EEG markers are associated to gray matter changes in thalamus and basal ganglia in subjects with mild cognitive impairment

Background: Gray matter (GM) changes of thalamus and basal ganglia have been demonstrated to be involved in Alzheimer's disease (AD). Moreover, the increase of two EEG markers, alpha3/alpha2 and theta/gamma ratio, have been associated with, respectively, AD converter and non-AD converter subjects with mild cognitive impairment (MCI). Objective: To study the association of prognostic EEG markers with specific GM changes of thalamus and basal ganglia in subjects with MCI to identify different MCI populations. Methods: 74 adult subjects with mild cognitive impairment underwent EEG recording and high resolution 3D magnetic resonance imaging (MRI). The theta/gamma and alpha3/alpha2 ratio was computed for each subject. Three groups were obtained according to increasing tertile values of both alpha3/alpha2 and theta/gamma ratio. Gray matter density differences between groups were investigated using a voxel-based morphometry technique. Results: Subjects with higher a3/a2 ratios when compared to subjects with lower and middle a3/a2 ratios showed minor atrophy in the ventral stream of basal ganglia (head of caudate nuclei and accumbens nuclei bilaterally) and of the pulvinar nuclei in the thalamus; subjects with higher t/g ratio showed minor atrophy in putamina nuclei bilaterally than subjects with middle ratio. Conclusion: The integrated analysis of EEG and morpho-structural markers could be useful in the comprehension of anatomo-physiological underpinning of the MCI entity.