Occipital sources of resting-state alpha rhythms are related to local gray matter density in subjects with amnesic mild cognitive impairment and Alzheimer's disease

Abstract

Occipital sources of resting state electroencephalographic (EEG) alpha rhythms are abnormal, at the group level, in patients with amnesic mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Here we evaluated the hypothesis that amplitude of these occipital sources is related to neurodegeneration in occipital lobe as measured by magnetic resonance imaging (MRI). Resting-state eyes-closed EEG rhythms were recorded in 45 healthy elderly (Nold), 100 MCI, and 90 AD subjects. Neurodegeneration of occipital lobe was indexed by weighted averages of gray matter density (GMD), estimated from structural MRIs. EEG rhythms of interest were alpha 1 (8–10.5 Hz) and alpha 2 (10.5–13 Hz). EEG cortical sources were estimated by low resolution brain electromagnetic tomography (LORETA). Results showed a positive correlation between occipital GMD and amplitude of occipital alpha 1 sources in Nold, MCI and AD subjects as a whole group (r=0.3, p=0.000004, N=235). Furthermore, there was a positive correlation between amplitude of occipital alpha 1 sources and cognitive status as revealed by Mini Mental State Evaluation (MMSE) score across all subjects (r=0.38, p=0.000001, N=235). Finally, amplitude of occipital alpha 1 sources allowed a moderate classification of individual Nold and AD subjects (sensitivity: 87.8%; specificity: 66.7%; area under the Receiver Operating Characteristic (ROC) curve: 0.81). These results suggest that the amplitude of occipital sources of resting state alpha rhythms is related to AD neurodegeneration in occipital lobe along pathological aging.

Electroencephalogram dynamics during general anesthesia predict the later incidence and duration of burst-suppression during cardiopulmonary bypass

“…We note that healthy aging is associated with an age-dependent decrease in anesthesia-induced frontal alpha oscillation power (Akeju et al , 2015, Purdon et al , 2015, Lee et al , 2017). However, similar to the accelerated decrease in the awake-occipital alpha oscillation power that is associated with neurodegeneration in patients with mild cognitive impairment and Alzheimer’s disease (Rossini et al , 2007, Babiloni et al , 2013, Babiloni et al , 2015), significantly decreased anesthesia-induced frontal alpha and beta power may reflect sub-clinical neurodegenerative changes.…”

Revolution of Alzheimer Precision Neurology. Passageway of Systems Biology and Neurophysiology

“…They may probe the neurophysiological “reserve” in AD patients, as one of the dimensions of the brain reserve [311]. This neurophysiological “reserve” may reflect residual mechanisms for 1) “synchronization” of neural activity in a given cortical region and 2) the coupling of activity between nodes of a given brain neural networks as a sign of functional cortical “connectivity” [310, 312]. …”

“…Abnormal posterior cortical delta rhythms in ADD patients might reflect an upregulation of their generation mechanisms in quiet wakefulness, possibly due to cortical blood hypoperfusion and synaptic dysfunction in the same regions [363–366] and atrophy in the posterior cortex [312, 352, 367–369]. Furthermore, reduced posterior cortical alpha rhythms in ADD subjects might be due to an unselective tonic cortical excitation in populations of cortical pyramidal, thalamo-cortical, and reticular thalamic neurons generating those rhythms [370–372].…”

Clinical Neurophysiological and Automated EEG-Based Diagnosis of the Alzheimer's Disease

“…Babiloni et al [88] [89] analyze changes in EEG synchrony in the theta band and observe an increase in the EEG synchrony in its narrow frequency ranges. They also propose a synchrony ratio to enhance the difference between subjects with AD and control group.…”