Effects of dorsal premotor cortex rTMS on contingent negative variation and Bereitschaftspotential
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1
Goethe University, Motor Cortex Group, Department of Neurology, Germany
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2
Toyama Hospital, Department of Neurology, Japan
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3
China Medical University Hospital, Neuroscience Laboratory, Department of Neurology, Taiwan
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4
Goethe University, Institute for Cell Biology and Neuroscience, Germany
Background:Recently the repetitive transcranial magnetic stimulation (rTMS) technique has been broadly used to study the motor control system in humans. Low-frequency rTMS (1 Hz or less) produces long-term depression (LTD)-like plasticity and higher frequency rTMS produces long-term potential (LTP)-like plasticity in the primary motor cortex. However, studies of rTMS effects have been largely restricted to measuring corticospinal excitability by means of motor evoked potential amplitude. Here we were interested in studying rTMS effects on preparatory volitional motor activity. We examined the contingent negative variation (CNV) and the Bereitschaftspotential (BP), measures of externally cued vs. intrinsic volitional motor preparatory activity, respectively, using high-resolution electroencephalography (EEG). RTMS was targeted to the dorsal premotor cortex (PMd), are brain region thought to be primarily involved in externally cued motor preparation. Accordingly, we hypothesized that rTMS would alter CNV but leave BP unaffected.
Methods:Ten healthy, right-handed subjects (6 men, 27.9 ± 6.9 years) executed sequential right fingers movement via a computer-based interface for the CNV recordings. They were instructed to respond to imperative visual go-signals 2 seconds following a warning signal. Surface electromyography (SEMG) and motor performance including the reaction time and error rate were monitored. A total of 243 trials were completed before and after a 15 min-rTMS intervention. MRI-navigated 1 Hz rTMS (15 min continuous stimulation) or 5 Hz rTMS (15 times 12 s epochs, separated by 48 s pauses) was delivered to the left PMd in separate sessions. RTMS intensity was adjusted to 110% of the individual active motor threshold. For the BP recordings, nine subjects (5 men, 28.4 ± 7.1 years) performed the same type of fingers movement, but intrinsically, i.e. without external cues. Early (1500 to 500 ms before SEMG onset) and late (500 to 0 ms before SEMG onset) components of CNV and BP were quantified. RTMS effects were analyzed separately for CNV and BP by three-way ANOVAs with EEG electrode position (25 central electrodes) and time (before and after rTMS) as within-subject factors and rTMS frequency (1 Hz vs. 5 Hz) as between-subject factor.
Results:Motor performance and the early components of CNV and BP did not significantly change by the rTMS interventions. ANOVAs and scalp voltage map showed that the late component of CNV, but not BP, was facilitated significantly after 1 Hz left PMd rTMS but remained unchanged after 5 Hz rTMS. This facilitation was located mainly over the fronto-central scalp area with slight predominance to the left hemisphere.
Conclusions:RTMS of the motor-dominant PMd interferes with the preparatory motor activity of externally cued volitional movements, but not with preparatory activity of intrinsic volitional movement, supporting the pivotal role of the motor-dominant PMd in motor preparation of externally cued but not intrinsic movements. This effect was specific because it was observed only after low-frequency rTMS (not high-frequency rTMS), it affected only the late CNV component (not the early CNV component), and it occurred only at those electrode locations overlying the fronto-central brain region predominantly of the stimulated left motor-dominant hemisphere.
Conference:
Bernstein Conference on Computational Neuroscience, Frankfurt am Main, Germany, 30 Sep - 2 Oct, 2009.
Presentation Type:
Poster Presentation
Topic:
Decision, control and reward
Citation:
Lu
M,
Jung
P,
Arai
N,
Tsai
C,
Kossl
M and
Ziemann
U
(2009). Effects of dorsal premotor cortex rTMS on contingent negative variation and Bereitschaftspotential.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference on Computational Neuroscience.
doi: 10.3389/conf.neuro.10.2009.14.020
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Received:
25 Aug 2009;
Published Online:
25 Aug 2009.
*
Correspondence:
Ulf Ziemann, Goethe University, Motor Cortex Group, Department of Neurology, Frankfurt, Germany, ulf.ziemann@uni-tuebingen.de