Characterizing relationships of DTI, fMRI, and motor recovery in stroke rehabilitation utilizing brain-computer interface technology.

Jie Song,Zack Nigogosyan,Justin A Sattin,Vivek Prabhakaran,Justin C Williams,Kristin E Caldera,Veena A Nair,Brittany M Young,Scott W Grogan,Dorothy Farrar-Edwards,Mitchell E Tyler,Leo M Walton

doi:10.3389/fneng.2014.00031

Abstract

The relationship of the structural integrity of white matter tracts and cortical activity to motor functional outcomes in stroke patients is of particular interest in understanding mechanisms of brain structural and functional changes while recovering from stroke. This study aims to probe these underlying mechanisms using diffusion tensor imaging (DTI) and fMRI measures. We examined the structural integrity of the posterior limb of the internal capsule (PLIC) using DTI and corticomotor activity using motor-task fMRI in stroke patients who completed up to 15 sessions of rehabilitation therapy using Brain-Computer Interface (BCI) technology. We hypothesized that (1) the structural integrity of PLIC and corticomotor activity are affected by stroke; (2) changes in structural integrity and corticomotor activity following BCI intervention are related to motor recovery; (3) there is a potential relationship between structural integrity and corticomotor activity. We found that (1) the ipsilesional PLIC showed significantly decreased fractional anisotropy (FA) values when compared to the contralesional PLIC; (2) lower ipsilesional PLIC-FA values were significantly associated with worse motor outcomes (i.e., ipsilesional PLIC-FA and motor outcomes were positively correlated.); (3) lower ipsilesional PLIC-FA values were significantly associated with greater ipsilesional corticomotor activity during impaired-finger-tapping-task fMRI (i.e., ipsilesional PLIC-FA and ipsilesional corticomotor activity were negatively correlated), with an overall bilateral pattern of corticomotor activity observed; and (4) baseline FA values predicted motor recovery assessed after BCI intervention. These findings suggest that (1) greater vs. lesser microstructural integrity of the ipsilesional PLIC may contribute toward better vs. poor motor recovery respectively in the stroke-affected limb and demand lesser vs. greater cortical activity respectively from the ipsilesional motor cortex; and that (2) PLIC-FA is a promising biomarker in tracking and predicting motor functional recovery in stroke patients receiving BCI intervention.

Highlights

Studies have suggested that motor recovery after stroke is related to the structural remodeling of white matter tracts (Liu et al, 2008; Schaechter et al, 2009) and the reorganization of cortical activity (Dijkhuizen et al, 2001; Jaillard et al, 2005; Grefkes et al, 2008) in the ipsilesional and contralesional hemispheres
Given the significance of posterior limb of the internal capsule (PLIC) involved in motor recovery, one specific aim of this study is to evaluate the stroke-induced changes in structural integrity of the PLIC using Diffusion tensor imaging (DTI) fractional anisotropy (FA) and to investigate if these changes are related to motor recovery
In this study corticomotor activity is evaluated using motor-task fMRI and quantified by counts of statistically significantly active voxels within the ipsilesional and contralesional motor cortices. Another specific aim of this study is to evaluate the changes in corticomotor activity, and to further examine if these changes are related to motor recovery. Combining both DTI and fMRI analysis, we examine the potential relationship between structural integrity of PLIC and functional integrity of motor cortex, and examine how this relationship interact with motor recovery in patients receiving Brain-Computer Interface (BCI) intervention

Summary

Introduction

Studies have suggested that motor recovery after stroke is related to the structural remodeling of white matter tracts (Liu et al, 2008; Schaechter et al, 2009) and the reorganization of cortical activity (Dijkhuizen et al, 2001; Jaillard et al, 2005; Grefkes et al, 2008) in the ipsilesional and contralesional hemispheres. About the relationship between the white matter structural integrity and functional cortical activity of the sensorimotor region and how these two factors interact with motor recovery in stroke patients. Neuroimaging correlates of stroke recovery is one of these imaging methods, which allows for quantitative evaluations of the structural integrity of white matter tracts after a stroke (Werring et al, 2000; Stinear et al, 2007; Yu et al, 2009). DTI-derived measures have been shown as potential biomarkers used for tracking motor impairment (Schaechter et al, 2009; Lindenberg et al, 2010; Sterr et al, 2010; Yeo et al, 2010; Borich et al, 2012; Chen and Schlaug, 2013) and motor recovery (Liang et al, 2009) after stroke. Measures derived from fMRI have been shown as potential biomarkers to track recovery, with correlations between functional changes and fMRI measures demonstrated with treatments such as Brain-Computer Interface (BCI) therapy (Mukaino et al, 2014), constrain-induced movement therapy (Murayama et al, 2011; Kononen et al, 2012) and motor imagery therapy (Sun et al, 2013)

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