Reverse afferentation

Multi-parameter nature and species specificity

Signals returning to the brain from receptors are never homogeneous. They are always multi-parameter, as they collect data from various sensory systems: vision, hearing, olfaction, touch, taste, and thermoreception.

These parameters reflect the physical, chemical, and informational properties of the obtained result. In humans, it is the informational properties that play a key role, and the evaluation of many actions is based on speech (written or verbal).

Furthermore, the significance of specific parameters depends on the biological species. For instance, birds rely predominantly on vision, whereas for the mole, olfaction and tactile sensations are critically important. Regardless of the species, information from proprioceptors—receptors of the musculoskeletal apparatus—always enters the brain.

Role in the systemic organization of behavior

It is important not to confuse the reverse afferentation of a functional system with the "fourth link" of the classical reflex. A reflex is merely a partial component of holistic behavior. Reverse afferentation operates more broadly and plays a creative role in the organization of actions.

Its main functions include:

• Guiding the subject's behavior and spatial orientation.
• Active influence on the dominant functional system.
• Correction of errors during the course of activity.
• Revising plans when encountering obstacles.
• Triggering emotions (positive upon success or negative upon failure).

Connection with the action result acceptor (ARA)

The experience of successfully achieving a goal is fixed in the central nervous system. When an animal or human achieves an adaptive result, its parameters are "imprinted" in the structures of the action result acceptor (ARA).

Subsequently, when the need arises again, motivation elicits anticipatory excitation in the ARA. The brain "recalls" the parameters of past successes and directs the organism toward satisfying the need.

Various elements are programmed within the ARA, but with differing degrees of strictness:

• Only the parameters of the required result (the goal) are programmed strictly.
• Environmental parameters (both facilitating and hindering) and specific methods of achieving the goal are programmed probabilistically.

Control of motor acts

Any movement (from walking to speech) is impossible without sensory control by centripetal impulses. There are three levels of such control:

1. Exeteroceptive — signals from sense organs.
2. Proprioceptive — data from muscles, ligaments, and joints.
3. Intracerebral reafferentation — internal feedback loops in the CNS from lower centers to higher ones.

During the execution of a step-by-step movement, reverse afferentation is divided into guiding (from proprioceptors, regulating the very process of muscle contraction in real time) and resultant (from sense organs, reporting on the final outcome).

Motor control includes long feedback loops (informing the cortex about movement execution via long-loop feedback), spinal reflex arcs (automatic load compensation at the spinal cord segment level), and sensory correction (N.A. Bernstein's principle, where multisensory integration enables complex voluntary actions).

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanism of alpha- and gamma-motoneuron co-activation at the spinal level
• Sensory correction of complex voluntary movements according to N.A. Bernstein
• Multisensory integration (vision, proprioception, touch) in fine motor skills
• The role of the long feedback loop in cortical control

Other topics in the section "General Principles of Behavioral Organization"

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