The Differential Role of Motor Cortex in Stretch Reflex Modulation Induced by Changes in Environmental Mechanics and Verbal Instruction
| Autor: | Eric J. Perreault, Jonathan Shemmell, Je Hi An |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Adult
Reflex Stretch medicine.medical_treatment Posture Withdrawal reflex Electromyography Environment Mechanics Article Young Adult Physical Stimulation Task Performance and Analysis Elbow Reaction Time medicine Drosophila Proteins Humans Stretch reflex Muscle Skeletal Analysis of Variance medicine.diagnostic_test General Neuroscience Motor Cortex Escape reflex Evoked Potentials Motor Adaptation Physiological Transcranial Magnetic Stimulation DNA-Binding Proteins Transcranial magnetic stimulation medicine.anatomical_structure Acoustic Stimulation Reflex Silent period Cues Psychology Neuroscience Motor cortex |
| Zdroj: | The Journal of Neuroscience. 29:13255-13263 |
| ISSN: | 1529-2401 0270-6474 |
| DOI: | 10.1523/jneurosci.0892-09.2009 |
| Popis: | The motor cortex assumes an increasingly important role in higher mammals relative to that in lower mammals. This is true to such an extent that the human motor cortex is deeply involved in reflex regulation and it is common to speak of “transcortical reflex loops.” Such loops appear to add flexibility to the human stretch reflex, once considered to be immutable, allowing it to adapt across a range of functional tasks. However, the purpose of this adaptation remains unclear. A common proposal is that stretch reflexes contribute to the regulation of limb stability; increased reflex sensitivity during tasks performed in unstable environments supports this hypothesis. Alternatively, before movement onset, stretch reflexes can assist an imposed stretch, opposite to what would be expected from a stabilizing response. Here we show that stretch reflex modulation in tasks that require changes in limb stability is mediated by motor cortical pathways, and that these differ from pathways contributing to reflex modulation that depend on how the subject is instructed to react to an imposed perturbation. By timing muscle stretches such that the modulated portion of the reflex occurred within a cortical silent period induced by transcranial magnetic stimulation, we abolished the increase in reflex sensitivity observed when individuals stabilized arm posture within a compliant environment. Conversely, reflex modulation caused by altered task instruction was unaffected by cortical silence. These results demonstrate that task-dependent changes in reflex function can be mediated through multiple neural pathways and that these pathways have task-specific roles. |
| Databáze: | OpenAIRE |
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