ISSN:
1432-1106
Keywords:
Key words Paired-pulse transcranial magnetic stimulation
;
Threshold hunting
;
Intracortical inhibition
;
Intracortical I-wave facilitation
;
Human
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Short-interval, paired-pulse transcranial magnetic stimulation (TMS) is usually used to demonstrate intracortical inhibition. It was shown recently that with short-interval, paired-pulse TMS a facilitation – called intracortical I-wave facilitation – can also be demonstrated. It was the aim of this study to investigate which stimulus conditions lead to intracortical inhibition and what conditions yield an intracortical I-wave facilitation in a hand muscle of normal subjects. Paired-pulse TMS responses with an interstimulus interval of 1.2 ms were obtained from the abductor digiti minimi muscle of four normal subjects. A threshold-hunting paradigm with hunting through first or second stimulus variation was used to obtain a curve of threshold-pair strengths. All subjects showed two branches of stimulus interaction on this diagram. If the first stimulus of a threshold pair was below approximately 65% of resting motor threshold it modified the response primarily due to the second stimulus through intracortical inhibition. However, if the first stimulus of a threshold pair exceeded approximately 65% of resting motor threshold it became responsible for the spinal action-potential initiation. The subsequent second stimulus served as a ”booster” for the ongoing intracortical I-wave activity, making it impossible to observe the intracortical inhibition evoked by the first stimulus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002210050901
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