The cerebellum is a major motor structure. However, in humans, its efferent topographical organization remains controversial and indirectly inferred from neuroimaging and animal studies. Even central questions such as 'Can we evoke limb movements by stimulating the cerebellar cortex?' have no clear answer. To address this issue, we electrically stimulated the posterior cerebellum of 20 human patients undergoing surgery for tumours located outside this structure (e.g. pineal gland, quadrigeminal plate). Stimulation, delivered at a 60-Hz frequency for 2 s, evoked focal (single-joint) ipsilateral movements. Different regions were associated with the production of head (vermal lobule VI), face/mouth (hemispheric lobule VI) and lower-limb (hemispheric lobules VIIb-IX) responses. Upper-limb representations were more widely distributed. They intermingled with face/mouth representations in the superior posterior cerebellum (hemispheric lobule VI) and lower-limb representations in the inferior posterior cerebellum (hemispheric lobules VIIb-IX). No intra- or inter-limb somatotopy was found in these areas. Functionally, upper-limb (face/mouth movements) and upper limb-lower limb postural coordinations are major elements of our motor repertoire. Representation of these pairs of segments in common regions might favour the production of integrated motor behaviours. The intermediate region of the posterior cerebellum (hemispheric lobule VII and vermal lobules VII-VIII) was mostly silent. Latency results in conjunction with previous electrophysiological evidence in animals suggest that electrically evoked motor responses were not mediated by a cortical route but rather by brainstem structures. The potential role of this descending efferent pathway for fine motor control is discussed.

A recent study by Conde, Tomasevic et al. (2019) [1] puts a spotlight on the subtleties of experimental design and analysis of studies involving TMS-evoked EEG potentials (TEPs), specifically focusing on the challenge of disentangling genuine cortical responses to TMS from those resulting from concomitant sensory activation. This is a relevant topic that the TMSeEEG community has previously identified [2] and addressed with different strategies [3e6]. Based on the similarity of the evoked EEG responses they obtained in real TMS at different sites and in sham conditions (auditory and somatosensory scalp stimulation), the authors of [1] inferred that TEPs can be significantly contaminated by the effects of concurrent, non-transcranial stimulation.We acknowledge this is a valuable reminder to the TMS-EEG community; however, we contend that another fundamental implication of the work by Conde, Tomasevic and colleagues [1] -only incidentally mentioned at the end of their discussion e is that the evoked responses they obtain from both real TMS and sham conditions are substantially different from the TEPs reported in many of the previous studies (see, for example [7e11]). This discrepancy offers a timely opportunity to focus on the issue of the reproducibility of TEPs across laboratories and, most important, can encourage a constructive debate within the whole TMSeEEG community towards the optimization of shared procedures to obtain genuine responses to TMS.In this vein, Fig. 1 directly compares the TEPs reported in Ref.[1] with others previously published in different studies taken as a reference by Conde, Tomasevic and colleagues [1].The inspection of Fig. 1 clearly shows that it is possible to effectively trigger high-amplitude, sharply rising early (<50 ms) components and overall TEP wave-shapes that are specific for the angle and site of stimulation and that are very different from those obtained in Ref. [1]. This simple comparison highlights a general problem of reproducibility and offers an excellent opportunity to discuss two critical steps in TMSeEEG data acquisition: (i) maximising the impact of TMS on the cortex, and (ii) minimizing EEG confounding factors due to sensory co-stimulation.Regarding the impact of TMS on the cortex, it is very likely that the authors of [1] were not as effective as other investigators for the following reasons. First, they applied TMS with a maximum electric field (E-field) intensity between 70 and 90 V/m according to their estimation, assuming a priori that this would have warranted effective cortical activation based on a previous work [12]. However, in Ref. [1] the authors adopted a small coil (outer winding diameter: 45 mm) which, compared to the larger ones (outer winding