Alpha rhythms in mild dements during visual delayed choice reaction time tasks: a MEG study.
Can simple delayed response tasks affect latency and amplitude of magnetoencephalographic midline alpha rhythms (6-12 Hz) in early dementia? We recruited 15 mild Alzheimer's disease (AD) and 10 vascular dementia (VaD) patients (paired mini mental state exam of 17-24). The control groups comprised 18 young and 22 elderly normal subjects. In the first task, a simple "cue" stimulus (one bit) was memorized along a brief delay period (3.5-5.5s) up to a "go" stimulus triggering (right or left) button press. In the second task, the "cue" stimulus remained available along the delay period. Event-related reduction in power of the alpha rhythms indexed the cortical activation (event-related desynchronization, ERD) for the trials associated with correct behavioral responses. Behavioral performances to both tasks were lower in the AD and VaD patients than in the normal subjects. In particular, just four AD and five VaD patients executed a sufficient amount of correct responses for the alpha ERD analysis, so they were included in a unique group. In both tasks, the alpha ERD peak was later in latency in the demented and normal elderly subjects than in the normal young subjects. Furthermore, the alpha ERD peak was stronger in amplitude in the demented patients than in the normal subjects. These results suggest that simple delayed response tasks during physiological recordings are quite difficult for patients even at an early dementia stage. Such difficulty may induce the abnormal amount of the related cortical activation in dementia as revealed by the alpha ERD.
Babiloni
Claudio
C
Dipartimento di Fisiologia Umana e Farmacologia, Università La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. claudio.babiloni@uniroma1.it
Cassetta
Emanuele
E
Chiovenda
Paola
P
Del Percio
Claudio
C
Ercolani
Matilde
M
Moretti
Davide Vito
DV
Moffa
Filomena
F
Pasqualetti
Patrizio
P
Pizzella
Vittorio
V
Romani
Gian Luca
GL
Tecchio
Franca
F
Zappasodi
Filippo
F
Rossini
Paolo Maria
PM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000513:Alpha Rhythm; D000544:Alzheimer Disease / Q000503:physiopathology; D000704:Analysis of Variance; D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology*; D015140:Dementia, Vascular / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors