Some authors (Chassagnon et al., 2008, Ikeda et al., 1992, Nii et al., 1996 and Uematsu et al., 1992) report sites producing both inhibition of ongoing hand movements and also excitation

Epigenetics Compound Library solubility dmso of facial musculature. In one case, stimulation of SMA caused a negative motor response affecting all parts of the body (Ikeda et al., 1992). In summary, although NMAs often show some degree of somatotopical specificity, this is not always the case. The localisation data in the NMA literature is not systematic, and lacks a consistent coordinate system. All the reported sites are found in the frontal lobes. Clearly, this could reflect a sampling bias based on clinical requirements for electrode placement, or on scientific assumptions about localisation of inhibition. However, in a study with 35 patients, 21 of which had electrode grids placed over the frontal-parietal-temporal cortex, all NMAs were found anterior to the Rolandic line (Uematsu et al., 1992). Penfield (Penfield and Rasmussen, 1950) reported hand, leg and jaw and tongue arrest see more “in the lower sensorimotor strip, just above the fissure of Sylvius”. Lüders et al.,

1987 and Lüders et al., 1992 found NMAs most consistently in the IFG ‘immediately in front of the face motor area’. Several studies reported NMAs in the SMA (Chassagnon et al., 2008, Chauvel et al., 1996, Fried et al., 1991, Hanakawa et al., 2001, Lüders et al., 1988 and Penfield and Rasmussen, 1950) and around the Rolandic fissure

(Nii et al., 1996 and Uematsu et al., 1992). Mikuni (Mikuni et al., 2006) recently added the dorsal premotor cortex to this list. Fig. 1 shows the NMAs from the studies in Table 1, positioned as precisely as possible using the information from the original papers. Some of the studies reporting NMA sites on the lateral cortex do not report the hemisphere in which they were found (Nii et al., 1996 and Penfield and Rasmussen, 1949). Nii et al report that NMAs were found “in similar numbers in the Morin Hydrate left and right hemispheres”. Therefore, half of the reported sites were arbitrarily assigned to the left and half to the right hemisphere. In the case of Penfield and Rasmussen, the sites are shown on the right hemisphere. Overall, NMAs appear to be intermixed with sites where positive sensory or positive motor effects are found. This is not compatible with Lüders suggestion of a ‘negative motor homunculus’ (Lüders et al., 1995). Instead, it goes in line with recent views (Farrell et al., 2007) suggesting that the cortex presents a mosaic of functional organization, rather than the classic somatotopical sensory and motor organisations that Penfield described (Mazzola et al., 2009). There has been little systematic analysis of stimulation levels required for eliciting negative motor responses. Chauvel et al.