Toshiaki Isotani

EEG microstates associated with salience and frontoparietal networks in frontotemporal dementia, schizophrenia and Alzheimer’s disease

OBJECTIVE There are relevant links between resting-state fMRI networks, EEG microstate classes and psychopathological alterations in mental disorders associated with frontal lobe dysfunction. We hypothesized that a certain microstate class, labeled C and correlated with the salience network, was impaired early in frontotemporal dementia (FTD), and that microstate class D, correlated with the frontoparietal network, was impaired in schizophrenia. METHODS We measured resting EEG microstate parameters in patients with mild FTD (n = 18), schizophrenia (n = 20), mild Alzheimers disease (AD; n = 19) and age-matched controls (old n = 19, young n = 18) to investigate neuronal dynamics at the whole-brain level. RESULTS The duration of class C was significantly shorter in FTD than in controls and AD, and the duration of class D was significantly shorter in schizophrenia than in controls, FTD and AD. Transition analysis showed a reversed sequence of activation of classes C and D in FTD and schizophrenia patients compared with that in controls, with controls preferring transitions from C to D, and patients preferring D to C. CONCLUSION The duration and sequence of EEG microstates reflect specific aberrations of frontal lobe functions in FTD and schizophrenia. SIGNIFICANCE This study highlights the importance of subsecond brain dynamics for understanding of psychiatric disorders.

EEG Source Localization and Global Dimensional Complexity in High- and Low- Hypnotizable Subjects: A Pilot Study

Individuals differ in hypnotizability. Information on hypnotizability-related EEG characteristics is controversial and incomplete, particularly on intracerebral source localization and EEG dimensionality. 19-channel, eyes-closed resting EEGs from right-handed, healthy, 8 high- and 4 low-hynotizable subjects (age: 26.7 ± 7.3 years) were analyzed. Hypnotizability was rated after the subjects’ ability to attain a deep hypnotic stage (amnesia). FFT Dipole Approximation analysis in seven EEG frequency bands showed significant differences (p < 0.04) of source gravity center locations for theta (6.5–8 Hz, more posterior and more left for highs), beta-1 and beta-2 frequencies (12.5–18 and 18.5–21 Hz; both more posterior and more right for highs). Low Resolution Electromagnetic Tomography (LORETA) specified the cortical anteriorization of beta-1 and beta-2 in low hypnotizables. Power spectral analysis of Global Field Power time series (curves) showed no overall power differences in any band. Full-band Global Dimensional Complexity was higher in high-hypnotizable subjects (p < 0.02). Thus, before hypnosis, high and low hypnotizables were in different brain electric states, with more posterior brain activity gravity centers (excitatory right, routine or relaxation left) and higher dimensional complexity (higher arousal) in high than low hypnotizables.

Differences in quantitative EEG between frontotemporal dementia and Alzheimer’s disease as revealed by LORETA

OBJECTIVE To determine the electrophysiological characteristics of frontotemporal dementia (FTD) and the distinction with Alzheimers disease (AD). METHODS We performed analyses of global field power (GFP) which is a measure of whole brain electric field strength, and EEG neuroimaging analyses with sLORETA (standardized low resolution electromagnetic tomography), in the mild stages of FTD (n = 19; mean age = 68.11 ± 7.77) and AD (n = 19; mean age = 69.42 ± 9.57) patients, and normal control (NC) subjects (n = 22; mean age = 66.13 ± 6.02). RESULTS In the GFP analysis, significant group effects were observed in the delta (1.5-6.0 Hz), alpha1 (8.5-10.0 Hz), and beta1 (12.5-18.0 Hz) bands. In sLORETA analysis, differences in activity were observed in the alpha1 band (NC > FTD) in the orbital frontal and temporal lobe, in the delta band (AD>NC) in widespread areas including the frontal lobe, and in the beta1 band (FTD > AD) in the parietal lobe and sensorimotor area. CONCLUSIONS Differential patterns of brain regions and EEG frequency bands were observed between the FTD and AD groups in terms of pathological activity. SIGNIFICANCE FTD and AD patients in the early stages displayed different patterns in the cortical localization of oscillatory activity across different frequency bands.

1-A-D-16. The characteristics of resting-state EEG connectivity in patients with Alzheimer’s disease by the LORETA

Alzheimer’s disease (AD) is characterized by cognitive and memory dysfunctions, and is accompanied by default mode network (DMN) abnormalities. We investigated the neurophysiological basis of these dysfunctions by examining functional connectivity using standardized low resolution electromagnetic tomography (sLORETA). Resting, eyes closed EEGs were recorded from 19 patients with mild AD and 22 healthy control subjects. Electrophysiological connectivity maps between parahippocampal gyri and all other cortical regions were computed, as well as pairwise connectivity among DMN regions. Between-group comparisons in 7 frequency bands were carried out. Beta2 connectivity was marginally decreased between right parahippocampus and right superior frontal gyrus, right precentral gyrus, and right occipital lobe in AD patients. They also showed significantly decreased alpha2 and beta2 connectivity between posterior cingulate gyrus and right inferior parietal lobe within DMN. Previous fMRI studies have shown AD decreased connectivity between parahippocampus, where significant neurological degeneration appears, and other brain regions. The disconnection between the hubs of DMN in sLORETA connectivity suggest AD patients have an abnormal DMN, in agreement with previous fMRI resting state networks studies. sLORETA connectivity provides complimentary information on the neurophysiological dysfunction between parahippocampus and other cortical areas, and on the DMN aberrance in patients with AD.

Hyperactivation of the Frontal Control Network Revealed by Symptom Provocation in Obsessive-Compulsive Disorder Using EEG Microstate and sLORETA Analyses

The aim of this study was to investigate the changes of brain electric field induced by symptom provocation in patients with obsessive-compulsive disorder (OCD) in comparison to healthy controls in the resting state. For this purpose, EEG recordings in conditions of initial rest, clean control, symptom provocation by imaginal exposure, and final rest were used for computing spatiotemporal activity characteristics based on microstate segmentation. Within-group comparisons were significant for the symptom provocation condition: OCD showed high global field power (GFP) and transition rates into a medial frontal microstate, whereas healthy controls showed high frequency of occurrence and high percent of dwelling time for a medial occipitoparietal microstate. Between-group comparisons demonstrated significantly lower GFP and dwelling time for the medial occipitoparietal microstate in OCD in several conditions including initial rest and symptom provocation. In addition, OCD compared to healthy controls showed significant instability of the medial occipitoparietal microstate, with high preference for transitions into the medial frontal microstate. In conclusion, during rest and symptom provocation, OCD patients make preferential use of a medial frontal brain network, with concomitant reduction of use of a medial occipitoparietal network, as shown by dwelling times, explained variance, and dynamic transition rates. These findings support the idea of a possible biological marker for OCD, which might correspond to pathological hyperactivation of the frontal control network.

PO9.4 Global EEG Descriptors for Changes Induced by Antipsychotics

Background: Alzheimer disease is most common form of dementia and one of complicated neurodegenerative diseases. Quality of life of AD patient significantly lowed due to sleep disturbance. The sleep disturbance is mostly associated direct or indirectly with the appearance of theta waves. Appearance of this wave suggests a shift of wave discharge from physiological to pathological pattern. To study pathophysiological effects of theta wave appearance with relation to its physiological discharge site mostly hippocampus. Methods: It is a review to study pathophysiological effects of increased delta and theta waves during sleep in AD with relation to physiological site for theta wave discharge i.e. hippocampus. Results: The sleep of Alzheimer’s disease (AD) patients is often disturbed by medications, depression, circadian rhythm changes and sleep disorders. The patients of AD exhibit brain wave changes during sleep. These changes are present in parieto-temporal and frontal regions and are more prominent in REM sleep and consisted primarily in an increase in absolute delta and theta activities, and a decrease in absolute alpha and beta activities. The concentrations of delta sleep-inducing peptide (DSIP)-like (DSIP-LI) is significantly decrease in moderate to severe AD. This effects the delta wave mild decrease discharge and shift to increase theta discharge as relative compensation. Conclusions: In this review, effects of increased theta and altered delta wave discharge during sleep in patients of AD is discussed. The understanding of increased theta wave physiological and pathological effects in the process of AD with relation to sleep are important for improved quality of life of patient.