title: Brain oscillatory responses to an auditory-verbal working memory task in mild cognitive impairment and Alzheimer's disease.
abstract: We report preliminary findings on EEG oscillatory correlates of working memory in mild cognitive impairment (MCI) and Alzheimer's disease (AD). Event-related desynchronization (ERD) and synchronization (ERS) of the 1-20 Hz EEG frequencies were studied using wavelet transforms in elderly controls, MCI patients and mild probable AD patients performing an auditory-verbal Sternberg memory task. Behaviourally, the AD patients made more errors than the controls and the MCI group. Statistically significant differences during the encoding of the memory set were found between the controls and the MCI group, such that the latter group showed ERD in the approximately 10-20 Hz frequencies. The findings may reflect different, compensatory encoding strategies in MCI. During retrieval, the most obvious differences were observed between the controls and the AD group: the ERD in the approximately 7-17 Hz frequencies was absent in the AD group particularly in anterior and left temporal electrode locations. This finding might indicate that AD is associated with deficient lexical-semantic processing during the retrieval phase in working memory tasks. Future studies with larger patient groups are needed to establish the diagnostic value of ERD/ERS patterns in MCI and AD.
authors.affiliation: Department of Psychology, Abo Akademi University, FIN-20500, Abo, Finland. mira.karrasch@abo.fi
authors.forename: Mira
authors.initials: M
authors.lastname: Karrasch
authors.forename: Matti
authors.initials: M
authors.lastname: Laine
authors.forename: Juha O
authors.initials: JO
authors.lastname: Rinne
authors.forename: Pekka
authors.initials: P
authors.lastname: Rapinoja
authors.forename: Eija
authors.initials: E
authors.lastname: Sinervä
authors.forename: Christina M
authors.initials: CM
authors.lastname: Krause
mesh_terms: D000161:Acoustic Stimulation; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D000704:Analysis of Variance; D003072:Cognition Disorders / Q000175:diagnosis / Q000503:physiopathology*; D003344:Cortical Synchronization; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D016555:Matched-Pair Analysis; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D012016:Reference Values; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D014706:Verbal Learning / Q000502:physiology*