Long‐term effect of motor cortical repetitive transcranial magnetic stimulation induces

Abstract

Repetitive transcranial magnetic stimulation (rTMS) recently has been assessed as a noninvasive treatment modality for movement and psychiatric disorders, whereas the mechanism underlying the therapeutic effects is not fully understood. Studies in rodents showed lasting functional changes in some selected regions, such as limbic-associated structures, but unfocused brain stimulation did not clarify the regional effects. To address the topographical and temporal profiles of the effects on glucose metabolism in primate brain, we performed rTMS and repeated (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) before, during, and up to 16 days after rTMS in anesthetized cynomologous monkeys. We delivered a total of 2,000 pulses of 5 Hz-rTMS over the right precentral gyrus using a small-sized eight-figured coil that induced a localized electrical field. Voxel-based analysis in a standard space of the macaque brain showed statistically robust changes in FDG uptake: a decrease in the motor/premotor cortices and an increase in the limbic-associated areas involving the anterior/posterior cingulate, and orbitofrontal cortices. Interestingly, these uptake changes continued for at least 8 days and the magnitude of the lasting effects in the limbic-related areas was negatively correlated across subjects with those in the motor/premotor cortices. The results demonstrate that motor rTMS has a long-term lasting effect on motor-related regions and distant limbic-related areas via functional connections.

High-frequency rTMS over the supplementary motor area improves bradykinesia in Parkinson's disease: Subanalysis of double-blind sham-controlled study

“…Furthermore, these improvements were observed two weeks after the end of the rTMS protocol. Although the mechanism of this delay remains to be determined, possible cumulative effects of rTMS and a long-lasting effect of rTMS, which lasted up to 8 days in the primate brain [14], might partly explain this delay.…”

Cortico-Cortical Modulation Induced by 1-Hz Repetitive Transcranial Magnetic Stimulation of the Temporal Cortex

“…10 The above-mentioned studies addressed short-term effects, while another study that assessed the long-term effects of rTMS in monkeys found that 5-Hz rTMS applied to the precentral gyrus reduces glucose metabolism in the motor and premotor cortices and increased metabolism in the cingulate and orbitofrontal cortices for a period lasting at least 8 days. 14 One recent study demonstrated decreased functional magnetic resonance imaging activation in pain networks including the secondary somatosensory cortex after 10-Hz rTMS of the primary motor cortex. 15 However, the effects of rTMS on local and global cortical reorganization and the precise underlying mechanisms are still unknown.…”

“…The prefrontal and cingulate cortices are known as association cortical areas integrating cortical functions of other areas, such as decision making and/or inhibitory control on motor pathways. 29,30 The temporal relationships of the rTMS effects have been assessed in the primate brain 14 by performing FDG-PET serially before, during, and up to 16 days after 5-Hz rTMS of the precentral gyrus. Glucose metabolism decreased in the motor and premotor cortices and increased in the limbic-associated areas such as the cingulate and orbitofrontal cortices, and those changes continued for at least 8 days, suggesting relatively long-lasting effects of rTMS in the functionally connected cortical areas.…”

Combining functional imaging with brain stimulation in Parkinson's disease

“…This strongly suggests that brain activity can be differently excited if patients are drug-na ï ve or when comparing off versus on medication, or off versus on DBS. Similarly, a cumulative effect should also be considered (Hayashi et al, 2004;Khedr et al, 2006). Some studies reported greater motor improvement as measured by the UPDRS-III after the fourth week of rTMS, but not before (Hamada et al, 2008).…”