Premium
Early and late motor evoked potentials reflect preset agonist–antagonist organization in lower limb muscles
Author(s) -
Tarkka Ina M.,
McKay W. Barry,
Sherwood Arthur M.,
Dimitrijevic Milan R.
Publication year - 1995
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880180303
Subject(s) - stimulus (psychology) , evoked potential , transcranial magnetic stimulation , motor cortex , neuroscience , choice reaction time , electrophysiology , ankle , soleus muscle , psychology , electromyography , physical medicine and rehabilitation , anatomy , medicine , stimulation , cognition , cognitive psychology , skeletal muscle
A single transcranial magnetic stimulus can evoke two involuntary muscle responses in lower limb muscles of healthy humans. The purpose of the present study was to find out if these responses, when evoked during the processing period of a simple or choice reaction time task, such as ankle dorsiflexion, have specific characteristics related to the task. During the auditory reaction time, a transcranial magnetic stimulus was delivered to observe changes in the excitability of the central nervous system. A dual‐cone coil was used, which effectively stimulated the fairly deep‐lying lower limb motor cortex. Stimuli were delivered in a random order with 20–300‐ms delays from the auditory gosignal. Motor evoked potentials (MEP) in right and left anterior tibial and soleus muscles were analyzed while early MEPs were observed invariably in both muscles; late MEPs occurred consistently only in soleus muscles. Both early and late MEP amplitudes were larger in simple reaction time trials than in choice reaction time trials. The late MEP appeared earlier in the simple reaction time task than in the choice reaction time task, reflecting faster central processing of simple reaction time tasks. The amplitude of the soleus late MEP in the simple reaction time task followed closely the amplitude of anterior tibial early MEP, suggesting a preset agonist–antagonist organization. This relationship was not present in the choice reaction time task.© 1995 John Wiley &Sons, Inc.