In our study, in both humans and rats, the presentation of an auditory infrequently presented (rare/target) stimulus produced a robust and highly significant increase in phase locking of EROs, as compared to the frequently presented stimulus, both within and between brain areas in all frequency bands. We suggest that in this simple sensory paradigm the most likely explanation of this finding is that it represents a change in neural state associated with attending to a more novel, possibly environmentally relevant noise. However, since the humans are required to respond to the stimuli and the rats are not it is entirely possible that the increase in synchrony has different meanings in the two species. These findings are, however, consistent with a previous study that evaluated phase locking of EROs using a complex motor-learning task (Sauseng et al., 2007). In that task, long-range theta phase coherence was stronger in the novel condition compared to learned sequences, independent of task-difficulty. The authors interpreted those findings as a reflection of an increase in the amount of sensory information necessary to integrate novel sequences as
