GP input has been shown in brain slices to reset the phase of autonomous spiking within the STN (Baufreton et al., 2005), and resonant feedback

between GP and STN has been repeatedly proposed as an oscillatory mechanism (Bevan et al., 2002, Holgado et al., 2010 and Mallet et al., 2008a). Determining how BG interconnections contribute to behavior-linked beta change is an important challenge for future studies. We observed multiple, dissociable relationships between beta processes and behavioral events. First, each of the auditory cues resulted in very rapid beta phase reset, often without simultaneous changes in beta power. Reset of ongoing rhythms check details by salient cues has been previously reported in multiple cortical regions, for a range of oscillatory frequencies including beta (Lakatos et al., 2007). Such resets are largely independent of sensory modality, and have been proposed to reflect a rapid modulatory process that causes incoming sensory information to arrive in cortex when neurons are at a phase of peak excitability. The resulting facilitation of sensory processing may help reduce reaction times to attended instruction cues (Senkowski et al., 2006). Similarly, within monkey primary motor cortex the appearance of a visual reach

target, and/or an associated auditory cue, provokes very rapid beta reset (Reimer and Hatsopoulos, 2010) that appears to be the same reset phenomenon that we observed throughout cortical-BG circuits. Such a coordinated phase AZD8055 reset may enhance effective communication between regions (Fries, 2005). Both the short latency of the phase reset (within tens of milliseconds) PD184352 (CI-1040) and the fact that the reset to Stop cues did not differentiate between Stop-success and Stop-failure trials indicate that this aspect of cortical-BG coordination is linked to early stages of sensory processing. Each of the auditory

cues used in the task was also followed by an increase in beta power, with a latency of several hundred milliseconds. However, this beta ERS appeared only if the cues influenced behavioral output. Such selectivity was seen in two distinct situations: first, the beta ERS to the Stop cue occurred on Stop-success but not Stop-failure trials, and second, in the Deferred-Go task the beta ERS to the Go cue occurred only when the rats used this external cue to prompt their responses, rather than performing self-timed movements. These complementary observations clearly demonstrate that the beta ERS is not simply related to sensory processing. Nor is it simply related to movement, or the absence of movement. Beta power was reduced below baseline as animals held still while waiting for an instruction cue. Once this cue occurred, we saw an equivalent beta ERS whether rats initiated action (in the Immediate-GO condition) or continued to hold (in the Deferred-GO and NOGO conditions).