Abstract
Background: Temporo-parietal and medial temporal cortex atrophy are associated with mild cognitive impairment (MCI) due to Alzheimer disease (AD) as well as the reduction of regional cerebral blood perfusion in hippocampus. Moreover, the increase of EEG alpha3/alpha2 power ratio has been associated with MCI due to AD and with an increase in theta frequency power in a group of subjects with impaired cerebral perfusion in hippocampus.Methods: Seventy four adult subjects with MCI underwent clinical and neuropsychological evaluation, electroencephalogram (EEG) recording and high resolution 3D magnetic resonance imaging (MRI). Among the patients, a subset of 27 subjects underwent also perfusion single-photon emission computed tomography and hippocampal atrophy evaluation. Alpha3/alpha2 power ratio as well as cortical thickness was computed for each subject. Three MCI groups were detected according to increasing tertile values of alpha3/alpha2 power ratio and difference of cortical thickness among the groups estimated.Results: Higher alpha3/alpha2 power ratio group had wider cortical thinning than other groups, mapped to the Supramarginal and Precuneus bilaterally. Subjects with higher alpha3/alpha2 frequency power ratio showed a constant trend to a lower perfusion than lower alpha3/alpha2 group. Moreover, this group correlates with both a bigger hippocampal atrophy and an increase of theta frequency power.Conclusion: Higher EEG alpha3/alpha2 power ratio was associated with temporo-parietal cortical thinning, hippocampal atrophy and reduction of regional cerebral perfusion in medial temporal cortex. In this group an increase of theta frequency power was detected inMCI subjects. The combination of higher EEG alpha3/alpha2 power ratio, cortical thickness measure and regional cerebral perfusion reveals a complex interplay between EEG cerebral rhythms, structural and functional brain modifications.
Highlights
The mild cognitive impairment (MCI) commonly represent the ‘at-risk’ state of developing dementia
We investigated significance of the difference between the two groups (MCI at low and at high risk to develop Alzheimer disease (AD)) in socio-demographic, clinical and cognitive features using χ2 test for categorical variables and Student’s independent t test for continuous variables
MRI-EEG Table 1 shows the sociodemographic and neuropsychological characteristics of MCI subgroups defined by the tertile values of alpha3/alpha2
Summary
The MCI commonly represent the ‘at-risk’ state of developing dementia. In neurodegenerative disorders, like AD or other dementias, the brain networks modifies many years before clinical manifestations (Dubois et al, 2007; Hampel et al, 2007; Albert et al, 2011; Galluzzi et al, 2013). Recent single-photon emission computed tomography (SPECT) studies have demonstrated that a large neural network is altered in subjects with prodromal AD, including precuneus, medial temporal, parietal and frontal cortices (Rodriguez et al, 1999). It has been demonstrated that temporo-parietal and medial temporal cortex atrophy are associated with mild cognitive impairment (MCI) due to Alzheimer disease (AD) as well as the reduction of regional cerebral perfusion in hippocampus. The increase of EEG alpha3/alpha power ratio has been associated with MCI due to AD and with an increase in theta frequency power in a group of subjects with impaired cerebral perfusion in hippocampus (Moretti et al, 2009, 2011a,b, 2012a,b, 2013a,b). Temporo-parietal and medial temporal cortex atrophy are associated with mild cognitive impairment (MCI) due to Alzheimer disease (AD) as well as the reduction of regional cerebral blood perfusion in hippocampus.
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