The predominance find more of cells concerned with slow movement time scales is in line with an earlier recording study, which also showed that cells did not covary 1:1 with the whisking rhythm and that cells would globally turn off and on with whisking (Carvell et al., 1996). Hill et al. (2011) also show that motor cortical neurons accurately predict whisker movements. Most interestingly,

this covariation of motor cortical activity and whisker movements persist after removal of sensory feedback, implying that it reflects efferent control rather than afferent modulation. This finding differs from data in somatosensory cortex, where the removal of sensory feedback disrupts the comodulation of activity and whisking (Fee et al., 1997). This result is of great significance, because it presents one of the clearest dissociations of vibrissae motor and somatosensory cortical activity in sensorimotor integration discovered so far. The modulation of neural activity associated SB203580 chemical structure with whisking is fairly weak. Overall there is only a temporal redistribution of neural activity during whisking and no net firing rate increase during whisking! Does such weak modulation argue against a motor role of these neurons? Almost certainly not. In most mammalian motor cortices the activity during spontaneous behaviors is rather modest. The situation changes

when tasks become complicated or when animals are trained on certain movements. One might guess that for most of the day motor cortex is not in the driver’s seat, and instead acts like a mastermind of complicated, unusual, or very significant movements. As for the lesions to the motor cortical forelimb representation performed by Fritsch and Hitzig, damage to vibrissa motor cortex does not fully abolish whisker movements. The persistence of whisking after cortical ablation suggested early on the existence of a brain stem pattern generator for whisking. Lesions to vibrissa motor cortex do affect the amplitude distribution of whisker movements, a result much in line with the current results from Hill et al. (2011). The characteristics

of stimulation-evoked not movements in vibrissa motor cortex strongly depend on methodology of stimulation and the identity of the stimulated neurons (Brecht et al., 2006). Stimulation of pyramidal neurons and interneurons evokes movements of opposite directions. While movements evoked by brief trains of extracellular stimulation pulses are brief and restricted to few whiskers, movement fields observed with single-cell stimulation are large and single-cell-evoked movements persist for seconds (Brecht et al., 2004b). Single-cell stimulation effects are in line with the conclusion of Hill et al. (2011) that vibrissa motor cortex controls movements on long timescales. Vibrissa motor cortex distributes output to a wide variety of subcortical targets. Inputs to vibrissa motor cortex arrive from a wide variety of brain regions in an intricate extremely orderly laminar pattern.