Resting-state EEG spectral and fractal features in dementia with Lewy bodies with and without visual hallucinations

• Complex visual hallucinations are a core features of dementia with Lewy bodies, although not always present. • EEG Fractal Dimension discriminate patients with dementia with Lewy bodies showing visual hallucinations from other groups. • Linear spectral measures distinguish across patient groups less suggesting simpler brain dynamics in case of hallucinations. Complex visual hallucinations (VH) are a core feature of dementia with Lewy bodies (DLB), though they may not occur in all patients. Power spectral density (PSD) analysis of resting-state EEG (rs-EEG) shows associations between some frequency bands (e.g., theta), individual alpha frequency (IAF) and VH. However, new tools that improve early differential diagnosis and symptom-based stratification with higher sensitivity and specificity, even within the DLB population, are desirable. We aimed to assess differences in rs-EEG data between DLB patients with VH (DLB-VH+) and without VH (DLB-VH-), comparing innovative non-linear approaches with more traditional linear ones. We retrospectively analyzed rs-EEG recordings of DLB-VH+, DLB-VH-, Alzheimer’s disease patients and age-matched healthy controls. EEG was analyzed using the nonlinear Higuchi’s Fractal Dimension (FD) measure, and the results were compared with those of entropy and standard linear methods based on PSD and IAF. Only the FD measure could discriminate between DLB-VH+ and DLB-VH-. In conclusion, rs-EEG differences between DLB-VH+ and DLB-VH- are better characterized by FD analysis than by a more traditional power spectrum approach. This suggests that the presence of complex VH is associated with less complex brain dynamics at rest, as reflected by the FD measure.