Cocaine and pseudococaine: Comparative effects on electrical after-discharge in the limbic system of cats

The effects of cocaine and its dextroisomer pseudococaine on electrical after-discharge (AD) evoked by electrical stimulation of the hippocampus or amygdala were studied in cats with electrodes implanted in the brain. Intravenous injection of cocaine (2.0 to 4.0 mg/kg doses) produced a suppressive effect on the AD while producing low-voltage fast waves (LVFWs) in the electrical activities of the brain (EEG) associated with behavioral excitation. In contrast, pseudococaine at the same dose as cocaine failed to show a significant suppressive effect on the AD except at high doses (5.0 mg/kg). Pseudococaine produced high-voltage slow waves (HVSWs) in the EEG associated with behavioral depression. A linear dose-response relationship was observed for the suppressive effect of cocaine on the AD. The results suggested that the limbic system may be involved as a primary site of action of cocaine in the central nervous system (CNS).     

EEG Slow Waves and Memory Performance During the Intracarotid Amobarbital Test

Summary: During intracarotid sodium amobarbital (ISA) testing, EEG slow waves appear in the injected hemisphere and usually also contralaterally. They are frequently used to estimate duration of drug effect and thus the window of valid memory testing, but the relationship between slow waves and memory performance is not established. In 50 tests, we examined recognition for stimuli presented after amobarbital injection in relation to the quantified EEG. Performance was compared for injection ipsilateral versus contralateral to epileptic focus, with slow waves present bilaterally, unilaterally, or dissipated. Results showed that memory was impaired after injections contralateral to the focus when slow waves were present on the side of the focus (contralateral to injection). Injection contralateral to focus did not interfere with memory if slow waves were not also present, and slow waves contralateral to injection did not interfere with memory if the focus was not also present. This result emphasizes the functional significance of slow waves, which probably reflect decreased neuronal functioning.     

Electroencephalographic Changes During Simple Partial Seizures

Summary: We analyzed retrospectively the clinical and EEG data in 13 patients with simple partial seizures (SPS). All EEGs were recorded with surface electrodes with the standard 10–20 system and additional closely spaced scalp and subfrontotemporal skin electrodes. Seventy-seven seizures were recorded. We detected electrographic correlates with SPS in 10 of 13 patients (77%) and in 47 of 77 seizures (61%). The most common ictal correlatrd relates were rhythmic theta waves or spikes. Of the SPS with EEG changes, 58% were motor, 14% were sensory, and 28% were psychic seizures. Use of additional electrodes and recording channels may account for the higher incidence of EEG changes in this study than has been reported previously in the literature.     

不同背景波脑电图大鼠戊四氮致痫域值的探讨

目的 通过脑电图定量分析及戊四氮(PTZ)致痫观察,探讨不同背景波脑电图大鼠PTZ的致痫域值.方法 健康成年大鼠30只,采用头皮和皮层电极两种方法进行脑电图定量分析比较；建立大鼠急性脑外伤模型,采用头皮电极分别描记急性脑外伤组和对照组大鼠脑电图,并对各波段进行定量分析；探讨PTZ最小致痫量.结果 大鼠皮层脑电图的波形基本上与头皮导联的波形相似,但波幅较大,二者各波段的相对功率值比较差异无统计学意义(P＞0.05)；大鼠脑损伤组定量脑电图慢波(δ、θ波段)较健康大鼠对照组显著增加,快波α波显著减少,α、β、θ波相对功率值比较差异有统计学意义(P＜0.05)；大鼠脑损伤组致痫所需最小PTZ量值较对照组值要小(P＜0.05).结论 脑电图应用于临床非精确定位时,头皮导联可代替皮层导联；脑外伤后大鼠脑电图定量分析δ、θ慢波波段相对功率值明显增加,α、β快波波段相对功率值下降,其中α波减少更为显著；脑外伤后大鼠PTZ致痫域值下降.     

EEG and seizure threshold in normal and lissencephalic ferrets

Changes in EEG and susceptability to electrically induced seizures were examined in the ferret with lissencephaly produced by exposure to a single injection of methylazoxymethanol acetate (MAM Ac) given to the pregnant jill on gestation day 32. Ten lissencephalic and 11 normal ferrets were chronically implanted with 14 cortical stainless steel electrodes. EEG records were sampled from various stages of the sleep/awake cycle. Six of each group were subjected to electrical stimulation for seizure threshold. Although the number of stimulations and the current intensity required to produce epileptiform afterdischarges (AD) and seizures were not different between the two groups, the lissencephalic ferrets had significantly longer AD and seizures, and a greater number of generalized seizures, indicating an enhanced seizure susceptibility. The EEG of the lissencephalic ferrets was characterized by increased slow wave activity within the low theta band range, extreme spindle activity, focal or multifocal slow and sharp waves, spikes, or spike and slow wave complexes. The differences in the EEG were more pronounced during drowsiness and sleep stages. The brains of all of the treated animals were lissencephalic and hydrocephalic, and weighed significantly less than those of the normals. The cerebral cortex was thin and flattened, with the parieto-occipital region most severely affected. Heterotopic foci were found in the cerebellum as well as in the cerebral cortex. Abnormalities in the configuration of the cerebellar folia were also seen. Comparison between the electrophysiological and neuropathological data suggests that the extent of the extreme spindle activity, and longer AD and seizure duration depended on the degree of cerebellar dysplasia, whereas the EEG focal abnormalities were related to lesions in the cerebral hemispheres.     

Implication of sensorimotor integration in the generation of periodic dystonic myoclonus in subacute sclerosing panencephalitis (SSPE).

To clarify the mechanism of periodic dystonic myoclonus in subacute sclerosing panencephalitis (SSPE), a 22-year-old patient with a clinical diagnosis of SSPE was electrophysiologically investigated. Involuntary movements consisted of generalized dystonic posturing which occurred quasiperiodically once every 4 to 8 seconds. Effects of sensory stimuli and voluntary movements were studied by means of polygraphic recording of surface electromyogram (EMG), scalp electroencephalogram (EEG), and magnetoencephalogram (MEG). EEG showed quasi-periodic, generalized, transient complexes synchronous to each dystonic myoclonus, which were preceded by a slow negative EEG shift at the parietal region by approximately 5 seconds. Neither external stimuli nor self-paced movements alone influenced the periodicity of dystonic myoclonus or EEG complexes. In the reaction time task, however, the external stimuli given as an imperative cue to execute a motor task elicited dystonic myoclonus and generalized EEG complexes only if they were presented in the latter segment of the interval between the two successive EEG complexes while the slow negative EEG shift appeared. These findings suggest that EEG complexes and periodic movements spontaneously occur when cortical excitability reaches a certain critical level, but both phenomena are elicited even before if the sensory stimuli as an imperative signal requiring motor execution are presented. This finding most likely implies involvement of the sensorimotor integration mechanism in these periodic phenomena.     

Removing eye-movement artifacts from the EEG during the intracarotid amobarbital procedure

PURPOSE: The EEG is often recorded during the intracarotid amobarbital procedure (IAP) to help in the assessment of the spatial extent and the duration of the effect of the drug. In scalp recordings, the EEG is always heavily contaminated with eye movement artifacts as the patient actively performs visual tasks. METHODS: Independent component analysis (ICA) is a new technique for blind source separation. In this study, we separated the EEG data recorded during the IAP into independent components using ICA. The EEG signal was reconstructed by excluding the components related to eye movement and eye blinks. RESULTS: EEGs from 10 IAP tests were analyzed. The experimental results indicate that ICA is very efficient at subtracting eye-movement artifacts, while retaining the EEG slow waves and making their interpretation easier. CONCLUSIONS: ICA appears to be a generally applicable and effective method for removing ocular artifacts from EEG recordings during IAP, although slow waves and ocular artifacts share similar frequency distributions.     

Ipsilateral and Bilateral EEG Activity from the Hippocampus

Abstract: Using scalp and depth electroencephalography (EEG), we examined the relationship between the surface EEG activity and abnormal EEG discharges in the ipsilateral hippocampus in order to study the neuronal connection between the two cerebral regions. Ictal EEG was divided into 4 groups: 1) unitempo-ipsilateral-bifrontal slow waves, 2) unitempo-ipsilateral-bilateral slow waves, 3) bilateral slow waves, and 4) bilateral slow waves with repetitive spikes. Abnormal depth EEG activity in the hippocampus was classified into paroxysmal discharges and recruiting rhythms. Ictally and interictally, repetitive sharp waves or spikes in the unilateral hippocampus were associated with sharp waves or spikes in the ipsilateral temporal region. These findings suggest that the ipsilateral projection of seizure activity originating in the unilateral hippocampus is dependent upon the function of the subiculum.     

Benign epileptiform discharges in Rolandic region with mesial temporal lobe epilepsy: MEG, scalp and intracranial EEG features

AIM OF THE STUDY: To report benign epileptiform discharges (BEDs) in the Rolandic region, coexisting in a pediatric patient with intractable localization-related epilepsy, secondary to hippocampal sclerosis. METHODS: We describe the clinical features, MRI, scalp video EEG, magnetoencephalography (MEG) and intracranial video EEG findings, and surgical outcome in a 9-year-old boy with BEDs and intractable complex partial seizures. RESULTS: MRI showed left hippocampal sclerosis. Scalp video EEG interictally demonstrated left temporal spike and sharply contoured slow waves, and right fronto-centro-temporal spike and waves. Ictal scalp video EEG showed left temporal rhythmic sharp waves after the clinical onset of epigastric aura, followed by staring. MEG showed interictal dipoles in the bilateral Rolandic regions with a uniform orientation and right hemispheric predominance. Intracranial video EEG, with bilateral mesial temporal depth and fronto-temporo-parietal strip electrodes, interictally showed polyspikes and slow waves with superimposed low-amplitude fast waves in the left mesial and posterior lateral temporal regions, and spike and waves in the bilateral fronto-parietal regions. Ictal onset was marked by low-amplitude fast waves in the left mesial and posterior lateral temporal regions. He underwent left anterior temporal lobectomy with hippocampectomy. Pathology was hippocampal sclerosis. Predominant right fronto-centro-temporal spike and waves and MEG right Rolandic dipoles persisted after surgery. He was seizure-free 14 months after surgery. CONCLUSION: This is the first report on MEG and intracranial video EEG features of BEDs in the Rolandic region, coexisting with hippocampal sclerosis. Persistence of contralateral benign MEG Rolandic dipoles after surgery indicates that BEDs are coincidental in mesial temporal lobe epilepsy. MEG identified Rolandic dipoles, although was unable to localize the deep and focal epileptogenic dipoles from the hippocampal sclerosis.     

An open label study of the use of EEG biofeedback using beta training to reduce anxiety for patients with cardiac events

OBJECTIVE: To establish the effectiveness of EEG biofeedback using beta training as a relaxation technique and ultimately reducing anxiety levels of patients with confirmed unstable angina or myocardial infarction. METHODOLOGY: Patients with confirmed unstable angina or myocardial infarction referred by cardiologists were recruited 2-3 days after their cardiac event from the cardiology wards. Their initial anxiety scores were determined using the Hospital Anxiety and Depression Scale. Those that returned for therapy underwent instrument feedback training using EEG every two weeks for a total of five sessions. EEG frequencies were measured for all sessions. Dropouts who did not participate in the program agreed to return 3 months later for the second psychological assessment. The study design was uncontrolled. RESULTS: Subjects had significantly lower anxiety scores at the second screening (p < 0.001), while the dropouts had significantly higher scores (p < 0.001). Beta training was effective in increasing sensory motor rhythm (SMR) waves but no significant effect was present for the alpha waves. CONCLUSIONS: The uncontrolled nature of the study limits firm conclusions. However, the significantly lowered anxiety scores for subjects and enhancing of SMR waves indicate the effectiveness of beta training as a promising approach to EEG biofeedback for anxiety reduction.