Search

Background: Low-frequency rTMS can induce upregulation of excitability in the contralateral hemisphere by interhemispheric interaction. Objective: The aim of this study was to compare the effects of interhemispheric modulation on hemodynamic changes after applying low-frequency rTMS over the anatomical hand knob (HK) and the hand motor hotspot (hMHS) in the dominant motor cortex. Methods: Ten healthy right-handed participants without a history of neurological or psychiatric symptoms (five males; 29.8±2.8 years) participated in this single-blind, randomized, cross-over study. rTMS was applied under three conditions over the dominant (left) hemisphere for 20 minutes: 1) 1 Hz rTMS stimulation on the HK (HK-rTMS), 2) 1 Hz rTMS stimulation on the hMHS (hMHS-rTMS), and 3) sham stimulation (Sham-rTMS). For all participants, functional near-infrared spectroscopy (fNIRS) was applied for measurement of cerebral oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) concentration over the non-dominant (right) hemisphere during a serial reaction time task (SRTT) with the non-dominant (left) hand before and after each condition. Results: The average coordinates of the hMHS (x = – 39.60 mm, y = – 17.11 mm, z = 66.40 mm) were anterior and lateral to the HK (x = – 36.72 mm, y = – 28.87 mm, z = 56.41 mm). In fNIRS time-series analysis, the integral value of oxyHb was significantly increased over the motor cortical region of the non-dominant hemisphere after the hMHS-rTMS compared with Sham-rTMS. The HK-rTMS also showed slight increment of oxyHb concentration but without statistical significance. The SPM group analysis showed greater magnitude of the activity in hMHS-rTMS than that of HK-rTMS after stimulation (p < 0.05). Conclusions: These results demonstrated an interhemispheric modulation effect of hemodynamic changes by 1 Hz rTMS. The hMHS produced a more robust modulation effect of 1 Hz rTMS on the contralateral hemisphere than did the HK. Therefore, the rTMS can be considered a better stimulation target than the HK. [ABSTRACT FROM AUTHOR]

Objectives To confirm the interhemispheric modulation induced by low-frequency repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex, real-time regional cerebral blood flow (rCBF) was assessed using functional near-infrared spectroscopy (fNIRS) in the contralateral primary motor cortex (M1) and premotor cortex (PM). Methods Ten right-handed healthy subjects completed two experimental sessions that were randomly arranged for real or sham rTMS session. In the real rTMS session, fNIRS data were acquired from the right M1 and PM area, while the motor hot spot of the left M1 was stimulated with 1 Hz rTMS for 1200 pulses with two boosters. In the sham stimulation session, stimulation was delivered with a disconnected coil. Results During the real rTMS session, the concentration of oxyhemoglobin ([oxy-Hb]) in the right M1 increased continuously until the end of the stimulation. These changes lasted for 20 min, while the right PM did not show a change in [oxy-Hb] concentration. On the other hand, the concentration of deoxy-hemoglobin ([deoxy-Hb]) decreased continuously in the right M1 and PM during the real rTMS stimulation, and this change lasted for 20 min after the stimulation. The sham stimulation did not exhibit any significant change in both [oxy-Hb] and [deoxy-Hb] concentration during or after the stimulation. Conclusions Application of 1 Hz rTMS over M1 resulted in changes of rCBF in contralateral M1 and PM, which seemed to constitute a function of interhemispheric modulation of rTMS. The fNIRS data was able to detect this physiological change of neuromodulatory action of rTMS in real-time. [ABSTRACT FROM AUTHOR]

• Effects of rTMS target site on motor function were investigated in healthy subjects. • Changes of motor functional outcomes by targeting methods were examined. • Hand motor hotspot was located anteriorly and laterally than anatomical hand knob. • Application of 1 Hz rTMS on hand motor hotspot was more effective than hand knob. Repetitive transcranial magnetic stimulation (rTMS) is used to modulate neuronal excitability of the human brain. Distant effects on contralateral corticomotor excitability can be exerted by interhemispheric modulation by low-frequency rTMS on ipsilateral hemisphere. To modulate corticospinal excitability, accurate determination of the stimulation site is important to maximize the effects of rTMS. In the present study, we investigated the difference in the distant effect of 1 Hz rTMS with respect to inducing functional improvement in the non-dominant hand by inhibiting the dominant hemisphere depending on cortical target areas. Ten healthy right-handed volunteers without any neurological disorders were enrolled. The anatomical hand knob (HK) identified from individual magnetic resonance imaging and the transcranial magnetic stimulation (TMS) induced hand motor hotspot (hMHS) by recording motor evoked potentials (MEPs) in the contralateral first dorsal interosseous muscle were determined. All participants underwent three conditions of 1 Hz rTMS on left hemisphere intervention; rTMS application over the HK, rTMS application over the hMHS, and sham-rTMS. Before and after each intervention, all participants undergone motor function assessments with their left hand. The cortical mapping showed that the hMHS was located anteriorly and laterally compared to the HK. Motor function tests showed the most significant improvements after the hMHS stimulation. When we compared the distant effects of target site on corticospinal excitability and motor behavior, delivering 1 Hz rTMS to the hMHS was more effective than delivering it to the HK for improving corticomotor excitability, motor skill, and dexterity. These results suggest that TMS-induced hMHS is an optimal target area to induce distant effect of low-frequency rTMS in motor function. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effects of simultaneous, bihemispheric, dual-mode stimulation using repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) on motor functions and cortical excitability in healthy individuals., Methods: Twenty-five healthy, right-handed volunteers (10 men, 15 women; mean age, 25.5 years) were enrolled. All participants received four randomly arranged, dual-mode, simultaneous stimulations under the following conditions: condition 1, high-frequency rTMS over the right primary motor cortex (M1) and sham tDCS over the left M1; condition 2, high-frequency rTMS over the right M1 and anodal tDCS over the left M1; condition 3, high-frequency rTMS over the right M1 and cathodal tDCS over the left M1; and condition 4, sham rTMS and sham tDCS. The cortical excitability of the right M1 and motor functions of the left hand were assessed before and after each simulation., Results: Motor evoked potential (MEP) amplitudes after stimulation were significantly higher than before stimulation, under the conditions 1 and 2. The MEP amplitude in condition 2 was higher than both conditions 3 and 4, while the MEP amplitude in condition 1 was higher than condition 4. The results of the Purdue Pegboard test and the box and block test showed significant improvement in conditions 1 and 2 after stimulation., Conclusion: Simultaneous stimulation by anodal tDCS over the left M1 with high-frequency rTMS over the right M1 could produce interhemispheric modulation and homeostatic plasticity, which resulted in modulation of cortical excitability and motor functions.