The current directed to the brain surface or superficial layer is thought to reflect the depolarization of proximal apical dendrites, whereas the current in an opposite direction is thought to be a surface reflection of the depolarization of the distal apical dendrites (Landau 1967; Schlag 1973; Wood and Allison 1981). Under this condition, successive changes in sink–source configuration may occur. Actually, in animal studies, the presence of this BMS-907351 cost sequential reversal of sink–source configuration is commonly Inhibitors,research,lifescience,medical suggested in the somatosensory, visual, and auditory cortices (Towe 1966; Schlag 1973; Mitzdorf

1985). In human MEG studies, very similar polarity-reversed sequential Inhibitors,research,lifescience,medical activations in a cortical area have been shown among the somatosensory (Inui et al. 2004), nociceptive (Inui et al. 2003), auditory (Inui et al. 2006), and visual (Inui and Kakigi 2006) systems, suggesting the existence of a common intralaminar processing for feedforward sensory pathways. Therefore, such a common laminar mechanism is possibly present in the Inhibitors,research,lifescience,medical motor cortex and contributes to the successive reversals

of ECD direction in this study. The source activity used to model MRCFs in this study was apparently alternating in the anterior/posterior direction in cortical space (Fig. ​(Fig.1B).1B). Based on our single-dipole assumption for composing MRCFs, it is suggested that the intracellular current for the first premovement component MF was directed anteriorly. This is consistent with the previous observation that excitation of motor cortex neurons preceding movement originates in the superficial cortical layer of Inhibitors,research,lifescience,medical the anterior wall of the central sulcus (Roland 2002; Larkum et al. 2004). Thereafter, our results suggest that the intracellular current for the first postmovement Inhibitors,research,lifescience,medical component MEFI is directed posteriorly

(Fig. ​(Fig.1B-c).1B-c). Given that the MEFI component is driven by muscle spindle signals which depolarize the proximal apical dendrite of motor cortex neurons via the thalamocortical projections (Rosen and Asanuma 1972; Lemon et al. 1976; Evarts and Fromm 1977; Wong et al. 1978; Lemon 1981), a posterior direction current may happen as shown in Figure ​Figure1B-c1B-c (see also Fig. ​Fig.33). Another possibility for the alternating waveform in MEFs see more may be found in the fact that the pyramidal neurons of motor areas are under the control of two different types of thalamocortical afferents. Motor thalamic nuclei, mainly composed of ventral anterior (VA) and ventral lateral (VL) nuclei, receive massive afferents from the basal ganglia and cerebellum and project their axons to motor cortical areas (for a review, see Groenewegen and Witter 2004; Jones 2007). These two forms of information are differentially supplied to distal and proximal apical dendrites, respectively, of cortical pyramidal neurons.