Coherent neural oscillations predict future motor and language improvement after stroke

Abstract

Recent findings have demonstrated that stroke lesions affect neural communication in the entire brain. However, it is less clear whether network interactions are also relevant for plasticity and repair. This study investigated whether the coherence of neural oscillations at language or motor nodes is associated with future clinical improvement. Twenty-four stroke patients underwent high-density EEG recordings and standardized motor and language tests at 2-3 weeks (T0) and 3 months (T1) after stroke onset. In addition, EEG and motor assessments were obtained from a second population of 18 stroke patients. The graph theoretical measure of weighted node degree at language and motor areas was computed as the sum of absolute imaginary coherence with all other brain regions and compared to the amount of clinical improvement from T0 to T1. At T0, beta-band weighted node degree at the ipsilesional motor cortex was linearly correlated with better subsequent motor improvement, while beta-band weighted node degree at Broca's area was correlated with better language improvement. Clinical recovery was further associated with contralesional theta-band weighted node degree. These correlations were each specific to the corresponding brain area and independent of initial clinical severity, age, and lesion size. Findings were reproduced in the second stroke group. Conversely, later coherence increases occurring between T0 and T1 were associated with less clinical improvement. Improvement of language and motor functions after stroke is therefore associated with inter-regional synchronization of neural oscillations in the first weeks after stroke. A better understanding of network mechanisms of plasticity may lead to new prognostic biomarkers and therapeutic targets.See Ward (doi:10.1093/brain/awv265) for a scientific commentary on this article.

Early Rehabilitation After Stroke: a Narrative Review

“…In many cases, these plastic changes did not translate into functional gains. Nonetheless, research using tMS, fMRI, positron emission tomography (PET), or other novel tools such as high-density array EEG [90, 91] to understand how rehabilitation changes brain function after stroke is of great value in advancing the scientific underpinnings of the field and may aid in designing successful trials.…”

Spontaneous and Therapeutic-Induced Mechanisms of Functional Recovery After Stroke

“…EEG measures of coherence or phase and amplitude consistency of neural oscillations between two brain regions may function as additional probes of those processes evaluated with resting-state fMRI functional connectivity analyses as above [145, 146]. Dubovik et al [147] found greater disruption of functional connectivity in the alpha frequency band in individuals with stroke relative to healthy controls.…”

“…Additional work is warranted to substantiate these findings. Other examples of potential stroke biomarkers include total infarct volume [195], white matter tract injury [20–22, 138, 196], cortical activation [42, 52, 91, 175, 138, 197, 198] and connectivity [139, 137, 145, 147, 177, 138, 199], and genetic polymorphisms derived from simple blood tests [15, 16, 200]. These measures may serve an important role in guiding treatment, stratifying subjects in intervention studies, and ultimately predicting functional outcome and response to therapy.…”

Neuroplasticity of language in left‐hemisphere stroke: Evidence linking subsecond electrophysiology and structural connections

“…Similarly, neuroplasticity indexed by spectral and evoked potential changes in working memory and attention has been observed after strokes in lateral frontal cortex (Voytek et al 2010). The potential of such neuronal oscillations as biomarkers for monitoring neurorehabilitation and recovery of language function is largely unexplored (e.g., Kielar et al 2016; Meltzer et al 2013; Nicolo et al, 2015; Spironelli & Angrilli, 2009; Spironelli et al 2013). …”