Affiliations: Departments of Neurology and Neurosciences; Dokuz
Eylül University, Izmir, Turkey | Brain Dynamics and Multidisciplinary Research Center,
Dokuz Eylül University, Izmir, Turkey | Brain Dynamics, Cognition and Complex Systems Research
Center, Istanbul Kultur University, Istanbul, Turkey | Sisli Etfal State Hospital, Department of Neurology,
Istanbul, Turkey
Note: [] Corresponding author: Görsev G. Yener, M.D., Ph.D.,
Departments of Neurology and Neurosciences; Dokuz Eylül University, Izmir,
Turkey 35340. Tel.: +90 505 747 5957; Fax: +90 232 277 7721; E-mail: gorsev.yener@deu.edu.tr
Abstract: Background: Visual delta event-related (ERO) and evoked oscillations
(EO) of Alzheimer patients (AD) are different than healthy. In the present
study, the analysis is extented to include auditory ERO and EO in AD. The
rationale is to reveal whether the auditory ERO delta responses are also
reduced, and whether this is a general phenomenon in Alzheimer patients upon
applying stimuli with cognitive load. Methods: Thirty-four mild AD
subjects [17 de-novo and 17 medicated (cholinergic)] and seventeen healthy
controls were included. Auditory oddball paradigm and sensory auditory stimuli
were applied to the subjects. Oscillatory responses were analyzed by measuring
maximum amplitudes in delta frequency range (0.5–3.5 Hz). Results: Auditory delta ERO (0.5–3.5 Hz) responses of healthy controls were higher than
either de-novo AD or medicated AD group, without a difference between two AD
subgroups. Furthermore, the auditory EO after presentation of tone bursts
yielded no group difference. Conclusion: Our findings imply that delta
ERO is highly unstable in AD patients in comparison to age-matched healthy
controls only during the cognitive paradigm. Our results favor the hypothesis
that neural delta networks are activated during cognitive tasks and that the
reduced delta response is a general phenomenon in AD, due to cognitive impairment.
