Freely Chosen Cadence During Cycling Attenuates Intracortical Inhibition and Increases Intracortical Facilitation Compared to a Similar Fixed Cadence

Abstract Transcranial direct current stimulation (tDCS) is increasingly being used to affect the neurological conditions with deficient intracortical synaptic activities (i.e. Parkinson’s disease and epilepsy). In addition, it is suggested that the lasting effects of tDCS on corticospinal excitability (CSE) have intracortical origin. This systematic review and meta-analysis aimed to examine whether tDCS has any effect on intracortical circuits. Eleven electronic databases were searched for the studies investigating intracortical changes induced by anodal (a) and cathodal (c) tDCS, in healthy individuals, using two paired-pulse transcranial magnetic stimulation (TMS) paradigms: short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Additionally, motor-evoked potential (MEP) size alterations, assessed by single-pulse TMS, were extracted from these studies to investigate the probable intracortical origin of tDCS effects on CSE. The methodological quality of included studies was examined using Physiotherapy Evidence Database (PEDro) and Downs and Black’s (D&B) assessment tools. Thirteen research papers, including 24 experiments, were included in this study scoring good and medium quality in PEDro and D&B scales, respectively. Immediately following anodal tDCS (a-tDCS) applications, we found significant decreases in SICI, but increases in ICF and MEP size. However, ICF and MEP size significantly decreased, and SICI increased immediately following cathodal tDCS (c-tDCS). The results of this systematic review and meta-analysis reveal that a-tDCS changes intracortical activities (SICI and ICF) toward facilitation, whereas c-tDCS alters them toward inhibition. It can also be concluded that increases and decreases in CSE after tDCS application are associated with corresponding changes in intracortical activities. The results suggest that tDCS can be clinically useful to modulate intracortical circuits.

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Muscle Pain Differentially Modulates Short Interval Intracortical Inhibition and Intracortical Facilitation in Primary Motor Cortex

Journal of Pain ◽

10.1016/j.jpain.2011.10.013 ◽

2012 ◽

Vol 13 (2) ◽

pp. 187-194 ◽

Cited By ~ 57

Author(s):

Siobhan M. Schabrun ◽

Paul W. Hodges

Keyword(s):

Motor Cortex ◽

Muscle Pain ◽

Primary Motor Cortex ◽

Short Interval ◽

Intracortical Inhibition ◽

Intracortical Facilitation

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Freely chosen cadence during cycling attenuates intracortical inhibition and increases intracortical facilitation compared to a similar fixed cadence

10.1101/2020.04.23.056820 ◽

2020 ◽

Author(s):

Simranjit Sidhu ◽

Benedikt Lauber

Keyword(s):

Energy Consumption ◽

Transcranial Magnetic Stimulation ◽

Magnetic Stimulation ◽

Short Interval ◽

Intracortical Inhibition ◽

Movement Rate ◽

Intracortical Facilitation ◽

Neurophysiological Mechanisms

AbstractIn contrast to other rhythmic tasks such as running, the preferred movement rate in cycling does not minimize energy consumption. It is possible that neurophysiological mechanisms contribute to the choice of cadence, however this phenomenon is not well understood. Eleven participants cycled at a fixed workload of 125 W and different cadences including a freely chosen cadence (FCC, ∼72), and fixed cadences of 70, 80, 90 and 100 revolutions per minute (rpm) during which transcranial magnetic stimulation (TMS) was used to measure short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). There was significant increase in SICI at 70 (P = 0.004), 80 (P = 0.008) and 100 rpm (P = 0.041) compared to FCC. ICF was significantly reduced at 70 rpm compared to FCC (P = 0.04). Inhibition-excitation ratio (SICI divided by ICF) declined (P = 0.014) with an increase in cadence. The results demonstrate that SICI is attenuated during FCC compared to fixed cadences. The outcomes suggest that the attenuation of intracortical inhibition and augmentation of ICF may be a contributing factor for FCC.

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Abstract TMP43: Differential Cortical Effect Modulated by Anodal, Cathodal and Bihemispheric Transcranial Direct Current Stimulation (tDCS) in Patients With Ischemic Stroke

Stroke ◽

10.1161/str.51.suppl_1.tmp43 ◽

2020 ◽

Vol 51 (Suppl_1) ◽

Author(s):

Pratik Y Chhatbar ◽

William DeVries ◽

Emily Grattan ◽

Steven A Kautz ◽

Wuwei Feng

Keyword(s):

Ischemic Stroke ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Single Pulse ◽

Intracortical Inhibition ◽

Motor Threshold ◽

Stroke Patients ◽

Intracortical Facilitation ◽

Abductor Pollicis Brevis ◽

Resting Motor Threshold

Introduction: The differential brain modulatory effects across hemispheres from different montages in stroke patients is not well established. We aimed to investigate the cortical excitability on lesional and contra-lesional hemisphere modulated by anodal, cathodal and bihemispheric montage at 4 mA tDCS strengths. Hypothesis: Bihemispheric tDCS montage induces more cortical excitability on the lesional hemisphere. Methods: Eighteen aging stroke patients with unilateral ischemic stroke of 6 or more months and inducible motor evoked potentials (MEP) underwent 3 sessions of 30 minutes 4 mA tDCS combined with occupational therapy. Each session was at least 2 days apart and consisted of one of the 3 different montages: anodal (Anode: lesional C3/C4, Cathode: non-lesional FP1/FP2), cathodal (Anode: lesional FP1/FP2, Cathode: non-lesional C3/C4), or bihemispheric (Anode: lesional C3/C4, Cathode: non-lesional C3/C4). We collected MEP size, short intracortical inhibition (SICI, 3 ms) and intracortical facilitation (ICF, 15 ms) on bilateral abductor pollicis brevis (APB) muscles using single or paired pulse TMS at 5 timepoints (baseline and four post-tDCS 12 minutes apart sessions). Results: All 18 subjects had comparable resting motor threshold (rMT) across 3 montages (see A). Bihemispheric tDCS montage offered significantly larger peak-to-peak MEP responses on the lesioned cortex (ANOVA, F=8.97, P<0.01) but not on the non-lesioned cortex (ANOVA, F=0.86, P=0.42). These differences were apparent in single pulse, SICI and ICF (see B). Conclusion: Our findings support that bihemispheric montage is better suited in post-stroke motor recovery tDCS applications.

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Influence of Short-Interval Intracortical Inhibition on Short-Interval Intracortical Facilitation in Human Primary Motor Cortex

Journal of Neurophysiology ◽

10.1152/jn.00164.2010 ◽

2010 ◽

Vol 104 (3) ◽

pp. 1382-1391 ◽

Cited By ~ 26

Author(s):

Yuichiro Shirota ◽

Masashi Hamada ◽

Yasuo Terao ◽

Hideyuki Matsumoto ◽

Shinya Ohminami ◽

...

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Short Interval ◽

Conditioning Stimulus ◽

Intracortical Inhibition ◽

Intracortical Facilitation ◽

Paired Pulse ◽

Active Motor ◽

Second Peak ◽

Pulse Stimulation

Using the paired-pulse paradigm, transcranial magnetic stimulation (TMS) has revealed much about the human primary motor cortex (M1). A preceding subthreshold conditioning stimulus (CS) inhibits the excitability of the motor cortex, which is named short-interval intracortical inhibition (SICI). In contrast, facilitation is observed when the first pulse (S1) is followed by a second one at threshold (S2), named short-interval intracortical facilitation (SICF). SICI and SICF have been considered to be mediated by different neural circuits within M1, but more recent studies reported relations between them. In this study, we performed triple-pulse stimulation consisting of CS-S1-S2 to further explore putative interactions between these two effects. Three intensities of CS (80–120% of active motor threshold: AMT) and two intensities of S2 (120 and 140% AMT) were combined. The SICF in the paired-pulse paradigm exhibited clear facilitatory peaks at ISIs of 1.5 and 3 ms. The second peak at 3 ms was significantly suppressed by triple-pulse stimulation using 120% AMT CS, although the first peak was almost unaffected. Our present results obtained using triple-pulse stimulation suggest that each peak of SICF is differently modulated by different intensities of CS. The suppression of the second peak might be ascribed to the findings in the paired-pulse paradigm that CS mediates SICI by inhibiting later I waves such as I3 waves and that the second peak of SICF is most probably related to I3 waves. We propose that CS might inhibit the second peak of SICF at the interneurons responsible for I3 waves.

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Combining Fluoxetine and rTMS in Poststroke Motor Recovery: A Placebo-Controlled Double-Blind Randomized Phase 2 Clinical Trial

Neurorehabilitation and Neural Repair ◽

10.1177/1545968319860483 ◽

2019 ◽

Vol 33 (8) ◽

pp. 643-655 ◽

Cited By ~ 2

Author(s):

Camila Bonin Pinto ◽

Leon Morales-Quezada ◽

Polyana Vulcano de Toledo Piza ◽

Dian Zeng ◽

Faddi Ghassan Saleh Vélez ◽

...

Keyword(s):

Clinical Trial ◽

Motor Function ◽

Primary Motor Cortex ◽

Repetitive Transcranial Magnetic Stimulation ◽

Hand Function ◽

Intracortical Inhibition ◽

Motor Recovery ◽

Intracortical Facilitation ◽

Double Blind ◽

Phase 2 Clinical Trial

Background. Although recent evidence has shown a new role of fluoxetine in motor rehabilitation, results are mixed. We conducted a randomized clinical trial to evaluate whether combining repetitive transcranial magnetic stimulation (rTMS) with fluoxetine increases upper limb motor function in stroke. Methods. Twenty-seven hemiparetic patients within 2 years of ischemic stroke were randomized into 3 groups: Combined (active rTMS + fluoxetine), Fluoxetine (sham rTMS + fluoxetine), or Placebo (sham rTMS + placebo fluoxetine). Participants received 18 sessions of 1-Hz rTMS in the unaffected primary motor cortex and 90 days of fluoxetine (20 mg/d). Motor function was assessed using Jebsen-Taylor Hand Function (JTHF) and Fugl-Meyer Assessment (FMA) scales. Corticospinal excitability was assessed with TMS. Results. After adjusting for time since stroke, there was significantly greater improvement in JTHF in the combined rTMS + fluoxetine group (mean improvement: −214.33 seconds) than in the placebo (−177.98 seconds, P = 0.005) and fluoxetine (−50.16 seconds, P < 0.001) groups. The fluoxetine group had less improvement than placebo on both scales (respectively, JTHF: −50.16 vs −117.98 seconds, P = 0.038; and FMA: 6.72 vs 15.55 points, P = 0.039), suggesting that fluoxetine possibly had detrimental effects. The unaffected hemisphere showed decreased intracortical inhibition in the combined and fluoxetine groups, and increased intracortical facilitation in the fluoxetine group. This facilitation was negatively correlated with motor function improvement (FMA, r2 = −0.398, P = 0.0395). Conclusion. Combined fluoxetine and rTMS treatment leads to better motor function in stroke than fluoxetine alone and placebo. Moreover, fluoxetine leads to smaller improvements than placebo, and fluoxetine’s effects on intracortical facilitation suggest a potential diffuse mechanism that may hinder beneficial plasticity on motor recovery.

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