scholarly journals Paradoxical facilitation alongside interhemispheric inhibition

2021 ◽  
Author(s):  
Michel Belyk ◽  
Russell Banks ◽  
Anna Tendera ◽  
Robert Chen ◽  
Deryk S. Beal
Keyword(s):  
Motor Cortex ◽  
Corpus Callosum ◽  
Primary Motor Cortex ◽  
Conditioning Stimulus ◽  
Future Research ◽  
Homologous Region ◽  
Inhibitory Influence ◽  
Interhemispheric Inhibition ◽  
Opposite Hemisphere ◽  
Surprising Effect

AbstractNeurophysiological experiments using transcranial magnetic stimulation (TMS) have sought to probe the function of the motor division of the corpus callosum. Primary motor cortex sends projections via the corpus callosum with a net inhibitory influence on the homologous region of the opposite hemisphere. Interhemispheric inhibition (IHI) experiments probe this inhibitory pathway. A test stimulus (TS) delivered to the motor cortex in one hemisphere elicits motor evoked potentials (MEPs) in a target muscle, while a conditioning stimulus (CS) applied to the homologous region of the opposite hemisphere modulates the effect of the TS. We predicted that large CS MEPs would be associated with increased IHI since they should be a reliable index of how effectively contralateral motor cortex was stimulated and therefore of the magnitude of interhemispheric inhibition. However, we observed a strong tendency for larger CS MEPs to be associated with reduced interhemispheric inhibition which in the extreme lead to a net effect of facilitation. This surprising effect was large, systematic, and observed in nearly all participants. We outline several hypotheses for mechanisms which may underlie this phenomenon to guide future research.

Changes in interhemispheric inhibition from active to resting primary motor cortex during a fine-motor manipulation task

2012 ◽  
Vol 107 (11) ◽  
pp. 3086-3094 ◽  
Author(s):  
Takuya Morishita ◽  
Kazumasa Uehara ◽  
Kozo Funase
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Conditioning Stimulus ◽  
Fine Motor ◽  
Interhemispheric Inhibition ◽  
Left Hand ◽  
Resting Motor Threshold ◽  
Inhibitory Circuit ◽  
Task Conditions

The effect of performance of a sensorimotor task on the interhemispheric inhibition (IHI) induced from the active primary motor cortex (M1) to the resting M1 was examined in 10 right-handed subjects. Transcranial magnetic stimulation (TMS) was performed to produce motor evoked potentials (MEP) in the resting right (Rt)-first dorsal interosseous (FDI). For the paired-TMS paradigm, a conditioning stimulus (CS) was delivered to the Rt-M1, and its intensity was adjusted from 0.6 to 1.4 times the resting motor threshold of the MEP in the left (Lt)-FDI in 0.2 steps. The test stimulus was delivered to the Lt-M1, and its intensity was adjusted to evoke similar MEP amplitudes in the Rt-FDI among the task conditions. The interstimulus interval was fixed at 10 ms. As a sensorimotor task, a fine-motor manipulation (FM) task (using chopsticks to pick up, transport, and release glass balls) was adopted. In addition, an isometric abduction (IA) task was also performed as a control task. These tasks were carried out with the left hand. The IHI from the active to the resting M1 observed during the FM task was markedly increased compared with that induced during the IA task, and this effect was not dependent on the MEP amplitude evoked in the active Lt-FDI by the CS. The present findings suggest that the increased IHI from the active to the resting M1 observed during the FM task was linked to reductions in the activity of the ipsilateral intracortical inhibitory circuit, as we reported previously.

Short- and long-latency interhemispheric inhibitions are additive in human motor cortex

2013 ◽  
Vol 109 (12) ◽  
pp. 2955-2962 ◽  
Author(s):  
Soumya Ghosh ◽  
Arpan R. Mehta ◽  
Guan Huang ◽  
Carolyn Gunraj ◽  
Tasnuva Hoque ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Neural Circuits ◽  
Motor Evoked Potentials ◽  
Conditioning Stimulus ◽  
Interhemispheric Inhibition ◽  
Human Motor Cortex ◽  
Inhibitory Processes ◽  
Long Latency ◽  
The Right

Transcranial magnetic stimulation (TMS) of the human primary motor cortex (M1) at suprathreshold strength results in inhibition of M1 in the opposite hemisphere, a process termed interhemispheric inhibition (IHI). Two phases of IHI, termed short-latency interhemispheric inhibition (SIHI) and long-latency interhemispheric inhibition (LIHI), involving separate neural circuits, have been identified. In this study we evaluated how these two inhibitory processes interact with each other. We studied 10 healthy right-handed subjects. A test stimulus (TS) was delivered to the left M1, and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous (FDI) muscle. Contralateral conditioning stimuli (CCS) were applied to the right M1 either 10 ms or 50 ms prior to the TS, inducing SIHI and LIHI, respectively, in the left M1. The effects of SIHI and LIHI alone, and SIHI and LIHI delivered together, were compared. The TS was adjusted to produce 1-mV or 0.5-mV MEPs when applied alone or after CCS. SIHI and LIHI were found to be additive when delivered together, irrespective of the strength of the TS. The interactions were affected neither by varying the strength of the conditioning stimulus producing SIHI nor by altering the current direction of the TS. Small or opposing interactions, however, may not have been detected. These results support previous findings suggesting that SIHI and LIHI act through different neural circuits. Such inhibitory processes may be used individually or additively during motor tasks and should be studied as separate processes in functional studies.

scholarly journals Modulatory effects of the supplementary motor area on primary motor cortex outputs

2020 ◽  
Vol 123 (1) ◽  
pp. 407-419 ◽  
Author(s):  
Sandrine L. Côté ◽  
Guillaume Elgbeili ◽  
Stephan Quessy ◽  
Numa Dancause
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Supplementary Motor Area ◽  
Conditioning Stimulus ◽  
Motor Area ◽  
Hand Movements ◽  
Electromyographic Activity ◽  
Opposite Hemisphere ◽  
The Impact ◽  
Premotor Areas

Premotor areas of primates are specialized cortical regions that can contribute to hand movements by modulating the outputs of the primary motor cortex (M1). The goal of the present work was to study how the supplementary motor area (SMA) located within the same hemisphere [i.e., ipsilateral SMA (iSMA)] or the opposite hemisphere [i.e., contralateral (cSMA)] modulate the outputs of M1. We used paired-pulse protocols with intracortical stimulations in sedated capuchin monkeys. A conditioning stimulus in iSMA or cSMA was delivered simultaneously or before a test stimulus in M1 with different interstimulus intervals (ISIs) while electromyographic activity was recorded in hand and forearm muscles. The pattern of modulation from iSMA and cSMA shared some clear similarities. In particular, both areas predominantly induced facilitatory effects on M1 outputs with shorter ISIs and inhibitory effects with longer ISIs. However, the incidence and strength of facilitatory effects were greater for iSMA than cSMA. We then compared the pattern of modulatory effects from SMA to the ones from the dorsal and ventral premotor cortexes (PMd and PMv) collected in the same series of experiments. Among premotor areas, the impact of SMA on M1 outputs was always weaker than the one of either PMd or PMv, and this was regardless of the hemisphere, or the ISI, tested. These results show that SMA exerts a unique set of modulations on M1 outputs, which could support its specific function for the production of hand movements. NEW & NOTEWORTHY We unequivocally isolated stimulation to either the ipsilateral or contralateral supplementary motor area (SMA) using invasive techniques and compared their modulatory effects on the outputs of primary motor cortex (M1). Modulations from both SMAs shared many similarities. However, facilitatory effects evoked from ipsilateral SMA were more common and more powerful. This pattern differs from the ones of other premotor areas, which suggests that each premotor area makes unique contributions to the production of motor outputs.

scholarly journals Neuroplasticity Changes on Human Motor Cortex Induced by Acupuncture Therapy: A Preliminary Study

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Yi Yang ◽  
Ines Eisner ◽  
Siqi Chen ◽  
Shaosong Wang ◽  
Fan Zhang ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Acupuncture Therapy ◽  
Motor Cortex ◽  
Magnetic Stimulation ◽  
Primary Motor Cortex ◽  
Motor Evoked Potential ◽  
Interhemispheric Inhibition ◽  
Human Motor Cortex ◽  
Interhemispheric Competition ◽  
Resting Motor Threshold

While neuroplasticity changes measured by transcranial magnetic stimulation have been proved to be highly correlated to motor recovery and have been tested in various forms of interventions, it has not been applied to investigate the neurophysiologic mechanism of acupuncture therapy. The aim of this study is to investigate neuroplasticity changes induced by a single session of acupuncture therapy in healthy adults, regarding the excitability change on bilateral primary motor cortex and interhemispheric inhibition. Ten subjects took a 30-minute acupuncture therapy and the same length relaxing phase in separate days. Transcranial magnetic stimulation measures, including resting motor threshold, amplitudes of motor-evoked potential, and interhemispheric inhibition, were assessed before and 10 minutes after intervention. Acupuncture treatment showed significant changes on potential amplitude from both ipsilateral and contralateral hemispheres to acupuncture compared to baseline. Also, interhemispheric inhibition from the contralateral motor cortex to the opposite showed a significant decline. The results indicated that corticomotoneuronal excitability and interhemispheric competition could be modulated by acupuncture therapy on healthy subjects. The following question about whether these changes will be observed in the same way on stroke patients and whether they correlate with the therapeutic effect on movement need to be answered by following studies. This trial is registered with ISRCTN13074245.

Interhemispheric Inhibition in Distal and Proximal Arm Representations in the Primary Motor Cortex

2007 ◽  
Vol 97 (3) ◽  
pp. 2511-2515 ◽  
Author(s):  
Michelle L. Harris-Love ◽  
Monica A. Perez ◽  
Robert Chen ◽  
Leonardo G. Cohen
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Biceps Brachii ◽  
Conditioning Stimulus ◽  
Motor Evoked Potential ◽  
Triceps Brachii ◽  
Functional Movement ◽  
Resting Motor Threshold ◽  
Inhibitory Interactions

Interhemispheric inhibitory interactions (IHI) operate between homologous distal hand representations in primary motor cortex (M1). It is not known whether proximal arm representations exhibit comparable effects on their homologous counterparts. We studied IHI in different arm representations, targeting triceps brachii (TB, n = 13), first dorsal interosseous (FDI, n = 13), and biceps brachii (BB, n = 7) muscles in healthy volunteers. Transcranial magnetic stimulation test stimuli (TS) were delivered to M1 contralateral to the target muscle preceded 10 ms by a conditioning stimulus (CS) to the opposite M1 at 110–150% resting motor threshold (RMT). IHI was calculated as the ratio between motor-evoked potential (MEP) amplitudes in conditioned relative to unconditioned trials. Mean RMTs were 38.9, 46.9, and 46.0% of stimulator output in FDI, TB, and BB muscles, respectively. IHI was 0.45 ± 0.41 (FDI), 0.78 ± 0.38 (TB), and 0.52 ± 0.32 (BB, P < 0.01) when test MEP amplitudes were matched and 0.28 ± 0.17 (FDI) and 0.85 ± 0.31 (TB, P < 0.05) when TS intensities expressed as percentage RMT were matched. Significant IHI ( P < 0.05) was identified with minimal CS intensities (expressed as percentage stimulator output) in the 30 s for FDI, 60 s for TB, and 40 s for BB. Additionally, a CS of roughly 120% RMT suppressed the test MEP but not a test H-reflex in BB, suggesting IHI observed in BB is likely mediated by a supraspinal mechanism. We conclude that IHI differs between different arm muscle representations, comparable between BB and FDI but lesser for TB. This finding suggests the amount of IHI between different arm representations does not strictly follow a proximal-to-distal gradient, but may be related to the role of each muscle in functional movement synergies.

scholarly journals Primary motor cortex activity traces distinct trajectories of population dynamics during spontaneous facial motor sequences in mice

2021 ◽  
Author(s):  
Juan Carlos Boffi ◽  
Tristan Wiessalla ◽  
Robert Prevedel
Keyword(s):  
Population Dynamics ◽  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Neuronal Population ◽  
Future Research ◽  
Sequencing Analysis ◽  
Population Activity ◽  
Neuronal Populations ◽  
Custom Made ◽  
Facial Area

AbstractWe explore the link between on-going neuronal activity at primary motor cortex (M1) and face movement in awake mice. By combining custom-made behavioral sequencing analysis and fast volumetric Ca2+-imaging, we simultaneously tracked M1 population activity during many different facial motor sequences. We show that a facial area of M1 displays distinct trajectories of neuronal population dynamics across different spontaneous facial motor sequences, suggesting an underlying population dynamics code.Significance statementHow our brain controls a seemingly limitless diversity of body movements remains largely unknown. Recent research brings new light into this subject by showing that neuronal populations at the primary motor cortex display different dynamics during forelimb reaching movements versus grasping, which suggests that different motor sequences could be associated with distinct motor cortex population dynamics. To explore this possibility, we designed an experimental paradigm for simultaneously tracking the activity of neuronal populations in motor cortex across many different motor sequences. Our results support the concept that distinct population dynamics encode different motor sequences, bringing new insight into the role of motor cortex in sculpting behavior while opening new avenues for future research.

scholarly journals Using Dual-Site Transcranial Magnetic Stimulation to Probe Connectivity between the Dorsolateral Prefrontal Cortex and Ipsilateral Primary Motor Cortex in Humans

2019 ◽  
Vol 9 (8) ◽  
pp. 177 ◽  
Author(s):  
Matt J.N. Brown ◽  
Elana R. Goldenkoff ◽  
Robert Chen ◽  
Carolyn Gunraj ◽  
Michael Vesia
Keyword(s):  
Prefrontal Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Magnetic Stimulation ◽  
Dorsolateral Prefrontal Cortex ◽  
Primary Motor Cortex ◽  
Conditioning Stimulus ◽  
Resting Motor Threshold ◽  
Dorsolateral Prefrontal ◽  
Dual Site

Dual-site transcranial magnetic stimulation to the primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) can be used to probe functional connectivity between these regions. The purpose of this study was to characterize the effect of DLPFC stimulation on ipsilateral M1 excitability while participants were at rest and contracting the left- and right-hand first dorsal interosseous muscle. Twelve participants were tested in two separate sessions at varying inter-stimulus intervals (ISI: 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, and 20 ms) at two different conditioning stimulus intensities (80% and 120% of resting motor threshold). No significant effect on ipsilateral M1 excitability was found when applying a conditioning stimulus over DLPFC at any specific inter-stimulus interval or intensity in either the left or right hemisphere. Our findings suggest neither causal inhibitory nor faciliatory influences of DLPFC on ipsilateral M1 activity while participants were at rest or when performing an isometric contraction in the target hand muscle.

scholarly journals Two Phases of Interhemispheric Inhibition between Motor Related Cortical Areas and the Primary Motor Cortex in Human

2008 ◽  
Vol 19 (7) ◽  
pp. 1654-1665 ◽  
Author(s):  
Z. Ni ◽  
C. Gunraj ◽  
A. J. Nelson ◽  
I.-J. Yeh ◽  
G. Castillo ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Interhemispheric Inhibition ◽  
Cortical Areas ◽  
Two Phases
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