EEG Alpha Band Synchrony Predicts Cognitive and Motor Performance in Patients with Ischemic Stroke

Abstract

Functional brain networks are known to be affected by focal brain lesions. However, the clinical relevance of these changes remains unclear. This study assesses resting-state functional connectivity (FC) with electroencephalography (EEG) and relates observed topography of FC to cognitive and motor deficits in patients three months after ischemic stroke. Twenty patients (mean age 61.3 years, range 37–80, 9 females) and nineteen age-matched healthy participants (mean age 66.7 years, range 36–88, 13 females) underwent a ten-minute EEG-resting state examination. The neural oscillations at each grey matter voxel were reconstructed using an adaptive spatial filter and imaginary component of coherence (IC) was calculated as an index of FC. Maps representing mean connectivity value at each voxel were correlated with the clinical data. Compared to healthy controls, alpha band IC of stroke patients was locally reduced in brain regions critical to observed behavioral deficits. A voxel-wise Pearson correlation of clinical performances with FC yielded maps of the neural structures implicated in motor, language, and executive function. This correlation was again specific to alpha band coherence. Ischemic lesions decrease the synchrony of alpha band oscillations between affected brain regions and the rest of the brain. This decrease is linearly related to cognitive and motor deficits observed in the patients.

Neurorehabilitation in Stroke: The Role of Functional Connectivity

“…Compared to healthy subjects, patients with ischemic stroke exhibited decreased alpha coherence between the perilesional area and cortical regions critical to the behavioral deficits (e.g., language, motor, executive functions) observed in their clinical and neuropsychological assessments. This functional abnormality predicted cognitive performance, suggesting a role for alpha band connectivity in the processing of cognitive functions [10]. These findings are consistent with the fact that alpha band coherence of clinically dysfunctional areas like the right parietal lobe is able to predict the effects of cortical stimulation on parietal network functions, including visuospatial attention [5].…”

Neuroplasticity and network connectivity of the motor cortex following stroke: A transcranial direct current stimulation study

“…Functional connectivity in several different frequency bands were investigated, with connectivity in the alpha band providing the strongest association with anodal tDCS response. Previous studies have demonstrated the functional significance of alpha oscillations which have been associated with post stroke subacute clinical status, motor performance and functional recovery (Dubovik et al, ; Kawano et al, ; Westlake et al, ). Furthermore, studies have reported alpha oscillations are associated with attention, memory, motor learning and performance (Harris, Dux, Jones, & Mattingley, ; Jensen, Gelfand, Kounios, & Lisman, ; Mottaz et al, ; Pollok, Boysen, & Krause, ).…”

Investigating the ability of post-stroke EEG measures of brain dysfuntion to inform early prediction of cognitive impairment or depression outcomes

“…At 3-months post stroke, in 20 anterior territory ischaemic stroke patients alpha frequency synchronicity between lesion affected and unaffected regions of the brain was reduced compared to 19 matched healthy controls (Dubovik et al, 2013). In addition, the degree of reduction in alpha synchronicity in stroke patients shared a linear relationship with both cognitive and motor deficits (Dubovik et al, 2013). The relationship was only significant in regions involved in the function being tested, for example between verbal fluency performance and the left inferior frontal gyrus (Broca's area).…”

“…Dubovik et al (2013) investigated alpha frequency activity recorded at 3-months following ischaemic stroke in 20 patients and in 19 healthy controls (Dubovik et al, 2013). Cognitive domains including executive functioning, verbal and working memory were assessed in each patient.…”

“…Functional connectivity assessed using a coherence measuring the alpha frequency was significantly reduced over the lesion affected hemisphere in stroke patients and there was a correlation between increased functional connectivity in the alpha frequency and better performance on the cognitive tasks. Furthermore the regions of increased functional connectivity in the alpha frequency were critical for processing the specific cognitive function for example, good performance on verbal fluency tasks correlated with increased functional connectivity in Broca's areas (left inferior frontal gyrus) (Dubovik et al, 2013). This study outlines the value of post-stroke alpha frequency measures in assessing cognitive function and supports the postulation that in the current study power in the classical theta frequency is actually indexing slowed alpha frequency power and is associated with post-stroke cognitive impairment.…”