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Transcortical reflexes and servo control of movement
Canadian Journal of Physiology and Pharmacology
|July 1, 1981
Summary
Proprioceptive reflexes aid in small movements and stability, while exteroceptive reflexes manage environmental responses. Postcentral cortex neurons show activity before movement, suggesting a role in motor control.
Area of Science:
- Neuroscience
- Motor Control
- Somatosensation
Background:
- Proprioceptors process afferent inputs from active movements, with mild reflex effects.
- Segmental and transcortical proprioceptive reflexes are crucial for fine motor control and postural stability.
- Exteroceptive reflexes generate strong responses for environmental interaction.
Purpose of the Study:
- To investigate the role of proprioceptive and exteroceptive reflexes in motor control.
- To characterize the properties of postcentral (PoC) neurons during active and passive movements.
- To explore the relationship between PoC neuronal activity and motor commands.
Main Methods:
- Analysis of neuronal discharge patterns in the motor cortex (MI) and postcentral cortex (PoC).
- Recording of pyramidal tract neuron (PTN) activity during active and passive movements.
- Comparison of responses to proprioceptive and exteroceptive stimuli.
Main Results:
- Motor cortex (MI) has distinct regions for cutaneous (MI/c) and proprioceptive (MI/r) inputs.
- Transcortical reflexes via MI/r oppose muscle length changes, maintaining stability.
- Postcentral (PoC) neurons discharged prior to electromyogram (EMG) activity during active movement.
- PoC neurons showed similar discharge changes during both active and passive movements, unlike most MI neurons.
Conclusions:
- Proprioceptive reflexes are vital for fine motor adjustments and stability.
- Exteroceptive reflexes are critical for rapid responses to environmental changes.
- Postcentral cortex plays a role in motor control, potentially involving corollary discharge mechanisms.