Tremor entrainment by patterned low-frequency stimulation (original) (raw)
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Modulation of tremor amplitude during deep brain stimulation at different frequencies
Brain and Cognition, 2003
Rest tremor was quantified in the index finger tip of 16 patients with ParkinsonÕs disease (PD) receiving deep brain stimulation (DBS) of the ventro-intermediate nucleus (Vim) of the thalamus, the subthalamic nucleus (STN), or the internal part of the globus pallidus (GPi) while being off L L -dopa for 12 h. Clinically, without DBS, tremor amplitude varied from absent to high. Tremor was recorded continuously for about 5 min under three conditions of DBS repeated twice, namely, effective frequency (E), ineffective frequency (I), and no DBS (O). No changes in tremor were observed across conditions in subjects with little or no tremor. However, in subjects with moderate to large amplitude tremor, DBS decreased tremor amplitude to near normal values within a few seconds. Generally, transitions were progressive and occurred with a varying time delay. Occasionally, tremor escaped from control regardless of the stimulation condition considered. In some cases tremor amplitude in one condition appeared to depend on the preceding condition. Finally, the results were reproducible on two consecutive days. We conclude that tremor control with DBS follows specific dynamical rules, which must be compatible with the hypotheses proposed regarding the underlying mechanisms of DBS.
BackgroundIn Essential tremor (ET), involuntary shaking of the upper limbs during isometric muscle contraction closely reflects the patterns of neural activity measured in the thalamus - a key element of the tremorgenic circuit. Phase-specific deep brain stimulation (DBS) builds upon this observation while using accelerometery of the trembling limb to trigger repetitive electrical perturbations to the thalamus and surrounding areas at a specific time within the tremor cycle. This closed-loop strategy has been shown to induce clinically significant postural tremor relief while delivering less than half the energy of conventional DBS.ObjectiveThe main aim of the study was to evaluate treatment efficacy across different contexts and movement states.MethodsWe used accelerometery and a digitizing tablet to record the peripheral tremor dynamics of 4 DBS implanted ET patients while alternating stimulation strategies (no stimulation, continuous open-loop and phase-specific) and movement sta...
Short latency activation of cortex by clinically effective thalamic brain stimulation for tremor
Movement Disorders, 2012
Deep brain stimulation relieves disabling symptoms of neurologic and psychiatric diseases when medical treatments fail, yet its therapeutic mechanism is unknown. We hypothesized that ventral intermediate nucleus stimulation for essential tremor activates cortex at short latencies and that this potential is related to suppression of tremor in the contralateral arm. We measured cortical activity with electroencephalography in 5 subjects (7 brain hemispheres) across a range of stimulator settings, and reversal of the anode and cathode electrode contacts minimized the stimulus artifact, allowing visualization of brain activity. Regression quantified the relationship between stimulation parameters and both the peak of the short latency potential and tremor suppression. Stimulation generated a polyphasic event related potential in ipsilateral sensorimotor cortex with peaks at discrete latencies beginning less than one millisecond after stimulus onset (mean latencies 0.9±0.2, 5.6±0.7, and 13.9±1.4 milliseconds, denoted R1, R2, and R3, respectively). R1 showed more fixed timing than the subsequent peaks in the response (p<0.0001, Levene's test), and R1 amplitude and frequency were both closely associated with tremor suppression (p<0.0001, respectively). These findings demonstrate that effective ventral intermediate nucleus thalamic stimulation for essential tremor activates cerebral cortex at approximately one millisecond after the stimulus pulse. The association between this short latency potential and tremor suppression suggests that deep brain stimulation may improve tremor by synchronizing the precise timing of discharges in nearby axons, and by extension the distributed motor network, to the stimulation frequency or one of its subharmonics.
Frontiers in Computational Neuroscience, 2016
Deep brain stimulation (DBS) is an established therapy for movement disorders, including tremor, dystonia, and Parkinson's disease, but the mechanisms of action are not well understood. Symptom suppression by DBS typically requires stimulation frequencies ≥100 Hz, but when the frequency is increased above ∼2 kHz, the effectiveness in tremor suppression declines (Benabid et al., 1991). We sought to test the hypothesis that the decline in efficacy at high frequencies is associated with desynchronization of the activity generated within a population of stimulated neurons. Regularization of neuronal firing is strongly correlated with tremor suppression by DBS, and desynchronization would disrupt the regularization of neuronal activity. We implemented computational models of CNS axons with either deterministic or stochastic membrane dynamics, and quantified the response of populations of model nerve fibers to extracellular stimulation at different frequencies and amplitudes. As stimulation frequency was increased from 2 to 80 Hz the regularity of neuronal firing increased (as assessed with direct estimates of entropy), in accord with the clinical effects on tremor of increasing stimulation frequency (Kuncel et al., 2006). Further, at frequencies between 80 and 500 Hz, increasing the stimulation amplitude (i.e., the proportion of neurons activated by the stimulus) increased the regularity of neuronal activity across the population, in accord with the clinical effects on tremor of stimulation amplitude (Kuncel et al., 2007). However, at stimulation frequencies above 1 kHz the regularity of neuronal firing declined due to irregular patterns of action potential generation and conduction block. The reductions in neuronal regularity that occurred at high frequencies paralleled the previously reported decline in tremor reduction and may be responsible for the loss of efficacy of DBS at very high frequencies. This analysis provides further support for the hypothesis that effective DBS masks the intrinsic patterns of activity in the stimulated neurons and replaces it with regularized firing.
A slow axon antidromic blockade hypothesis for tremor reduction via deep brain stimulation
2013
Parkinsonian and essential tremor can often be effectively treated by deep brain stimulation. We propose a novel explanation for the mechanism by which this technique ameliorates tremor: a reduction of the delay in the relevant motor control loops via preferential antidromic blockade of slow axons. The antidromic blockade is preferential because the pulses more rapidly clear fast axons, and the distribution of axonal diameters, and therefore velocities, in the involved tracts, is sufficiently long-tailed to make this effect quite significant. The preferential blockade of slow axons, combined with gain adaptation, results in a reduction of the mean delay in the motor control loop, which serves to stabilize the feedback system, thus ameliorating tremor. This theory, without any tuning, accounts for several previously perplexing phenomena, and makes a variety of novel predictions. Citation: García MR, Pearlmutter BA, Wellstead PE, Middleton RH (2013) A Slow Axon Antidromic Blockade Hypothesis for Tremor Reduction via Deep Brain Stimulation. PLoS ONE 8(9): e73456.
Proceedings of the IEEE Conference on Decision and Control, 2011
Deep brain stimulation (DBS) has been used to ameliorate essential and Parkinsonian tremor, however the detailed mechanism by which tremor reduction is achieved remains unclear. We hypothesize that DBS works by reducing time delays in the feedback paths of the motor control loops. In particular, we suggest that antidromic activation of axonal pathways induced by stimulation will preferentially block axons with longer propagation times, reducing time delays in neuronal motor circuits in a stabilising manner. We demonstrate the plausibility of this hypothesis using two simple computational models which account for a variety of experimental results, and allow us to makes a number of testable predictions.
Scientific Reports, 2018
Transcranial alternating current stimulation (tACS) is a noninvasive neuromodulation method that can entrain physiological tremor in healthy volunteers. We conducted two experiments to investigate the effectiveness of high-amplitude and focused tACS montages at entraining physiological tremor. Experiment 1 used saline-soaked sponge electrodes with an extra-cephalic return electrode and compared the effects of a motor (MC) and prefrontal cortex (PFC) electrode location. Average peak-amplitude was 1.925 mA. Experiment 2 used gel-filled cup-electrodes in a 4 × 1 focused montage and compared the effects of MC and occipital cortex (OC) tACS. Average peak-amplitude was 4.45 mA. Experiment 1 showed that unfocused MC and PFC tACS both produced phosphenes and significant phase entrainment. Experiment 2 showed that focused MC and OC tACS produced no phosphenes but only focused MC tACS caused significant phase entrainment. At the group level, tACS did not have a significant effect on tremor am...
A method to quantitatively evaluate tremor during deep brain stimulation surgery
2013
Deep brain stimulation (DBS) of basal ganglia using surgically implanted electrodes is now an effective and widely-used method to treat neurological movement related disorders such as Parkinson's Disease (PD) and Essential Tremor (ET). The mechanism of action of DBS is not fully understood; optimal target definition is difficult and thus most groups use complementary intraoperative methods. Intraoperative stimulation tests are performed along the predetermined trajectories to evaluate the clinical effects on tremor while gradually increasing the stimulation parameters (voltage/current), determining the thresholds for clinical effects (subjective threshold) and side effects at each anatomical measurement position. Currently, these evaluations are performed semi quantitatively by the neurosurgeon or the neurologist. Our method intends to improve the targeting procedure and make it more objective by measuring the acceleration of the patient's wrist.
Expert Review of Neurotherapeutics, 2020
Introduction: Essential tremor (ET) is a common movement disorder with an estimated prevalence of 0.9% worldwide. Deep brain stimulation (DBS) is an established therapy for medication refractory and debilitating tremor. With the arrival of next generation technology, the implementation and delivery of DBS has been rapidly evolving. This review will highlight the current applications and constraints for DBS in ET. Areas covered: The mechanism of action, targets for neuromodulation, next generation guidance techniques, symptom specific applications, and long-term efficacy will be reviewed. A c c e p t e d M a n u s c r i p t Expert opinion: The posterior subthalamic area and zona incerta are alternative targets to thalamic DBS in ET. However, they may be associated with additional stimulation induced side effects. Novel stimulation paradigms and segmented electrodes provide innovative approaches to DBS programming and stimulation induced side effects.