DECIDE EEG facilities FOR TRAINING AND DISSEMINATION: The basis of the EEG science for Alzheimer’s disease
S P A T I A L R E S O L U T I O N TEMPORAL RESOLUTION
Spontaneous delta rhythms ISOLATED of cerebral cortex when disconnected from cortical CORTEX and sub-cortical inputs pyramidal neurons oscillating at synchronized =All neurons delta frequencies (around synchronized at around about 1 1 Hz) Reticular neurons Relay neurons Hz BRAIN STEM THALAMUS
RESTING Dominant resting (eyes- closed) alpha rhythms are EYES synchronous and coherent over wide cortical areas and CLOSED corresponding thalamic nuclei pyramidal neurons oscillating at synchronized =All neurons alpha frequencies (around synchronized at around 10 Hz 10 Hz) Reticular neurons Relay neurons BRAIN STEM THALAMUS
High-frequency EEG rhythms (20 EVENT to 100 Hz orhighest) substitute alpha during eyes opening. These rhythms are coherent over small cortical areas and corresponding thalamic nuclei, and different sub- populations show different frequencies for opening their Gamma rhythms communication channel. pyramidal neurons = synchronous at oscillating at several around 20 Hz peculiar high = synchronous at frequencies (beta- around 40 Hz Reticular neurons Relay neurons gamma) = synchronous at BRAIN STEM THALAMUS around 100 Hz
When and how would you choose competing electrophysiologic methods: fluctuations of EEG rhythms (ERD) vs. impulse responses (ERPs)? ERD reflects reduction of alpha or beta EEG rhythms nonphase-locked to the event ERD ERPs Hidden into the EEG rhythms, ERPs indicate small neuronal synchronization phase-locked to the event 0 (EMGo) +1 sec -3.5 -3.0 EEG related to a voluntary finger movement 17/4 5
MRP and alpha ERD reveal different brain dynamics From –1 before (movie start) to +0.1 sec post-movement MRPs Right finger movement alpha ERD Babiloni C. et al., 2000; NeuroImage
Parallel but different physiological processes are captured by fMRI and EEG- MEG fMRI (blood/oxygen supply) MRPs (excitability, event- phase locking) ERD (ThC channels, brain rhythms) Babiloni C., Babiloni F., Carducci F., Cincotti F, Del Percio C., Hallett M., Moretti D.V., Romani G.L. and Rossini P.M. “High Resolution EEG of Sensorimotor Brain Functions: Mapping ERPs or Mu ERD?” Advances in Clinical Neurophysiology (Supplements to Clinical Neurophysiology Vol. 54: 365-371) Editors: R.C. Reisin, M.R. Nuwer, M. Hallett, C. Medina, 2002, Shannon, Ireland, Elsevier Science B.V.
ESTIMATION OF EEG/MEG SOURCES
Which sources of EEG and MEG? EEG MEG EEG is sensitive to radial and tangential sources MEG is sensitive only to tangential sources (radial + tangential sources cannot be confounded by MEG)
+ + + + poorly conductive + + + electrical skull blurs + + reference + + spatially scalp Neural + depresses near EEG potentials sources sources High temporal resolution (ms) Low spatial resolution (cm) MEG no reference effect, transparent to many tissues. Relatively higher spatial resolution
EEG sources by surface Laplacian spatial filtering (no explicit source modeling) Your speaker has a brain Right finger movement Babiloni et al., 1995, 1996, 1997, 1998; Electroenceph. Clin. Neurophysiol.
Distributed source estimation: thousands of dipoles Scalp EEG Right finger movement (EMGo) Babiloni C. et al., 2002 in Recent advances in Clinical Neurophysiology “Virtual” electrode
LORETA provides distributed linear inverse source estimations selecting maximally smoothed 3-D tomographic cortical source solutions fitting the recorded scalp EEG data Z Spherical head X model fitting a cortex model in the Talairach space Y Matrix inversion regularization LORETA inverse linear through minimization of the Laplacian solution estimation Visualization of 3-D LORETA solutions LORETA EEG CORTICAL SOURCES (Pascual-Marqui et al., 1994) Axiale Sagittal Coronal
STEPS OF THE EEG DATA ANALYSIS
Electrode over primary sensorimotor cortex 0 (EMGo) +1 sec -3.5 -3.0 EEG related to a voluntary finger movement 17/4 5
10 Hz α EEG signal can be divided in 20 Hz β β sinusoids at different frequencies by FFT 40 Hz γ Magnitude of each EEG sinusoid is represented by spectral power at that frequency
Individual Alpha Frequency (IAF) peak is the higher power density in the 6-12 Hz spectrum. With reference to the IAF, the sub-bands of interest are: Theta band as IAF -6 Hz to IAF -4 Hz Alpha1 band as IAF -4 Hz to IAF -2 Hz Alpha2 band as IAF -2 Hz to IAF Alpha3 band as IAF to IAF +2 Hz Problematic determination of the individual peaks of other bands in most subjects Fixed bands of interest: beta1 (13-20 Hz), beta2 (21-30 Hz), and gamma (31-44 Hz)
APPLICATION OF EEG MARKERS TO ALZHEIMER’S DISEASE
APPLICATION TO CLINICAL NEUROPHYSIOLOGY Which qEEG markers for early diagnosis, prognosis, and monitoring of Alzheimer disease? Normal elderly (Nold) Mild cognitive impairment (MCI) AD
Basic methodology: 10-20 electrode montage and LORETA for source analysis of resting eyes-closed EEG Resting eyes closed (2 min), LORETA 10-20 electrode system eyes open (2 min) LORETA solutions averaged with cortical lobes (frontal, central, parietal, temporal, occipital, limbic) Psychometric testing and neurological evaluation
A new approach to LORETA analysis: MACROREGIONS based on Brodmann areas Regions of interest (ROIs) Frontal (areas) 8, 9, 10, 11, 44, 45, 46, 47 Central 1, 2, 3, 4, 6 Parietal 5, 7, 30, 39, 40, 43 Temporal 20, 21, 22, 37, 38, 41, 42 Occipital 17, 18, 19 Limbic 12, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36
qEEG markers of physiological aging: cortical resting EEG rhythms characterizing normal elderly (Nold) subjects compared to normal young subjects (physiological aging)
Physiological aging Nyoung Nold N 108 107 Age (years) 27.3 (±7.3SD) 67.3 (±9.2 SD) Gender (F/M) 56/52 67/40 MMSE 30 28.5 (±1.2 SD) Education 15.9 (±2.6 SD) 9.6 (±4.2 SD) (years) Diagnosis: DSM-IV and NINCDS-ADRDA criteria EEG data: 5 min of resting EEG (closed eyes) Data analysis: artifact rejection, LORETA at ROIs, statistical analysis (age, MMSE, IAF, and education as covariates)
Posterior sources of resting alpha rhythms were lower in power in normal elderly than young subjects, despite similar degree of global cognition. Resting EEG data Babiloni C, Binetti G, Cassarino A, Dal Forno G, Del Percio C, Ferreri F, Ferri R, Frisoni G, Galderisi S, Hirata K, Lanuzza B, Miniussi C, Mucci A, Nobili F, Rodriguez G, Romani GL, and Rossini PM. Sources of cortical rhythms in adults during physiological aging: a multi-centric EEG study. Human Brain Mapping 2006 Feb;27(2):162-72..
qEEG markers for differential diagnosis: cortical resting EEG rhythms characterizing mild AD compared to cerebrovascular dementia (VaD) and Parkinson disease with dementia
Posterior sources of resting alpha rhythms were lower in power in mild AD than VaD subjects, despite similar degree of global cognition. Resting EEG data: 38 Nold 48 mild AD 20 VaD Babiloni C, Binetti G, Cassetta E, Cerboneschi D, Dal Forno G, Del Percio C, Ferreri F, Ferri R, Lanuzza B, Miniussi C, Moretti DV, Nobili F, Pascual-Marqui RD, Rodriguez G, Romani GL, Salinari S, Tecchio F, Vitali P, Zanetti O, Zappasodi F, Rossini PM. Mapping distributed sources of cortical rhythms in mild Alzheimer's disease. A multicentric EEG study. Neuroimage. 2004; 22(1): 57-67.
Posterior sources of resting alpha rhythms were lower in power in mild AD than PDD subjects but the opposite was true for widespread theta rhythms Resting EEG data: 20 Nold 13 PDD 20 mild AD Babiloni Claudio, De Pandis Francesca, Vecchio Fabrizio, Buffo Paola, Sorpresi Fabiola, Frisoni Giovanni B. and Rossini Paolo M. Cortical sources of resting state electroencephalographic rhythms in Parkinson’s disease related dementia and Alzheimer’s disease (Clinical Neurophysiology, 2011)
qEEG markers for preclinical diagnosis of AD: cortical resting EEG rhythms characterizing mild cognitive impairment (MCI) and subjective memory complaint (SMC)
Posterior sources of resting delta and alpha rhythms gradually change in amplitude along Nold, MCI, and mild AD continuum Resting EEG data: 126 Nold 155 MCI 193 mild AD Babiloni C, Binetti G, Cassetta E, Dal Forno G, Del Percio C, Ferreri F, Ferri R, Frisoni G, Hirata K, Lanuzza B, Miniussi C, Moretti DV, Nobili F, Rodriguez G, Romani GL, Salinari S, and Rossini PM Sources of cortical rhythms in subjects with mild cognitive impairment: a multi-centric study Clinical Neurophysiology 2006
Babiloni Claudio, Cassetta Emanuele, Binetti Giuliano, Tombini Mario, Del Percio Claudio, Ferreri Florinda, Ferri Raffaele, Frisoni Giovanni, Lanuzza Bartolo, Nobili Flavio, Parisi Laura, Rodriguez Guido, Frigerio Leonardo, Gurzì Mariella, Prestia Annapaola, Eusebi Fabrizio and Rossini Paolo M. Resting EEG sources correlate with attentional span in mild cognitive impairment and Alzheimer’s disease European Journal of Neuroscience, 2007.
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