Boundary EEG Asymmetry Is Associated to Linguistic Competence in Vascular Cognitive Impairments.

Background and Purpose: We recently noted a gradual change in the boundary electroencephalography (EEG) oscillation of 7.8 Hz between theta (θ) and alpha (α) bands in response to increased atherosclerosis levels in the elderly. The aim of this study was to investigate the role of boundary EEG oscillations of θ-α bands on cognitive functions in vascular cognitive impairments (VCI) patients. Materials and Methods: We examined 55 patients with VCI in carotid stenosis, and underwent EEG in a resting state with closed eyes for 5 min. The asymmetry index (AI) along homologous channel pairs (e.g., F7-8) was assessed using neuronal activity topography (NAT). AI referring to 10 frequency components ranging from 4 to 20 Hz and neuropsychological assessments including linguistic competence were analyzed. Results: The main findings was that the language score had a positive association with AI in 7.8 Hz at F7-8 and a negative association with AI in 6.3 Hz at C3-4 and 14.1 Hz at F3-4. Conclusion: EEG asymmetry in a boundary range might have a special role in linguistic competence, suggesting the application of neural oscillation on the cognitive function evaluation and neurorehabilition induced by a frequency-specific transcranial alternating current stimulation.

Altered Neuronal Activity Topography Markers in the Elderly with Increased Atherosclerosis.

Background: Previously, we reported on vascular cognitive impairment (VCI) templates, consisting of patients with VCI associated with carotid stenosis (>60%) using a quantitative electroencephalographic (EEG) technique called neuronal activity topography (NAT). Here using the VCI templates, we investigated the hypothesis that internal carotid artery-intima-media thickness (ICA-IMT) is associated with EEG spectrum intensity (sNAT) and spectrum steepness (vNAT). Methods: A total of 221 community-dwelling elderly subjects were recruited. Four groups were classified according to quartiles of ICA-IMT as assessed by ultrasonography: control group A, normal (≤0.9 mm); group B, mild atherosclerosis (1-1.1 mm); group C, moderate atherosclerosis (1.2-1.8 mm); and group D, severe atherosclerosis (≥1.9 mm). EEG markers of power ratio index (PRI), and the binary likelihood of being in the VCI group vs. the that of being in control group A (sL x:VCI-A , vL x:VCI-A ) were assessed, respectively. Differences in mean total scores for PRI, sL x:VCI-A , vL x:VCI-A , between control group A and the other groups were compared using Dunnett's test, respectively. Results: The mean total scores of the PRI were 3.25, 3.00, 2.77, and 2.26 for groups A, B, C, and D, respectively. There was a significant decrease in the PRI in group D compared with group A (P = 0.0066). The mean total scores of the sL x:VCI-A were -0.14, -0.11, -0.1, and -0.03 for groups A, B, C, and D, respectively. The sL x:VCI-A in group D was significantly higher compared to that in group A (P < 0.0001). The mean total scores of the vL x:VCI-A were -0.04,-0.01, 0.01, and 0.06 for group A, B, C, and D, respectively. The vL x:VCI-A in group D and group C was significantly higher compared to that in group A, respectively (P < 0.0001, P = 0.02). Conclusion: Community-dwelling elderly subjects in the increased carotid atherosclerosis of ICA-IMT (≥1.9 mm) were at greatest risk of an EEG change as assessed by NAT.

Neuronal activity topography parameters as a marker for differentiating vascular cognitive impairment in carotid stenosis.

Previously, we reported on the differentiation between patients with Alzheimer disease and normal controls using a quantitative electroencephalographic technique called neuronal activity topography (NAT). In this technique, cerebral neuronal activities are characterized by the signal intensity and coherence (sNAT and vNAT, respectively). In the present study, we examined 47 patients with vascular cognitive impairment in carotid stenosis and 52 normal controls. All subjects underwent electroencephalography in a resting state with closed eyes for 5 minutes. Electroencephalographic markers of the differential likelihood, that is, the sensitivity-versus-specificity characteristics, sL(x:VCI-NLc) and vL(x:VCI-NLc), were assessed with neuronal activity topography and were compared between the 2 groups. sL(x:VCI-NLc) and vL(x:VCI-NLc) crossed each other at a cutoff value of the differential likelihood. Separation of the patients and controls was made with a sensitivity of 92% and 88%, as well as a false-positive rate of 8% and 12% for sL(x:VCI-NLc) and vL(x:VCI-NLc), respectively. Using sNAT, we accurately differentiated 92% patients with vascular cognitive impairment. We recommend that sNAT, rather than vNAT, should be used in detecting vascular cognitive impaired patients.