Can a single pulse transcranial magnetic stimulation targeted to the motor cortex interrupt pain processing?

Abstract

The modulatory role of the primary motor cortex (M1), reflected by an inhibitory effect of M1-stimulation on clinical pain, motivated us to deepen our understanding of M1’s role in pain modulation. We used Transcranial Magnetic Stimulation (TMS)-induced virtual lesion (VL) to interrupt with M1 activity during noxious heat pain. We hypothesized that TMS-VL will effect experimental pain ratings. Three VL protocols were applied consisting of single-pulse TMS to transiently interfere with right M1 activity: (1) VLM1- TMS applied to 11 subjects, 20 msec before the individual’s first pain-related M1 peak activation, as determined by source analysis (sLORETA), (2) VL-50 (N = 16; TMS applied 50 ms prior to noxious stimulus onset), and (3) VL+150 (N = 16; TMS applied 150 ms after noxious stimulus onset). Each protocol included 3 conditions ('pain-alone', ' TMS-VL', and ‘SHAM-VL’), each consisted of 30 noxious heat stimuli. Pain ratings were compared, in each protocol, for TMS-VL vs. SHAM-VL and vs. pain-alone conditions. Repeated measures analysis of variance, corrected for multiple comparisons revealed no significant differences in the pain ratings between the different conditions within each protocol. Therefore, our results from this exploratory study suggest that a single pulse TMS-induced VL that is targeted to M1 failed to interrupt experimental pain processing in the specific three stimulation timing examined here.

The “virtual lesion” approach to transcranial magnetic stimulation: studying the brain–behavioral relationships in experimental pain

“…The number of subjects per group ranged from 4 to 30 subjects (a mean of 11.6 ± 5.7). However, only one study 35 performed a power analysis calculation to justify the number of subjects they used in their study. Despite the study cohort including a mean of 50.1% males, the majority of the studies had a sex imbalance.…”

“…In 10 of the within-group design studies, 5,10,16,24,31,41,61,67,68,73 the VL interventions to different brain sites, including sham, were conducted in separate sessions on different days. Moreover, in 12 5,10,16,24,31,35,42,50,61,67,68,73 of the within-subject design studies, the order of the stimulated areas was randomized or counterbalanced among participants.…”

“…The stimulated cortical areas were M1 in 6 studies 23,24,35,50,67,73 ; S1 in 1 study 42 ; sensory-motor cortex (SMC) in 1 study 31 ; secondary somatosensory cortex (S2) in 2 studies 31,42 ; medial frontal cortex (MFC) in 2 studies 31,51 ; dorsolateral PFC (DLPFC) in 5 studies 4,5,16,23,67 ; the vertex in 1 study 23,41 ; and PAR in 2 studies. 61,68 A further 2 studies used for their stimulation protocol the international 10-10 or 10-20 system of cortical electrode placement including frontocentroparietal electrodes 10,75 (Ref.…”

Accuracy in Pinch Force Control Can Be Altered by Static Magnetic Field Stimulation Over the Primary Motor Cortex

“…This difference in results could be because the threshold of modulation in pain perception might be higher than that in motor behavior. Indeed, the virtual lesion technique using single TMS with the intensity of 120% motor threshold for the M1 affects motor behavior but not pain perception . Therefore, the intensity of tSMS might not be sufficient to modulate pain perception.…”

Developing an optimized strategy with transcranial direct current stimulation to enhance the endogenous pain control system in fibromyalgia

“…Tsubokawa et al [35] have shown that chronic epidural stimulation of M1 can be very useful for controlling deafferentation pain secondary to thalamic lesions. The hyperactivity of nociceptive neurons in this kind of central pain is thought to be suppressed by the stimulation of the motor cortex, which not only inhibits burst firing in the vicinity of the damaged thalamus, but also induces neuroplastic effects on the thalamus itself [36].…”