Movement-Related Electroencephalographic Reactivity in Alzheimer Disease

Clinical Neurophysiology

Binetti

et al. 2004

336

251

Objective: This EEG study investigates the role of the cholinergic system, cortico-cortical connections, and sub-cortical white matter on the relationship between individual EEG frequencies and their relative power bands.Methods: EEGs were recorded at rest in 30 normal elderly subjects (Nold), 60 mild Alzheimer disease (AD) and 20 vascular dementia (VaD) patients, comparable for Mini Mental State Evaluation scores . Individual EEG frequencies were indexed by the theta/alpha transition frequency (TF) and by the individual alpha frequency (IAF) with power peak in the extended alpha range (5 -14 Hz). Relative power was separately computed for delta, theta, alpha1, alpha2, and alpha3 bands, on the basis of the TF and IAF.Results: Using normal subjects as a reference, VaD patients showed 'slowing' of alpha frequency (TF-IAF) and lower alpha2 power; Mild AD patients showed lower alpha2 and alpha3 power; delta power was higher in both AD and VaD patients; Theta power was higher only in VaD patients.Conclusions: Individual analysis of the alpha frequency and power can discriminate mild AD from VaD and normal elderly subjects.Significance: This analysis may probe pathophysiological mechanisms causing AD and VaD.

Section: Relative Power and Frequency Of Alpha Rhythms In Mild Dementiasupporting

confidence: 89%

Individual analysis of EEG frequency and band power in mild Alzheimer's disease

Moretti

Clinical Neurophysiology

Binetti

et al. 2004

336

251

“…For example, in working memory tasks, age-related bi-hemispheric activation versus the hemispheric asymmetry of the young has been interpreted as a compensatory mechanism similar to what happens for the execution of simple motor tasks (Babiloni et al, 2000;ReuterLorenz et al, 2000;Smith et al, 2001;Mattay et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Age-Related Functional Changes of Prefrontal Cortex in Long-Term Memory: A Repetitive Transcranial Magnetic Stimulation Study

Rossi¹,

Miniussi²,

Pasqualetti³

et al. 2004

J. Neurosci.

168

134

Neuroimaging findings suggest that the lateralization of prefrontal cortex activation associated with episodic memory performance is reduced by aging. It is still a matter of debate whether this loss of asymmetry during encoding and retrieval reflects compensatory mechanisms or de-differentiation processes. We addressed this issue by the transient interference produced by repetitive transcranial magnetic stimulation (rTMS), which directly assesses causal relationships between performance and stimulated regions. We compared the effects of rTMS (a rapid-rate train occurring simultaneously to the presentation of memoranda) applied to the left or right dorsolateral prefrontal cortex (DLPFC) on visuospatial recognition memory in 66 healthy subjects divided in two classes of age (Ͻ45 and Ͼ50 years).In young subjects, rTMS of the right DLPFC interfered with retrieval more than left DLPFC stimulation. The asymmetry of the effect progressively vanished with aging, as indicated by bilateral interference effects on recognition performance. Conversely, the predominance of left DLPFC effect during encoding was not abolished in elders, thus probing its causal role for encoding along the life span. Findings confirm that the neural correlates of retrieval modify along aging, suggesting that the bilateral engagement of the DLPFC has a compensatory role on the elders' episodic memory performance.

“…A more precise source analysis might have been obtained by dipole localization or linear inverse estimation of EEG data [6]. However, we anchored to a simple mapping of surface Laplacian ERD/ERS that has provided very interesting findings on human cortical responses to somatosensory and motor demands [4,5,7,8]. This approach avoided any kind of computational assumptions at an early stage of research (i.e., number of dipoles, regularization parameters of the linear inverse estimation, etc).…”

Section: Methodological Remarksmentioning

confidence: 99%

Sub-second “temporal attention” modulates alpha rhythms. A high-resolution EEG study

Miniussi

Cognitive Brain Research

et al. 2004

123

In the present high-resolution electroencephalographic (EEG) study, event-related desynchronization/synchronization (ERD/ERS) of alpha rhythms was computed during an S1 -S2 paradigm, in which a visual cue (S1) predicted a SHORT (600 ms) or LONG (1400 ms) foreperiod, preceding a visual go stimulus (S2) triggering right or left finger movement. Could orienting attention to a selective point in time influence the alpha rhythms as a function of the SHORT vs. LONG foreperiod? Stronger selective attentional modulations were predicted for the SHORT than LONG condition. EEG data from 54 channels were ''depurated'' from phase-locked visual evoked potentials and spatially enhanced by surface Laplacian estimation (i.e., final data analysis was conducted on 16 subjects having a sufficient number of artifact-free EEG single trials). Low-band alpha rhythms (about 6 -10 Hz) were supposed to be related to anticipatory attentional processes, whereas high-band alpha rhythms (10 -12 Hz) would indicate task-specific visuo-motor processes.Compared to the LONG condition (foreperiod), the SHORT condition induced a quicker and stronger ERS at low-band alpha rhythm (about 6 -8 Hz) over midline and bilateral prefrontal, sensorimotor, and posterior parietal areas. In contrast, the concomitant high-band alpha (about 10 -12 Hz) ERD/ERS showed no significant difference between the two conditions. In conclusion, temporal attention for a sub-second delay (800 ms) did modulate low-band alpha rhythm over large regions of both cortical hemispheres. D 2004 Elsevier B.V. All rights reserved.Theme: Neural basis of behavior Topic: Cognition