TY - JOUR
T1 - Conventional or threshold-hunting TMS? A tale of two SICIs
AU - Cirillo, John
AU - Semmler, John G.
AU - Mooney, Ronan A.
AU - Byblow, Winston D.
N1 - Funding Information:
Funding provided by the Health Research Council of New Zealand ( 14/136 ). We also thank Mr Terry Corrin for help with technical assistance.
Publisher Copyright:
© 2018 Elsevier Inc.
PY - 2018/11/1
Y1 - 2018/11/1
N2 - Background: In human primary motor cortex (M1), the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI) can be expressed conventionally as a percent change in the relative amplitude of a conditioned motor evoked potential to non-conditioned; or adaptive threshold-hunting a target motor evoked potential amplitude in the absence or presence of a conditioning stimulus, and noting the relative change in stimulation intensity. The suitability of each approach may depend on the induced current direction, which probe separate M1 interneuronal populations. Objective: To examine the influence of conditioning stimulus intensity, interstimulus interval (ISI) and current direction for adaptive threshold-hunting and conventional SICI using equivalent TMS intensities. Methods: In 16 participants (21–32 years), SICI was examined using adaptive threshold-hunting and conventional paired-pulse TMS with posterior-anterior and anterior-posterior stimulation, ISIs of 2 and 3 ms, and a range of conditioning intensities. Results: Inhibition with adaptive threshold-hunting was greater for anterior-posterior stimulation with an ISI of 3 ms (23.6 ± 9.0%) compared with 2 ms (7.5 ± 7.8%, P < 0.001) and posterior-anterior stimulation at both ISIs (2 ms 8.6 ± 8.7%, 3 ms 5.9 ± 4.8%; P < 0.001). There was an association between inhibition obtained with conventional and adaptive threshold-hunting for posterior-anterior but not anterior-posterior stimulation (2 ms only, r = 0.68, P = 0.03). Conclusions: More inhibition was evident with anterior-posterior than posterior-anterior current for both adaptive threshold-hunting and conventional paired-pulse TMS. Assessment of SICI with anterior-posterior stimulation was not directly comparable between the two approaches. However, the amount of inhibition was dependent on conditioning stimulus intensity and ISI for both SICI techniques.
AB - Background: In human primary motor cortex (M1), the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI) can be expressed conventionally as a percent change in the relative amplitude of a conditioned motor evoked potential to non-conditioned; or adaptive threshold-hunting a target motor evoked potential amplitude in the absence or presence of a conditioning stimulus, and noting the relative change in stimulation intensity. The suitability of each approach may depend on the induced current direction, which probe separate M1 interneuronal populations. Objective: To examine the influence of conditioning stimulus intensity, interstimulus interval (ISI) and current direction for adaptive threshold-hunting and conventional SICI using equivalent TMS intensities. Methods: In 16 participants (21–32 years), SICI was examined using adaptive threshold-hunting and conventional paired-pulse TMS with posterior-anterior and anterior-posterior stimulation, ISIs of 2 and 3 ms, and a range of conditioning intensities. Results: Inhibition with adaptive threshold-hunting was greater for anterior-posterior stimulation with an ISI of 3 ms (23.6 ± 9.0%) compared with 2 ms (7.5 ± 7.8%, P < 0.001) and posterior-anterior stimulation at both ISIs (2 ms 8.6 ± 8.7%, 3 ms 5.9 ± 4.8%; P < 0.001). There was an association between inhibition obtained with conventional and adaptive threshold-hunting for posterior-anterior but not anterior-posterior stimulation (2 ms only, r = 0.68, P = 0.03). Conclusions: More inhibition was evident with anterior-posterior than posterior-anterior current for both adaptive threshold-hunting and conventional paired-pulse TMS. Assessment of SICI with anterior-posterior stimulation was not directly comparable between the two approaches. However, the amount of inhibition was dependent on conditioning stimulus intensity and ISI for both SICI techniques.
KW - Adaptive threshold-hunting
KW - Current direction
KW - Interstimulus interval
KW - Short-interval intracortical inhibition
KW - Transcranial magnetic stimulation
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U2 - 10.1016/j.brs.2018.07.047
DO - 10.1016/j.brs.2018.07.047
M3 - Article
C2 - 30033042
AN - SCOPUS:85050080108
SN - 1935-861X
VL - 11
SP - 1296
EP - 1305
JO - Brain Stimulation
JF - Brain Stimulation
IS - 6
ER -