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  1. Article ; Online: Impaired motor cortical facilitatory-inhibitory circuit interaction in Parkinson's disease.

    Saravanamuttu, James / Radhu, Natasha / Udupa, Kaviraja / Baarbé, Julianne / Gunraj, Carolyn / Chen, Robert

    Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology

    2021  Volume 132, Issue 10, Page(s) 2685–2692

    Abstract: Objective: Motor cortical (M1) inhibition and facilitation can be studied with short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF). These circuits are altered in Parkinson's disease (PD). The sensorimotor ... ...

    Abstract Objective: Motor cortical (M1) inhibition and facilitation can be studied with short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF). These circuits are altered in Parkinson's disease (PD). The sensorimotor measure short latency afferent inhibition (SAI) is possibly altered in PD. The aim was to determine if the manner in which these circuits interact with each other is abnormal in PD.
    Methods: Fifteen PD patients were studied at rest in ON and OFF medication states, and were compared to 16 age-matched controls. A triple-stimulus transcranial magnetic stimulation paradigm was used to elicit a circuit of interest in the presence of another circuit.
    Results: SICF was increased in PD OFF and PD ON conditions compared to controls. SICI facilitated SICF in controls and PD ON, but not in PD OFF. SICF in the presence of SICI negatively correlated with UPDRS-III scores in OFF and ON medication conditions. SAI showed similar inhibition of SICI in controls, PD OFF and PD ON conditions.
    Conclusions: The facilitatory effect of SICI on SICF is absent in PD OFF, but is restored with dopaminergic medication.
    Significance: Impaired interaction between M1 circuits is a pathophysiological feature of PD.
    MeSH term(s) Aged ; Electromyography/methods ; Evoked Potentials, Motor/physiology ; Female ; Humans ; Male ; Middle Aged ; Motor Cortex/physiopathology ; Nerve Net/physiopathology ; Neural Inhibition/physiology ; Parkinson Disease/diagnosis ; Parkinson Disease/physiopathology ; Transcranial Magnetic Stimulation/methods
    Language English
    Publishing date 2021-07-06
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1463630-x
    ISSN 1872-8952 ; 0921-884X ; 1388-2457
    ISSN (online) 1872-8952
    ISSN 0921-884X ; 1388-2457
    DOI 10.1016/j.clinph.2021.05.032
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  2. Article ; Online: Cortical GABAergic dysfunction underlying abnormal hand movements in ARX mutation.

    Lizarraga, Karlo J / Baarbé, Julianne K / Saravanamuttu, James / Lang, Anthony E / Chen, Robert

    Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology

    2019  Volume 130, Issue 10, Page(s) 1750–1751

    MeSH term(s) Adolescent ; Electromyography/methods ; GABAergic Neurons/physiology ; Hand/pathology ; Homeodomain Proteins/genetics ; Humans ; Male ; Motor Cortex/physiopathology ; Movement Disorders/diagnosis ; Movement Disorders/genetics ; Movement Disorders/physiopathology ; Mutation/genetics ; Transcranial Magnetic Stimulation/methods ; Transcription Factors/genetics
    Chemical Substances ARX protein, human ; Homeodomain Proteins ; Transcription Factors
    Language English
    Publishing date 2019-07-16
    Publishing country Netherlands
    Document type Case Reports ; Letter ; Research Support, Non-U.S. Gov't
    ZDB-ID 1463630-x
    ISSN 1872-8952 ; 0921-884X ; 1388-2457
    ISSN (online) 1872-8952
    ISSN 0921-884X ; 1388-2457
    DOI 10.1016/j.clinph.2019.07.003
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  3. Article ; Online: Interhemispheric pathways in agenesis of the corpus callosum and Parkinson's disease.

    Lizarraga, Karlo J / Saravanamuttu, James / Baarbé, Julianne K / Lang, Anthony E / Chen, Robert

    Brain stimulation

    2019  Volume 13, Issue 2, Page(s) 360–362

    Language English
    Publishing date 2019-11-04
    Publishing country United States
    Document type Letter
    ZDB-ID 2394410-9
    ISSN 1876-4754 ; 1935-861X
    ISSN (online) 1876-4754
    ISSN 1935-861X
    DOI 10.1016/j.brs.2019.11.003
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  4. Article ; Online: Coordinating long-latency stretch responses across the shoulder, elbow, and wrist during goal-directed reaching.

    Weiler, Jeffrey / Saravanamuttu, James / Gribble, Paul L / Pruszynski, J Andrew

    Journal of neurophysiology

    2016  Volume 116, Issue 5, Page(s) 2236–2249

    Abstract: The long-latency stretch response (muscle activity 50-100 ms after a mechanical perturbation) can be coordinated across multiple joints to support goal-directed actions. Here we assessed the flexibility of such coordination and whether it serves to ... ...

    Abstract The long-latency stretch response (muscle activity 50-100 ms after a mechanical perturbation) can be coordinated across multiple joints to support goal-directed actions. Here we assessed the flexibility of such coordination and whether it serves to counteract intersegmental dynamics and exploit kinematic redundancy. In three experiments, participants made planar reaches to visual targets after elbow perturbations and we assessed the coordination of long-latency stretch responses across shoulder, elbow, and wrist muscles. Importantly, targets were placed such that elbow and wrist (but not shoulder) rotations could help transport the hand to the target-a simple form of kinematic redundancy. In experiment 1 we applied perturbations of different magnitudes to the elbow and found that long-latency stretch responses in shoulder, elbow, and wrist muscles scaled with perturbation magnitude. In experiment 2 we examined the trial-by-trial relationship between long-latency stretch responses at adjacent joints and found that the magnitudes of the responses in shoulder and elbow muscles, as well as elbow and wrist muscles, were positively correlated. In experiment 3 we explicitly instructed participants how to use their wrist to move their hand to the target after the perturbation. We found that long-latency stretch responses in wrist muscles were not sensitive to our instructions, despite the fact that participants incorporated these instructions into their voluntary behavior. Taken together, our results indicate that, during reaching, the coordination of long-latency stretch responses across multiple joints counteracts intersegmental dynamics but may not be able to exploit kinematic redundancy.
    MeSH term(s) Elbow/physiology ; Electromyography/methods ; Exoskeleton Device ; Female ; Goals ; Humans ; Male ; Movement/physiology ; Muscle, Skeletal/physiology ; Reaction Time/physiology ; Reflex, Stretch/physiology ; Shoulder/physiology ; Time Factors ; Wrist/physiology ; Young Adult
    Language English
    Publishing date 2016-08-17
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 80161-6
    ISSN 1522-1598 ; 0022-3077
    ISSN (online) 1522-1598
    ISSN 0022-3077
    DOI 10.1152/jn.00524.2016
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  5. Article ; Online: Interhemispheric interactions between the right angular gyrus and the left motor cortex: a transcranial magnetic stimulation study.

    Baarbé, Julianne / Vesia, Michael / Brown, Matt J N / Lizarraga, Karlo J / Gunraj, Carolyn / Jegatheeswaran, Gaayathiri / Drummond, Neil M / Rinchon, Cricia / Weissbach, Anne / Saravanamuttu, James / Chen, Robert

    Journal of neurophysiology

    2021  Volume 125, Issue 4, Page(s) 1236–1250

    Abstract: The interconnection of the angular gyrus of right posterior parietal cortex (PPC) and the left motor cortex (LM1) is essential for goal-directed hand movements. Previous work with transcranial magnetic stimulation (TMS) showed that right PPC stimulation ... ...

    Abstract The interconnection of the angular gyrus of right posterior parietal cortex (PPC) and the left motor cortex (LM1) is essential for goal-directed hand movements. Previous work with transcranial magnetic stimulation (TMS) showed that right PPC stimulation increases LM1 excitability, but right PPC followed by left PPC-LM1 stimulation (LPPC-LM1) inhibits LM1 corticospinal output compared with LPPC-LM1 alone. It is not clear if right PPC-mediated inhibition of LPPC-LM1 is due to inhibition of left PPC or to combined effects of right and left PPC stimulation on LM1 excitability. We used paired-pulse TMS to study the extent to which combined right and left PPC stimulation, targeting the angular gyri, influences LM1 excitability. We tested 16 healthy subjects in five paired-pulsed TMS experiments using MRI-guided neuronavigation to target the angular gyri within PPC. We tested the effects of different right angular gyrus (RAG) and LM1 stimulation intensities on the influence of RAG on LM1 and on influence of left angular gyrus (LAG) on LM1 (LAG-LM1). We then tested the effects of RAG and LAG stimulation on LM1 short-interval intracortical facilitation (SICF), short-interval intracortical inhibition (SICI), and long-interval intracortical inhibition (LICI). The results revealed that RAG facilitated LM1, inhibited SICF, and inhibited LAG-LM1. Combined RAG-LAG stimulation did not affect SICI but increased LICI. These experiments suggest that RAG-mediated inhibition of LAG-LM1 is related to inhibition of early indirect (I)-wave activity and enhancement of GABA
    MeSH term(s) Adult ; Electromyography ; Female ; Hand/physiology ; Humans ; Male ; Middle Aged ; Motor Activity/physiology ; Motor Cortex/physiology ; Neural Inhibition/physiology ; Neuronal Plasticity/physiology ; Parietal Lobe/physiology ; Transcranial Magnetic Stimulation ; Young Adult
    Language English
    Publishing date 2021-02-24
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 80161-6
    ISSN 1522-1598 ; 0022-3077
    ISSN (online) 1522-1598
    ISSN 0022-3077
    DOI 10.1152/jn.00642.2020
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  6. Article ; Online: Systematic examination of low-intensity ultrasound parameters on human motor cortex excitability and behavior.

    Fomenko, Anton / Chen, Kai-Hsiang Stanley / Nankoo, Jean-François / Saravanamuttu, James / Wang, Yanqiu / El-Baba, Mazen / Xia, Xue / Seerala, Shakthi Sanjana / Hynynen, Kullervo / Lozano, Andres M / Chen, Robert

    eLife

    2020  Volume 9

    Abstract: Low-intensity transcranial ultrasound (TUS) can non-invasively modulate human neural activity. We investigated how different fundamental sonication parameters influence the effects of TUS on the motor cortex (M1) of 16 healthy subjects by probing cortico- ...

    Abstract Low-intensity transcranial ultrasound (TUS) can non-invasively modulate human neural activity. We investigated how different fundamental sonication parameters influence the effects of TUS on the motor cortex (M1) of 16 healthy subjects by probing cortico-cortical excitability and behavior. A low-intensity 500 kHz TUS transducer was coupled to a transcranial magnetic stimulation (TMS) coil. TMS was delivered 10 ms before the end of TUS to the left M1 hotspot of the first dorsal interosseous muscle. Varying acoustic parameters (pulse repetition frequency, duty cycle, and sonication duration) on motor-evoked potential amplitude were examined. Paired-pulse measures of cortical inhibition and facilitation, and performance on a visuomotor task was also assessed. TUS safely suppressed TMS-elicited motor cortical activity, with longer sonication durations and shorter duty cycles when delivered in a blocked paradigm. TUS increased GABA
    MeSH term(s) Adult ; Double-Blind Method ; Evoked Potentials, Motor ; Female ; Healthy Volunteers ; Humans ; Magnetic Resonance Imaging ; Male ; Middle Aged ; Motor Cortex/diagnostic imaging ; Motor Cortex/physiology ; Motor Skills ; Muscle Contraction ; Muscle, Skeletal/innervation ; Neural Inhibition ; Reaction Time ; Time Factors ; Transcranial Magnetic Stimulation ; Ultrasonic Waves
    Language English
    Publishing date 2020-11-25
    Publishing country England
    Document type Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2687154-3
    ISSN 2050-084X ; 2050-084X
    ISSN (online) 2050-084X
    ISSN 2050-084X
    DOI 10.7554/eLife.54497
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  7. Article ; Online: A Distinct EEG Marker of Celiac Disease-Related Cortical Myoclonus.

    Swinkin, Emily / Lizárraga, Karlo J / Algarni, Musleh / Garcia Dominguez, Luis / Baarbé, Julianne K / Saravanamuttu, James / Chen, Robert / Slow, Elizabeth / Lang, Anthony E / Wennberg, Richard A

    Movement disorders : official journal of the Movement Disorder Society

    2020  Volume 36, Issue 4, Page(s) 999–1005

    Abstract: Background: Celiac disease is associated with motor cortex hyperexcitability and neurological manifestations including cortical myoclonus. Electroencephalography abnormalities have been described, but no distinct pattern has been reported.: Methods: ... ...

    Abstract Background: Celiac disease is associated with motor cortex hyperexcitability and neurological manifestations including cortical myoclonus. Electroencephalography abnormalities have been described, but no distinct pattern has been reported.
    Methods: We describe the neurophysiological characteristics of 3 patients with celiac-associated cortical myoclonus using electroencephalography, magnetoencephalography, and transcranial magnetic stimulation.
    Results: Electroencephalography in all cases demonstrated lateralized low-amplitude, electropositive beta-frequency polyspike activity over the central head region, corresponding to motor cortex contralateral to the myoclonic limb. Jerk-locked back-averaging demonstrated a preceding cortical potential; magnetoencephalography source localization revealed a cortical generator in the posterior wall of the precentral gyrus for the back-averaged potential and oscillatory abnormality. In 1 patient, cerebellar inhibition of the motor cortex was physiologically normal.
    Conclusions: Central head oscillatory, low-amplitude, electropositive electroencephalography polyspike activity may be a distinct marker of celiac-related cortical myoclonus and is consistent with celiac-related motor cortex hyperexcitability, which may not necessarily result from cerebellar disinhibition. © 2020 International Parkinson and Movement Disorder Society.
    MeSH term(s) Celiac Disease/complications ; Electroencephalography ; Electromyography ; Humans ; Magnetoencephalography ; Myoclonus/etiology
    Language English
    Publishing date 2020-11-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 607633-6
    ISSN 1531-8257 ; 0885-3185
    ISSN (online) 1531-8257
    ISSN 0885-3185
    DOI 10.1002/mds.28407
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