Severity: Warning
Message: file_get_contents(https://...@pubfacts.com&api_key=b8daa3ad693db53b1410957c26c9a51b4908&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 176
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 176
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 250
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 1034
Function: getPubMedXML
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3152
Function: GetPubMedArticleOutput_2016
File: /var/www/html/application/controllers/Detail.php
Line: 575
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 489
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Reciprocal control of antagonists is essential for coordinated limb movement. While Ia afferent dependent reciprocal inhibition has been extensively studied, reports of the control of antagonists during preparation for a motor action are limited. It has been demonstrated that corticomotor (CM) excitability of antagonists is suppressed prior to wrist extension/flexion suggesting the existence of a pre-contraction cortical control mechanism for distal upper limb antagonists. It is unknown whether pre-contraction suppression is evident in the control of proximal upper limb antagonists. Here we used transcranial magnetic stimulation and a rhythmic motor task to assess pre-contraction changes in excitability of corticospinal pathways projecting to biceps brachii (BB), when BB was an agonist (forearm supinator) or an antagonist. We found a suppression of motor evoked potential (MEP) amplitude in BB prior to pronator contraction and facilitation prior to BB contracting as a supinator. The extent of modulation was more profound as the agonist contraction approached. In contrast, there was no suppression evident in brachioradialis and triceps brachii under similar conditions indicating that pre-contraction suppression was specific to the antagonist BB. Our data in combination with published data from wrist muscles suggest that pre-contraction suppression of CM excitability may be a centrally induced mechanism to prevent antagonistic activity before Ia afferent dependent reciprocal inhibition is imposed. The importance of assessment of this inhibitory mechanism in neurologically impaired populations is discussed.
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Source |
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http://dx.doi.org/10.1007/s00221-007-1071-4 | DOI Listing |
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