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J Gotman

Publications and source records attributed to J Gotman.

17 recordsLinked to original sources
PubMed1992

State dependent spike detection: validation.

We present a formal validation of the method of state dependent spike detection; its principle and initial results were given in Gotman and Wang (1991). The method utilizes different procedures for elimination of non-epileptic transients according to state (active or quiet wakefulness, sleep stages); it also varies detection sensitivity according to state. Twenty new 100 min recordings were obtained from 20 unselected patients, covering active wakefulness, quiet wakefulness and various sleep stages. Results indicated that, while the total number of detections was reduced by 15%, true detections increased by 39% and false detections decreased by 60%. This significant improvement is due to the fact that wave morphology is now considered within its spatial context and particularly within a wide temporal context.

Adolescent↗
PubMed1992

Intracranial EEG study of brain structures affected by internal carotid injection of amobarbital.

Hippocampal function, considered critical in memory processing, is supposedly tested in the intracarotid sodium amobarbital (ISA) procedure; however, since the hippocampus is not completely irrigated by the internal carotid artery, some believe the procedure may be invalid for memory testing. We quantified delta activity in intracerebral EEGs during ISA tests. There was increased delta in ipsilateral structures as follows: amygdala (6.4 minutes), anterior hippocampus (7.2), middle hippocampus (7.4), temporal neocortex (9.1), frontal lobe (8.4), central/parietal area (11.0), and occipital lobe (9.7). Contralateral structures usually (> 64%) showed increased delta lasting 4 to 5 minutes. The ipsilateral hippocampus had delta waves in over 90% of injections. We conclude that the hippocampus is clearly affected by the ISA injection. We argue that the slow waves may not be caused by a direct effect of the drug, but rather by a functional deafferentation due to the profound inactivation of structures surrounding the hippocampus. Similarly, slow waves contralateral to injection may be caused by sudden removal of neuronal input from the regions receiving the amobarbital.

Amobarbital↗
PubMed1991

State-dependent spike detection: concepts and preliminary results.

In traditional methods of spike detection, spikes are defined in absolute terms (duration, amplitude) or relative to a few seconds of background. These methods result in many false positive detections during long-term epilepsy monitoring because of numerous artefacts and non-epileptic transients. To reduce significantly false detection, we propose to render spike detection sensitive to the state of the EEG. We thus defined 5 states (active wakefulness, quiet wakefulness, desynchronized EEG, phasic EEG and slow EEG) and designed a method for automatic state classification. We then designed procedures for identification of non-epileptic transients (eye blinks, EMG, alpha, spindles, vertex sharp waves). These procedures are to be applied only in the state in which they are likely to occur (e.g., eye blinks in wakefulness). We present preliminary results from 14 recordings each lasting 100 min, which indicate a state classification reliability of 85-90%, reduction in false detection of 65-90% if state classification were perfect; true spikes lost as a result of these procedures were under 5%. These results are encouraging and validate the concept of a spike detection system which analyses a wide temporal and spatial context before deciding the significance of a wave form.

Blinking↗
PubMed1991

Effects of seizures and carbamazepine on interictal spiking in amygdala kindled cats.

We examined the influence of seizures and carbamazepine (CBZ) on spiking rates in kindled cats. In the first experiment, spiking rates were measured before and after seizures, with and without CBZ. CBZ was administered immediately after seizures in order not to affect them. Spiking rates were measured over 9 h during the different sleep stages. In a second experiment, CBZ was administered before and after seizures so as to affect seizure strength and thus measure its effect on spiking. Results confirmed earlier findings of a large increase in spiking following a stage 6 seizure in fully kindled animals. We also established that: (1) repeated daily seizures caused a further increase in spiking until a ceiling was reached; (2) increased spiking was not a direct effect of postictal alterations in sleep stages; (3) CBZ, despite its effectiveness as an anticonvulsant, did not reduce spiking but rather increased it; (4) postictal increases in spiking were related to seizure 'strength'. These findings support the hypothesis that spiking rates are primarily influenced by seizure occurrence, as was found in patients with temporal lobe seizures, and that anticonvulsants act differently on seizures and spikes. This emphasizes the possibility of distinct pathophysiological mechanisms for interictal spikes and seizures.

Action Potentials↗
PubMed1991

Relationships between interictal spiking and seizures: human and experimental evidence.

Epileptic seizures of focal origin often occur unpredictably as do interictal spikes. It is often assumed that spikes increase prior to seizures of focal origin and that antiepileptic medication affects spikes and seizures in a parallel fashion. We review evidence that this assumption is invalid and that there is a clear dissociation between spikes and seizures: increases in spiking before seizures have not been clearly documented; decreases in antiepileptic medication do not result directly in increased spiking; seizures are often followed by long-lasting increases in spiking; finally, seizures are no more likely when spikes are frequent than when spikes are rare. It therefore appears that spikes and seizures are two quite distinct phenomena, both originating in the epileptic focus but varying over time differently from what is most often believed.

Anticonvulsants↗
PubMed1991

Interictal spiking during wakefulness and sleep and the localization of foci in temporal lobe epilepsy.

We examined variations in interictal spiking during sleep and wakefulness to assess differences in reliability for localizing epileptic foci. Forty patients were studied prospectively. Spikes were assessed for rates, field, and appearance of new foci. Final localization was determined by surgery, electrocorticography, and seizure onset. Comparison of interictal EEG foci with final localization was made. In 39 patients, slow-wave sleep activated spiking compared with wakefulness. Most patients showed maximal spiking in sleep stages 3 or 4. Restriction of field in rapid eye movement (REM) sleep and wakefulness, and extension of field in slow-wave sleep occurred. New foci appeared in non-rapid eye movement sleep in 53% of patients. Similar but not identical spiking rates, foci, and field distributions were seen in wakefulness and REM sleep. All REM foci were unilateral. Our findings suggest that localization of the primary epileptogenic area is more reliable in REM sleep than in wakefulness, and in wakefulness more than in slow-wave sleep.

Action Potentials↗
PubMed1990

Automatic seizure detection: improvements and evaluation.

Improvements to an existing automatic seizure detection program are described. They are aimed at taking into account a larger temporal context and thus improving the specificity of the detections. Results were evaluated on 293 recordings from 49 patients, totaling 5303 h of 16-channel recording. They showed that 24% of the 244 seizures recorded were missed by the automatic detection; in 41% of the seizures, the patient alarm was not pressed but the computer made detections. The false detection rate was of the order of 1 false detection per hour of recording. Conclusions are: (1) automatic seizure detection must be used in conjunction with a patient alarm button since some seizures, having poorly defined EEG activity, are not detected; (2) the automatic detection allowed capture of many seizures, clinical and subclinical, for which the alarm was not pressed; (3) the low false detection rate indicates that lower detection threshold could be used, yielding better seizure detection.

Adolescent↗
PubMed1990

Quantitative EEG analysis of carbamazepine effects on amygdaloid kindled seizures in cats.

We studied the effects of carbamazepine (CBZ) on seizure behaviour and electroencephalographic (EEG) activity in 6 amygdala kindled cats. CBZ reduced the behavioural severity of kindled seizures and prolonged the earlier seizure stages (latency to stage 4). These effects were not always paralleled by a reduction in the duration of seizure activity. EEG activity paradoxically increased in amplitude during early and mid-seizure, then fell in late seizure after CBZ. CBZ also caused an overall decrease in EEG coherence during mid and late seizure. These observations represent a first attempt to use quantitative EEG analysis to investigate the effects of anticonvulsants on electrographic seizure activity. The duration of postictal EEG suppression was reduced after CBZ treatment. The results support the view that CBZ has a major effect on limiting the spread of seizure discharges.

Administration, Oral↗
PubMed1990

Can slow waves in the electrocorticogram (ECoG) help localize epileptic foci?

In patients operated for medically refractory epilepsy, ECoGs are often performed to help further localize the epileptogenic focus. During the necessarily short recording, spikes may be rare or absent, or may be only a partial representation of the epileptic activity. The usefulness of background abnormality in localizing the focus in ECoGs was therefore determined. The relationships of MRI, CT, and pathological findings with ECoG background were also noted. The ECoGs of 40 patients were recorded. Delta activity was evaluated by spectral analysis. In 22 ECoGs, maximum delta activity coincided spatially with maximum spiking or was adjacent to it. The region of maximum delta activity rarely coincided with CT, MRI and pathological findings. Although the relationship between delta activity and spiking was much stronger than expected by chance, it may not be sufficient to allow the use of delta activity to localize a focus in individual cases.

Action Potentials↗
PubMed1990

Asymmetry in delta activity in patients with focal epilepsy.

The localization of epileptogenic foci usually relies on multiple factors. The validity of background EEG abnormalities in lateralizing or localizing the focus was examined. Asymmetries in delta activity were measured by comparing EEGs of epileptic subjects to that of control subjects. The relationships of MRI, CT and pathological findings with delta asymmetries were also noted. In only 2 of 22 patients, delta activity showed no asymmetry. In 17 patients, delta asymmetries correlated with the side of the focus, and in the remaining 3 patients, predominant delta activity was observed in the hemisphere contralateral to the focus. The analysis of the relationship between delta activity and lesions observed on the CT scan was inconclusive. The area exhibiting predominant delta activity frequently coincided with the regions showing solitary discrete lesions on MRI scans. The results suggest that slow wave abnormalities, when measured by comparison to a control population, can be useful in lateralizing the epileptogenic focus.

Adult↗
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↗
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↗
PubMed1976

Automatic recognition and quantification of interictal epileptic activity in the human scalp EEG.

An attempt was made at using a small computer to recognize and quantify interictal epileptic activity (spikes and sharp waves) in the human scalp EEG. To perform the automatic recognition, the EEG of each channel is broken down into half-waves. A half-wave is characterized by its duration and its amplitude relative to the background activity. A wave is characterized by the durations and amplitudes of its two component half-waves, by the second derivative at its apex measured relative to the background activity, and by the duration and amplitude of the following half-wave. Particular combinations of these parameters were found to characterize spikes and sharp waves and are used for their recognition and quantification. Specific methods are used for the rejection of spike-like or sharp wave-like wave forms such as eye blinks, muscle potentials and sharp alpha activity and were found to perform with a high level of reliability. Interchannel relationships are thoroughly examined to determine areas of maximal epileptogenicity. Sixteen channels can be analyzed in real time. Results are presented in a simple picture containing localizing and quantitative information. Specific questions regarding the time relationships of spikes in different channels can be asked interactively by the user. The system is of potential use in clinical electroencephalography.

Alpha Rhythm↗
PubMed1975

A quantitative comparison of traditional reading of the EEG and interpretation of computer-extracted features in patients with supratentorial brain lesions.

The EEGs of adult patients with suspected supratentorial brain lesions were recorded on paper and on magnetic tape, using a small computer. The spectra of 16 channels were computed on a 40 sec sample. For each channel, a ratio of the type (delta + theta)/(alpha + beta) was computed and displayed on the computer terminal, a measure of the asymmetry in slow wave activity between homologous areas of the head was also displayed. This display is called a canonogram. It is believed to be a meaningful representation of the important characteristics of the EEG in the presence of supratentorial lesions. In order to assess the clinical value of the canonogram, the presumed localization of the lesion obtained from the interpretation of the traditional EEG and from that of the canonogram were compared to the known location of the lesion is a group of 87 subjects. The comparison was made quantitative by the use of a structured report encoding the traditional interpretation and that of the canonogram as well as the reference data (unequivocal surgical, radiological and clinical localizing evidence). The results varied among the anatomical regions: whereas in the frontal and occipital regions the EEG was slightly more accurate than the canonogram, both methods were similar in the temporal areas and the canonogram seemed more accurate in the centro-parietal regions. An attempt was made to interpret these differences. Furthermore, three readers read the cononograms and gave very consistent interpretations. These results show the reliability and value of this simple computer display for the particular type of EEG studied.

Adult↗
PubMedDate not supplied

Effects of seizures, kindling, and carbamazepine on sleep organization in cats.

We studied the relationships between epilepsy, sleep, and anticonvulsant drugs in kindled cats. No sleep alteration was present at midkindling. When the animals became fully kindled, a reduction in REM sleep percentage and the number of entries into REM sleep were observed compared to baseline. In addition, with further seizures, an increase in the percentage of wakefulness appeared, accompanied by a further reduction in the number of entries into REM sleep. It therefore seems that there is a progressive disruption of sleep, dependent on the increasing number of tonic-clonic generalized seizures. After a seizure-free interval, REM sleep and wakefulness returned to baseline values. A reduction in the percentage of stage II compared to baseline was found and remained as a long-term effect of the kindling process. Acute administration of carbamazepine (CBZ) reduced the REM sleep percentage. This effect, paralleled by a reduction in the number of entries into REM sleep, was evident both at baseline and when the animals were fully kindled. After a large number of seizures, however, CBZ administration did not cause a further reduction in the already low percentage of REM sleep. Results are discussed with reference to previous literature. We propose a hypothesis of competition between seizure and REM sleep in the elimination of epileptogenic and hypnogenic factors.

Animals↗