The averaged eLORETA solutions in patients and controls for each frequency band are shown in Fig. 1. The highest current density values were found in the delta frequency band (AD 3.5±2.4; HC: 2.6±1.9), followed by alpha1 band (AD: 1.3±0.6; HC: 2.5±1.7). There was a similar cortical distribution of maximal delta activity across groups over the frontal cortex, whereas alpha1 sources with high current density maxima over the parieto-occipital region were seen only in controls. The statistical analysis revealed significant differences between groups exclusively in the alpha1 frequency band, patients with AD exhibiting reduced activity in the parieto-occipital cortex bilaterally, with the right precuneus showing the highest significance (x = 10, y = −75, z = 50; Log F-ratio: −1.03, p = 0.034 corrected) (Fig. 2). An increase in delta oscillations in fronto-central regions nearly reached statistical significance (Log F-ratio: −0.78, p = 0.063 corrected). Among patients with AD, those carrying the APOE-4 allele exhibited a significant reduction in alpha1 activity compared with noncarriers. These oscillations localized to the left temporo-occipital region and the inferior parietal cortex; the latter showing the highest difference (x = −64, y = −37, z = 30; Log F-ratio: −1.05, p = 0.045 corrected) (Fig. 3).
