Startle reveals independent preparation and initiation of triphasic EMG burst components in targeted ballistic movements

2013 ◽  
Vol 110 (9) ◽  
pp. 2129-2139 ◽  
Author(s):  
Christopher J. Forgaard ◽  
Dana Maslovat ◽  
Anthony N. Carlsen ◽  
Romeo Chua ◽  
Ian M. Franks
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Acoustic Stimulus ◽  
Elbow Extension ◽  
Movement Onset ◽  
Startling Acoustic Stimulus ◽  
Agonist And Antagonist ◽  
Triphasic Pattern ◽  
Ballistic Movements ◽  
Close Temporal Proximity

Muscles involved in rapid, targeted movements about a single joint often display a triphasic [agonist (AG1)-antagonist (ANT)-agonist (AG2)] electromyographic (EMG) pattern. Early work using movement perturbations suggested that for short movements, the entire EMG pattern was prepared and initiated in advance (Wadman WJ, Dernier van der Gon JJ, Geuze RH, Mol CR. J Hum Mov Stud 5: 3–17, 1979), whereas more recent transcranial magnetic stimulation evidence indicates that the ANT may be programmed separately (MacKinnon CD, Rothwell JC. J Physiol 528: 633–645, 2000) with execution of the bursts occurring serially (Irlbacher K, Voss M, Meyer BU, Rothwell JC. J Physiol 574: 917–928, 2006). The purpose of the current study was to investigate the generation of triphasic EMG bursts for movements of different amplitudes. In experiment 1, participants performed rapid elbow extension movements to 20° and 60° targets, and on some trials, a startling acoustic stimulus (SAS), which is thought to trigger prepared motor commands at short latency, was delivered at the onset of AG1. For short movements, this perturbation elicited ANT and AG2 early, suggesting the agonist and antagonist bursts may have been programmed independently. In contrast, the same manipulation did not disrupt EMG timing parameters for the long movements, raising the possibility that ANT and AG2 were not fully programmed in advance of movement onset. In experiment 2, an SAS was delivered later in the movement, which produced early onset of both ANT and AG2. We propose that the triphasic pattern is executed serially but believe the trigger signal for initiating the ANT burst occurs not in relation to the AG1 burst, but rather in close temporal proximity to the expected onset of ANT.

scholarly journals High-intensity transcranial magnetic stimulation reveals differential cortical contributions to prepared responses

2019 ◽  
Vol 121 (5) ◽  
pp. 1809-1821 ◽  
Author(s):  
Victoria Smith ◽  
Dana Maslovat ◽  
Neil M. Drummond ◽  
Joëlle Hajj ◽  
Alexandra Leguerrier ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
High Intensity ◽  
Magnetic Stimulation ◽  
Acoustic Stimulus ◽  
Silent Period ◽  
Voluntary Movements ◽  
Wrist Flexion ◽  
Primary Driver ◽  
Startling Acoustic Stimulus ◽  
Movement Type

Corticospinal output pathways have typically been considered to be the primary driver for voluntary movements of the hand/forearm; however, more recently, reticulospinal drive has also been implicated in the production of these movements. Although both pathways may play a role, the reticulospinal tract is thought to have stronger connections to flexor muscles than to extensors. Similarly, movements involuntarily triggered via a startling acoustic stimulus (SAS) are believed to receive greater reticular input than voluntary movements. To investigate a differential role of reticulospinal drive depending on movement type or acoustic stimulus, corticospinal drive was transiently interrupted using high-intensity transcranial magnetic stimulation (TMS) applied during the reaction time (RT) interval. This TMS-induced suppression of cortical drive leads to RT delays that can be used to assess cortical contributions to movement. Participants completed targeted flexion and extension movements of the wrist in a simple RT paradigm in response to a control auditory go signal or SAS. Occasionally, suprathreshold TMS was applied over the motor cortical representation for the prime mover. Results revealed that TMS significantly increased RT in all conditions. There was a significantly longer TMS-induced RT delay seen in extension movements than in flexion movements and a greater RT delay in movements initiated in response to control stimuli compared with SAS. These results suggest that the contribution of reticulospinal drive is larger for wrist flexion than for extension. Similarly, movements triggered involuntarily by an SAS appear to involve greater reticulospinal drive, and relatively less corticospinal drive, than those that are voluntarily initiated.NEW & NOTEWORTHY Through the use of the transcranial magnetic stimulation-induced silent period, we provide novel evidence for a greater contribution of reticulospinal drive, and a relative decrease in corticospinal drive, to movements involuntarily triggered by a startle compared with voluntary movements. These results also provide support for the notion that both cortical and reticular structures are involved in the neural pathway underlying startle-triggered movements. Furthermore, our results indicate greater reticulospinal contribution to wrist flexion than extension movements.

scholarly journals Posture-Dependent Corticomotor Excitability Differs Between the Transferred Biceps in Individuals With Tetraplegia and the Biceps of Nonimpaired Individuals

2016 ◽  
Vol 31 (4) ◽  
pp. 354-363
Author(s):  
Carrie L. Peterson ◽  
Lynn M. Rogers ◽  
Michael S. Bednar ◽  
Anne M. Bryden ◽  
Michael W. Keith ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Muscle Length ◽  
Motor Evoked Potential ◽  
Biomechanical Model ◽  
Single Pulse ◽  
Elbow Extension ◽  
Corticomotor Excitability ◽  
Potential Amplitude

Background. Following biceps transfer to enable elbow extension in individuals with tetraplegia, motor re-education may be facilitated by greater corticomotor excitability. Arm posture modulates corticomotor excitability of the nonimpaired biceps. If arm posture also modulates excitability of the transferred biceps, posture may aid in motor re-education. Objective. Our objective was to determine whether multi-joint arm posture affects corticomotor excitability of the transferred biceps similar to the nonimpaired biceps. We also aimed to determine whether corticomotor excitability of the transferred biceps is related to elbow extension strength and muscle length. Methods. Corticomotor excitability was assessed in 7 arms of individuals with tetraplegia and biceps transfer using transcranial magnetic stimulation and compared to biceps excitability of nonimpaired individuals. Single-pulse transcranial magnetic stimulation was delivered to the motor cortex with the arm in functional postures at rest. Motor-evoked potential amplitude was recorded via surface electromyography. Elbow moment was recorded during maximum isometric extension trials, and muscle length was estimated using a biomechanical model. Results. Arm posture modulated corticomotor excitability of the transferred biceps differently than the nonimpaired biceps. Elbow extension strength was positively related and muscle length was unrelated, respectively, to motor-evoked potential amplitude across the arms with biceps transfer. Conclusions. Corticomotor excitability of the transferred biceps is modulated by arm posture and may contribute to strength outcomes after tendon transfer. Future work should determine whether modulating corticomotor excitability via posture promotes motor re-education during the rehabilitative period following surgery.

scholarly journals Considerations on tinnitus retraining therapy and transcranial magnetic stimulation

2021 ◽  
Vol 29 ◽  
pp. 1-22
Author(s):  
Fernanda Santos Fernandes ◽  
Carlos Eduardo Batista de Sousa
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Acoustic Stimulus ◽  
Economic Life ◽  
Subjective Perception ◽  
Neural Pathways ◽  
Tinnitus Retraining Therapy ◽  
The Social ◽  
Retraining Therapy ◽  
Negative Feelings

Introduction. Tinnitus is a subjective perception of sound in the absence of an external acoustic stimulus. It has negative behavioral feelings associated, e.g., depression, insomnia, difficulty of concentration, anxiety, irritability, and panic. The feelings impact negatively on the social and economic life of individuals. Empirical data suggest that disorders in the auditory cortex and its neural pathways give rise to abnormal spontaneous activations associated with tinnitus. Understanding the causes remains challenging. However, the current hypothesis suggests that clusters of neural networks and subnetworks are involved in tinnitus generation. Central dynamic neuroplasticity induced by a peripheral loss of auditory input can cause tinnitus noise. To date, there is no widespread consensus about the most effective therapy for treating tinnitus. Objective. To reflect on two tinnitus therapies: Tinnitus Retraining Therapy (TRT) and Transcranial Magnetic Stimulation (TMS). Method. A narrative review. Explicit and systematic criteria were not adopted in searching for the theoretical framework. Results. TMS is promising compared to TRT because TMS acts on tinnitus neural mechanisms. TRT is effective on a behavioral level since it relieves mild and moderate tinnitus' negative feelings. Conclusion. TRT does not advance on the neural source, but only on the tinnitus perception. TMS acts directly on the neural causes. Both therapies have limitations and can work for some patients. However, the effect of TMS seems more efficient, although transient.

scholarly journals Cadence-dependent changes in corticospinal excitability of the biceps brachii during arm cycling

2015 ◽  
Vol 114 (4) ◽  
pp. 2285-2294 ◽  
Author(s):  
Davis A. Forman ◽  
Devin T. G. Philpott ◽  
Duane C. Button ◽  
Kevin E. Power
Keyword(s):  
Electrical Stimulation ◽  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Biceps Brachii ◽  
Elbow Flexion ◽  
Elbow Extension ◽  
Arm Cycling ◽  
Spinal Excitability ◽  
Stimulation Of

This is the first study to report the influence of different cadences on the modulation of supraspinal and spinal excitability during arm cycling. Supraspinal and spinal excitability were assessed using transcranial magnetic stimulation of the motor cortex and transmastoid electrical stimulation of the corticospinal tract, respectively. Transcranial magnetic stimulation-induced motor evoked potentials and transmastoid electrical stimulation-induced cervicomedullary evoked potentials (CMEPs) were recorded from the biceps brachii at two separate positions corresponding to elbow flexion and extension (6 and 12 o'clock relative to a clock face, respectively) while arm cycling at 30, 60 and 90 rpm. Motor evoked potential amplitudes increased significantly as cadence increased during both elbow flexion ( P < 0.001) and extension ( P = 0.027). CMEP amplitudes also increased with cadence during elbow flexion ( P < 0.01); however, the opposite occurred during elbow extension (i.e., decreased CMEP amplitude; P = 0.01). The data indicate an overall increase in the excitability of corticospinal neurons which ultimately project to biceps brachii throughout arm cycling as cadence increased. Conversely, changes in spinal excitability as cadence increased were phase dependent (i.e., increased during elbow flexion and decreased during elbow extension). Phase- and cadence-dependent changes in spinal excitability are suggested to be mediated via changes in the balance of excitatory and inhibitory synaptic input to the motor pool, as opposed to changes in the intrinsic properties of spinal motoneurons.

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