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Suppression of enhanced physiological tremor via stochastic noise: initial observations.

Trenado C, Amtage F, Huethe F, Schulte-Mönting J, Mendez-Balbuena I, Baker SN, Baker M, Hepp-Reymond MC, Manjarrez E, Kristeva R - PLoS ONE (2014)

Bottom Line: Two different conditions were compared: with and without superimposed noise at optimal amplitude (determined at the beginning of the experiment).The application of optimum noise reduced tremor (accelerometric amplitude and EMG activity) and improved the motor performance (reduced mean absolute deviation from zero).These data provide the first evidence of a significant reduction of enhanced physiological tremor in the human sensorimotor system due to application of external stochastic noise.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology and Neurophysiology, University Freiburg, Freiburg, Germany.

ABSTRACT
Enhanced physiological tremor is a disabling condition that arises because of unstable interactions between central tremor generators and the biomechanics of the spinal stretch reflex. Previous work has shown that peripheral input may push the tremor-related spinal and cortical systems closer to anti-phase firing, potentially leading to a reduction in tremor through phase cancellation. The aim of the present study was to investigate whether peripherally applied mechanical stochastic noise can attenuate enhanced physiological tremor and improve motor performance. Eight subjects with enhanced physiological tremor performed a visuomotor task requiring the right index finger to compensate a static force generated by a manipulandum to which Gaussian noise (3-35 Hz) was applied. The finger position was displayed on-line on a monitor as a small white dot which the subjects had to maintain in the center of a larger green circle. Electromyogram (EMG) from the active hand muscles and finger position were recorded. Performance was measured by the mean absolute deviation of the white dot from the zero position. Tremor was identified by the acceleration in the frequency range 7-12 Hz. Two different conditions were compared: with and without superimposed noise at optimal amplitude (determined at the beginning of the experiment). The application of optimum noise reduced tremor (accelerometric amplitude and EMG activity) and improved the motor performance (reduced mean absolute deviation from zero). These data provide the first evidence of a significant reduction of enhanced physiological tremor in the human sensorimotor system due to application of external stochastic noise.

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Experimental setup.(A) Home-made index finger manipulandum producing a target static force (8% of individual maximum voluntary contraction) on which noise in the frequency bandwidth 3–35 Hz is added. Profile of the target static force in E and F. EMG from the right first dorsal interosseus (FDI), the right flexor digitorum superficialis (FDS) and the right extensor digitorum communis (EDC) muscles were recorded. (B) Visual feedback of the finger position as a solid white dot within a green circle indicating the tolerance for position errors, displayed on a monitor in front of the subject. (C) Spectral power of the noise of the manipulandum in arbitrary units (au) for the frequency bandwidths 3–35 Hz). (D) Effect of the stochastic resonance (SR) on the motor performance of one subject recorded prior to the experimental session and computed as the inverse of the mean absolute deviation (1/MAD) of the finger position. Note the inverted U-shape like curve. During the experiment only two noise levels were individually chosen, i. e. zero noise (ZN, black filled dots) and optimal noise (ON, red filled dots). (E, F) Original signals for target force and finger position (representing the exerted force) for ZN (E) and ON (F). Transitory phase of the task between markers T0 and T1 and stationary phase between markers T1 and T2. Only data belonging to the stationary part of the force (between T1 and T2) was taken for the analysis. Note in the magnified position traces the better performance for ON than for ZN.
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pone-0112782-g001: Experimental setup.(A) Home-made index finger manipulandum producing a target static force (8% of individual maximum voluntary contraction) on which noise in the frequency bandwidth 3–35 Hz is added. Profile of the target static force in E and F. EMG from the right first dorsal interosseus (FDI), the right flexor digitorum superficialis (FDS) and the right extensor digitorum communis (EDC) muscles were recorded. (B) Visual feedback of the finger position as a solid white dot within a green circle indicating the tolerance for position errors, displayed on a monitor in front of the subject. (C) Spectral power of the noise of the manipulandum in arbitrary units (au) for the frequency bandwidths 3–35 Hz). (D) Effect of the stochastic resonance (SR) on the motor performance of one subject recorded prior to the experimental session and computed as the inverse of the mean absolute deviation (1/MAD) of the finger position. Note the inverted U-shape like curve. During the experiment only two noise levels were individually chosen, i. e. zero noise (ZN, black filled dots) and optimal noise (ON, red filled dots). (E, F) Original signals for target force and finger position (representing the exerted force) for ZN (E) and ON (F). Transitory phase of the task between markers T0 and T1 and stationary phase between markers T1 and T2. Only data belonging to the stationary part of the force (between T1 and T2) was taken for the analysis. Note in the magnified position traces the better performance for ON than for ZN.

Mentions: During the experiment, the patient sat in an electrically shielded, dimly lit room. The right arm was supported by a splint and the subject was instructed to place the right hand over a sphere and the index finger in the ring of a custom-made manipulandum (seeFig. 1A).


Suppression of enhanced physiological tremor via stochastic noise: initial observations.

Trenado C, Amtage F, Huethe F, Schulte-Mönting J, Mendez-Balbuena I, Baker SN, Baker M, Hepp-Reymond MC, Manjarrez E, Kristeva R - PLoS ONE (2014)

Experimental setup.(A) Home-made index finger manipulandum producing a target static force (8% of individual maximum voluntary contraction) on which noise in the frequency bandwidth 3–35 Hz is added. Profile of the target static force in E and F. EMG from the right first dorsal interosseus (FDI), the right flexor digitorum superficialis (FDS) and the right extensor digitorum communis (EDC) muscles were recorded. (B) Visual feedback of the finger position as a solid white dot within a green circle indicating the tolerance for position errors, displayed on a monitor in front of the subject. (C) Spectral power of the noise of the manipulandum in arbitrary units (au) for the frequency bandwidths 3–35 Hz). (D) Effect of the stochastic resonance (SR) on the motor performance of one subject recorded prior to the experimental session and computed as the inverse of the mean absolute deviation (1/MAD) of the finger position. Note the inverted U-shape like curve. During the experiment only two noise levels were individually chosen, i. e. zero noise (ZN, black filled dots) and optimal noise (ON, red filled dots). (E, F) Original signals for target force and finger position (representing the exerted force) for ZN (E) and ON (F). Transitory phase of the task between markers T0 and T1 and stationary phase between markers T1 and T2. Only data belonging to the stationary part of the force (between T1 and T2) was taken for the analysis. Note in the magnified position traces the better performance for ON than for ZN.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232445&req=5

pone-0112782-g001: Experimental setup.(A) Home-made index finger manipulandum producing a target static force (8% of individual maximum voluntary contraction) on which noise in the frequency bandwidth 3–35 Hz is added. Profile of the target static force in E and F. EMG from the right first dorsal interosseus (FDI), the right flexor digitorum superficialis (FDS) and the right extensor digitorum communis (EDC) muscles were recorded. (B) Visual feedback of the finger position as a solid white dot within a green circle indicating the tolerance for position errors, displayed on a monitor in front of the subject. (C) Spectral power of the noise of the manipulandum in arbitrary units (au) for the frequency bandwidths 3–35 Hz). (D) Effect of the stochastic resonance (SR) on the motor performance of one subject recorded prior to the experimental session and computed as the inverse of the mean absolute deviation (1/MAD) of the finger position. Note the inverted U-shape like curve. During the experiment only two noise levels were individually chosen, i. e. zero noise (ZN, black filled dots) and optimal noise (ON, red filled dots). (E, F) Original signals for target force and finger position (representing the exerted force) for ZN (E) and ON (F). Transitory phase of the task between markers T0 and T1 and stationary phase between markers T1 and T2. Only data belonging to the stationary part of the force (between T1 and T2) was taken for the analysis. Note in the magnified position traces the better performance for ON than for ZN.
Mentions: During the experiment, the patient sat in an electrically shielded, dimly lit room. The right arm was supported by a splint and the subject was instructed to place the right hand over a sphere and the index finger in the ring of a custom-made manipulandum (seeFig. 1A).

Bottom Line: Two different conditions were compared: with and without superimposed noise at optimal amplitude (determined at the beginning of the experiment).The application of optimum noise reduced tremor (accelerometric amplitude and EMG activity) and improved the motor performance (reduced mean absolute deviation from zero).These data provide the first evidence of a significant reduction of enhanced physiological tremor in the human sensorimotor system due to application of external stochastic noise.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology and Neurophysiology, University Freiburg, Freiburg, Germany.

ABSTRACT
Enhanced physiological tremor is a disabling condition that arises because of unstable interactions between central tremor generators and the biomechanics of the spinal stretch reflex. Previous work has shown that peripheral input may push the tremor-related spinal and cortical systems closer to anti-phase firing, potentially leading to a reduction in tremor through phase cancellation. The aim of the present study was to investigate whether peripherally applied mechanical stochastic noise can attenuate enhanced physiological tremor and improve motor performance. Eight subjects with enhanced physiological tremor performed a visuomotor task requiring the right index finger to compensate a static force generated by a manipulandum to which Gaussian noise (3-35 Hz) was applied. The finger position was displayed on-line on a monitor as a small white dot which the subjects had to maintain in the center of a larger green circle. Electromyogram (EMG) from the active hand muscles and finger position were recorded. Performance was measured by the mean absolute deviation of the white dot from the zero position. Tremor was identified by the acceleration in the frequency range 7-12 Hz. Two different conditions were compared: with and without superimposed noise at optimal amplitude (determined at the beginning of the experiment). The application of optimum noise reduced tremor (accelerometric amplitude and EMG activity) and improved the motor performance (reduced mean absolute deviation from zero). These data provide the first evidence of a significant reduction of enhanced physiological tremor in the human sensorimotor system due to application of external stochastic noise.

Show MeSH
Related in: MedlinePlus