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E Halgren

Publications and source records attributed to E Halgren.

83 records · Page 5Linked to original sources
PubMed1978

Human hippocampal formation EEG desynchronizes during attentiveness and movement.

The relation of the hippocampal EEG to behavior and to the neocortical EEG is being studied in psychomotor epileptics. Hippocampal recordings displaying only rare epileptiform spikes and slow waves are found to follow grossly the simultaneously recorded neocortical EEG, becoming desynchronized during wakefulness and paradoxical sleep (PS), and displaying large irregular slow waves during slow-wave sleep. In the one patient reported in this clinical note, strong rhythmic 5--6 c/sec waves dominated the neocortical and hippocampal EEG during quiet wakefulness. These slow waves were replaced by desynchronized activity during PS and during difficult tasks, suggesting a further desynchronizing influence. The findings in all patients suggest that the rhythmic slow activity ('theta') found in rats and cats during specific behaviors is not observed in the human hippocampal formation during the homologous behaviors.

Adult↗
PubMed1977

Post-EEG seizure depression of human limbic neurons is not determined by their response to probable hypoxia.

A subclinical EEG seizure occurred in each of 2 patients during a test that repeatedly evoked probable mild cerebral hypoxia. The firing rate of the neurons was unaffected until the EEG seizure had been ongoing for over a minute. After the EEG seizures, all neurons were profoundly depressed regardless of whether their responses to hypoxia had been an increase, decrease, or no change in firing rate. These observations indicate that the mechanism responsible for post-EEG seizure depression of neuronal firing is probably not cerebral hypoxia.

Action Potentials↗
PubMedDate not supplied

Multidisciplinary analysis of patients with extratemporal complex partial seizures. I. Intertest agreement.

In 15 patients we hypothesized the origin of epilepsies to be 'extratemporal' based on videotaped seizures and surface EEG. Neuropsychological tests and neuroimaging (CAT, MRI, and PET scans) were then compared to the hypothesized ictal sites. Neuropsychological tests were abnormal in 86.6% and FDG-PET scans were abnormal in 73%. The neuropsychological tests and PET localized or lateralized areas of dysfunction to the same sites as electroclinical characteristics did in 85% of patients (P less than 0.01, Fisher exact test). No statistically significant correlation between lesion sites on CT and MRI and the ictal origin was observed due to the high proportion of normal or non-specific scans. These observations should be verified in a larger series of extratemporal seizures.

Adolescent↗
PubMedDate not supplied

Effects of muscarinic and adrenergic agonism on auditory P300 in the macaque.

Homologs of human endogenous evoked potentials are known in several species of nonhuman primates, but the neurotransmitter substrates of these potentials remain uncertain. In particular, the role of central cholinergic and adrenergic systems is not yet clearly defined. We recorded cognitive evoked potentials from the scalp in four adult bonnet macaque monkeys during a passive version of the auditory oddball paradigm with unique novel stimuli under saline control conditions. In two subjects each, cognitive evoked potentials were also recorded following intramuscular administration of the m1 muscarinic agonist AF102B or of the alpha-2A noradrenergic agonist guanfacine. On saline, large positivities resembling the human P300 were recorded over midline sites in response to rare or novel auditory stimuli in all four monkeys. The amplitude of these positivities was sensitive to the delivery of fruit-juice reward in association with rare stimuli in three monkeys tested. At cognition-enhancing doses, AF102B enlarged the amplitude of P300-like positivities in both monkeys tested; guanfacine enlarged the amplitude of P300-like positivities in one of two monkeys tested. These results add to existing evidence of human-like endogenous late positivities in monkeys that are influenced by the cholinergic and adrenergic systems, and suggest a possible role of m1 muscarinic and alpha-2A noradrenergic receptor subtypes.

Acoustic Stimulation↗
PubMedDate not supplied

Arousal-related P3a to novel auditory stimuli is abolished by a moderately low alcohol dose.

Concurrent measures of event-related potentials (ERPs) and skin conductance responses were obtained in an auditory oddball task consisting of rare target, rare non-signal unique novel and frequent standard tones. Twelve right-handed male social drinkers participated in all four cells of the balanced placebo design in which effects of beverage and instructions as to the beverage content (expectancy) were independently manipulated. The beverage contained either juice only, or vodka mixed with juice in the ratio that successfully disguised the taste of alcohol and raised average peak blood-alcohol level to 0.045% (45 mg/dl). ERPs were sensitive to adverse effects of mild inebriation, whereas behavioural measures were not affected. Alcohol ingestion reliably increased N2 amplitude and reduced the late positive complex (LPC). A large, fronto-central P3a (280 ms latency) was recorded to novel sounds in the placebo condition, but only on the trials that also evoked electrodermal-orienting responses. Both novel and target stimuli evoked a posterior P3b (340 ms), which was independent of orienting. Alcohol selectively attenuated the P3a to novel sounds on trials with autonomic arousal. This evidence confirms the previously suggested distinction between the subcomponents of the LPC: P3a may be a central index of orienting to novel, task-irrelevant but potentially significant stimuli and is an important component of the arousal system. P3b does not have a clear relationship with arousal and may embody voluntary cognitive processing of rare task-related stimuli. Overall, these results indicate that alcohol affects multiple brain systems concerned with arousal, attentional processes and cognitive-autonomic integration.

Adult↗
PubMedDate not supplied

Cortical metabolic activation in humans during a visual memory task.

A delayed match-to-sample (DMS) task of abstract, visual memory was performed during the uptake period of 18F-fluorodeoxyglucose. The increase in glucose uptake of cortical and subcortical regions ("activation") during the DMS task was compared with that during a control, immediate match-to-sample task using positron emission tomography. Both discriminant analysis and paired t tests supported the observation that the dorsolateral prefrontal area underwent the greatest activation, while a factor analysis revealed the functional correlation matrices of the tasks. Activations in the ventral premotor cortex and supramarginal and angular gyri were highly correlated with the change in the dorsolateral prefrontal cortex. The basal forebrain/ventral pole region showed a smaller but independently significant change. The findings support the role of the dorsal prefrontal region in the nonspatial working memory of humans.

Adult↗
PubMedDate not supplied

Focal medial temporal lobe spike-wave complexes evoked by a memory task.

Several factors are known to modulate the occurrence of interictal spike-wave complexes (SWC). During performance of a recent memory task by a patient with uncontrolled complex partial seizures and implanted electrodes, visually presented stimuli consistently evoked focal medial temporal lobe interictal SWC with an average latency of 228 +/- 29 ms. The SWC were more often lateralized to the left medial temporal lobe. No consistent change in interictal spike rate was observed during performance of several other cognitive tasks during which visual or auditory stimuli were presented. This suggests that performance of specific cognitive tasks--in this case, recognition memory of words--can trigger interictal SWC.

Amygdala↗
PubMedDate not supplied

Neuroimaging in patients with seizures of probable frontal lobe origin.

Twenty-two patients whose electroclinical ictal characteristics suggested frontal lobe seizure foci were studied. Computed tomography (CT) scans showed abnormalities in only 32% of patients whereas magnetic resonance imaging was informative in 45%. 18FDG-Positron emission tomography (PET) scanning revealed decreased metabolism in 64% of the group. The areas of hypometabolism were focal, regional, or hemispheric. Focal frontal hypometabolism was significantly correlated with the electroclinical (semiologic) ictal localization. Therefore, FDG-PET scanning is a sensitive and specific technique for investigating patients with seizures of probable frontal lobe origins.

Deoxyglucose↗