Third, there is much more consensus about motor organization than suggested by the plethora of area names. For example—even though everyone refers to it by a different name—there is excellent agreement between studies about the stereotaxic coordinates of whisker motor cortex. We thus know that vibrissae motor cortex is a large

frontal/medial cortical area. ZD1839 clinical trial Recent work that incorporated cytoarchitectonic data (Neafsey et al., 1986) and identified neurons (Brecht et al., 2004a) suggested that there is one major motor map in rodent frontal cortex (Figure 1A). This scheme is not unlike the motor map identified by early investigators such as Woolsey and Penfield in primates (Figure 1B). This scheme recognized in monkeys and humans a major motor map along the precentral sulcus and a smaller, medially situated motor field referred to as supplementary motor area (not shown in Figure 1B). When Asanuma and colleagues introduced a novel method of brain stimulation for which they used microelectrodes (originally developed for extracellular single-cell recordings), which they inserted directly into the cortical tissue rather than apply surface stimulation as Fritsch and Hitzig did, a much more fine-grained picture of primate motor cortices emerged (Figure 1C). In those recent

maps the major precentral motor field click here is divided into a primary motor cortex M1, premotor cortices, and a frontal eye field (FEF), which is spatially segregated from M1. It is noteworthy, however, that eye movements are conspicuously absent from M1 as defined in this scheme. It seems possible that the primate frontal eye fields are simply a segregated part of what once was a single major precentral motor map. Thus, the different views of motor organization outlined in Figures 1A–1C are not all too incompatible (for a review of the full complexity in assessing frontal cortex

homologies between primates and rodents, see Preuss, 1995). How then does the vibrissa motor cortex control whisker movements? How is motor control through motor cortex different from activity in somatosensory cortex, whose stimulation also evokes movements? Addressing this question has been remarkably difficult, not the least Mannose-binding protein-associated serine protease because whisker movements are among the fastest movements performed by mammals. Hill and et al. (2011) tackle this problem by performing recordings in vibrissa motor cortex combined with high-speed videography and electromyographic recordings of whisker muscle activity. They find that a large fraction of neurons in vibrissa motor cortex is modulated in their activity during whisker movements (Figure 2A). Interestingly, only a few neurons appear to be involved in the precise timing of movements (the phase of the whisking rhythm).