Lack of Evidence for Direct Corticospinal Contributions to Control of the Ipsilateral Forelimb in Monkey
| Autor: | Stuart N. Baker, Steve A. Edgley, Demetris S. Soteropoulos |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Movement
Pyramidal Tracts Action Potentials Stimulation Electromyography Multiple methods Article Functional Laterality Forearm Forelimb Reaction Time Animals Medicine Wakefulness Muscle Skeletal Motor Neurons medicine.diagnostic_test business.industry General Neuroscience Excitatory Postsynaptic Potentials Anatomy Macaca mulatta Electric Stimulation medicine.anatomical_structure Corticospinal tract Arm Excitatory postsynaptic potential Female Primary motor cortex business Neuroscience |
| Zdroj: | The Journal of Neuroscience. 31:11208-11219 |
| ISSN: | 1529-2401 0270-6474 |
| DOI: | 10.1523/jneurosci.0257-11.2011 |
| Popis: | Strong experimental evidence implicates the corticospinal tract in voluntary control of the contralateral forelimb. Its potential role in controlling the ipsilateral forelimb is less well understood, although anatomical projections to ipsilateral spinal circuits are identified. We investigated inputs to motoneurons innervating hand and forearm muscles from the ipsilateral corticospinal tract using multiple methods. Intracellular recordings from 62 motoneurons in three anaesthetized monkeys revealed no monosynaptic, and only one weak oligosynaptic excitatory post-synaptic potential following stimulation of the ipsilateral corticospinal tract. Single stimulus intracortical microstimulation of the primary motor cortex (M1) in awake animals failed to produce any responses in ipsilateral muscles. Strong stimulation (>500μA, single stimulus) of the majority of corticospinal axons at the medullary pyramids revealed only weak suppressions in ipsilateral muscles at longer latencies than the robust facilitations seen contralaterally. Spike triggered averaging of ipsilateral muscle activity from M1 neural discharge (184 cells) did not reveal any post-spike effects consistent with monosynaptic corticomotoneuronal connections. We also examined the activity of 191 M1 neurons during ipsilateral or contralateral ‘reach to precision grip’ movements. Many cells (67%) modulated their activity during ipsilateral limb movement trials (compared with 90% with contralateral trials), but timing of this activity was best correlated with weak muscle activity in the contralateral non-moving arm. We conclude that, in normal adults, any inputs to forelimb motoneurons from the ipsilateral corticospinal tract are weak and indirect, and that modulation of M1 cell firing seems to be related primarily to control of the contralateral limb. |
| Databáze: | OpenAIRE |
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