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Combining Non-Invasive Brain Stimulation (NIBS) techniques with the recording of brain electrophysiological activity is an increasingly widespread approach in neuroscience. Particularly successful has been the simultaneous combination of Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG). Unfortunately, the strong magnetic pulse required to effectively interact with brain activity inevitably induces artifacts in the concurrent EEG acquisition. Therefore, a careful but aggressive pre-processing is required to efficiently remove artifacts. Unfortunately, as already reported in the literature, different preprocessing approaches can introduce variability in the results. Here we aim at characterizing the three main TMS-EEG preprocessing pipelines currently available, namely ARTIST (Wu et al., 2018), TESA (Rogasch et al., 2017) and SOUND/SSP-SIR (Mutanen et al., 2018, 2016), providing an insight to researchers who need to choose between different approaches. Differently from previous works, we tested the pipelines using a synthetic TMS-EEG signal with a known ground-truth (the artifacts-free to-be-reconstructed signal). In this way, it was possible to assess the reliability of each pipeline precisely and quantitatively, providing a more robust reference for future research. In summary, we found that all pipelines performed well, but with differences in terms of the spatio-temporal precision of the ground-truth reconstruction. Crucially, the three pipelines impacted differently on the inter-trial variability, with ARTIST introducing inter-trial variability not already intrinsic to the ground-truth signal., Competing Interests: Declaration of competing interest UZ received grants from the European Research Council (ERC), German Ministry of Education and Research (BMBF), German Research Foundation (DFG), and consulting fees from CorTec GmbH. All the other authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) allow one to assess cortical excitability and effective connectivity in clinical and basic research. However, obtaining clean TEPs is challenging due to the various TMS-related artifacts that contaminate the electroencephalographic (EEG) signal when the TMS pulse is delivered. Different preprocessing approaches have been employed to remove the artifacts, but the degree of artifact reduction or signal distortion introduced in this phase of analysis is still unknown. Knowing and controlling this potential source of uncertainty will increase the inter-rater reliability of TEPs and improve the comparability between TMS-EEG studies. The goal of this study was to assess the variability in TEP waveforms due to of the use of different preprocessing pipelines. To accomplish this aim, we preprocessed the same TMS-EEG data with four different pipelines and compared the results. The dataset was obtained from 16 subjects in two identical recording sessions, each session consisting of both left dorsolateral prefrontal cortex and left inferior parietal lobule stimulation at 100% of the resting motor threshold. Considerable differences in TEP amplitudes and global mean field power (GMFP) were found between the preprocessing pipelines. Topographies of TEPs from the different pipelines were all highly correlated (ρ>0.8) at latencies over 100 ms. By contrast, waveforms at latencies under 100 ms showed a variable level of correlation, with ρ ranging between 0.2 and 0.9. Moreover, the test-retest reliability of TEPs depended on the preprocessing pipeline. Taken together, these results take us to suggest that the choice of the preprocessing approach has a marked impact on the final TEP, and that further studies are needed to understand advantages and disadvantages of the different approaches., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interests., (Copyright © 2021. Published by Elsevier Inc.)

Motor timing is essential for performing self-initiated movement sequences. Here, we investigated how sequence rhythm, or the timing for co-ordinating movements within a sequence, contributes to action preparation, compared with other processes occurring during sequence planning. First, we recorded the readiness potential (RP) in a condition of complex sequence rhythm and in condition of high demand on the timing for sequence initiation. We found that sequence rhythm and sequence initiation are independent processes, with sequence initiation contributing to early RP. Second, we compared the RP recorded in a condition of complex sequence rhythm and in a condition of complex sequence order, in which a complex combination of finger sub-movements had to be correctly ordered within a sequence. We found that sequence rhythm and sequence order share common processes occurring late RP. We suggest that the preparation for movement involves independent processes devoted to different aspects of motor timing and sequencing., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The memory-guided saccade paradigm is an ideal experimental model for studying spatial working memory. Both the posterior parietal cortex and frontal cortex are known to play a role in working memory; however, there is much debate about the degree of their involvement in the retention of information. We used event-related potentials and electromagnetic tomography to clarify the precise time course and location of the neural correlates of spatial working memory during a memory-guided saccade task in humans. We observed sustained activity in the inferior parietal lobe and extrastriate areas that persisted for the entire duration of the sensory- and memory-phases. This time course reveals that these regions participate in both initial sensory processing of visual cues and in the short-term maintenance of spatial location memory. Similar sustained activation was also observed in the anterior cingulate cortex, probably reflecting attentive control during the task. Differential activity between conditions was also recorded in the dorsolateral prefrontal cortex and in the frontal eye fields, but only during the initial part of the memory-phase. This finding suggests that these areas are not involved in the storage of spatial information, but rather in response selection and in transformation of spatial information into a motor coordinate framework, respectively. By exploiting techniques that provide exquisite temporal resolution and reasonably precise anatomical localization, this study provides evidence supporting the key role of inferior parietal lobe in the storage of spatial information during a working memory guided saccade., (Copyright 2010 Elsevier Inc. All rights reserved.)

Two crucial processes preceding voluntary action are determining the time for movement initiation and planning of the specific sequence of motor output. In this study we aimed to differentiate the neural activity related to motor timing and motor sequencing and to examine over what time periods they contribute to premovement activity during the readiness for voluntary action. Eighteen participants performed self-initiated voluntary finger movements in a readiness potential paradigm, both during EEG measurement and during fMRI. The finger movement task involved three conditions: (1) simple repetitive sequences; (2) increased demand on the sequencing of movement order; and (3) increased demand on the timing of movement initiation. Functional MRI and 64 channels EEG were conducted in two separate sessions. Motor timing and motor sequencing were found to involve different neural processes occurring at different times prior to movement initiation. Motor timing involved greater activation in lateral prefrontal regions over the earliest part of premovement activity, from 1200 ms before movement onset. Motor sequencing involved greater activation of dorsal premotor and parietal areas and was reflected in central and parietal scalp regions only over the later part of premovement activity, within 600 ms of movement onset. We suggest that different neural processes contribute to different aspects of the intended action over different time periods during the preparation for movement, and it is the coordinated activity of these multiple regions that is represented in premovement activity during the readiness for voluntary action., (Copyright 2009 Elsevier Inc. All rights reserved.)