(Speer et al., 2009), it was demonstrated that depressed patients with global baseline hypoperfusion had improvement after 20-Hz rTMS and worsening after 1-Hz rTMS; conversely, patients with hyperperfusion in specific cortical regions showed improvement after 1-Hz rTMS (no relationship was found for 20-Hz rTMS in this subpopulation). Another study looking at blood flow changes after rTMS also demonstrated relatively increased blood flow in prefrontal cortex after high-frequency stimulation, and relatively decreased blood flow after low-frequency stimulation (Loo et al., 2003). However, the pattern of changes in other cortical regions after high or low frequency rTMS was complex, with increases in some regions and decreases in others. Fregni et al (2006b) used SPECT to study the effects of rTMS of left prefrontal cortex versus an SSRI (fluoxetine) in patients with Parkinson’s Disease and comorbid depression. rTMS produced blood flow changes in a widespread cortical network involving the prefrontal and temporal cortices, as well as the posterior cingulate. Importantly, the clinical improvement in depression was significantly correlated with the rTMS-induced blood flow changes. Thus, these studies all demonstrated that prefrontal rTMS modulates the activity of a widespread network involving regions known from prior functional connectivity studies to be involved in depression. These
