. It became completely obvious that internal inhibition does not affect or destroy the basic structure of the formed reflex arc itself. The inhibitory process is localized and implemented exclusively on the effector pathways, that is, at the stage where the final execution components of the reflex are formed.
Experimental Confirmation: The Double Reinforcement Experiment
To clearly demonstrate the mechanisms of response splitting and prove the effector localization of inhibition, physiologists use a classical methodology with double reinforcement. In this experiment, a laboratory dog is restrained in a special apparatus equipped with two independent feeders located on the right and left sides of the animal.
The experiment includes several successive stages:
- First Stage (Establishment of the baseline reflex). An auditory stimulus—the tone "A"—is presented to the animal. This sound is always accompanied by food reinforcement delivered strictly from the right feeder. As a result, the dog forms a complex conditioned reflex response: upon hearing the tone "A", salivation begins (secretory response), and it makes a targeted movement to the right (motor response).
- Second Stage (Change of signaling meaning). A new stimulus is introduced—the tone "F". This sound signals to the dog that food will now appear in the left feeder. The dynamics of acquiring the new skill are quite specific: initially, the animal regularly makes mistakes and heads toward the right feeder out of habit when hearing the tone "F".
- Stage of Pronounced Inhibition. As the experiment continues, a critical moment arrives. Upon hearing the tone "F", the dog no longer makes erroneous movements to the right, but has not yet learned to consistently go to the left. It remains sitting precisely in the middle of the apparatus. Meanwhile, objective recording shows a striking picture:
- Salivation: present in full volume (conditioned secretory response is preserved, the animal expects food).
- Movement: completely absent (motor response is inhibited).
Conclusion on the Experiment: This experiment brilliantly demonstrates that the inhibition of a conditioned reflex response occurs precisely at the level of effector components. A classical dissociation (separation) of the motor and secretory responses is observed in the apparatus, confirming the preservation of the reflex arc during selective blockade of the effector pathway.