Neural oscillations modulation during working memory in pre-manifest and early Huntington's disease

Introduction: We recently demonstrated specific spectral signatures associated with updating of memory information, working memory (WM) maintenance and readout, with relatively high spatial resolution by means of high-density electroencephalography (hdEEG). WM is impaired already in early symptomatic HD (early-HD) and in pre-manifest HD (pre-HD). The aim of this study was to test whether hdEEG coupled to source localization allows for the identification of neuronal oscillations in specific frequency bands in 16 pre-HD and early-HD during different phases of a WM task. Methods: We examined modulation of neural oscillations by event-related synchronization and desynchronization (ERS/ERD) of 0, beta, gamma low, gamma LOW and gamma HIGH EEG bands in a-priori selected large fronto-parietal network, including the insula and the cerebellum. Results: We found: (i) Reduced 0 oscillations in HD with respect to controls in almost all the areas of the WM network during the update and readout phases; (ii) Modulation of beta oscillations, which increased during the maintenance phase of the WM task in both groups; (iii) correlation of gamma HIGH oscillations during WM task with disease burden score in HD patients.Conclusions: Our data show reduced phase-specific modulation of oscillations in pre-HD and early-HD, even in the presence of preserved dynamic of modulation. Particularly, reduced synchronization in the 0 band in the areas of the WM network, consistent with abnormal long-range coordination of neuronal activity within this network, was found in update and readout phases in HD groups.