Hz Magnetic Stimulation Research Articles

Effect of rTMS intervention on upper limb motor function after stroke: A study based on fNIRS.

Stroke is a disease with a high fatality rate worldwide and a major cause of long-term disability. In the rehabilitation of limb motor function after stroke, the rehabilitation of upper limb function takes a long time and the recovery progress is slow, which seriously affects the patients' self-care ability in daily life. Repeated transcranial magnetic stimulation (rTMS) has been increasingly used to improve limb dysfunction in patients with stroke. However, a standardized reference for selecting a magnetic stimulation regimen is not available. Whether to increase the inhibition of the contralateral hemispheric motor cortex remains controversial. This study has evaluated the effects of different rTMS stimulation programs on upper limb function and corresponding brain functional network characteristics of patients with stroke and sought a new objective standard based on changes in brain network parameters to guide accurate rTMS stimulation programs. Thirty-six patients with stroke were selected and divided into control group and treatment group by number table method, with 18 patients in each group, and 3 patients in the control group were turned out and lost due to changes in disease condition. The treatment group was divided into two groups. TMS1 group was given 1 Hz magnetic stimulation in the M1 region of the contralesional hemisphere +10 Hz magnetic stimulation in the M1 region of the affected hemisphere, and the TMS2 group was given 10 Hz magnetic stimulation in the M1 region of the affected hemisphere. The control group was given false stimulation. The treatment course was once a day for 5 days a week for 4 weeks. The Fugl-Meyer Assessment for upper extremity (FMA-UE) sand near-infrared brain function were collected before treatment, 2 weeks after treatment, and 4 weeks after treatment, and the brain function network was constructed. Changes in brain oxygenated hemoglobin concentration and brain network parameters were analyzed with the recovery of motor function (i.e., increased FMA score). Meanwhile, according to the average increment of brain network parameters, the rTMS stimulation group was divided into two groups with good efficacy and poor efficacy. Network parameters of the two groups before and after rTMS treatment were analyzed statistically. (1) Before treatment, there was no statistical difference in Fugl-Meyer score between the control group and the magnetic stimulation group (p = 0.178).Compared with before treatment, Fugl-Meyer scores of 2 and 4 weeks after treatment were significantly increased in both groups (p <0.001), and FMA scores of 4 weeks after treatment were significantly improved compared with 2 weeks after treatment (p < 0.001). FMA scores increased faster in the magnetic stimulation group at 2 and 4 weeks compared with the control group at the same time point (p <0.001).TMS1 and TMS2 were compared at the same time point, FMA score in TMS2 group increased more significantly after 4 weeks of treatment (p = 0.010). (2) Before treatment, HbO2 content in healthy sensory motor cortex (SMC) area of magnetic stimulation group and control group was higher than that in other region of interest (ROI) area, but there was no significant difference in ROI between the two groups. After 4 weeks of treatment, the HbO2 content in the healthy SMC area was significantly decreased (p < 0.001), while the HbO2 content in the affected SMC area was significantly increased, and the change was more significant in the magnetic stimulation group (p < 0.001). (3) In-depth study found that with the recovery of motor function (FMA upper limb score increase ≥4 points) after magnetic stimulation intervention, brain network parameters were significantly improved. The mean increment of network parameters in TMS1 group and TMS2 group was significantly different (χ 2 = 5.844, p = 0.016). TMS2 group was more advantageous than TMS1 group in improving the mean increment of brain network parameters. (1) The rTMS treatment is beneficial to the recovery of upper limb motor function in stroke patients, and can significantly improve the intensity of brain network connection and reduce the island area. The island area refers to an isolated activated brain area that cannot transmit excitation to other related brain areas. (2) When the node degree of M1_Healthy region less than 0.52, it is suggested to perform promotion therapy only in the affected hemisphere. While the node degree greater than 0.52, and much larger than that in the M1_affected region. it is suggested that both inhibition in the contralesional hemisphere and high-frequency excitatory magnetic stimulation in the affected hemisphere can be performed. (3) In different brain functional network connection states, corresponding adjustment should be made to the treatment plan of rTMS to achieve optimal therapeutic effect and precise rehabilitation treatment.

Using repetitive paired-pulse transcranial magnetic stimulation for evaluation motor cortex excitability

In this study, we investigated the effects of repetitive paired-pulse transcranial magnetic stimulation (TMS) on the motor cortex excitability. The interstimulus intervals (ISIs) between the conditioning (first) stimulus and test (second) stimulus were 1,000, 200 and 100 ms. A total of 20 stimuli were delivered to the primary motor cortex using paired-pulse TMS at 10 s intervals, and the intensity of the magnetic stimulus was 110% of the resting motor threshold for each subject. For all ISIs, there was no significant correlation between the number of stimuli and the motor evoked potential (MEP) amplitude. However, there was slight correlation between the number of stimuli and the MEP amplitude in the 200 and 100 ms ISIs (200 and 100 ms ISIs: approximately r = −0.40; 1,000 ms ISI: r = −0.17). In addition, MEP amplitude increased during the second paired pulse stimulation when an ISI of 200 ms was used, but it decreased dramatically when an ISI of 100 ms was used. In contrast, MEP amplitude did not change significantly when a 1,000 ms ISI was employed. Therefore, 10 consecutive paired-pulse TMS stimuli with a 1,000 ms ISI may not have a cumulative effect on cortical excitability. Previous studies used a long duration (e.g., 6 minutes or longer by 0.1 Hz magnetic stimulation) of magnetic stimulation to evaluate cortical excitability. In evaluating cortical excitability by magnetic stimulation, it is important to shorten the period to reduce the subject’s burden and to prevent body movement. Thus, our present findings suggest that repetitive paired-pulse TMS with an ISI of 1,000 ms is suitable for the rapid evaluation of cortical excitability.

Low-Frequency Pulsed Magnetic Field Improves Depression-Like Behaviors and Cognitive Impairments in Depressive Rats Mainly via Modulating Synaptic Function.

Transcranial magnetic stimulation (TMS) has shown great promise as a medical treatment of depression. The effectiveness of TMS treatment at high frequency has been well investigated; however, low-frequency TMS in depression treatment has rarely been investigated in depression-induced cognitive deficits. Herein, this study was carried out to assess the possible modulatory role of low-frequency pulsed magnetic field (LFPMF) on reversing cognitive impairment in a model of depression induced by chronic unpredictable stress (CUS). Wistar rats were randomly allocated into four groups as follows: a control group (CON), a control applied with LFPMF (CON + LFPMF), a CUS group, and a CUS treated with LFPMF (CUS + LFPMF) group. During 8 weeks of CUS, compared to those in the CON group, animals not only gained less weight but also exhibited anhedonia, anxiety, and cognitive decline in behavioral tests. After 2-week treatment of LFPMF, a 20 mT, 1 Hz magnetic stimulation, it reversed the impairment of spatial cognition as well as hippocampal synaptic function including long-term potentiation and related protein expression. Thus, LFPMF has shown effectively improvements on depressant behavior and cognitive dysfunction in CUS rats, possibly via regulating synaptic function.

Alterations in Motor Cortical Excitability Induced by Peripheral Stimulation With Magnetic Stimulation

The conditioning of cortical excitability by transcranial magnetic stimulation (TMS) has become a valuable technique to promote recovery of motor function after stroke. As TMS is not used in all patients, we investigated the hypothesis that peripheral stimulation may have an adjustment effect on motor cortical excitability. Our experimental paradigm was divided into three phases. In the first phase, TMS was delivered to the left or right primary motor cortex to induce a motor evoked potential (MEP) from the contralateral first dorsal interosseous muscle. The measured MEPs in this phase were used to evaluate the effect of peripheral stimulation. In the second phase, 1 Hz magnetic stimulation was applied over the contralateral or ipsilateral forearm for motor cortex as peripheral stimulation. In the third phase, the MEP was evoked by TMS and recorded using the same setting as the first phase. We found that a decrease in MEP amplitude was observed in the left motor cortex following peripheral stimulation over the right forearm. By contrast, the MEP amplitude was not altered in the right motor cortex by peripheral stimulation over the left forearm. An increase in MEP amplitude was observed in the ipsilateral motor cortex induced by peripheral stimulation over the left or right forearm. We also found that by changing the MEP amplitude, the motor cortex excitability varied according to magnetic stimulation of the forearm. These data suggest that peripheral stimulation may have an adjustment effect on motor cortical excitability, via changes in the stimulus site.

Magnetic Field Projector for Deep Brain Stimulation

Deep brain stimulation (DBS) is an established surgical therapy for treatment of a number of neurological and neuropsychiatric disorders based on the modulation of neuronal firing deep in the brain. However, the delicate surgical operation and extremely expensive cost of the current DBS technology impede its wide applications. For non-invasive brain stimulation, transcranial magnetic stimulation and transcranial direct current stimulation have been tried in various therapeutic applications with little success due to two major imitations with their applied electromagnetic field: 1) the field does not focus on targeted brain functional sites, and 2) the field penetration depth is too shallow to be effective in stimulating targeted brain functional sites. In this paper, a novel magnetic field projector (MFP) capable of magnetically inducing deep brain modulation of neuronal firing is presented. The MFP projects a focused magnetic field to deep brain regions while suppressing the field on the scalp. The field penetration depth can be adjusted by configuring the structure parameters of the device as well as the excitation pulse current amplitude. An MFP prototype has been developed and tested on rats to modulate upward the neuronal firing frequency at the brain functional site ventrolateral preoptic nucleus for sleep induction, with the brain responses measured by EEG. The results showed that EEG sleep spindles were induced by a train of 9 Hz magnetic stimulation pulses for 10 s.

Change of Cognition Effects by Impact of the Transcranial Magnetic Stimulation

The purpose of this paper is to investigate the effects of sub- or supra-threshold low-frequency repetitive transcranial magnetic stimulation (rTMS) on cognitive function. The magnetic stimulation was delivered at 1 Hz to the left supramarginal gyrus, which is considered to be the area of origin of the P300 event-related potential component. The intensity of magnetic stimulation was 80% or 120% of motor threshold, and 100 magnetic pulses were applied. The auditory oddball task, consisting of tone burst waves, was used to elicit P300 before and shortly after magnetic stimulation. We found that P300 latency depended on the intensity of the 1 Hz magnetic stimulation. With subthreshold rTMS, P300 latency was significantly shortened compared with before magnetic stimulation by around 10 ms (Cz: p<;0.05) on average. With the suprathreshold rTMS, the latency was significantly delayed compared with before magnetic stimulation by around 10 ms (Cz: p<; 0.01) on average. The facilitation of cortical excitability by rTMS may induce the shortening of P300 latency, whereas the inhibition of cortical excitability may induce its delay. Thus, P300 latency can be altered by both sub- and supra-threshold low-frequency magnetic stimulation.

Brain Responses Evoked by Different-Frequency Magnetic Stimulation at an Acupuncture Point

Time-varying magnetic stimulation can induce electric fields in the neuronal tissues and has been increasingly used in medical researches and clinical applications, such as peripheral nerve stimulation and transcranial magnetic stimulation. An acupuncture point (called acupoint) is a specific point in the human body with high sensitivity to various stimuli. In this paper, different-frequency magnetic stimulation was used to stimulate the Neiguan (PC6) acupoint. The 64 channel electroencephalogram (EEG) signals were recorded before, during, and after stimulation to determine whether magnetic stimulation at PC6 point would modulate cortex excitability and whether the frequency parameter would impact stimulation effects. The results showed that when the stimulation frequency was 0.5 Hz, the amplitudes of brain evoked potentials were much bigger and more cortex areas were activated. It suggested that 0.5 Hz magnetic stimulation at the PC6 acupoint could possess more complicated effects.

Modulation of frequency and duration of repetitive magnetic stimulation affects catecholamine levels and tyrosine hydroxylase activity in human neuroblastoma cells: implication for the antidepressant effect of rTMS.

Transcranial magnetic stimulation (TMS), which is produced by strong non-static magnetic fields, is a non-invasive means to stimulate the cerebral cortex. Studies from recent years show that TMS affects mood in healthy subjects and improves depressive symptoms in patients with major depression. However, the relationship between the clinical efficacy of TMS and stimulation parameters is still obscure. In the present study we have investigated the effects of different stimulation frequencies and number of treatments on catecholamine turnover in SH-SY5Y cell cultures. A single session of magnetic stimulation (1.7 T) caused a significant decrease in intracellular dopamine and L-DOPA and in noradrenaline (NE) release at a rate of 3 Hz for 10 s but increased NE release at a rate of 9 Hz. These alterations were associated with a reduction (47.8%) or an increase (48%) in tyrosine hydroxylase (TH) activity after 3 and 9 Hz magnetic stimulation, respectively. The latter may be related to the known sensitivity of TH to neuronal firing rates and NE concentrations. Higher stimulation frequencies (15, 20, 45 Hz) had no effect on catecholamine metabolism. Unlike 3 Hz acute treatment, chronic treatment (3 Hz, 11 sessions, for 4 d) had no effect on monoamines and TH activity was increased by 54.5% with no change in its protein level. The results of the present study demonstrate that in tissue culture system frequency and treatment duration of the magnetic stimulation are important factors in affecting catecholamine turnover. Considering the major role of catecholamine in the pathophysiology of depression, these findings may be of relevance to the application of rTMS in humans with major depression.

Transcranial magnetic stimulation over the cerebellum evokes late potential in the soleus muscle

Transcranial magnetic stimulation (TMS) with a double cone coil placed over the left lateral side of the basal occiput was able to elicit late electromyographic (EMG) responses at the bilateral soleus muscles (SOL) averaged over 30 stimulation events, with a mean latency of approximately 100 ms. These EMG responses were detected using a low frequency bandpass filter with 0.05 Hz magnetic stimulation on ten healthy subjects in standing posture. As magnetic stimulation over the left basal occiput with a double cone coil can stimulate cerebellar structure, this late response seems to be conducted from the cerebellar structure to the SOL via an as yet unknown descending pathway. Here, we report new late EMG responses in relation to cerebellum or cerebellum related structures.