Invited Speaker

Brain Oscillations in Alzheimer's disease and their Modulation by Cholinesterase Inhibitors
Görsev G. Yener
Turkey

Brain oscillations are electrophysiological responses that are elicited after either simple sensory stimulations or cognitive tasks. In the present study, we investigated simple sensory and cognitive task related visual evoked oscillations in healthy elderly subjects and two groups of AD subjects, (1) de novo, (2) treated with cholinesterase inhibitors. We tentatively propose that there exist different visual theta oscillatory networks, depending on type of stimuli (sensory or cognitive), and that cholinergic medication may have modulating effects on these circuits. After a simple sensory stimulation, (1) The amplitude of theta oscillatory responses changes, as contra-intuitively incremental responses are seen in untreated AD over primary and secondary sensory areas of the brain. (2) A different scalp distribution is seen, as posterior regions show higher theta activity in untreated AD. This may be an indication of a different circuit for the sensory network, since oddball target stimuli elicit lower frontal theta and delta responses in untreated AD. (3) The effects of cholinergic medication appear in theta visual evoked oscillation responses to sensory stimuli. (4) It is clear that the prefrontal area plays an important role in a visual cognitive task, but it appears to have a different role after a visual sensory stimulus.