Different Modulation of the Cortical Silent Period by Two Phases of Short Interval Intracortical Inhibition.
10.3349/ymj.2007.48.5.795
- Author:
Suk Yun KANG
1
;
Hae Won SHIN
;
Young Ho SOHN
Author Information
1. Department of Neurology, Yonsei University College of Medicine, Seoul, Korea. yhsohn62@yuhs.ac
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Transcranial magnetic stimulation;
motor cortex;
neurophysiology;
motor evoked potential
- MeSH:
Adult;
Evoked Potentials, Motor/*physiology;
Female;
Humans;
Male;
Motor Cortex/*physiology;
Transcranial Magnetic Stimulation
- From:Yonsei Medical Journal
2007;48(5):795-801
- CountryRepublic of Korea
- Language:English
-
Abstract:
PURPOSE: To investigate the influence of 2 phases of short interval intracortical inhibition (SICI) on the cortical silent period (SP). MATERIALS AND METHODS: Single- and paired-pulse transcranial magnetic stimulations (TMSs) at 1 and 2.5ms interstimulus intervals (ISIs) were applied to the left motor cortex in 12 healthy subjects while their right hand muscles were moderately activated. Conditioning stimulation intensity was 90% of the active motor threshold (AMT). Test stimulation intensities were 120, 140, 160, 180, 200, 220, 240, 260% of the AMT and at 100% of the maximal stimulator output, the order of which was arranged randomly. The rectified electromyography area of motor evoked potential (MEP) and duration of the SP were measured off-line using a computerized program. RESULTS: At high-test stimulation intensities, MEP areas were saturated in both single- and paired-pulse stimulations, except that saturated MEPs were smaller for the paired-pulse TMS at 1ms ISI than for the other conditions. As the test stimulation intensity increased, SP was progressively prolonged in both single- and paired-pulse stimulations but was shorter in paired-pulse than single-pulse TMS. Overall, the ratio of SP duration/MEP area was comparable between single- and paired-pulse TMS except for the paired-pulse TMS at 1 ms ISI with a test stimulation intensity at 140-180% of the AMT, in which the ratio was significantly higher than in the single pulse TMS. CONCLUSION: These results suggest that 2 phases of SICI modulate MEP saturation and SP duration differently and provide additional evidence supporting the view that 2 phases of SICI are mediated by different inhibitory mechanisms.
