Unilateral left prefrontal transcranial magnetic stimulation (TMS) produces intensity-dependent bilateral effects as measured by interleaved BOLD fMRI

Interleaved Transcranial Magnetic Stimulation/Functional MRI Confirms that Lamotrigine Inhibits Cortical Excitability in Healthy Young Men

“…However, we found no significant difference between the activation at 100% rMT and activation at 120% rMT (in the presence of placebo). Interestingly, in contrast to motor cortex TMS, as well as our previous findings with prefrontal TMS (Nahas et al, 2001), we also failed to observe activation of the cortex directly underneath the coil. A possible explanation for this could relate to the absence of sensory feedback in the case of prefrontal stimulation.…”

“…However, while the pattern of activation following TMS over the motor cortex replicated our previous work, the prefrontal TMS data failed to replicate our earlier finding of activation of the cortex directly underneath the coil (Nahas et al, 2001). In addition, although the present data from the motor cortex TMS showed that higher-intensity stimulation produced greater activation in the cortex under the stimulation site, we failed to find an intensity-dependent brain activation when stimulation was applied over the prefrontal cortex (Figure 4).…”

“…In this case, we were limited to examining the fMRI measurements alone, since there is no overt behavioral response, such as an MEP, to assess the effect of prefrontal cortical stimulation. We have shown previously that unilateral TMS applied over the prefrontal cortex (left) has bilateral effects and that higher intensity stimulation produces greater ipsi-and contralateral activation (Nahas et al, 2001). In addition, other PET and SPECT studies have shown that increases and decreases in blood flow or metabolism occur during and shortly after repetitive TMS (rTMS) applied over the prefrontal cortex (Kimbrell et al, Figure 3 Changes of significant active voxel number by LTG in the motor cortex and hippocampus.…”

Repetitive Transcranial Magnetic Stimulation Increases the Release of Dopamine in the Nucleus Accumbens Shell of Morphine-Sensitized Rats During Abstinence

“…rTMS is a noninvasive method for electrical stimulation of neurons in the cerebral cortex and is able to modify neuronal activity locally and in remote brain structures via transsynaptic connections (Nahas et al, 2001;Post and Keck, 2001). The neurobiological effects of this novel therapeutic tool in humans are not sufficiently explained so far, but it has repeatedly been reported that the mesolimbic dopaminergic system plays an important role in mediating the mood improvements in depressed patients (review: Padberg and Möller, 2003;Schlaepfer et al, 2003).…”

Time-course of “off-line” prefrontal rTMS effects — a PET study

“…Third, related to the second point, one should consider that applying rTMS to a given brain region not only affects the target site itself, but also brain areas effectively connected to the target area. Such remote effects evoked by low frequency rTMS over prefrontal areas have been shown in several studies (Kimbrell et al, 2002;Knoch et al, 2006c;Nahas et al, 2001;Ohnishi et al, 2004;Speer et al, 2003). These studies, however, differed from the usual "offline" protocol in that either regional cerebral blood flow (rCBF) (Nahas et al, 2001;Speer et al, 2003) or glucose uptake (Kimbrell et al, 2002) was measured "online" (i.e., during rTMS application), or in that the duration of the stimulation trains were shorter than usual in the "off-line" approach (Knoch et al, 2006c;Ohnishi et al, 2004).…”