A direct demonstration of cortical LTP in humans: a combined TMS/EEG study.
Repetitive transcranial magnetic stimulation (rTMS) is increasingly being used to promote cortical reorganization, under the assumption that it can induce long-term potentiation (LTP) of neural responses. This assumption is supported by several lines of indirect evidence. For example, rTMS of motor cortex can induce a potentiation of muscle motor evoked potentials that outlasts the stimulation by several minutes. In animal models, a direct demonstration of LTP is typically obtained by high-frequency electrical stimulation coupled with local field recordings of population responses. In this study, we exploited a new approach based on combined rTMS/high-density electroencephalography (hd-EEG) to obtain direct, noninvasive evidence for LTP in humans. Cortical responses to single TMS pulses were measured with hd-EEG before and after applying rTMS to motor cortex (5Hz, 1500 pulses). The results demonstrate that, after rTMS, EEG responses at latencies of 15-55ms were significantly potentiated. A topographic analysis revealed that this potentiation was significant at EEG electrodes located bilaterally over premotor cortex. Thus, these findings provide a direct demonstration in humans of LTP induced by rTMS.
Esser
S K
SK
Department of Psychiatry, University of Wisconsin, 6001 Research Park Boulevard, Madison, WI 53719, USA.
Huber
R
R
Massimini
M
M
Peterson
M J
MJ
Ferrarelli
F
F
Tononi
G
G
D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation