Mirrored Feedback in Chronic Stroke: Recruitment and Effective Connectivity of Ipsilesional Sensorimotor Networks

Did your doctor or hospital do ONE DAMN THING with this in the past 7.5 years? Or are you going to continuously let incompetence infect your hospital? 

Do you fell better about them being incompetent for 8.7 years instead of just 7.5 years?

• mirror therapy (86 posts to October 2012) 

Mirrored Feedback in Chronic Stroke: Recruitment and Effective Connectivity of Ipsilesional Sensorimotor Networks

Soha Saleh, PhD, Sergei V. Adamovich, PhD, Eugene Tunik, PhD, PT

First Published December 26, 2013 Research Article Find in PubMed 

https://doi.org/10.1177/1545968313513074

Article information

Abstract

Background. 

Mirrored feedback has potential as a therapeutic intervention to restore hand function after stroke. However, the functional (effective) connectivity of neural networks involved in processing mirrored feedback after stroke is not known.  

Objective. 

To determine if regions recruited by mirrored feedback topographically overlap with those involved in control of the paretic hand and to identify the effective connectivity of activated nodes within the mirrored feedback network.  

Methods. 

Fifteen patients with chronic stroke performed a finger flexion task with their unaffected hand during event-related functional magnetic resonance imaging (fMRI). Real-time hand kinematics was recorded during fMRI and used to actuate hand models presented in virtual reality (VR). Visual feedback of the unaffected hand motion was manipulated pseudorandomly by either actuating the VR hand corresponding to the moving unaffected side (veridical feedback) or the affected side (mirrored feedback). In 2 control conditions, the VR hands were replaced with moving nonanthropomorphic shapes. 

Results. 

Mirrored feedback was associated with significant activation of regions within and outside the ipsilesional sensorimotor cortex, overlapping with areas engaged when patients performed the task with their affected hand. Effective connectivity analysis showed a significantly interconnected ipsilesional somatosensory and motor cortex in the mirrored feedback condition.  

Conclusions. 

Mirrored feedback recruits ipsilesional brain areas relevant for control of the affected hand. These data provide a neurophysiological basis by which mirrored feedback may be beneficial as a therapy for restoring function after stroke.

Keywords mirrored feedback, motor control, fMRI, virtual reality, visuomotor integration

The excitability of the ipsilesional corticospinal system after stroke is a marker of long-term functional recovery, ¹ which may explain why therapies that foster activation of the ipsilesional motor cortex have therapeutic value.^2,3 We suggest that providing mirrored feedback during movement, by visually mirroring the actual limb movement in real time, can facilitate activity of the ipsilesional motor cortex via rich intrahemispheric^4-6 and interhemispheric^7-10 connections among frontoparietal areas. Mirror therapy was originally introduced by Ramachandran and Rogers-Ramachandran¹¹ to reduce phantom limb pain in amputees and may benefit the recovery of hand function after stroke.^12-14 The core feature of mirror therapy is the incongruence between actual performance and mirrored feedback, which can be delivered by means of an actual mirror or through virtual reality (VR).

To our knowledge, only one group has so far investigated the neural correlates of mirror therapy in populations with chronic stroke. Michielsen and coworkers¹⁵ showed that mirror therapy may activate the precuneus and posterior cingulate cortex and that 6 weeks of bimanual exercises with mirrored feedback leads to significant increases in the blood oxygen level–dependent signal and its relateralization toward the ipsilesional side (compared to similar training without mirrored feedback).¹² A number of investigations have revealed similar effects in healthy individuals,^16,17 along with increases in corticospinal excitability (measured with motor evoked potentials).^18-21 Together, these findings suggest that mirrored feedback can modify the activation of sensorimotor brain areas in healthy populations and those with chronic stroke. However, the effective connectivity for mirrored feedback within the sensorimotor network, that is, how nodes in the sensorimotor network functionally interact in response to mirrored feedback, is still unknown. Studies by our group^22-24 and others^25,26 have shown that feedback of hand motion presented through high-fidelity VR can facilitate classic visuomotor networks in healthy and patient populations. Therefore, the aims of this study in patients with chronic stroke were the following: (1) To identify areas of the visuomotor system where activation is facilitated by mirrored feedback of unaffected hand motion. We hypothesized that mirrored feedback would activate the ipsilesional motor cortex. (2) To identify the functionally interconnected brain networks during mirrored feedback. We hypothesized that regions in the ipsilesional posterior parietal cortex and motor cortex would show increased functional connectivity elicited by mirrored feedback. (3) To test the relationship between changes in mirrored feedback–induced brain activation and the level of hand function. We hypothesized that the degree of activation elicited by mirrored feedback would depend on the level of hand function. (4) To test if regions with activation elicited by mirrored feedback overlap with those that are involved in volitional control of the affected hand. We hypothesized that mirrored feedback would facilitate brain regions that are relevant for control of the affected hand.

For this, patients with chronic stroke underwent event-related functional magnetic resonance imaging (fMRI). Participants performed simple finger movements during scanning, with their finger motion recorded using instrumented data gloves. Kinematic data from the gloves were used to actuate, in real time, the motion of virtual hand models. In any given trial, the VR hand motion corresponded either to the moving unaffected hand (veridical feedback) or to the affected hand (mirrored feedback). The use of a VR mirror setup with simultaneous performance of fMRI and hand kinematics allowed us to (1) ensure that patients focused exclusively on mirrored feedback without being distracted by seeing motion of the other hand, as might occur when using a physical mirror setup; (2) use an event-related design to pseudorandomize the conditions (which would be impossible if using a physical mirror); (3) identify and exclude from analysis any trials confounded by inadvertent motion of the fingers; and (4) deliver a set of control conditions to rule out confounders in activation that may be attributed to motor output, visual field, or arbitrary visual motion effects.

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