Biological significance and essence of the phenomenon
Living organisms do not simply react mechanically to stimuli, but are capable of predicting the consequences of their actions. This process is inextricably linked with the mechanisms of afferent synthesis and decision-making.
The formation of the action result acceptor reflects the process of goal-setting and relies on dominant motivation. For instance, when a person anticipates how an exam will go or what they will buy at a store, this exact mechanism is at work. Its foundation consists of past reinforcements—the experience of interacting with factors that previously helped successfully satisfy social or biological needs.
Neurophysiological mechanisms of function
The mechanism is based on interneurons in various parts of the brain. The process of forming anticipation includes several stages:
- Preparation and decision-making. Pyramidal neurons of the cerebral cortex process motivational, triggering, and situational influences, engaging memory mechanisms. This culminates in decision-making, which is expressed in a specific configuration of nerve impulses.
- Efference copy (Efference copy). Motor commands are sent via the pyramidal tract to the effector organs. Simultaneously, exact copies of these commands are transmitted via special branches (collaterals) to interneurons. This creates a predictive model.
- Matching. Once the actual result is achieved, the signal regarding its parameters (feedback afferentation) returns to the same interneurons. A comparison (matching) of the prediction with reality takes place.
The dynamics of ARA formation itself go through three stages. At the activation stage, motivation excites the neural network via collaterals. At the reinforcement stage, signals regarding achieved success selectively consolidate the required connections. Ultimately, the anticipatory excitation stage is formed: upon the re-emergence of motivation, the brain activates the entire neural ensemble in advance, anticipating the outcome.
What happens in case of a mismatch: the "surprise" effect
To experimentally prove the existence of the anticipation mechanism, physiologists use the substitution of expected reinforcement. If the prediction does not match the fact, a mismatch occurs.
A classic example from P.K. Anokhin's laboratory: a conditioned reflex to receiving a meat-and-rusk powder was developed in a dog. In one of the experiments, the powder was quietly replaced with natural meat. It was expected that the hungry animal would eat it greedily, but its behavior changed dramatically. Instead of eating, a pronounced orienting-investigatory reaction occurred. The dog ran away from the feeder, looked at the experimenter, and only started eating after some time and with great apprehension.
A similar mechanism operates in the wild. Egyptian vultures break the shells of ostrich eggs using stones brought from the mountains. If, in the bird's absence, a white egg is painted a bright yellow color, the program fails. The image of the egg programmed in the ARA does not match reality: upon returning, the vulture drops the stone, opens its beak, and exhibits an orienting-investigatory reaction without completing the goal-directed action.
Information base of anticipation
The acceptor is constructed from two main information sources:
- Genetic basis. Includes innate knowledge about needs, ways to satisfy them, and the parameters of results that can fulfill these needs.
- Acquired memory. Replenished as one interacts with the external environment.
During the accumulation of individual experience, reinforcing factors affect receptors. Thanks to feedback afferentation, a detailed informational "image" of reinforcement is built in the brain (these concepts regarding animal behavior were formulated by I.S. Beritashvili). Subsequently, the triggering stimulus and motivation anticipatorily activate this image, indicating ways to achieve the goal.
It is precisely due to such mechanisms during mental activity that the formation of thought is carried out—the brain continuously compares achieved results with the prediction and evaluates them.
Briefly: answers to topical questions
Which components of the afferent synthesis stage precede the formation of the action result acceptor?
The formation of the action result acceptor is preceded by the stage of afferent synthesis. Its components:
- Dominant motivation — the leading component of the stage; built on the basis of various metabolic needs; mechanism — neurohumoral signaling.
- Memory — a component of afferent synthesis; includes genetic and individually acquired memory.
- Situational afferentation — input signals in the context of afferent synthesis.
- Trigger afferentation — the stimulus.
Which brain structures (besides the cortex) participate in the formation of the action result acceptor?
In addition to pyramidal neurons of the cortex, the following participate in the formation of the action result acceptor:
- Interneurons of various parts of the brain — form the basis of the action result acceptor mechanism; copies of generated commands are transmitted to them via collaterals of the pyramidal tract, forming a model of the expected result.
- Brain neural network at various levels: dominant motivation encompasses this network via collaterals of the pyramidal tract, and during subsequent behavioral formation, the neural ensemble previously formed by reinforcement is anticipatorily activated.
The word "acceptor" comes from the Latin acceptare meaning "to receive". Imagine a quality control inspector at a factory standing at the end of the conveyor belt with a blueprint (predictive model) and accepting the finished part (actual result). If the part does not match the blueprint, they press a red alarm button (a mismatch and orienting reaction occur).
Class and exam questions
At what stage of the behavioral act is the acceptor formed?
It is formed strictly prior to the execution of the action itself, preceding the output of excitation to muscles and organs.
What happens if the actual result does not match the model in the ARA?
A mismatch occurs, which interrupts the current goal-directed action and triggers a pronounced orienting-investigatory reaction.
Through which neural structures is the anticipation mechanism formed?
Its basis is formed by interneurons, which receive copies of motor commands (efference copies) via collaterals of the pyramidal tract.
What else to study on this topic
- Stages and components of afferent synthesis
- Decision-making mechanisms in the functional system
- The role of feedback afferentation in behavioral correction
- Dynamics of ARA construction at the neural level (activation and reinforcement)
- Figurative brain activity according to I.S. Beritashvili
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