PubMed Health⌕ Search

Biomedical subjects

E R John

Publications and source records attributed to E R John.

At least 19 recordsLinked to original sources
PubMed1992

QEEG profiles of psychiatric disorders.

While reports of EEG correlates of psychiatric disorders date back five decades, clinical sensitivity of the EEG to psychiatric disorders has been greatly enhanced with the advent of quantitative methods of analysis (QEEG). Using a QEEG methodology known as neurometrics we have identified distinctive electrophysiological profiles associated with different psychiatric disorders. With this method quantitative features are extracted from 2 minutes of artifact- free eyes closed resting EEG data, log transformed to obtain Gaussianity, age-regressed, and Z-transformed relative to population norms. Using small subsets of neurometric features, multiple stepwise discriminant analyses were used to construct mathematical classifier functions, the values of which are different for members of different a priori defined diagnostic groups. Using this approach, we have demonstrated high discriminant accuracy in independent replications separating many populations of psychiatric patients from normal as well as from each other, including major affective disorder, schizophrenia, dementia, alcoholism, and learning disabilities, as well as high accuracy of discrimination between known subtypes of depression (unipolar vs bipolar). The use of classification accuracy curves (CACs) which allow one to assess the sensitivity and specificity achieved by the discriminant functions is discussed. In addition, using cluster analysis, neurometric subtypes can be identified in several clinically homogenous populations. Preliminary results suggest that baseline membership in some neurometric subtypes may be highly correlated with response to treatment.

Adolescent↗
PubMed1992

Subtyping of psychiatric patients by cluster analysis of QEEG.

We have previously reported successful classification of patients with a variety of psychiatric disorders, using multiple discriminant functions based upon selected neurometric QEEG variables. In independent replications, these functions accurately separate patients with different DSM-III-R diagnoses from one another and from normals. This capability demonstrates that distinctive and replicable patterns of neurometric abnormalities are correlated with the clinical symptom clusters upon which DSM-III-R diagnostic criteria are based. However, patients with the same clinical diagnoses often respond very differently to the same treatments. Similar symptoms may arise from different pathophysiology. This study explored the 'natural structure' of a population of psychiatric patients in 8 diagnostic categories, using uninformed cluster analysis based upon the same set of neurometric variables found useful in separating each of these categories from normal. This preliminary numerical taxonomic approach reveals that groups of patients in each of these DSM-III-R categories contain subtypes with markedly different pathophysiology; further, patients in different DSM-III-R categories were aggregated together within each cluster, displaying similar pathophysiological profiles. Objective classification based on such physiological measurements may add information useful to improve treatment outcomes.

Brain↗
PubMed1990

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.

Adult↗
PubMed1986

The effect of reconstructive vascular surgery on clinical status, quantitative EEG and cerebral blood flow in patients with cerebral ischaemia. A three month follow-up study in operated and unoperated stroke patients.

Follow-up studies over a period of 3 months were carried out on 100 patients with a unilateral ischaemia in the territory of the middle cerebral artery. Twenty-six patients underwent an STA-MCA bypass operation and 23 patients, a carotid endarterectomy. Fifty-one unoperated patients served as a reference group. A clinical examination, quantitative electroencephalogram (qEEG) and cerebral blood flow study (CBF) were performed before, 2 weeks after and 3 months after surgery. In the unoperated patients these examinations were carried out shortly after admission, 3 weeks later and 3 months thereafter. In the unoperated group, a highly significant improvement of clinical score and qEEG was found, but there were no changes in CBF values. The bypass patients showed a transient deterioration of clinical score and qEEG after surgery. Further, over the 3 month post-operative period, the bypass patients and the endarterectomy patients showed no improvement in CBF and qEEG. Thus, a beneficial effect of reconstructive surgery over the period studied could not be demonstrated.

Brain↗
PubMed1985

The use of neurometrics in the study of patients with cerebral ischaemia.

The 'neurometric' method, as developed by John, was used for the study of patients with one-sided supratentorial ischaemia. The results of a reference group of 64 normal volunteers were compared with those of a group of 94 patients. This patient group included 54 patients with permanent neurological deficit (completed stroke or partial non-progressive stroke) and 40 patients with transient neurological symptoms (reversible ischaemic neurological deficit or transient ischaemic attacks). In 90% of all patients the neurometric method indicated that the EEG had to be considered as abnormal (compared with 3% of false positives in the reference group). A significant overall asymmetry was found in 82% of all patients compared with 2% in the reference group. During the follow-up period of 3 months there was a significant improvement of the EEG (as indicated by 3 neurometric parameters) as well as an improvement in clinical condition. In 57.5% of the EEGs, both the neurometric score and the visual assessment of the EEG indicated that some abnormality was present. In 6.6% of the cases both methods failed to indicate any abnormality. In 34.0% the neurometrics method revealed an abnormality in the EEG which was not found by visual assessment. In only 1.9% of the patients did visual assessment suggest abnormalities which could not be confirmed by neurometrics. In the group of EEGs which were considered as normal by visual assessment, the neurometrics method revealed abnormalities in 84%. The neurometric method is at the moment the most sensitive approach for detecting abnormalities in the EEG of patients with unilateral cerebral ischaemia. However, the method seems not very accurate for lateralization or localization of the lesions.

Adult↗
PubMed1978

Evoked response correlate of symbol and significate.

Changing the source and intensity of the auditory signal to six trained cats responding to meaningful auditory stimuli permits exogenous and endogenous processes in the auditory evoked potential to be separated. For short-latency exogenous processes, latency and amplitude depend on the parameters of the physical stimulus. However, the amplitude and shape of longer-latency endogenous processes are essentially independent of the location and intensity of the signal source and seem to be invariant concomitants of the significance of the signal.

Animals↗
PubMed1977

Neurometrics.

Explore the source record for details and available documents.

Aged↗
PubMed1976

Stable and plastic unit discharge patterns during behavioral generalization.

A movable microelectrode was implanted in adult cats trained to respond differentially to two different frequencies of light flicker. Unit responses were recorded along cortical and thalamic trajectories. The late components of the poststimulus response of 29% of the cells examined showed statistically significant differences when data from different behavioral outcomes to the same neutral generalization stimulus were compared.

Action Potentials↗
PubMed1975

Contradiction of auditory and visual information by brain stimulation.

Cats with permanently implanted electrodes were trained to discriminate between trains of flashes or clicks at two different repetition frequencies. After substantial overtraining with these sensory stimuli, high levels of stimulus generalization were obtained to electrical stimulation of the reticular formation at either frequency stimultaneously with contradictory flicker or click stimulation at the opposite frequency resulted in control of the behavior by the reticualr stimulus. Lateral geniculate stimulation failed to show this effect.

Acoustic Stimulation↗