Decreased theta event-related synchronization during working memory activation is associated with progressive mild cognitive impairment.
BACKGROUND
Among the different quantitative electroencephalographic markers, theta activity is known to reflect neural resources involved in memory processes and directed attention. Previous studies suggested that synchronization likelihood analysis in theta-band frequency might be a sensitive method to identify early alterations of neuronal networks in mild cognitive impairment (MCI).


METHODS
We report here a longitudinal study of 24 MCI patients with theta event-related synchronization (ERS) analysis during the n-back working memory task and neuropsychological follow-up after 1 year. Statistical analysis included analysis of variance and logistic regression to assess the relationship between cognitive decline and theta ERS.


RESULTS
Upon follow-up, 13 MCI patients showed progressive MCI and 11 remained stable. In both groups, the phasic increase in theta amplitude after stimulus presentation did not depend on working memory load and electrode sites. Progressive MCI cases displayed significantly lower theta ERS power over all electrode sites compared to stable MCI cases. Theta ERS was significantly related to the cognitive outcome explaining 15.5% of its variability. In terms of MCI classification, the best combination of sensitivity and specificity was 0.87 and 0.60, respectively, with an area under the corresponding receiver operating characteristic curve reaching 76%.


CONCLUSIONS
The present data indicate that a decrease in the early phasic theta ERS power during working memory activation may predict cognitive decline in MCI. This phenomenon is not related to working memory load but may reflect the presence of early deficits in directed attention-related neural circuits in MCI.
Missonnier
Pascal
P
Neuroimaging Unit, University Hospitals of Geneva, Geneva, Switzerland.
Gold
Gabriel
G
Herrmann
François R
FR
Fazio-Costa
Lara
L
Michel
Jean-Pierre
JP
Deiber
Marie-Pierre
MP
Michon
Agnès
A
Giannakopoulos
Panteleimon
P
D000368:Aged; D000369:Aged, 80 and over; D001288:Attention / Q000502:physiology; D003072:Cognition Disorders / Q000503:physiopathology* / Q000523:psychology*; D015331:Cohort Studies; D003344:Cortical Synchronization; D018450:Disease Progression; D004569:Electroencephalography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D019579:Neocortex / Q000503:physiopathology; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000502:physiology; D012372:ROC Curve; D011930:Reaction Time / Q000502:physiology; D013826:Theta Rhythm / Q000523:psychology*; D014705:Verbal Behavior