The relation between EMG activity and kinematic parameters strongly supports a role of the action tremor in parkinsonian bradykinesia

Abstract

The kinematics characteristics of an upper arm extension of large amplitude (90°) performed in the horizontal plane and the simultaneous activity of the shoulder muscles were recorded in 12 parkinsonian patients and in six normal control subjects. The movement, triggered by an acoustic “go” signal, was preceded by an isometric adduction. Within the whole population of individuals (n = 18) a strong, positive correlation was observed between the root mean square value of agonist EMG activity, evaluated during the acceleration phase of the movement, and both peak velocity and acceleration. In six patients tremor bursts at the frequency of 8–14 Hz (action tremor) were observed during the movement phase in the anterior, middle, and posterior deltoid: all these patients showed low root mean square values and were bradykinetic with respect to the control subjects. The remaining six patients did not show this action tremor during the movement phase. All but one had an agonist activation of normal duration and amplitude, showed high root mean square values, and performed well in the range of control subjects. We conclude that the inability to suppress the activity of pathological oscillator(s) responsible for the action tremor plays a fundamental role in the bradykinesia associated with Parkinson's disease. Mov. Disord. 16:47–57, 2001. © 2001 Movement Disorder Society.

Motor behaviors in the sheep evoked by electrical stimulation of the subthalamic nucleus

“…In contrast, fixed opening or closing of the eyelid evoked by high frequency stimulation was associated with tonic highamplitude EMG activity ( Figure 9C). Spectral analysis of the EMG activity evoked by low frequency stimulation detected several high-power peaks in the 2-20 Hz range (Figure 9D, which is consistent with physiological tremor [38][39][40]. No high-power peaks within this frequency range were detected in the spontaneous activity or in the activity evoked by 180 Hz stimulation ( Figure 9D).…”

“…In the current study, low-frequency (5-30 Hz) stimulation also evoked movements in the sheep that were phenomenologically consistent with human tremor and dyskinesia. EMG recordings of the stimulation-evoked tremor-like movements in the sheep revealed that the underlying muscle activity was similar to that associated with human tremor [38][39][40]. Most of the EMG activity also occurred at the stimulation frequency or an octave, which is reminiscent of the…”

“…Fast Fourier Transformations (FFT) of the EMG amplitude RMS data consistently revealed several prominent low-frequency peaks, from ~2-30 Hz, in recordings during low-frequency stimulation but not during high frequency stimulation or no stimulation (see Figure 9). To analyze tremor-like EMG activity, average power within the 2-20 Hz range was calculated and expressed as a percentage of the 2-20 Hz power average without stimulation because this frequency range is consistent with physiological tremor [38][39][40]. All analyses were performed using the statistical software package Statview (SAS Institute, Cary, NC).…”

Power spectral density analysis of physiological, rest and action tremor in Parkinson’s disease patients treated with deep brain stimulation

“…In contrast, according to Findley et al [3] and Wenzelburger et al [9] a different pathophysiology of oscillations during motion must be considered compared to the generation of tremor at rest, and they hypothesized that action tremor is an exaggeration of physiological tremor. In differentiating between rest and action tremor Carboncini et al [11] propose the concept of pathological oscillators of central origin [12], which can be differentially recruited according to the behavioural condition. They conclude that the inability to suppress the activity of pathological oscillator(s) responsible for the action tremor plays a fundamental role in the bradykinesia associated with PD [11].…”

“…In differentiating between rest and action tremor Carboncini et al [11] propose the concept of pathological oscillators of central origin [12], which can be differentially recruited according to the behavioural condition. They conclude that the inability to suppress the activity of pathological oscillator(s) responsible for the action tremor plays a fundamental role in the bradykinesia associated with PD [11]. …”