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Task-relevant selective modulation of somatosensory afferent paths from the lower limb
W R Staines1, J D Brooke, W E McIlroy
1Department of Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada.
Neuroreport
|June 14, 2000
Summary
Movement selectively enhances specific sensory pathways. Somatosensory evoked potentials (SEPs) are reduced by leg movement, but task relevance can boost relevant sensory inputs, like cutaneous or proprioceptive signals.
Area of Science:
- Neuroscience
- Somatosensory System
- Motor Control
Background:
- Leg movement typically reduces somatosensory evoked potentials (SEPs) from both cutaneous and muscle afferents.
- Selective facilitation of sensory inputs based on task relevance during movement has not been previously demonstrated.
Purpose of the Study:
- To investigate if the amplitude of initial SEPs from cutaneous (sural nerve, SN) and muscle afferent (tibial nerve, TN) sources is modulated by the relevance of sensory information to a concurrent task.
- To determine if movement-related gating of SEPs can be selectively influenced by task demands.
Main Methods:
- SEPs were recorded at rest and during three passive leg movement conditions: relaxation, a cutaneous task (responding to tactile cues), and a position task (responding to movement trajectory).
- Sensory inputs included passive foot movement and cutaneous stimuli applied to the foot.
- Participants were instructed to either relax or perform a task contingent on either the cutaneous cue or the movement itself.
Main Results:
- Passive leg movement significantly attenuated initial SEPs from both TN and SN by approximately 40% compared to rest.
- When cutaneous inputs were task-relevant, SN SEPs significantly increased compared to passive movement.
- When proprioceptive inputs (movement trajectory) were task-relevant, TN SEPs significantly increased compared to passive movement.
Conclusions:
- Sensory information relevance selectively facilitates specific somatosensory pathways.
- Movement-related attenuation of SEPs can be overcome by task demands, demonstrating selective gating of sensory processing.
- This highlights the brain's ability to prioritize and enhance sensory information crucial for ongoing motor tasks.