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P Gloor

Publications and source records attributed to P Gloor.

At least 19 recordsLinked to original sources
PubMed1979

Automatic recognition of inter-ictal epileptic activity in prolonged EEG recordings.

A method of automatic recognition and quantification of inter-ictal epileptic activity in the human EEG had previously been developed and tested using short recordings from awake subjects. This paper describes the adaptation of the method for use during overnight recordings in free-moving unattended patients, in combination with the already existing seizure monitoring system. EEG s were recorded from scalp and sphenoidal electrodes, using cable telemetry and a PDP-12 computer. The spike and sharp wave recognition method allowed the on-line analysis of 16 channels. A section of the 16-channel EEG including 1 sec before and 1 sec after each detected spike was saved on digital magnetic tape. Upon completion of the monitoring session, the tape was played back on the EEG machine, giving a discontinuous tracing of spike sections; this constituted a highly concentrated view of the inter-ictal epileptic activity, in traditional paper form. The spike sections were further analyzed by computer to determine and display on the computer terminal the spatial and temporal distributions of the epileptic activity, providing a complete synopsis of the recording. Several examples of the type of information available from this anslysis are discussed in detail. False detection rates are given for 34 six hour recordings, indicating a high vari ability in the performance, mainly because of artefacts. It is concluded that the final computer displays could only be trusted after visual inspection of the EEG sections provided on paper. The variety of morphologies of artefacts appeared to preclude a total automatic elimination.

Electroencephalography↗
PubMed1979

Effects of changes in cortical excitability upon the epileptic bursts in generalized penicillin epilepsy of the cat.

Previous studies had suggested that the epileptic bursts of feline generalized penicillin epilepsy represent the response of hyperexcitable cortex to thalamocortical volleys normally evoking spindles. If this were the case, it should be possible to convert the epileptic bursts of generalized penicillin epilepsy into spindles by decreasing the excitability of cortical neurons. In cats exhibiting the EEG signs of feline generalized penicillin epilepsy cortical excitability was decreased by hypoxia, by the topical application to the cortex of KCl (inducing spreading depression), barbiturates, GABA, AMP or noradrenaline. During generalized penicillin epilepsy, hypoxia and KCl-induced spreading depression abolished epileptic bursts which were replaced by spindles. When spindles and epileptic complexes occurring in the same animal were compared, a direct correlation between the frequencies of these two rhythms could be demonstrated, that of the epileptic complexes being about half that of the spindle waves. These observations support the hypothesis that the epileptic bursts of feline generalized penicillin epilepsy are induced by thalamocortical volleys normally involved in spindle genesis. Topical cortical applications of barbiturates, GABA, AMP and noradrenaline reduced or inverted the negative spikes of the spike and wave complexes, while augmenting the negative slow waves, or revealing them clearly in instances in which they had been poorly developed. This effect is interpreted as being due to a selective inactivation of the superficial cortical layers. That topical cortical application of barbiturates, GABA, AMP and noradrenaline was capable of transforming into typical spike and wave complex epileptic bursts, which had not previously conformed to this pattern, indicates that the intracortical electrophysiological events of typical and atypical epileptic bursts in feline generalized penicillin epilepsy are fundamentally the same and reflect an alternation between excitatory and inhibitory sequences.

Adenosine Monophosphate↗
PubMed1978

The electromicrophysiology of delta waves induced by systemic atropine.

Delta waves in the EEG can be induced by the intravenous administration of atropine. In cats we have investigated with several computer averaging programs the relationship of extracellular unit discharge to the EEG on the surface and within the cortex. We have also studied the laminar profiles and the vertical current density profiles of these slow waves. Our results indicate that surface-positive delta waves are related to events associated with excitation of cortical neurons, while surface-negative delta waves are related to a decreased probability of unit firing suggesting the possibility of inhibition. Laminar analysis of atropine-induced slow waves indicated that these were probably generated by pyramidal cells in a similar way to delta waves induced by brain lesions. These results suggest that a disturbance in cholinergic input to the cortex might be responsible for delta waves in the EEG.

Animals↗
PubMed1978

A long term time-lapse video system to document the patients spontaneous clinical seizure synchronized with the EEG.

A long term audio/video clinical seizure monitoring system is described which is complementary to a previously described EEG seizure monitoring system. The video unit is mobile and based on time-lapsed video recording techniques to extend the unattended continuous video recording of the patient to many days if necessary. The simultaneous coverage of the EEG and behavior of the patient particularly during his seizure has been very useful in the workup of intractable epileptic patients being considered for neurosurgical treatment.

Electroencephalography↗
PubMed1978

Update: chronic sphenoidal electrodes.

A technical modification in the type of material used in the chronic sphenoidal electrode previously described (Ives and Gloor 1977) has further improved their clinical use and benefit of the EEG work-up of epileptic patients. This procedure has become a routine investigation for all patients with suspected temporal lobe epilepsy at the Montreal Neurological Hospital.

Electrodes, Implanted↗
PubMed1978

Generalized epilepsy with bilateral synchronous spike and wave discharge. New findings concerning its physiological mechanisms.

A hypothesis for the mechanism of generalized spike and wave discharge in human generalized epilepsy is proposed in the light of findings obtained in feline generalized penicillin epilepsy. It is postulated that generalized bilaterally synchronous spike and wave discharge depends upon a diffuse and relatively mild state of cortical hyperexcitability which increases the responsiveness of cortical neurons. Afferent thalamo-cortical volleys normally involved in the genesis of spindles and recruiting responses are most likely to precipitate spike and wave discharges under these conditions. The spike and wave pattern probably results from the activation of a recurrent intracortical inhibitory pathway which becomes activated when cortical neurons discharge in greater number and more repetitively than is normally the case. During spike and wave discharges a large number of neurons oscillate between short periods of excitation, corresponding to the spike, and longer periods of inhibition, corresponding to the slow wave component of the spike and wave complex. This disrupts the normal transactional processes of cortical neurons which are presumably responsible for mental activity, particularly for the close integration of perception, cognition and voluntary motor responsiveness. The degree of this interference varies greatly and in mild absence seizure it is not justified to speak of "loss of consciousness". The fundamental disturbance in absence seizures brought about by the generalized cortical spike and wave discharges is therefore better regarded as a "clouding of the mind". Loss of consciousness can be said to occur only when the interference with mental activity becomes particularly intense. Loss of consciousness in absence seizures can therefore not be used as an argument in favor of primary involvement of higher brain-stem mechanisms.

Animals↗
PubMed1977

Automatic noctural sleep sampling: a useful method in clinical electroencephalography.

The clinical usefulness of obtaining a sleep record in epileptic patients is well established. However, in many clinical EEG laboratories, it is difficult to obtain records at night during the patient's natural sleep. Thus, most sleep EEGs are recorded in the EEG laboratory during daytime and are induced by drugs. A 16 channel cable-telemetry system is described which automatically samples throughout the night the EEG of patients while sleeping in their room or ward without the aid of any medication. The electrodes and the cable-telemetry unit are applied to the patient in the afternoon and the system is checked. The patient is then instructed to plug the system into a wall box upon retiring and to disconnect it when he wakes up in the morning. The EEG samples are automatically written out during the night on one of the EEG machines located in the EEG laboratory to which the system is connected via spectral intra-hospital wiring. The duration of the samples and of the intervals separating them can be varied according to the circumstances. We have found this method to be very helpful in the investigation of epileptic patients, especially those considered for surgical treatment.

Electroencephalography↗
PubMed1977

New sphenoidal electrode assembly to permit long-term monitoring of the patient's ictal or interictal EEG.

A new sphenoidal wire electrode is described which greatly increases the clinical and diagnostic usefulness of sphenoidal electrode recordings. These very fine wire electrodes are easy to insert; they are comfortable and acceptable to the patient. In contrast to sphenoidal needle electrodes they expose the patient to no risk should he have a seizure during recording. These electrodes also allow one to extend the recording time to several days, thus increasing the chances of recording a spontaneous seizure, for instance while the patient's EEG is being recorded with a telemetry system. The extended recording time also allows for continuous automatic sampling of the interictal EEG over a period of several days. The quality and the reliability of the EEG record are also enhanced. The new sphenoidal electrodes have been used on over 100 patients and are now being used routinely on suspected temporal lobe epileptics recorded with conventional techniques, while 50 of the patients have also been recorded with a cable-telemetry seizure monitoring system which has captured 65 spontaneous seizures.

Electrodes, Implanted↗
PubMed1977

Pathophysiology of generalized penicillin epilepsy in the cat: the role of cortical and subcortical structures. I. Systemic application of penicillin.

The mechanism of precipitation of generalized epileptiform discharges in feline generalized penicillin epilepsy, a model of human generalized corticoreticular ('centrencephalic') epilepsy, was studied in acute and chronic experiments in cats with implanted skull and intracerebral electrodes. Single shock and low frequency repetitive stimulation of subcortical sites from which prior to penicillin administration spindle activity and recruiting responses could be elicited, readily triggered epileptiform discharges in the same animals after penicillin. These structures comprised the intralaminar and midline thalamic nuclei, the neostriatum, and some posterior thalamic association nuclei (Pulvinar and nucleus lateralis posterior). Subcortical and cortical structures which prior to penicillin elicited neither spindle activity nor recruiting responses were significantly less effective in triggering generalized epileptic bursts after penicillin injection. The probability with which such bursts were elicited from these structures was still, however, in many instances above chance level. It is concluded that the generalized epileptiform discharges in feline generalized penicillin epilepsy can be triggered from a large number of brain sites, but most reliably so from subcortical nuclei involved in spindle generation and recruiting responses. The experimental evidence presented still does not allow one to determine whether epileptic alteration of neuronal function in this form of epilepsy primarily resides in cortical or subcortical nerve cells or in both.

Animals↗