Posts Tagged interhemispheric inhibition

[Abstract] Role of Interhemispheric Cortical Interactions in Poststroke Motor Function

Background/Objective. We investigated interhemispheric interactions in stroke survivors by measuring transcranial magnetic stimulation (TMS)–evoked cortical coherence. We tested the effect of TMS on interhemispheric coherence during rest and active muscle contraction and compared coherence in stroke and older adults. We evaluated the relationships between interhemispheric coherence, paretic motor function, and the ipsilateral cortical silent period (iSP).

Methods. Participants with (n = 19) and without (n = 14) chronic stroke either rested or maintained a contraction of the ipsilateral hand muscle during simultaneous recordings of evoked responses to TMS of the ipsilesional/nondominant (i/ndM1) and contralesional/dominant (c/dM1) primary motor cortex with EEG and in the hand muscle with EMG. We calculated pre- and post-TMS interhemispheric beta coherence (15-30 Hz) between motor areas in both conditions and the iSP duration during the active condition.

Results. During active i/ndM1 TMS, interhemispheric coherence increased immediately following TMS in controls but not in stroke. Coherence during active cM1 TMS was greater than iM1 TMS in the stroke group. Coherence during active iM1 TMS was less in stroke participants and was negatively associated with measures of paretic arm motor function. Paretic iSP was longer compared with controls and negatively associated with clinical measures of manual dexterity. There was no relationship between coherence and. iSP for either group. No within- or between-group differences in coherence were observed at rest.

Conclusions. TMS-evoked cortical coherence during hand muscle activation can index interhemispheric interactions associated with poststroke motor function and potentially offer new insights into neural mechanisms influencing functional recovery.

 

via Role of Interhemispheric Cortical Interactions in Poststroke Motor Function – Jacqueline A. Palmer, Lewis A. Wheaton, Whitney A. Gray, Mary Alice Saltão da Silva, Steven L. Wolf, Michael R. Borich, 2019

, , , , , , ,

1 Comment

[Abstract] Targeting interhemispheric inhibition with neuromodulation to enhance stroke rehabilitation

Highlights

  • This review focuses on interhemispheric inhibition and its role in the healthy and stroke lesioned brain.
  • Measurement method and movement phase should be considered when comparing studies associating interhemispheric inhibition with functional recovery.
  • Neuromodulation of interhemispheric inhibition to augment stroke recovery requires the targeting of specific neural circuitry. We discuss the effectiveness of current and novel neurostimulation techniques at targeting interhemispheric inhibition and enhancing stroke rehabilitation.

Abstract

Background/Objectives

Interhemispheric inhibition in the brain plays a dynamic role in the production of voluntary unimanual actions. In stroke, the interhemispheric imbalance model predicts the presence of asymmetry in interhemispheric inhibition, with excessive inhibition from the contralesional hemisphere limiting maximal recovery. Stimulation methods to reduce this asymmetry in the brain may be promising as a stroke therapy, however determining how to best measure and modulate interhemispheric inhibition and who is likely to benefit, remain important questions.

Methods

This review addresses current understanding of interhemispheric inhibition in the healthy and stroke lesioned brain. We present a review of studies that have measured interhemispheric inhibition using different paradigms in the clinic, as well as results from recent animal studies investigating stimulation methods to target abnormal inhibition after stroke.

Main findings/Discussion

The degree to which asymmetric interhemispheric inhibition impacts on stroke recovery is controversial, and we consider sources of variation between studies which may contribute to this debate. We suggest that interhemispheric inhibition is not static following stroke in terms of the movement phase in which it is aberrantly engaged. Instead it may be dynamically increased onto perilesional areas during early movement, thus impairing motor initiation. Hence, its effect on stroke recovery may differ between studies depending on the technique and movement phase of eliciting the measurement. Finally, we propose how modulating excitability in the brain through more specific targeting of neural elements underlying interhemispheric inhibition via stimulation type, location and intensity may raise the ceiling of recovery following stroke and enhance functional return.

Source: Targeting interhemispheric inhibition with neuromodulation to enhance stroke rehabilitation – Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation

, , , , ,

Leave a comment

[Abstract] Targeting interhemispheric inhibition with neuromodulation to enhance stroke rehabilitation. – Brain Stimulation

Highlights

  • This review focuses on interhemispheric inhibition and its role in the healthy and stroke lesioned brain.
  • Measurement method and movement phase should be considered when comparing studies associating interhemispheric inhibition with functional recovery.
  • Neuromodulation of interhemispheric inhibition to augment stroke recovery requires the targeting of specific neural circuitry. We discuss the effectiveness of current and novel neurostimulation techniques at targeting interhemispheric inhibition and enhancing stroke rehabilitation.

Abstract

Background/Objectives

Interhemispheric inhibition in the brain plays a dynamic role in the production of voluntary unimanual actions. In stroke, the interhemispheric imbalance model predicts the presence of asymmetry in interhemispheric inhibition, with excessive inhibition from the contralesional hemisphere limiting maximal recovery. Stimulation methods to reduce this asymmetry in the brain may be promising as a stroke therapy, however determining how to best measure and modulate interhemispheric inhibition and who is likely to benefit, remain important questions.

Methods

This review addresses current understanding of interhemispheric inhibition in the healthy and stroke lesioned brain. We present a review of studies that have measured interhemispheric inhibition using different paradigms in the clinic, as well as results from recent animal studies investigating stimulation methods to target abnormal inhibition after stroke.

Main findings/Discussion

The degree to which asymmetric interhemispheric inhibition impacts on stroke recovery is controversial, and we consider sources of variation between studies which may contribute to this debate. We suggest that interhemispheric inhibition is not static following stroke in terms of the movement phase in which it is aberrantly engaged. Instead it may be dynamically increased onto perilesional areas during early movement, thus impairing motor initiation. Hence, its effect on stroke recovery may differ between studies depending on the technique and movement phase of eliciting the measurement. Finally, we propose how modulating excitability in the brain through more specific targeting of neural elements underlying interhemispheric inhibition via stimulation type, location and intensity may raise the ceiling of recovery following stroke and enhance functional return.

Source: Targeting interhemispheric inhibition with neuromodulation to enhance stroke rehabilitation – Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation

, , , , ,

Leave a comment

[ARTICLE] Neural Substrates of Motor Recovery in Severely Impaired Stroke Patients With Hand Paralysis

Abstract

In well-recovered stroke patients with preserved hand movement, motor dysfunction relates to interhemispheric and intracortical inhibition in affected hand muscles. In less fully recovered patients unable to move their hand, the neural substrates of recovered arm movements, crucial for performance of daily living tasks, are not well understood.

Here, we evaluated interhemispheric and intracortical inhibition in paretic arm muscles of patients with no recovery of hand movement (n = 16, upper extremity Fugl-Meyer Assessment = 27.0 ± 8.6). We recorded silent periods (contralateral and ipsilateral) induced by transcranial magnetic stimulation during voluntary isometric contraction of the paretic biceps and triceps brachii muscles (correlates of intracortical and interhemispheric inhibition, respectively) and investigated links between the silent periods and motor recovery, an issue that has not been previously explored.

We report that interhemispheric inhibition, stronger in the paretic triceps than biceps brachii muscles, significantly correlated with the magnitude of residual impairment (lower Fugl-Meyer scores). In contrast, intracortical inhibition in the paretic biceps brachii, but not in the triceps, correlated positively with motor recovery (Fugl-Meyer scores) and negatively with spasticity (lower Modified Ashworth scores).

Our results suggest that interhemispheric inhibition and intracortical inhibition of paretic upper arm muscles relate to motor recovery in different ways. While interhemispheric inhibition may contribute to poorer recovery, muscle-specific intracortical inhibition may relate to successful motor recovery and lesser spasticity.

via Neural Substrates of Motor Recovery in Severely Impaired Stroke Patients With Hand Paralysis.

, , , , , , , , , ,

Leave a comment

[ARTICLE] Neurorehabilitation and Neural Repair

Abstract

Background. Motor deficits after a stroke are thought to be compounded by the development of asymmetric interhemispheric inhibition. Bilateral priming was developed to rebalance this asymmetry and thus improve therapy efficacy.

Objective. This study investigated the effect of bilateral priming before Wii-based Movement Therapy to improve rehabilitation after stroke.

Methods. Ten patients who had suffered a stroke (age, 23-77 years; 3-123 months after stroke) underwent a 14-day program of Wii-based Movement Therapy for upper limb rehabilitation. Formal Wii-based Movement Therapy sessions were immediately preceded by 15 minutes of bilateral priming, whereby active flexion-extension of the less affected wrist drove mirror-symmetric passive movements of the more affected wrist through a custom device. Functional movement was assessed at weeks 0 (before therapy), 3 (after therapy), and 28 (follow-up) using the Wolf Motor Function Test (WMFT), upper limb Fugl-Meyer Assessment (FMA), upper limb range of motion, and Motor Activity Log (MAL). Case-matched controls were patients who had suffered a stroke who received Wii-based Movement Therapy but not bilateral priming.

Results. Upper limb functional ability improved for both groups on all measures tested. Posttherapy improvement on the FMA for primed patients was twice that of the unprimed patients (37.3% vs 14.6%, respectively) and was significantly better maintained at 28 weeks (P = .02). Improvements on the WMFT and MAL were similar for both groups, but the pattern of change in range of motion was strikingly different.

Conclusions. Bilateral priming before Wii-based Movement Therapy led to a greater magnitude and retention of improvement compared to control, especially measured with the FMA. These data suggest that bilateral priming can enhance the efficacy of Wii-based Movement Therapy, particularly for patients with low motor function after a stroke.

via Neurorehabilitation and Neural Repair.

, , , , , , , ,

Leave a comment

%d bloggers like this: