Although Mab and Mad occupy the same cortical territory as mouse CFA and RFA (Tennant et al., 2011), important differences exist between them. First, Mab and Mad are contiguous and equal in area, whereas CFA is larger than RFA and they are separated buy ABT-737 by a representation of the neck (Tennant et al., 2011). Second, RFA is not apparent in all experiments or animals (Tennant et al., 2011), whereas Mab and Mad almost always co-occur. It is interesting

to note that in rats, mapping with short stimulus durations produces maps that include RFA and CFA, whereas long (500 ms) durations reveal maps containing movement representations similar to Mab and Mad (Ramanathan et al., 2006). Primate motor cortex is commonly described as a hierarchical arrangement of primary motor cortex, premotor areas, and supplementary motor cortex where premotor areas can facilitate motor output from primary motor

cortex (Cerri et al., 2003). It has been suggested based on their connectivity that rodent RFA and CFA are homologous to premotor and primary motor cortex, respectively (Rouiller et al., 1993). Our observation that Mad expands after http://www.selleckchem.com/products/pci-32765.html application of GABA receptor antagonists but Mab does not suggests that these regions may be differentially regulated Adenosine by feed-forward or lateral inhibition. Coupled with the relatively longer latencies for movements evoked from the more caudal Mad region, this could be viewed as evidence for a hierarchical arrangement of mouse motor cortex. Although intracortical connections are obviously critical for motor function, it is also known that multiple motor cortical regions project in parallel to the spinal cord (Rouiller et al., 1993 and Dum

and Strick, 2002). This implies that multiple motor regions can contribute directly to movement, and may not be arranged hierarchically (Graziano and Aflalo, 2007). This view is corroborated by the results of our experiments with glutamate and GABA receptor antagonists, which demonstrated that the Mab and Mad representations could function independently after a diminution of intracortical synaptic transmission. If multiple motor regions do not form a hierarchical chain, they may instead encode various behaviors or postures (Graziano et al., 2002 and Graziano et al., 2005). This is consistent with our observation that stimulation of Mab and Mad drives limb movements to different end positions in space. This result could be produced with optogenetic or electrical stimulation, suggesting that it is not an artifact of passive electrical current spread from the stimulation site (Strick, 2002).