More subjects are required for ventrolateral than dorsolateral prefrontal TMS because of intolerability and potential drop-out

Abstract

Transcranial magnetic stimulation (TMS) of the human lateral prefrontal cortex, particularly the ventral region, often causes considerable discomfort to subjects. To date, in contrast to abundant literature on stimulations to the dorsolateral prefrontal cortex, the ventrolateral prefrontal cortex has been less frequently stimulated, partly because some subjects are intolerable of stimulation to the ventrolateral prefrontal cortex. To predict the additional number of subjects required for the stimulation of the dorsolateral and ventrolateral prefrontal cortices, 20 young healthy subjects reported two evaluation scores: the discomfort caused by TMS and the resulting intolerability to complete the TMS experiments. Single-pulse stimulation (SPS) or theta-burst stimulation (TBS) was administered to the lateral prefrontal cortex. The high-resolution extended 10–20 system was used to provide accurate estimation of the voxelwise scores. The discomfort ratings with the SPS and TBS were relatively higher in the ventrolateral prefrontal cortex than those in the dorsolateral prefrontal cortex. Both the SPS and TBS elicited maximal discomfort at the stimulation position F8. The SPS and TBS to F8 under the standard TMS protocols were intolerable for approximately one half (11 and 10, respectively) of the subjects. The intolerability was further calculated for all voxels in the lateral prefrontal cortex, which enabled us to estimate the additional number of subjects required for specific target areas. These results suggest that prior knowledge of subjects’ discomfort during stimulation of the lateral prefrontal cortex can be of practical use in the experimental planning of the appropriate number of recruited subjects and provide the database for the probability of intolerability that can be used to predict the additional number of subjects.

MRI-based visualization of rTMS-induced cortical plasticity in the primary motor cortex

“…The signals were sent to an amplifier (MEG-5200, Nihon Kohden, Japan) through filters set at 150 Hz to 3 kHz. The AMT was defined as the lowest intensity that evoked a small response (>100 μV) in more than 5 of 10 consecutive trials when the subjects maintained a slight contraction of the right FDI (10% of the maximum voluntary contraction [MVC]) [33, 45–47]. MVC was calculated approximately 10 min before QPS administration.…”

A causal role of anterior prefrontal-putamen circuit for response inhibition revealed by transcranial ultrasound stimulation in humans

“…At Stage 1, MEPs were recorded from the right FDI muscle using Ag/AgCl sheet electrodes placed over the belly of the muscle (active) and metacarpophalangeal joint of the index finger (reference) as described previously (Han et al, 2019;Ogawa et al, 2022;Osada et al, 2019Osada et al, , 2021Tamura et al, 2019;Watanabe et al, 2014Watanabe et al, , 2015. The signals were sent to an amplifier (MEG-5200, Nihon Kohden, Japan) through filters set at 5 Hz to 3 kHz.…”

Parallel cognitive processing streams in human prefrontal cortex: Parsing areal-level brain network for response inhibition

“…The stimulation intensity was set at 120% of the RMT. For some subjects, the stimulation intensity was further adjusted to accommodate comfort (Han et al, 2019). The mean (±SD) stimulation intensity was 46.7 (±3.6) % of the maximum stimulator output.…”

“…2 and 3). Three other subjects failed to complete the TMS experiments due to stimulation discomfort (Han et al, 2019) and were not included in the analysis. Written informed consent was obtained from all subjects according to the Declaration of Helsinki.…”