Structure of a complex motor act
Using weapon shooting as an example, the process of performing a targeted movement can be divided into four strict stages, each with its own physiological significance:
- Postural stabilization. Creation of a stable support. The body fixes the position of the torso and feet, providing a base for subsequent actions.
- Tool stabilization. Point work of the arm musculature for rigid fixation of the working instrument (e.g., a weapon) in space.
- Motor action. Direct execution of the task — for example, pulling the trigger through isolated contraction of the index finger muscles.
- Result evaluation. Use of feedback mechanisms. The person evaluates the success of the action (bullet hole position on the target) to correct subsequent attempts.
Instrumental assessment: stabilogram and hodogram
To objectively assess how well a motor skill is formed, graphical methods are used. The graphs analyze the X and Y axes, which reflect foot movement and, accordingly, oscillations of the body's total center of gravity.
- Stabilogram shows the amplitude of these oscillations over time.
- Hodogram demonstrates the spatial scatter (area) occupied by these oscillations projected onto a plane.
Learning dynamics: from beginner to professional
A comparative characteristic of the parameters clearly demonstrates the physiological difference between the start of training and a formed skill.
Start of training (Beginner):
- Graphs: A very high oscillation amplitude is recorded on the stabilogram. The hodogram occupies a vast area, and its lines are chaotic.
- Physiology: The motor control system is not yet optimized. Extremely low coordination is observed, the feet make significant movements, and the total center of gravity oscillates markedly.
Experienced person (Formed skill):
- Graphs: Stabilogram lines become smoothed, and the oscillation amplitude drops sharply. The hodogram looks compact and is concentrated in the very center (small scatter area).
- Physiology: Movement economy occurs. Oscillations of the center of gravity and foot movements become minimal. Postural muscles work with maximum efficiency without performing unnecessary work.
Briefly: answers to topical questions
What CNS structures participate in the formation and automation of a motor skill?
Various divisions of the central nervous system interact to ensure the accuracy and smoothness of voluntary movements.
The following main structures are distinguished:
- Cerebral cortex — includes the associative, sensory, and motor cortex.
- Basal ganglia — striatum (Striatum, uniting the caudate nucleus and putamen), globus pallidus (Globus pallidus), and substantia nigra (Substantia nigra).
- Diencephalic and brainstem structures — thalamus (acts as a relay between the basal ganglia and the cortex), reticular formation, and red nucleus.
- Cerebellum — the center of coordination, including the hemispheres, vermis, and deep nuclei.
The key mechanism of coordination is a feedback loop that sequentially connects the cerebral cortex, pontine nuclei, cerebellum, and thalamus.
The acronym P-T-M-E (Posture — Tool — Motor skill — Evaluation) helps remember the 4 stages of a motor act.
Class and exam questions
What does a beginner's hodogram look like compared to an experienced person's?
In a beginner, the hodogram occupies a large area and consists of chaotic lines. In an experienced person, it is compact and concentrated in the center with a small scatter area.
What is the main physiological significance of a formed skill?
In the high efficiency of postural muscle work and overall movement economy, which minimizes unnecessary body oscillations.
What else to study on this topic
- Physiological mechanisms of postural stabilization
- The role of feedback in evaluating the result of a motor act
- The process of movement economy at the CNS level
- Analysis and interpretation of stabilograms
- Muscle interaction during the fixation of a work tool
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