Quantifying stimulus evoked electroencephalographic variability in mild dementia

Twenty four participants diagnosed with mild dementia due to possible or probable Alzheimer's disease (MDAD), and 24 age matched controls (CN), will be recruited through a Cognitive Dementia and Memory Service (CADMS) Clinic. All participants will have their time locked, 64 channel electroencephalogram (EEG), recorded in response to three simple cognitive tasks delivered by a laptop computer connected to headphones: an active visual semantic priming task, a passive visual memory repetition priming task and an active three level auditory oddball task. The active visual semantic priming task requires participants to indicate via button press whether a sequential pair of briefly presented images are semantically related. The passive visual memory repetition task involves the participant viewing a sequence of images that may be novel or repeated once or twice. The active three level auditory oddball task requires participants to listen to a sequence of randomly presented tones (drawn from one of three frequencies) and to indicate via button press when a defined target tone is heard. EEG recordings will be performed by trained research staff. Tasks will be run consecutively in random order, with 2 minutes each of eyes-closed and eyes-open resting EEG recorded at the beginning of the testing session. The total testing time will be approximately 60 minutes.