There is limited overlap between the brain regions identified using differing imaging methods. The most consistently identified regions include areas of the anterior cingulate, dorsolateral, medial and inferior prefrontal cortex, insula, superior temporal gyrus, basal ganglia and cerebellum. Further research is required to identify if different imaging methods are identifying complementary networks that are equally involved in the disorder.

The aim of this study is to investigate whether repetitive transcranial magnetic stimulation (rTMS) targeted to a specific site in the dorsolateral prefrontal cortex (DLPFC), with a neuro-navigational method based on structural MRI, would be more effective than rTMS applied using the standard localization technique. Fifty-one patients with treatment-resistant depression were randomized to receive a 3-week course (with a potential 1-week extension) of high-frequency (10 Hz) left-sided rTMS. Thirty trains (5 s duration) were applied daily 5 days per week at 100% of the resting motor threshold. Treatment was targeted with either the standard 5 cm technique (n ¼ 27) or using a neuro-navigational approach (n ¼ 24). This involved localizing the scalp location that corresponds to a specific site at the junction of Brodmann areas 46 and 9 in the DLPFC based on each individual subject's MRI scan. There was an overall significant reduction in the Montgomery-Asberg Depression Rating Scale scores over the course of the trial, and a better outcome in the targeted group compared with the standard localization group at 4 weeks (p ¼ 0.02). Significant differences were also found on secondary outcome variables. The use of neuro-navigational methods to target a specific DLPFC site appears to enhance response to rTMS treatment in depression. Further research is required to confirm this in larger samples, or to establish whether an alternate method based on surface anatomy, including measurement from motor cortex, can be substituted for the standard 5 cm method.

Several studies have demonstrated that cortical inhibition (CI) can be recorded by paired transcranial magnetic stimulation (TMS) of the motor cortex and recorded by surface electromyography (EMG). However, recording CI from other cortical regions that are more closely associated with the pathophysiology of some neurological and psychiatric disorders (eg, dorsolateral prefrontal cortex (DLPFC) in schizophrenia) was previously unattainable. This study, therefore, was designed to investigate whether CI could be measured directly from the motor cortex and DLPFC by combining TMS with electroencephalography (EEG). Long-interval CI (LICI) is a TMS paradigm that was used to index CI in the motor cortex and DLPFC in healthy subjects. In the motor cortex, LICI resulted in significant suppression (32.8 ± 30.5%) of mean cortical evoked activity on EEG, which was strongly correlated with LICI recorded by EMG. In the DLPFC, LICI resulted in significant suppression (30.1±26.9%) of mean cortical evoked activity and also correlated with LICI in the motor cortex. These data suggest that CI can be recorded by combining TMS with EEG and may facilitate future research attempting to ascertain the role of CI in the pathophysiology of several neurological and psychiatric disorders.