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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chaos theory is a rapidly growing field. As a technical term, "chaos" refers to deterministic but unpredictable processes being sensitively dependent upon initial conditions. Neurobiological models and experimental results are very complicated and some research groups have tried to pursue the "neuronal chaos". Babloyantz's group has studied the fractal dimension (d) of electroencephalograms (EEG) in various physiological and pathological states. From deep sleep (d = 4) to full awakening (d > 8), a hierarchy of "strange" attractors paralles the hierarchy of states of consciousness. In epilepsy (petit mal), despite the turbulent aspect of a seizure, the attractor dimension was near to 2. In Creutzfeld-Jacob disease, the regular EEG activity corresponded to an attractor dimension less than the one measured in deep sleep. Is it healthy to be chaotic? An "active desynchronisation" could be favourable to a physiological system. Rapp's group reported variations of fractal dimension according to particular tasks. During a mental arithmetic task, this dimension increased. In another task, a P300 fractal index decreased when a target was identified. It is clear that the EEG is not representing noise. Its underlying dynamics depends on only a few degrees of freedom despite yet it is difficult to compute accurately the relevant parameters. What is the cognitive role of such a chaotic dynamics? Freeman has studied the olfactory bulb in rabbits and rats for 15 years. Multi-electrode recordings of a few mm2 showed a chaotic hierarchy from deep anaesthesia to alert state. When an animal identified a previously learned odour, the fractal dimension of the dynamics dropped off (near limit cycles).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:On the existence and the role of chaotic processes in the nervous system. 146 29

The relationship between psychiatric symptoms that respond to anticonvulsants and epileptic activity is still debated. Evidence linking electroencephalographic changes to treatment response is scarce and controversial, partly because of the poor scalp representation of limbic electrical activity. We studied the clinical relevance of focal topographic changes in the resting EEG, the visual evoked potential and the P300 response in 90 psychiatric patients, by evaluating response to anticonvulsants and development of neurological complications. The group with focal changes was compared to a group with epileptiform activity but no focal changes and a group with normal or diffusely altered EEG. Focal EEG and EP changes predicted good response to anticonvulsants, while the presence of epileptiform activity did not. Clinical seizures developed only in patients with focal changes and no anticonvulsants medication. Structural abnormalities and selective neuropsychological deficits were seen only in the focal group. There was an association of symptom type and the site of focus. We concluded that focal EEG and EP changes in psychiatric patients have important theoretical as well as practical implications.
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PMID:Clinical significance of focal topographic changes in the electroencephalogram (EEG) and evoked potentials (EP) of psychiatric patients. 146 57

In order to isolate the anatomical locus of neural activity primarily responsible for generating the scalp-recorded P3 (or P300), the topography of event-related potentials (ERPs) elicited during an auditory oddball task was compared between medial-to-lateral aspects of the frontal, parietal, and temporal lobes in 10 epileptic patients undergoing stereoelectroencephalography for seizure localization. Evidence of local ERP generation was obtained from each of these areas. Small amplitude P3-type potentials were sometimes observed to invert polarity across recording contacts in the frontal lobe. Large amplitude positive polarity P3-type components were observed in the lateral neocortex of the inferior parietal lobule (IPL), that rapidly attenuated in amplitude at more anterior, posterior, superior, inferior, and medial recording contacts. Large amplitude polarity inverting P3-type components were also observed to be highly localized to hippocampal contacts of temporal lobe electrodes. These data are discussed in the context of other recent studies of lesion effects, scalp topography, and intracranial recordings, and it is concluded that activity generated in the IPL is likely to make the major contribution to the scalp-recorded P3, with smaller contributions from these other sources. Finally, salient topographical differences between the intracranial distribution of the P3 and those of the N2 (or N200) and slow wave (SW) suggest that the generators of these components are not identical.
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PMID:The intracranial topography of the P3 event-related potential elicited during auditory oddball. 169 55

Event-related potentials were recorded over occipital and parietal scalp from 20 patients suffering from intractable partial complex seizures prior to undergoing a temporal lobectomy. Subjects were presented with language and nonlanguage visual stimuli using a divided-field, "odd-ball" paradigm. Although behavioral performance (button-press accuracy, reaction time, and running counts) was comparable across all groups (although accuracy was worse for those in the left temporal group), patients showed tremendous variability in both the amplitude and latency of the P300 response. Particularly notable was the observation that more slow wave activity was present among the patients than among the control subjects, and those scheduled for a left temporal resection evinced more amplitude reduction than those scheduled for a right temporal resection. In addition, a number of patients appeared not to show a P300 response at all. These results are discussed in the context of the utility of using noninvasive event-related potential measures to examine both memory impairment and the integrity of the neural structures that mediate memory functioning in certain patient populations.
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PMID:P300 brain activity in seizure patients preceding temporal lobectomy. 153 21

The P3 component to an auditory "oddball" stimulus was compared between 30 epilepsy patients and 27 age-matched normal controls. The P3 latency was significantly increased in the patients, but an increase beyond 3 standard deviations on two trials occurred in only 10 percent of the total sample and 13 percent when the age was restricted to less than 50 years. There were no significant differences in latencies for different seizure type or anticonvulsant levels. The best relationship on neuropsychologic performance was with the Trails B test. Since the exact latency of the P3 peak is at times difficult to determine and may involve arbitrary choices, it is proposed that when the test is used for clinical diagnostic purposes of dementia, the interpretation be limited to those instances where the P300 peak is either clearly normal or clearly present but prolonged beyond 3 standard deviations from age-matched normals. In the first instance, significant cognitive impairment is unlikely while it becomes very probable in the latter instance.
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PMID:The cognitive evoked potential in epilepsy patients. 275 89

A retrospective study of 14 patients with epileptic seizures and 11 with nonepileptic seizures, all taking antiepileptic drugs, found epileptic patients had significantly longer P160, N200, and P300 latencies on auditory event-related potential recordings. Patients with nonepileptic seizures had generally higher IQs and significantly greater psychopathology on neuropsychological scales.
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PMID:Neuropsychological and event-related potential correlates of nonepileptic seizures. 842 29

Auditory event-related potentials (ERPs) were recorded from 131 epileptic children of 4 to 20 years of age, and the related factors affecting P300 latencies were evaluated using multiple regression analysis. The examined factors were as follows: (1) age at P300 recording and duration of illness, (2) seizure types and epileptic syndromes, (3) anti-epileptic drugs (AEDs), (4) seizure prognosis, (5) organic brain dysfunctions, (6) x-ray CT and (7) EEG background activity and frequency of paroxysms. ERPs were elicited with the oddball paradigm. Five factors of them had significant correlations with P300 latencies. 1) P300 latencies were gradually shortened with age. 2) P300 latencies were prolonged in the patients before and during AED medication compared with those during the period of off-therapy. 3) Symptomatic partial epilepsy showed obviously prolonged P300 latencies. 4) P300 latencies were shortened with increasing alpha 2 power of EEG. 5) P300 latencies became prolonged with the length of illness.
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PMID:[Factors affecting P300 latencies in epileptic children]. 851 81

Unilateral temporal lobe ablations have become a common treatment procedure for intractable epilepsy. Five children, ranging in age from 11 to 16 years, received a battery of tests to evaluate possible postoperative changes in central auditory processing functions. Children were tested before surgery and at 1 year following surgery. Tests included the SCAN test for central auditory processing, the duration pattern and dichotic digits tests, and the P300 event-related potential. With each test, some children exhibited postoperative improvement, while others exhibited either no changes or poorer postoperative performances. These results indicate that temporal lobectomies, while controlling seizures, may not always result in improved central auditory processing.
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PMID:Changes in central auditory processing following temporal lobectomies in children. 882 24

To clarify the relationship between cognitive function and clinical seizures, auditory event-related potentials (P300) were examined in 72 patients (185 trials) with partial epilepsy. Twenty-six patients (67 trials) had idiopathic partial epilepsies (IPE), and 46 (118 trials) symptomatic or cryptogenic partial epilepsies (SPE). In this study, to rule out the effects of epileptogenesis and other factors, we only examined patients with partial epilepsies undergoing carbamazepine (CBZ) monotherapy at doses of less than 16 mg/kg/day. The results were: 1) the mean age-corrected P300 latency in the patients with SPE (394 +/- 38 msec) was significantly prolonged compared with that in the patients with IPE (378 +/- 28). 2) The prolongation of the P300 latency had no relationship to the seizure frequency, seizure type or seizure duration. 3) In both epileptic groups, there was no significant correlation between the seizure-free period and the age-corrected P300 latency. Our results suggest that the effect of clinical seizures on the cognitive function may be relatively little, and that the cognitive dysfunction in partial epilepsies may mainly originate from epileptogenesis or other factors.
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PMID:Epileptic seizures and event-related potentials (P300) in childhood partial epilepsies. 913 74

We evaluated the P300 components of event-related potentials (ERP) in 64 cryptogenic partial epilepsy (CPE) patients, and 52 idiopathic generalized epilepsy (IGE) patients as well as in their age-matched control groups. The P200, N200 and P300 latencies recorded from Cz were significantly longer in CPE patients compared with those of their control group (P = 0.0371, P = 0.0092 and P = 0.0405, respectively). The P200 and N200 latencies recorded from Fz were significantly longer than in their control group (P = 0.0448 and P = 0.0107) while the prolongation in the P300 latencies was not found to be statistically significant (P = 0.0733). All latencies were longer in IGE patients, and the amplitudes of the N200/P300 components of ERP were lower in both epileptic groups compared with their control groups, but these differences were not significant. The prolongation of the P300 latencies was not correlated with the type or serum level of antiepileptic drug or seizure control. Our findings suggest that the prolongation of the P300 latency of ERP is related to the type of epilepsy.
Seizure 1999 Apr
PMID:Auditory event-related potentials (P300) in partial and generalized epileptic patients. 1022 3


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