alpha 2-adrenergic antagonists suppress epileptiform EEG activity in a petit mal seizure model

Experiments were performed to determine the effects of yohimbine, piperoxan, and mianserin on the flash-evoked afterdischarge (FEAD) in rat. All three drugs are alpha-adrenergic antagonists, which block the inhibition of norepinephrine-release mediated by presynaptic (alpha 2) receptors. It was predicted that these drugs would exert dose-dependent biphasic effects on FEAD: at low doses, which act presynaptically, the FEAD would be suppressed; while at higher doses, which also block postsynaptic (alpha 1) receptors, the FEAD would be disinhibited. The dose response curves for yohimbine and piperoxan were, in fact, biphasic with low doses decreasing the amount of FEAD, while higher doses returned the amount of FEAD to baseline. No biphasic effect was seen with mianserin. These observations are consistent with the fact that yohimbine and piperoxan are more potent antagonists at alpha 2- than at alpha 1-receptors, whereas the affinities of mianserin for the two receptor types is comparable. The results of these experiments support the hypothesis that norepinephrine modulates FEAD.     

A new model of petit mal epilepsy: spontaneous spike and wave discharges in tremor rats

A mutant rat, which was found in a colony of Kyoto:Wistar rats and genetically defined as a tremor rat (tm/tm), developed tremor of the whole body at 2 weeks of age but the tremor gradually disappeared between 6 and 8 weeks of age. The electroencephalogram (EEG) recorded using chronically implanted electrodes showed a 5-7 Hz (mostly 6 Hz) spike and wave complex synchronously in the cerebral cortex and hippocampus accompanied by absence-like seizure in all six tremor rats examined. The spike and wave complex appeared 0.8-1.9 times per minute and lasted for 1-17 s. However, normal EEG activity was observed in the intervening periods, free of absence-like seizure. Thus the tremor rat is considered to be a possible model for studying the pathogenesis and therapy of petit mal epilepsy in humans.     

Chaotic EEG patterns during recall of stressful memory related to panic attack

Chaotic transitions likely emerge in a wide variety of cognitive phenomena and may be linked to specific changes during the development of mental disorders. They represent relatively short periods in the behavior of a system, which are extremely sensitive to very small changes. This increased sensitivity has been suggested to occur also during retrieval of stressful emotional experiences because of their fragmentary, temporally and spatially disorganized character. To test this hypothesis we recorded EEG during retrieval of fearful memories related to panic attack in 7 patients and retrieval of anxiety-related memories in 11 healthy controls. Nonlinear data analysis of EEG records showed a statistically significant increase in degree of chaotic dynamics after retrieval of stressful memories in majority of patients as well as in control subjects. This change correlated with subjective intensity of anxiety induced during the memory retrieval. The data suggest a role of nonlinear changes of neural dynamics in the processing of stressful anxiety-related memories, which may play an important role in the pathophysiology of panic disorder.     

The relationship between vigilance and cortical EEG manifestations after electrical stimulation of the thalamus and hippocampus in unrestrained rats.

The thalamus or hippocampus of unanaesthetized rats with impaired cortical and subcortical electrodes was stimulated with rhythmic series of electrical pulses of 3--15/sec frequency. In both cases, stimulation either did not affect vigilance, or led to a higher degree of wakefulness. The incidence of recruiting responses (RR) and of self-sustained afterdischarges (SSAD) evoked by stimulation of the thalamus was not correlated to the preceding state of vigilance. In stimulation of the hippocampus, a significantly higher incidence of SSAD was found in the quiet waking state. The correlation between the elicitation of RR and SSAD was also significantly the highest after stimulation of the hippocampus during wakefulness.     

The tussiphonogram during asthmatic attack

By tussiphonography the voluntarily induced cough sound was registered in the course of asthmatic attacks and in the state of quinescence. Evaluation of the recordings revealed that in the course of the asthmatic attack, the intensity of voluntarily induced cough sound was significantly decreased.     

Simultaneous fMRI and EEG during the Multi-Source Interference Task

Background

fMRI and EEG are two non-invasive functional imaging techniques within cognitive neuroscience that have complementary advantages to obtain both temporal and spatial information. The multi-source interference task (MSIT) has been shown to generate robust activations of the dorsal anterior cingulate cortex (dACC) on both a single-subject level and in group averages, in fMRI studies. We have now simultaneously acquired fMRI and EEG during a cognitive interference task.

Materials and Methods

Healthy volunteers were tested in an MRI scanner with simultaneous EEG and fMRI recordings during the MSIT.

Results

The interference condition significantly increased the reaction time in the task. The fMRI analyses revealed activation of dACC as expected, in all subjects at the individual level and in group analyses. The posterior cingulate cortex was de-activated. Simultaneous EEG showed the expected anterior distribution of the interference effect, as it was restricted to frontal sites within a time frame of 80–120 ms post response.

Conclusion

The MSIT task is a reliable task for interference evaluation. fMRI shows robust activation of dACC and by adding EEG, an interference effect can be noticed within a temporal interval of 80–120 ms after the response, as a CRN (correct response negativity). This means that EEG could add a more detailed temporal aspect to the fMRI data from an interference task, and that despite the hostile environment within an MRI scanner, EEG data could be used.