Time‐frequency analysis in a working memory task in pre‐clinical stage and symptomatic stage of Alzheimer’s disease

Background The characteristic deterioration of the working memory (WM) in Alzheimer’s disease (AD), is also one of its first symptoms. Alterations of oscillatory activity have been evidenced in frequency bands in underlined neuronal processes during WM task execution; in comparison to healthy individuals; since the first clinical manifestation of the disease – in patients with mild cognitive impairment (MCI) ‐ until the lasts phases of the disease. However, those alterations in the WM have not been widely studied in individuals that refer subjective cognitive decline (SCD) without objective evidence of cognitive deterioration. Method The power of the underlined oscillatory activity during the maintenance period after an interruptor in a WM task was calculated by conducting a time‐frequency analysis. The results of three groups were compared: Controls (n = 46); SCD (n = 40), and MCI (n = 35). Result Statistically significant results were found between‐group. Patients with MCI evidenced a decrease in alpha band in temporal, parietal and occipital sensors of both hemispheres in comparison to controls (clusterF = 3.22e+04, p= 4.99e‐05, η 2 =0.09). SCD group showed a decrease in beta band in left hemisphere in frontal and parietal sensors (clusterF=3.65e+03, p= 0.02, η 2 =0.06) in comparison to controls. SCD evidenced a decrement in theta band in the left hemisphere in fronto‐temporals sensors (clusterF=4.05e+03, p= 0.02, η 2 =0.06). Conclusion As a conclusion, the subjective perception of SCD seems to have a biological correlate, assessable through alterations in the neuronal activity associated with WM maintenance.