Activity of Cerebral Networks, Amyloid and Microglia in Aging and Alzheimer's Disease

MRI data acquisition was performed on a 3 Tesla MRI scanner with parallel transmission and reception technology (Skyra Magnetom, Siemens Healthcare, Erlangen, Germany). Imaging is performed with a maximum gradient strength of 45mT/m and a maximum slew rate of 200 T/m/s and a 64-element head coil.

A 20-channel resting EEG (Brain Products, Gilching, Germany) is recorded as part of routine clinical diagnostics in the Department of Psychiatry and Psychotherapy at the LMU to rule out focal neurophysiological pathologies. Within the scope of the present study, an extended examination will be carried out, which includes a 64-channel EEG, including a passive visual paradigm. After completion of the clinical evaluation, the neurophysiological changes in resting activity will be scientifically analyzed in comparison to the MRI and PET data.

Aβ1-42 and 1-40, total tau protein and phosphorylated tau protein 181 (p-Tau), apolipoprotein E (APOE), soluble TREM2 protein, neurofilament light chain and glial fibrillary protein (GFAP) will be determined.

According to an established and standardized protocol, PET scans are performed with the TSPO receptor ligand \[18F\]-GE-180, \[18F\]flutemetamol for assessment of fibrillar Aβ 162 accumulation and the Tau ligand \[18F\]-PI-2620. In brief, \[18F\]GE-180 TSPO PET images (mean dose: 177 ± 17 MBq) with an emission window of 60-80 min after injection will be acquired to measure the activation of glial cells. \[18F\]Flutemetamol Aβ PET images (average dose: 182 ± 11 MBq) are acquired with an emission window of 90-110 min after injection to assess fibrillar Aβ accumulation. Dynamic \[18F\]PI-2620 tau PET (average dose: 186 ± 14 MBq) with an emission window of 0-60 minutes after injection are performed for quantification of tau aggregation. Static images of the late phase (20-40 min) are reconstructed. These images are used for further processing and analysis.

Trained psychologists at the Memory Clinic of the LMU Hospital administered the CDR, CERAD-NB and Mini-Mental State Examination (MMSE). The CERAD-NB battery was used to generate a total score for the six subscales: semantic fluency (animals/60 s), modified Boston naming test, lexical items, construction practice, lexical items retrieval, and lexical items discrimination, with higher scores indicating better performance.