Characterisation of paired-pulse transcranial magnetic stimulation conditions yielding intracortical inhibition or I-wave facilitation using a threshold-hunting paradigm

Citation
F. Awiszus et al., Characterisation of paired-pulse transcranial magnetic stimulation conditions yielding intracortical inhibition or I-wave facilitation using a threshold-hunting paradigm, EXP BRAIN R, 129(2), 1999, pp. 317-324
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences & Behavoir
Journal title
EXPERIMENTAL BRAIN RESEARCH
ISSN journal
0014-4819 → ACNP
Volume
129
Issue
2
Year of publication
1999
Pages
317 - 324
Database
ISI
SICI code
0014-4819(199911)129:2<317:COPTMS>2.0.ZU;2-Q
Abstract
Short-interval, paired-pulse transcranial magnetic stimulation (TMS) is usu ally used to demonstrate intracortical inhibition. It was shown recently th at with short-interval, paired-pulse TMS a facilitation - called intracorti cal I-wave facilitation - can also be demonstrated. It was the aim of this study to investigate which stimulus conditions lead to intracortical inhibi tion and what conditions yield an intracortical I-wave facilitation in a ha nd muscle of normal subjects. Paired-pulse TMS responses with an interstimu lus 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 o n this diagram. If the first stimulus of a threshold pair was below approxi mately 65% of resting motor threshold it modified the response primarily du e to the second stimulus through intracortical inhibition. However, if the first stimulus of a threshold pair exceeded approximately 65% of resting mo tor threshold it became responsible for the spinal action-potential initiat ion. The subsequent second stimulus served as a "booster" for the ongoing i ntracortical I-wave activity, making it impossible to observe the intracort ical inhibition evoked by the first stimulus.