Motor Facilitation While Observing Hand Actions: Specificity of the Effect and Role of Observer's Orientation

Action observation enhances cortico-spinal excitability. Here we tested the specificity of this effect and the role played by the orientation of the observer. Ten normal subjects observed video clips of right hand performing three different finger movements ( thumb ab-/adduction, index ab-/adduction, index extens-/flexion) in two different orientations ( Away, i.e., natural hand-orientation facing out from the observer; or Toward, i.e., unnatural hand-orientation facing toward the observer). Motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) were recorded from the abductor pollicis brevis (APB) and the first dorsal interosseus (FDI) muscles. Movement direction of the index finger was recorded using force transducers. Facilitation of MEP size was significantly greater for APB during observation of thumb movements and for FDI during observation of index finger movements. Facilitation of MEP size was significantly greater when the hand presented on screen was facing out from and corresponding to that of the observer (Away orientation). The direction of the index finger movement evoked by TMS shifted toward extension/flexion versus ab-/adduction matching the observed movement. Our results give further evidence that observation of a movement enhances motor output to the muscles involved in the movement and facilitates the observed action. In addition, we provide novel evidence about the high degree of specificity of this observation-induced motor cortical modulation. The degree of modulation depends on hand orientation. The modulation is maximal when the observed action corresponds to the orientation of the observer.

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Motor facilitation during action observation: a magnetic stimulation study

Journal of Neurophysiology ◽

10.1152/jn.1995.73.6.2608 ◽

1995 ◽

Vol 73 (6) ◽

pp. 2608-2611 ◽

Cited By ~ 1386

Author(s):

L. Fadiga ◽

L. Fogassi ◽

G. Pavesi ◽

G. Rizzolatti

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Muscle Activity ◽

Magnetic Stimulation ◽

Motor Evoked Potentials ◽

Action Observation ◽

Normal Subjects ◽

Hand Muscles ◽

3D Objects ◽

The One

1. We stimulated the motor cortex of normal subjects (transcranial magnetic stimulation) while they 1) observed an experimenter grasping 3D-objects, 2) looked at the same 3D-objects, 3) observed an experimenter tracing geometrical figures in the air with his arm, and 4) detected the dimming of a light. Motor evoked potentials (MEPs) were recorded from hand muscles. 2. We found that MEPs significantly increased during the conditions in which subjects observed movements. The MEP pattern reflected the pattern of muscle activity recorded when the subjects executed the observed actions. 3. We conclude that in humans there is a system matching action observation and execution. This system resembles the one recently described in the monkey.

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Comparison of the on-line effects of different motor simulation conditions on corticospinal excitability in healthy participants

Scientific Reports ◽

10.1038/s41598-021-92591-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

C. Pfenninger ◽

S. Grosprêtre ◽

A. Remontet ◽

T. Lapole

Keyword(s):

Motor Evoked Potentials ◽

Action Observation ◽

Corticospinal Excitability ◽

Mirror Therapy ◽

Abductor Pollicis Brevis ◽

M Wave ◽

On Line ◽

Additional Influence ◽

The Right ◽

Healthy Participants

AbstractIn healthy participants, corticospinal excitability is known to increase during motor simulations such as motor imagery (MI), action observation (AO) and mirror therapy (MT), suggesting their interest to promote plasticity in neurorehabilitation. Further comparing these methods and investigating their combination may potentially provide clues to optimize their use in patients. To this end, we compared in 18 healthy participants abductor pollicis brevis (APB) corticospinal excitability during MI, AO or MT, as well as MI combined with either AO or MT. In each condition, 15 motor-evoked potentials (MEPs) and three maximal M-wave were elicited in the right APB. Compared to the control condition, mean normalized MEP amplitude (i.e. MEP/M) increased during MI (P = .003), MT (P < .001) and MT + MI (P < .001), without any difference between the three conditions. No MEP modulation was evidenced during AO or AO + MI. Because MI provided no additional influence when combined with AO or MT, our results may suggest that, in healthy subjects, visual feedback and unilateral movement with a mirror may provide the greatest effects among all the tested motor simulations.

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Context-dependent relationship in high-resolution micro-ECoG studies during finger movements

Journal of Neurosurgery ◽

10.3171/2019.1.jns181840 ◽

2020 ◽

Vol 132 (5) ◽

pp. 1358-1366

Author(s):

Chao-Hung Kuo ◽

Timothy M. Blakely ◽

Jeremiah D. Wander ◽

Devapratim Sarma ◽

Jing Wu ◽

...

Keyword(s):

High Resolution ◽

Sensorimotor Cortex ◽

Index Finger ◽

Hand Movement ◽

Cortical Activation ◽

Hand Movements ◽

Finger Movements ◽

Thumb Movement ◽

Neurosurgical Patients ◽

The Relationship

OBJECTIVEThe activation of the sensorimotor cortex as measured by electrocorticographic (ECoG) signals has been correlated with contralateral hand movements in humans, as precisely as the level of individual digits. However, the relationship between individual and multiple synergistic finger movements and the neural signal as detected by ECoG has not been fully explored. The authors used intraoperative high-resolution micro-ECoG (µECoG) on the sensorimotor cortex to link neural signals to finger movements across several context-specific motor tasks.METHODSThree neurosurgical patients with cortical lesions over eloquent regions participated. During awake craniotomy, a sensorimotor cortex area of hand movement was localized by high-frequency responses measured by an 8 × 8 µECoG grid of 3-mm interelectrode spacing. Patients performed a flexion movement of the thumb or index finger, or a pinch movement of both, based on a visual cue. High-gamma (HG; 70–230 Hz) filtered µECoG was used to identify dominant electrodes associated with thumb and index movement. Hand movements were recorded by a dataglove simultaneously with µECoG recording.RESULTSIn all 3 patients, the electrodes controlling thumb and index finger movements were identifiable approximately 3–6-mm apart by the HG-filtered µECoG signal. For HG power of cortical activation measured with µECoG, the thumb and index signals in the pinch movement were similar to those observed during thumb-only and index-only movement, respectively (all p > 0.05). Index finger movements, measured by the dataglove joint angles, were similar in both the index-only and pinch movements (p > 0.05). However, despite similar activation across the conditions, markedly decreased thumb movement was observed in pinch relative to independent thumb-only movement (all p < 0.05).CONCLUSIONSHG-filtered µECoG signals effectively identify dominant regions associated with thumb and index finger movement. For pinch, the µECoG signal comprises a combination of the signals from individual thumb and index movements. However, while the relationship between the index finger joint angle and HG-filtered signal remains consistent between conditions, there is not a fixed relationship for thumb movement. Although the HG-filtered µECoG signal is similar in both thumb-only and pinch conditions, the actual thumb movement is markedly smaller in the pinch condition than in the thumb-only condition. This implies a nonlinear relationship between the cortical signal and the motor output for some, but importantly not all, movement types. This analysis provides insight into the tuning of the motor cortex toward specific types of motor behaviors.

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Modulation of intracortical inhibition during physically performed and mentally simulated balance tasks

European Journal of Applied Physiology ◽

10.1007/s00421-020-04577-1 ◽

2021 ◽

Vol 121 (5) ◽

pp. 1379-1388

Author(s):

A. Mouthon ◽

J. Ruffieux ◽

W. Taube

Keyword(s):

Motor Evoked Potentials ◽

Action Observation ◽

Short Interval ◽

Intracortical Inhibition ◽

Mental Simulation ◽

Task Execution ◽

Postural Tasks ◽

Execution Condition ◽

The One ◽

Postural Task

Abstract Purpose Action observation (AO) during motor imagery (MI), so-called AO + MI, has been proposed as a new form of non-physical training, but the neural mechanisms involved remains largely unknown. Therefore, this study aimed to explore whether there were similarities in the modulation of short-interval intracortical inhibition (SICI) during execution and mental simulation of postural tasks, and if there was a difference in modulation of SICI between AO + MI and AO alone. Method 21 young adults (mean ± SD = 24 ± 6.3 years) were asked to either passively observe (AO) or imagine while observing (AO + MI) or physically perform a stable and an unstable standing task, while motor evoked potentials and SICI were assessed in the soleus muscle. Result SICI results showed a modulation by condition (F2,40 = 6.42, p = 0.009) with less SICI in the execution condition compared to the AO + MI (p = 0.009) and AO (p = 0.002) condition. Moreover, switching from the stable to the unstable stance condition reduced significantly SICI (F1,20 = 8.34, p = 0.009) during both, physically performed (− 38.5%; p = 0.03) and mentally simulated balance (− 10%, p < 0.001, AO + MI and AO taken together). Conclusion The data demonstrate that SICI is reduced when switching from a stable to a more unstable standing task during both real task execution and mental simulation. Therefore, our results strengthen and further support the existence of similarities between executed and mentally simulated actions by showing that not only corticospinal excitability is similarly modulated but also SICI. This proposes that the activity of the inhibitory cortical network during mental simulation of balance tasks resembles the one during physical postural task execution.

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Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures

Journal of Neurophysiology ◽

10.1152/jn.00620.2018 ◽

2019 ◽

Vol 122 (1) ◽

pp. 413-423 ◽

Cited By ~ 2

Author(s):

Davis A. Forman ◽

Daniel Abdel-Malek ◽

Christopher M. F. Bunce ◽

Michael W. R. Holmes

Keyword(s):

Isometric Contraction ◽

Elbow Joint ◽

Joint Angle ◽

Biceps Brachii ◽

Motor Evoked Potentials ◽

Muscle Length ◽

Elbow Flexion ◽

Corticospinal Excitability ◽

Biceps Brachii Muscle ◽

Spinal Excitability

Forearm rotation (supination/pronation) alters corticospinal excitability to the biceps brachii, but it is unclear whether corticospinal excitability is influenced by joint angle, muscle length, or both. Thus the purpose of this study was to separately examine elbow joint angle and muscle length on corticospinal excitability. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Spinal excitability was measured using cervicomedullary motor evoked potentials (CMEPs) elicited via transmastoid electrical stimulation. Elbow angles were manipulated with a fixed biceps brachii muscle length (and vice versa) across five unique postures: 1) forearm neutral, elbow flexion 90°; 2) forearm supinated, elbow flexion 90°; 3) forearm pronated, elbow flexion 90°; 4) forearm supinated, elbow flexion 78°; and 5) forearm pronated, elbow flexion 113°. A musculoskeletal model determined biceps brachii muscle length for postures 1–3, and elbow joint angles ( postures 4–5) were selected to maintain biceps length across forearm orientations. MEPs and CMEPs were elicited at rest and during an isometric contraction of 10% of maximal biceps muscle activity. At rest, MEP amplitudes to the biceps were largest during supination, which was independent of elbow joint angle. CMEP amplitudes were not different when the elbow was fixed at 90° but were largest in pronation when muscle length was controlled. During an isometric contraction, there were no significant differences across forearm postures for either MEP or CMEP amplitudes. These results highlight that elbow joint angle and biceps brachii muscle length can each independently influence spinal excitability. NEW & NOTEWORTHY Changes in upper limb posture can influence the responsiveness of the central nervous system to artificial stimulations. We established a novel approach integrating neurophysiology techniques with biomechanical modeling. Through this approach, the effects of elbow joint angle and biceps brachii muscle length on corticospinal and spinal excitability were assessed. We demonstrate that spinal excitability is uniquely influenced by joint angle and muscle length, and this highlights the importance of accounting for muscle length in neurophysiological studies.

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Index finger position and force of the human first dorsal interosseus and its ulnar nerve antagonist

Journal of Applied Physiology ◽

10.1152/jappl.1994.77.2.987 ◽

1994 ◽

Vol 77 (2) ◽

pp. 987-997 ◽

Cited By ~ 26

Author(s):

I. Zijdewind ◽

D. Kernell

Keyword(s):

Ulnar Nerve ◽

Index Finger ◽

Maximum Voluntary Contraction ◽

Normal Subjects ◽

Voluntary Contraction ◽

Abduction Angle ◽

Hand Position ◽

First Dorsal Interosseus ◽

Length Analysis ◽

Neutral Angle

In normal subjects, maximum voluntary contraction (MVC) and electrical ulnar nerve stimulation (UNS; 30-Hz bursts of 0.33 s) were systematically compared with regard to the forces generated in different directions (abduction/adduction and flexion) and at different degrees of index finger abduction. With a “resting” hand position in which there was no index finger abduction, UNS produced about one-half of the abduction force elicited by an MVC (mean ratio 51%). Qualitatively, such a discrepancy would be expected, because UNS activates two index finger muscles with opposing actions in the abduction/adduction plane of torques: the first dorsal interosseus (FDI) and the first palmar interosseus (FPI). The abduction forces produced by MVC and UNS were very sensitive to index finger abduction angle: at a maximum degree of abduction, the UNS-generated force even reversed its direction of action to adduction (with FPI dominating) and the abduction MVC declined to 37% of that in the resting hand position. Inasmuch as these declines in MVC- and UNS-generated abduction force could not be explained by a change in moment arm, the main alternative seemed to be abduction-associated alterations in FDI fiber length (analysis by previously published biomechanical data). The FDI and FPI were further compared by application of a UNS-generated fatigue test (5-min burst stimulation), with the index finger kept at a "neutral" angle, i.e., the abduction angle at which, in the unfatigued state, the forces of the FDI and FPI were in balance (zero net UNS-generated abduction/adduction force).(ABSTRACT TRUNCATED AT 250 WORDS)

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Action Observation Treatment-Based Exoskeleton (AOT-EXO) for Upper Extremity After Stroke: Study Protocol for a Randomised Controlled Trial

10.21203/rs.3.rs-58170/v1 ◽

2021 ◽

Author(s):

Zejian Chen ◽

Nan Xia ◽

Chang He ◽

Minghui Gu ◽

Jiang Xu ◽

...

Keyword(s):

Upper Extremity ◽

Functional Disability ◽

Motor Evoked Potentials ◽

Action Observation ◽

Controlled Trial ◽

Measurement Unit ◽

Motor Deficit ◽

Robot Assisted ◽

Clinical Trial Registry ◽

Resting Motor Threshold

Abstract Background Stroke produces multiple symptoms, including sensory, motor, cognitive and psychological dysfunctions, among which motor deficit is the most common and is widely recognized as a major contributor to long-term functional disability. Robot-assisted training is effective in promoting upper extremity muscle strength and motor impairment recovery after stroke. Additionally, action observation treatment can enhance the effects of physical and occupational therapy by increasing neural activation. The AOT-EXO trial aims to investigate whether action observation treatment coupled with robot-assisted training could enhance motor circuit activation and improve upper extremity motor outcomes. Methods The AOT-EXO trial is a multicentre, prospective, three-group randomized controlled trial (RCT). We will screen and enrol 132 eligible patients in the trial implemented in the Department of Rehabilitation Medicine of Tongji Hospital, Optical Valley Branch of Tongji Hospital and Hubei Province Hospital of Integrated Chinese & Western Medicine in Wuhan, China. Prior to study participation, written informed consent will be obtained from eligible patients in accordance with the Declaration of Helsinki. The enrolled stroke patients will be randomised to three groups: the CT group (conventional therapy); EXO group (exoskeleton therapy) and AOT-EXO group (action observation treatment-based exoskeleton therapy). The patients will undergo blinded assessments at baseline, post-intervention (after 4 weeks) and follow-up (after 12 weeks). The primary outcome will be the Fugl-Meyer Assessment for Upper Extremity (FMA-UE). Secondary outcomes will include the Action Research Arm Test (ARAT), modified Barthel Index (MBI), kinematic metrics assessed by inertial measurement unit (IMU), resting motor threshold (rMT), motor evoked potentials (MEP), functional magnetic resonance imaging (fMRI) and safety outcomes. Discussion This trial will provide evidence regarding the feasibility and efficacy of the action observation treatment-based exoskeleton (AOT-EXO) for post-stroke upper extremity rehabilitation and elucidate the potential underlying kinematic and neurological mechanisms. Trial Registration: Chinese Clinical Trial Registry identifier: ChiCTR1900026656. Registered on 17 October 2019.

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Time-dependent modulation of spinal excitability during action observation in the macaque monkey

10.1101/768804 ◽

2019 ◽

Author(s):

S.J. Jerjian ◽

R.N. Lemon ◽

A. Kraskov

Keyword(s):

Pyramidal Tract ◽

Rhesus Macaques ◽

Action Observation ◽

Macaque Monkey ◽

Reach To Grasp ◽

Hand Muscles ◽

Spinal Circuitry ◽

Hand Muscle ◽

Spinal Excitability ◽

Muscle Responses

ABSTRACTNeurons in the primate motor cortex, including identified pyramidal tract neurons projecting to the spinal cord, respond to the observation of others’ actions, yet this does not cause movement in the observer. Here, we investigated changes in spinal excitability during action observation by monitoring short latency electromyographic responses produced by single shocks delivered directly to the pyramidal tract. Responses in hand and digit muscles were recorded from two adult rhesus macaques while they performed, observed or withheld reach-to-grasp and hold actions. We found modest grasp-specific facilitation of hand muscle responses during hand shaping for grasp, which persisted when the grasp was predictable but obscured from the monkey’s vision. We also found evidence of a more general inhibition before observed movement onset, and the size of this inhibition effect was comparable to the inhibition after an explicit NoGo signal. These results confirm that the spinal circuitry controlling hand muscles is modulated during action observation, and this may be driven by internal representations of actions. The relatively modest changes in spinal excitability during observation suggest net corticospinal outflow exerts only minor, sub-threshold changes on hand motoneuron pools, thereby preventing any overflow of mirror activity into overt movement.

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CHEMICAL METHOD FOR THE DETERMINATION OF URINARY ALDOSTERONE

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y57-052 ◽

1957 ◽

Vol 35 (1) ◽

pp. 425-443 ◽

Cited By ~ 5

Author(s):

Wojciech Nowaczynski ◽

Erich Koiw ◽

Jacques Genest

Keyword(s):

Normal Subjects ◽

Ultraviolet Absorption ◽

Anxiety State ◽

High Potassium ◽

High Sodium ◽

Pregnancy Anxiety ◽

Potassium Intake ◽

High Degree ◽

Sodium And Potassium

A new method of purification of crude neutral extracts of urine for the isolation and determination of aldosterone is presented. The specificity and accuracy of the method depend upon the high degree of purity of the aldosterone isolated. The assertion that the substance isolated is aldosterone is based on the mobilities in the three chromatographic systems used, on the typical ultraviolet absorption curve, on the satisfactory agreement between the values obtained by ultraviolet absorption and by blue tetrazolium reaction, and by the typical chromogen spectra in concentrated sulphuric acid and in 100% phosphoric acid. Values obtained in nine normal subjects on ordinary diets vary from 2.2 to 10 μg. per day with a mean of 5.1. Illustrations of results obtained during pregnancy, anxiety state, and periods of high potassium and combined high sodium and potassium intake are presented.

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Spinal excitability is increased in the torque-depressed isometric steady state following active muscle shortening

Royal Society Open Science ◽

10.1098/rsos.171101 ◽

2017 ◽

Vol 4 (11) ◽

pp. 171101 ◽

Cited By ~ 7

Author(s):

Caleb T. Sypkes ◽

Benjamin Kozlowski ◽

Jordan Grant ◽

Leah R. Bent ◽

Chris J. McNeil ◽

...

Keyword(s):

Steady State ◽

Evoked Potentials ◽

Motor Evoked Potentials ◽

Muscle Length ◽

Electromyographic Activity ◽

Active Muscle ◽

Isometric Condition ◽

Compound Muscle Action Potentials ◽

Muscle Shortening ◽

Spinal Excitability

Torque depression (TD) is the reduction in steady-state isometric torque following active muscle shortening when compared with a purely isometric contraction at the same muscle length and level of activation. The purpose of the present study was to assess spinal and supraspinal excitability in the TD state during submaximal contractions of the dorsiflexors. Eleven young (24 ± 2 yrs) males performed 16 contractions at a constant level of electromyographic activity (40% of maximum). Half of the contractions were purely isometric (8 s at an ankle angle of 100°), whereas the other half induced TD (2 s isometric at 140°, a 1 s shortening phase at 40° s −1 and 5 s at 100°). Motor evoked potentials (MEPs), cervicomedullary motor evoked potentials (CMEPs) and compound muscle action potentials (M-waves) were recorded from tibialis anterior during the TD steady-state and purely isometric contractions. When compared with values in the purely isometric condition, following active shortening, there was a 13% decrease in torque ( p < 0.05), with a 10% increase in normalized CMEP amplitude (CMEP/Mmax) ( p < 0.05) and no change in normalized MEP amplitude (MEP/CMEP) in the TD state ( p > 0.05). These findings indicate that during voluntary contractions in the TD state, the history-dependent properties of muscle can increase spinal excitability and influence voluntary control of submaximal torque production.

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