Evoked Potentials in Hyperkinetic and Normal Children Under Certainty and Uncertainty: A Placebo and Methylphenidate Study

Differences between hyperkinetic children and normal children and the effects of methylphenidate on hyperkinetic children were investigated under conditions of differential attentional demands. Auditory average evoked potentials were recorded from vertex using a single/double click guessing paradigm under conditions of certainty and uncertainty. Under conditions of certainty (low attention), in which the subject was told the identity of each stimulus in advance, few significant group differences were found. Under conditions of uncertainty (high attention), in which the subject was asked to guess which stimulus would be presented, large group differences were found. In response to the second click the P200 component was found to be smaller and the N250 component was larger in hyperkinetic children than in normal children. Treatment with methylphenidate “normalized” the evoked potentials of the hyperkinetic children making them more like those of normal children. The findings are believed: 1) to reflect the deficit in attention observed behaviorally in hyperkinetic children, 2) to support a model of hypoarousal in hyperkinetic children, and 3) to reflect the behavioral “normalization” observed in hyperkinetic children treated with melhylphenidate.     

Multivariate analyses of the EEG in normal adolescents

We investigated the computerized electroencephalography (cEEG) in a group of 85 normal adolescents. The spatial frequency of the cEEG was analyzed using various multivariate statistical techniques. The factor analyses revealed three factors that accounted for most of the variability in the data and that could be interpreted as a low versus high frequency, a beta frequency, and a frontal versus posterior factor. The cluster analysis revealed various EEG patterns that distinguished among subgroups of normal individuals.     

Electrophysiological subtypes of psychotic states

Objective: This research sought neurobiological features common to psychotic states displayed by patients with different clinical diagnoses. Method: Cluster analysis with quantitative electroencephalographic (QEEG) variables was used to subtype drug‐naïve, non‐medicated, and medicated schizophrenic, depressed and alcoholic patients with psychotic symptoms, from the USA and Germany. QEEG source localization brain images were computed for each cluster. Results: Psychotic patients with schizophrenia, depression and alcoholism, and drug‐ naïve schizophrenic patients, were distributed among six clusters. QEEG images revealed one set of brain regions differentially upregulated in each cluster and another group of structures downregulated in the same way in every cluster. Conclusion: Subtypes previously found among 94 schizophrenic patients were replicated in a sample of 390 non‐schizophrenic as well as schizophrenic psychotics, and displayed common neurobiological abnormalities. Collaborative longitudinal studies using these economical methods might improve differential understanding and treatment of patients based upon these features rather than clinical symptoms.     

Topographic imaging of quantitative EEG in response to smoked cocaine self-administration in humans.

Quantitative electroencephalographic (qEEG) profiles were studied in cocaine-dependent patients in response to an acute, single-blind, self-administered dose of smoked cocaine base (50 mg) vs placebo. qEEG data were averaged using neurometric analytical methods and the spectral power of each primary bandwidth was computed and topographically imaged. Additional measures included cocaine-induced high, craving, and related subjective ratings, heart rate, blood pressure, and plasma cortisol and homovanillic acid levels. In all, 13 crack cocaine-dependent subjects were tested. Cocaine produced a rapid increase in subjective ratings of cocaine high and good drug effect, and a more persistent increase in cocaine craving and nervousness. Cocaine also produced a rapid rise in heart rate and a prolonged increase in plasma cortisol. Placebo, administered in the context of cocaine cues and dosing expectations, had no cocaine-like subjective or physiological effects. Cocaine produced a rapid increase in absolute theta, alpha, and beta power over the prefrontal cortex (FP1, FP2), lasting up to 25 min after dosing. The increase in theta power was correlated with good drug effect, and the increase in alpha power was correlated with nervousness. Cocaine also produced a similar increase in delta coherence over the prefrontal cortex, which was positively correlated with plasma cortisol, and negatively correlated with nervousness. Placebo resulted in an increase in alpha power over the prefrontal cortex. These data demonstrate the involvement of prefrontal cortex in the qEEG response to acute cocaine. Evidence indicates slow wave qEEG, delta and theta activity, involvement in the rewarding properties of cocaine.     

Quantitative EEG correlates of crack cocaine dependence

Evidence for a distinctive syndrome of neuroadaptation in cocaine dependence has accumulated from behavioral, neurophysiological, and preclinical and clinical pharmacological studies. The authors report on the results of a preliminary investigation of the quantitative electroencephalographic (QEEG) correlates of severe DSM-III-R crack cocaine dependence in seven patients abstinent from cocaine for 1 to 68 days. The major QEEG finding was increased absolute and relative alpha power. Increased alpha power has also been reported in multiple previous studies of depressed patients. This series of crack-dependent patients showed significant depressive morbidity; four patients attempted suicide subsequent to initiating their use of crack and the group mean (+/- SD) Beck Depression Scale score was 18.9 (+/- 6.5). These results complement other studies that support the concept of neuroadaptation to chronic cocaine exposure. Prospective studies correlating QEEG measures with subsequent response to pharmacological interventions for cocaine dependence should be considered.     

Patient State Index: Titration of Delivery and Recovery from Propofol, Alfentanil, and Nitrous Oxide Anesthesia

Background: The Patient State Index (PSI) uses derived quantitative electroencephalogram features in a multivariate algorithm that varies as a function of hypnotic state. Data are recorded from two anterior, one midline central, and one midline posterior scalp locations. PSI has been demonstrated to have a significant relation to level of hypnosis during intravenous propofol, inhalation, and nitrous oxide-narcotic anesthesia. This multisite study evaluated the utility of PSI monitoring as an adjunct to standard anesthetic practice for guiding the delivery of propofol and alfentanil to accelerate emergence from anesthesia.

Methods: Three hundred six patients were enrolled in this multicenter prospective randomized clinical study. Using continuous monitoring throughout the period of propofol-alfentanil-nitrous oxide anesthesia delivery, PSI guidance was compared with use of standard practice guidelines (both before [historic controls] and after exposure to the PSA 4000 monitor [Physiometrix, Inc., N. Billerica, MA; standard practice controls]). Anesthesia was always administered with the aim of providing hemodynamic stability, with rapid recovery.

Results: No significant differences were found for demographic variables or for site. The PSI group received significantly less propofol than the standard practice control group (11.9 [mu]g [middle dot] kg-1 [middle dot] min-1;P < 0.01) and historic control group (18.2 [mu]g [middle dot] kg-1 [middle dot] min-1;P < 0.001). Verbal response time, emergence time, extubation time, and eligibility for operating room discharge time were all significantly shorter for the PSI group compared with the historic control (3.3-3.8 min;P < 0.001) and standard practice control (1.4-1.5 min;P < 0.05 or P < 0.01) groups. No significant differences in the number of unwanted somatic events or hemodynamic instability and no incidences of reported awareness were found.     

Cocaine cue versus cocaine dosing in humans: evidence for distinct neurophysiological response profiles

Subjective, physiological and electroencephalographic (EEG) profiles were studied in cocaine dependent study participants in response to cocaine cue exposure or a dose of smoked cocaine. Both stimuli increased subjective ratings of cocaine high and craving, enhanced negative affect, and boosted plasma ACTH and skin conductance levels. However, cocaine dose produced a greater increase in high and a more prolonged increase in plasma ACTH, while cocaine cue produced a decline in skin temperature. Both stimuli produced increases in absolute theta, alpha and beta EEG power over the prefrontal cortex. However, interhemispheric EEG coherence over the prefrontal cortex decreased during cocaine cue exposure but increased following cocaine dose. Moreover, correlation analysis of subjective, physiological and EEG responding to cocaine cue and dose revealed distinct profiles. Delta and theta activity were associated with negative affect during cocaine cue exposure, but were associated with cocaine craving and reward following cocaine dosing. In both conditions, alpha activity was marker for anxiousness but not high. These data demonstrate similar subjective, physiological responding in clinical laboratory states of cocaine craving and reward. However, differences in EEG response profiles, and their relationship to function, indicate distinct neurophysiological mediators of cocaine craving and reward within the prefrontal cortex.     

On the “Dependence” of “Independent” Group EEG Sources; an EEG Study on Two Large Databases

The aim of this work is to study the coherence profile (dependence) of robust eyes-closed resting EEG sources isolated by group blind source separation (gBSS). We employ a test–retest strategy using two large sample normative databases (N = 57 and 84). Using a BSS method in the complex Fourier domain, we show that we can rigourously study the out-of-phase dependence of the extracted components, albeit they are extracted so as to be in-phase independent (by BSS definition). Our focus on lagged communication between components effectively yields dependence measures unbiased by volume conduction effects, which is a major concern about the validity of any dependence measures issued by EEG measurements. We are able to show the organization of the extracted components in two networks. Within each network components oscillate coherently with multiple-frequency dynamics, whereas between networks they exchange information at non-random multiple time-lag rates.