Another important limitation in this study: psychomotor agitation and autonomic dysregulation (e.g. tachycardia/ tachypnea) are common in bipolar mania and may generate BOLD signal changes which do not reflect oscillations in neuronal activity. Motion parameters did not vary significantly between groups in our study, indicating this is not a likely. On the other hand, we did not collect eye movement data in our scans, and group differences in eye movements may underlie our Brodmann's Area 7 findings in mania, since this region is involved in the planning and modulation of eye movements (Buneo and Andersen 2006). In addition, we did not collect heart or respiratory rate data. Tachycardia/tachypnea could drive coherent BOLD signal changes in multiple cortical areas and explain some findings. It is unlikely, however, that autonomic differences would lead to both reductions in coherence in the PFC and increases in coherence in posterior cortical areas.
