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Biomedical subjects

J Gotman

Publications and source records attributed to J Gotman.

At least 91 records · Page 5Linked to original sources
PubMed1988

Excitatory amino acids are elevated in human epileptic cerebral cortex.

We used intraoperative electrocorticography to identify and compare specimens from two groups of patients undergoing temporal lobectomy: (1) spiking cortex (12 patients)--epileptic activity recorded over much of the temporal convexity; and (2) nonspiking cortex (9 patients)--temporal convexity free of interictal spiking, epileptic activity confined to the hippocampus and/or amygdala. Comparative amino acid levels were (mumol/g protein, mean +/- SEM): glutamate--spiking 109.8 +/- 1.8, nonspiking 87.4 +/- 2.0 (p less than 0.001); aspartate--spiking 15.2 +/- 0.9, nonspiking 12.2 +/- 0.5 (p less than 0.05); GABA--spiking 15.0 +/- 1.0, nonspiking 13.9 +/- 1.4 (NS); taurine--spiking 14.5 +/- 0.8, nonspiking 12.2 +/- 0.8 (NS); and glycine--spiking 11.5 +/- 0.8, nonspiking 7.4 +/- 0.6 (p less than 0.01). Cortical epileptic activity appears to be associated with elevated concentrations of glutamate, aspartate, and glycine, but not GABA and taurine, perhaps indicating a relative imbalance between putative excitatory and inhibitory amino acid neurotransmitters.

Adolescent↗
PubMed1987

Interhemispheric interactions in seizures of focal onset: data from human intracranial recordings.

Interactions between the two hemispheres were studied during seizures recorded in 8 epileptic patients having chronic intracranial electrodes. Seven had temporal lobe foci and one a fronto-central focus. Strength of interaction was measured by the coherence between the EEGs from symmetrical contralateral locations. Time delays of a few milliseconds between discharges were computed by the coherence and phase method. The evolution of interactions was followed from the time a seizure of focal onset had become bilateral to its end. It was found that interhemispheric coherence was generally low throughout seizures, highest values being reached early in the seizure at the time of spread, or at the very end. Time delays most often indicated a lead from the side of onset, whether they were measured early or late in the seizure. Exceptions to these results were found in 2 of 3 patients with bilateral independent onsets: interhemispheric coherence was higher and time leads were always from the same side, independently of the side of onset. If it is assumed that high interhemispheric coherence is mediated by direct connections such as corpus callosum and anterior commissure, then these results can be interpreted as follows: the major commissures do not play an important role in contralateral spread of temporal lobe seizures although they are sometimes active, particularly at initial spread and at seizure end. Time leads from the side of onset indicate that the focus retains an influence over the contralateral discharge throughout the seizure. A different situation may exist with independent bitemporal foci.

Brain↗
PubMed1986

Structural determinants of electroencephalographic findings in acute hemispheric lesions.

We studied electroencephalograms and computed tomographic scans of 54 patients with acute hemispheric strokes. Electrographic parameters evaluated included field, amplitude, frequency, persistence, and reactivity of focal or lateralized slow-wave activity. Ipsilateral and contralateral background activity were also assessed. Structural and clinical features studied were lesion size, density, mass effect, location, tissue involvement, deep structure involvement, level of consciousness, and outcome. The data were analyzed using computer sorting and the chi 2 test. The field, amplitude, and frequency of focal slow-wave abnormalities generally failed to show a specific association with structural details. Continuous focal abnormalities correlated with large lesions (p less than 0.05), mass effect (p less than 0.05), and altered state of consciousness (p less than 0.05). Reactive focal abnormalities were associated with small lesions (p less than 0.05) and the absence of mass effect (p less than 0.02). Ipsilateral background activity abnormalities correlated with lesion size (p less than 0.001) and mass effect (p less than 0.01). Attenuation of ipsilateral background activity was more important than irregularity. Abnormal background activity contralateral to the lesion side was associated with alteration of consciousness (p less than 0.05).

Adult↗
PubMed1985

Electroencephalographic spiking activity, drug levels, and seizure occurrence in epileptic patients.

We investigated the relationships among the electroencephalographic spiking rate, drug levels, and seizure occurrence in 44 patients with focal epilepsy. Seizure occurrence was continuously monitored by personnel or videorecording and spiking rate was quantified by an automatic detection method. Results indicate that drug levels do not influence spiking rate, and spiking rate does not change before seizures but increases markedly after them, particularly secondarily generalized seizures. This increase can last several days and is observed during wakefulness and sleep. High or low spiking rates do not influence the occurrence of seizures. We suggest that interictal spikes may passively reflect damage to the brain, a damage which is worsened by further seizures. Spikes may not be directly related to seizure generation.

Adult↗
PubMed1985

Automatic detection of spike-and-wave bursts in ambulatory EEG recordings.

The spike-and-wave detection scheme described in this report is based on the recognition of groups of spikes and sharp waves with loosely defined temporal and inter-channel relationships; presence of a slow wave is required only with spikes of low amplitude. Particular attention is paid to artefacts. This method allows the detection of classical 3/sec spike-and-wave activity as well as irregular patterns. The analysis produces a standard EEG tracing containing only the detected bursts, allowing conventional visual examination by an electroencephalographer. After interactive editing of false detections, a quantitative display of burst distribution can be obtained. The rate of false detections due to artefacts or non-epileptiform patterns was evaluated on eight 20 h cassette recordings; an average of 2.4-10 false detections were made per hour. When tested against hand-scoring by two EEGers of eight 2 h recordings which included very irregular spike-and-wave patterns, the computer detected 70% of the spike-and-wave activity identified by both readers (i.e., 30% false negatives), while 12% of the computer detections were not identified by either reader (false positives). The context in which such a computer method with imperfect performance can be clinically useful is discussed.

Adolescent↗
PubMed1985

Practical use of computer-assisted EEG interpretation in epilepsy.

Computer methods can automatically recognize interictal spikes and seizures quite reliably, but they still make a large number of false detections because of physiological or artifactual nonepileptiform transients. In the context of long-term monitoring, these methods can be used efficiently and safely despite their imperfection. They allow considerable data reduction, by selecting epileptiform activity and discarding the largest part of the recording. In addition to data reduction, computer methods can be useful in refining the analysis of epileptic seizures, revealing information not available from visual inspection of the paper tracing. Recent technological advances make these applications affordable in a clinical EEG laboratory.

Cerebral Cortex↗
PubMed1985

Patterns of seizure activation after withdrawal of antiepileptic medication.

Effects of withdrawal of anticonvulsant drugs on the temporal profile of occurrence and the type of seizures were investigated in 40 intractable epileptic patients who were candidates for surgical treatment. EEG and behavior were monitored while drugs were reduced to allow localization of the epileptogenic region. The rapid withdrawal of drugs caused a rebound effect, triggering either generalized seizures during a brief period or a longer-lasting increase in partial seizures. These increases in seizure frequency appeared related to change in dosage rather than to dosage itself, since they remained largely confined to the early period following reduction of an anticonvulsant.

Adult↗
PubMed1985

Seizure recognition and analysis.

The processing of EEGs with respect to epileptic seizures falls in two main categories: automatic recognition of seizures during long-term monitoring and analysis of seizures to extract information not available from visual inspection. Automatic seizure recognition is a complex problem because the EEG during seizures is not well defined morphologically; imperfect automatic recognition is nevertheless possible and it can simplify the task of monitoring and increase its diagnostic yield. The widespread use of monitoring techniques has made the recording of seizures relatively frequent. It has therefore become worthwhile to develop procedures for analyzing seizure patterns in detail, particularly the propagation of seizure activity between different brain structures. The computation of time differences of a few milliseconds between two channels is possible and has been shown to be meaningful. Such an analysis allows to follow the structures involved and the different stages of evolution of a seizure, the structures likely to be 'driving' seizure activity and the possible routes of propagation. These methods are reviewed and their use is illustrated.

Animals↗
PubMed1985

Monitoring at the Montreal Neurological Institute.

Long-term monitoring of epileptic patients who are candidates for surgical therapy has developed at the Montreal Neurological Institute and Hospital over the last 15 years. Given the large number of patients being investigated, we had to develop procedures which were not labor-intensive. Our monitoring sessions require only the regular supervision of nursing staff. This allows monitoring to take place 7 days a week and 24 h a day on 2 or 3 patients, with minimal personnel requirement. The work of the EEGer is greatly simplified by the fact that the EEG tracing is reduced to the 'interesting' sections only. This was originally possible because of the concept developed by Ives et al. (1976) of delaying the EEG so that activity prior to perceptible clinical signs were always retained. The automatic detection of interictal spikes and seizures in the EEG complemented very effectively this original method of seizure recording. Video recording plays a critical role in the evaluation of seizure disorders. In order to have the maximum quality of EEG and behavior, we record them on their most appropriate medium, paper and video tape respectively; the two are synchronized by a common clock. EEGs are also recorded on a computer tape or disk and can be further analyzed for clinical and research purposes.

Canada↗
PubMed1985

Automatic recognition of interictal spikes.

This paper reviews numerous methods which have been developed for the automatic recognition of isolated epileptic spikes in the EEG. Computer displays of results and difficult problems caused by artefacts and non-epileptiform sharp transients are discussed. We then examine the complexity of validating the performance of automatic methods. The implementation of computer methods in a clinical environment has only rarely been attempted and some of the reasons for this situation are presented. Finally we review several research projects which relied heavily on using quantitative analysis of spike activity: studies of morphological characteristics of spikes and sharp waves and studies of the temporal and spatial distribution of interictal spikes in relation to seizure occurrences and stages of sleep.

Action Potentials↗
PubMed1984

Computer assisted analysis of relations between single-unit activity and spontaneous EEG.

Two mutually complementary computer methods are described which can be used for the study of unit-EEG relationships during spontaneous EEG waves. The first one consists of using the unit activity to trigger the averaging of sections of EEG preceding and following each unit; the same unit activity is used for building a histogram of unit firing from another cell. Sections of data subjected to this analysis need not be continuous; they may be chosen interactively on the computer terminal, thus allowing to analyze intermittent phenomena. The second method consists of using a particular point of an EEG wave to trigger EEG averages from other channels as well as unit histograms. Here again the waves are chosen interactively. The unit-triggered EEG averages are more objective and less time consuming. However, they do not describe accurately the characteristics of the individual wave to which a unit firing is associated and also they give no information about inhibitory phenomena. Both these drawbacks are corrected by the wave-triggered unit histograms where the experimenter interactively selects and stores for analysis EEG waves with the appropriate characteristics. Several examples are given from the utilization of these programs in neurophysiological and neuropharmacological experiments, with special emphasis on generalized epilepsy.

Animals↗
PubMed1984

Relationships between triggered seizures, spontaneous seizures, and interictal spiking in the kindling model of epilepsy.

Cats were kindled in the amygdala. After completion of kindling, their EEG was monitored almost continuously by a computer system which allowed the detection of spontaneous seizures and the quantification of interictal spikes. The relationships between seizures triggered by stimulation, spontaneous seizures, and interictal spikes in kindled and contralateral amygdalas were examined. Very few spontaneous seizures were observed; their occurrence appeared facilitated by a few triggered seizures after a long seizure-free interval. Stimulation-triggered seizures were followed first by a decrease in spiking activity during a few hours and then by an increase which could take 3 to 8 days to return to baseline. Spontaneous seizures were also, but less systematically, followed by such a sequence. Spontaneous seizures could occur when the interictal spiking rate was high as well as when it was low. It is concluded that, in the fully kindled cat, interictal spiking appears to be mainly regulated by the occurrence of seizures; the rate of spiking appears to have no bearing on the probability of occurrence of spontaneous seizures. Hence, seizures and interictal spiking could be generated by separate pathophysiologic mechanisms, the seizure-generating mechanism influencing the spike-generating mechanism but not the reverse.

Animals↗
PubMed1983

Measurement of small time differences between EEG channels: method and application to epileptic seizure propagation.

Small time differences between the EEG activities of two channels were measured by a method based on the use of coherence and phase spectra over a certain frequency range. In many cases this method allowed to establish that time differences of the order of 5-50 msec were actually present between two channels which appeared synchronous on visual inspection. The method was applied to seizure activity from the penicillin and kindling models in the cat and to seizures recorded from scalp and intracerebral electrodes in epileptic patients. When the seizure activity was widespread but was known to be related to an epileptic focus, it was found that the area of the focus had a consistent time lead over the other recording sites. It was concluded that the method could frequently allow to: (1) assess the presence of an epileptic focus even when only widespread seizure activity could be recorded; (2) make inferences about the possible routes of propagation of seizure activity.

Animals↗
PubMed1983

An analysis of penicillin-induced generalized spike and wave discharges using simultaneous recordings of cortical and thalamic single neurons.

To study the relationship between cortical and thalamic single-neuron activity during spike and wave (SW) discharge of feline generalized penicillin epilepsy (FGPE), extracellular single-unit and local electroencephalogram (EEG) activity were recorded simultaneously from pairs of neurons, one located in the cortex of the middle suprasylvian gyrus (MSS), the other in the dorsal thalamic nuclei (n. lateralis posterior or pulvinar). These two areas are anatomically and functionally closely interrelated. Computer-generated EEG averages and histograms of single-unit activity triggered by either peaks of cortical or thalamic EEG transients or by cortical or thalamic action potentials (aps) showed that cortical neurons in the MSS fired at the time of the spike of the SW complex, while at the time of the wave they became silent. Two populations of thalamic neurons also fired maximally during the spike of SW discharge, but they differed in the precise timing of their firing in relation to that of the simultaneously recorded cortical neuron. The first group of thalamic neurons tended to fire 5-45 ms before the cortical neuron. Of these 28 neurons, 9 were antidromically and 2 orthodromically activated by cortical stimulation. The neurons of the second group tended to fire 0-45 ms after the cortical neuron. Cortical stimulation activated 15 of these 19 neurons orthodromically and 2 antidromically. A third and smaller population of thalamic neurons (n = 8) increased its firing probability during the wave of the SW complex and decreased it during the spike. In 74% of the pairs of neurons the cyclic alternation of excitation and "inhibition" associated with SW activity appeared in the cortex by 1-3 cycles earlier than in the thalamus. This was most common when the thalamic neuron of the pair reached its peak firing probability before the simultaneously recorded cortical neuron. In 11 pairs of neurons the same rhythmic alternation of excitation and "inhibition" of neuronal firing was seen in both the cortex and thalamus during SW discharges evoked by single-shock stimulation of nucleus centralis medialis. These data demonstrate that both cortical and thalamic neurons participate in the SW firing pattern of FGPE by undergoing periods of mutually phase-locked cyclic alternations of excitation and "inhibition" at the frequency of the EEG SW rhythm. Although the initial steps leading to generalized SW discharge in FGPE take place in the cortex, the thalamus soon becomes entrained in the SW rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1982

Automatic recognition of epileptic seizures in the EEG.

During prolonged EEG monitoring of epileptic patients, the continuous EEG tracing may be replaced by a selective recording of ictal and interictal epileptic activity. We have described previously methods for the EEG recording of seizures with overt clinical manifestations and for the automatic detection of spikes. This paper describes a method for the automatic detection of seizures in the EEG, independently of the presence of clinical signs; it is based on the decomposition of the EEG into elementary waves and the detection of paroxysmal bursts of rhythmic activity having a frequency between 3 and 20 c/sec. Simple procedures are used to measure the amplitude of waves relative to the background, their duration and rhythmicity. The evaluation of the method on 24 surface recordings (average duration 12.4 h) and 44 recordings from intracerebral electrodes (average duration 18.7 h) indicated that it was capable of recognizing numerous types of seizures. False detections due to non-epileptiform rhythmic EEG bursts and to artefacts were quite frequent but were not a serious problem because they did not unduly lengthen the EEG tracing and they could be easily identified by the electroencephalographer. The program can perform on-line and simultaneously the automatic recognition of spikes and of seizures in 16 channels.

Brain↗