In a study from our group (Dolbcrg et al, unpublished data), changes in MT

were explored in a group of 46 patients with MDD treated with rTMS and in normal controls. No differences were identified in MT between patients and controls. In addition, MT did not change with treatment, and showed no association with severity, age, or the presence of psychosis. It is possible that, the differences observed in our study and those reported by Triggs et al were related to differences in the methods of determining MT. Triggs et al defined MT as 100-μV MET deflections in the EMG, whereas we used the more widely Inhibitors,research,lifescience,medical accepted cutoff of 50 μV. Postexercise facilitation It is well established that muscular activation increases the size of the MEPs during TMS. Samii et al59 and Shajahan et al60,61 explored this paradigm in

patients with acute depression, in recovered depressed patients, and in normal controls. They found that patients in the acute stage of the illness had significantly less postexercise facilitation Inhibitors,research,lifescience,medical than normal controls or recovered patients. They speculated that this lack of facilitation in depressed patients is due to decreased cortical excitability (which may be secondary to increased inhibitory outflow from interneurons), and that the normalization seen with recovery reflects the normalization of underlying neurobiological processes. Silent period A variable period of EMG absence follows Inhibitors,research,lifescience,medical an MEP This period is referred to as the silent, period

and it is XL184 concentration believed to be, at least in part, secondary to increased inhibitory forces in the motor cortex.13 Steele et Inhibitors,research,lifescience,medical al62 looked at the post-TMS silent, period in patients with depression and compared it with that of normal controls. They found that depressed patients had longer post-TMS silent, periods than normal controls. They concluded that their findings were indirect evidence for the presence of state-dependent increased inhibitory mechanisms in the motor cortex, and possibly Inhibitors,research,lifescience,medical other areas of the brain, in depression. It has not been reported whether recovery from depression was associated with a normalization of the silent, period. Paired-pulse stimulation Paired-pulse stimulation of the motor cortex is considered today to be the gold standard of motor cortex excitability.13,56,63 The paired TMS stimulations unless are given with short, intervals between them (interstimulus intervals [ISIs]). The effects depend on the intensity of the conditioning and test, stimulus, and on the ISI. Short ISIs are believed to reveal inhibitory cortical mechanisms, whereas long ISI are thought to reveal excitatory cortical mechanisms. Paired-pulse stimulation has been studied extensively in neurology, but much less in depression. Maeda et al63 studied eight subjects with major depression with the paired-pulse paradigm and compared their responses with that of normal controls.