Abstract
40Hz Oscillations (LORETA Source Analysis): Male/Female Differences in Depression, Mania, Schizophrenia and Controls
Among those studied were 65 male controls, 80 female controls, 44 female depressives, 31 male depressives, 15 female manics, 11 male manics, 18 female schizophrenics, 69 male schizophrenics. All patients were unmedicated.
Quantitative EEG analyses were carried out with 48 electrodes system during four conditions: Eyes Open, Eyes Closed, Dot Localization and Word Finding.
It was found that in the 40Hz band: in normals males have increased sources in the left and females have increased sources in the right hemisphere; compared to controls female depressives had predominantly left hemispheric sources whereas male depressives had predominantly right hemispheric sources; both male and female manics had predominantly left hemispheric sources when compared to controls, male schizophrenics (including sinistrals and ambilaterals), when compared to controls, had increased left hemispheric sources whilst consistent dextral male schizophrenics showed increased right hemispheric sources; when female schizophrenics are compared to female controls it is the controls who have increased sources in the right hemisphere. In depression, mania and schizophrenia there are changes in lateral hemispheric (dis)organization which, in each of the 3 psychosis, are gender dependent.
Alpha Phase Synchrony Model of Consciousness: Clinical Applications
Our previous report (Hebert, 2005) identified two types of alpha standing waves. The new in-phase waveform found in transcendental meditation was associated with a content-free “ground state” hypothesized by Roy John (2002). We evaluated the wavelength of alpha as a possible physical explanation for these standing waves.
We used 1) Neurorep QEEG that allows the millisecond measure of a half cycle of alpha 2) application of “wavelength formula” consisting of frequency of alpha, cortical travel distance and traveling speed. We determined the wavelength of alpha to be ∼50-cm; half a cycle=25 cm, =A-P length of the cortex favorable for standing waves.
Our “phase synchrony model of consciousness” describes alpha phase synchrony in the context of phase reset, evoked potential, comparator processing, traveling waves, standing waves, memory access, perceptual frames and cross-frequency phase synchrony. We describe how in-phase standing wave alpha may provide a restorative mechanism we call the “rebooting operating system”. These new-found alpha roles may explain the negative clinical impact of low alpha phase synchrony. We propose the enhancement of alpha through the EEG-based ground state as a method of restoring homeostasis in brain function. As John (2002) hypothesized: “when the ground state is restored psychiatric disorders often normalize”.
Subanesthetic Dose of Ketamine Decreases Prefrontal Theta-Cordance in Healthy Volunteers: Implications for Antidepressant Effect
Theta-cordance is a novel clinically highly relevant quantitative electroencephalography measure that correlates with cerebral perfusion. A series of clinical studies demonstrated that the prefrontal theta-cordance value decreases after one week of treatment in responders to antidepressants and that this effect precedes clinical improvement. Ketamine, a non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptors, has a unique rapid antidepressant effect but its influence on theta-cordance is still unknown.
In an acute double-blind, cross-over, placebo-controlled experiment we studied the influence of ketamine (0.54 mg/kg within 30 min) on theta-cordance in a group of 20 healthy volunteers.
Ketamine infusion induced a decrease in prefrontal theta-cordance and increase in the central region theta-cordance after 10 and 30 min. The change of prefrontal theta-cordance correlates with ketamine and norketamine blood levels after 10 min of ketamine infusion.
In conclusion, our data indicate that ketamine infusion immediately induces similar changes as monoamineric-based antidepressants do gradually. The reduction in theta-cordance could be a marker and predictor of a fast antidepressant effect of ketamine, a hypothesis that could be tested in depressive patients treated with ketamine.
Early Auditory Gamma Band Response Abnormalities in First Hospitalized Schizophrenia
Recent theory suggests abnormalities in the coherent function of cortical cells in local and distributed processing assemblies through synchronous firing in the gamma range may be a core neurophysiologic deficit in schizophrenia. Although several recent studies have noted gamma band abnormalities to complex second order transforms in the visual system or to exogenously driven auditory gamma function, an endogenous gamma burst occurs early within the auditory system that may serve as a simple probe of coherent cortical circuit functioning in the disorder. This early auditory gamma band response (EAGBR), due to its occurrence early in the processing stream, is easily dissectible and localized to primary auditory structures.
To determine if the EAGBR was abnormal in power and trial-to-trial phase locking, 24 first hospitalized schizophrenia and schizoaffective patients and 32 matched control subjects were compared on the EAGBR to standard tones recorded during an oddball target detection task.
Both overall evoked power (p =.039) and phase locking (p=.004) were reduced in patients.
Abnormalities in the coherent functioning of local cell assemblies within primary auditory cortex are apparent in schizophrenia even near psychosis onset. This supports the contention that basic sensory processes are impaired in schizophrenia
Enhanced Intensity Dependence and Aggressive Behavior History Indicate Previous Ecstasy Use in Abstinent Polydrug Users
Intensity dependence is an electrophysiological measure of intra-individual stability of the augmenting/reducing characteristic of the N1/ P2 event-related potential amplitudes in response to stimuli of varying intensities. Ecstasy (MDMA, MDA, and MDEA) is a group of popular recreational drugs. Abstinent ecstasy users typically show enhanced intensity dependence and higher levels of impulsivity and aggression. Enhanced intensity dependence and high impulsivity and aggression levels may be due to damage in the brain's serotonergic neurons as a result of ecstasy use. The present study investigated whether intensity dependence, impulsivity and aggressive behavior history can be used as indictors of previous ecstasy usage. Forty-four abstinent polydrug users (8 women; age 19 to 61 years old) were recruited. All participants were currently residents at a local substance abuse facility receiving treatment and had been free of all drugs for a minimum of 21 days. The study found significantly enhanced intensity dependence of tangential dipole source activity and more aggressive behavior history in participants who had used ecstasy before. Intensity dependence of the tangential dipole source and aggressive behavior history correctly identified 73.3% of those who had used ecstasy and 78.3% of those who had not. Overall, 76.3% of the participants were correctly classified.