EEG functional connectivity of the intrahemispheric cortico-cortical network of idiopathic generalized epilepsy.

AIMS: Intrahemispheric, cortico-cortical EEG functional connectivity (fC) was investigated in untreated patients with idiopathic generalized epilepsy (IGE) in this explorative study. PATIENTS AND METHODS: Group comparison was carried out between 19, drug-naive IGE patients and 19, matched healthy persons. 90×2s of 19 channels waking, interictal background EEG signal (without epileptiform potentials) were processed to the LORETA (low resolution electromagnetic tomography) software to compute current source density for 2394 voxels representing parcels of the cerebral cortex for 25 very narrow bands of 1Hz bandwidth (VNBs) from 1 to 25Hz. EEG fC was investigated among the already localized sources. Pearson correlation coefficients (R) were computed among the 33 regions of interest (ROI) within the left and within the right hemisphere, separately. Group differences were computed by means of t-statistics. Corrected p<0.05 differences were accepted as statistically significant. MAIN RESULTS: (1) The anatomical patterns of the fC differences showed great frequency-dependency. (2) Hemispheric asymmetry was prominent within most VNBs. (3) Decreased fC in the IGE group was found across all VNBs in the 1-6Hz frequency range as compared to mixed patterns comprising both increased and decreased fC at >6Hz frequencies. (4) In the 5-25Hz range, decreased fC dominated in the anterior, increased fC in the posterior parts of the cortex. (5) The results delineated an anterior and a posterior network. DISCUSSION: (1) Decreased fC in the 1-6Hz band might indicate some relationship to yet hidden structure network abnormalities. (2) The anatomical patterns of fC indicate frequency-dependent, pathological coupling and decoupling processes in the interictal state. (3) The two networks might help to understand seizure liability and seizure precipitation in IGE. SIGNIFICANCE: This is the first study to explore EEG fC in the interictal condition of IGE patients. The importance of EEG frequencies in evaluating fC in IGE was demonstrated and starting points for further research were given.

Quantitative EEG abnormalities in persons with "pure" epileptic predisposition without epilepsy: a low resolution electromagnetic tomography (LORETA) study.

OBJECTIVE: Epileptic predisposition means genetically determined, increased seizure susceptibility. Neurophysiological evaluation of this condition is still lacking. In order to investigate "pure epileptic predisposition" (without epilepsy) in this pilot study the authors prospectively recruited ten persons who displayed generalized tonic-clonic seizures precipitated by 24 or more hours of sleep deprivation but were healthy in any other respects. METHODS: 21-channel EEGs were recorded in the morning, in the waking state, after a night of sufficient sleep in the interictal period. For each person, a total of 120s artifact-free EEG was processed to low resolution electromagnetic tomography (LORETA) analysis. LORETA activity (Ampers/meters squared) was computed for 2394 voxels, 19 active electrodes and 1Hz very narrow bands from 1 to 25Hz. The data were compressed into four frequency bands (delta: 0.5-4.0Hz, theta: 4.5-8.0Hz, alpha: 8.5-12.0Hz, beta: 12.5-25.0Hz) and projected onto the MRI figures of a digitized standard brain atlas. The band-related LORETA results were compared to those of ten, age- and sex-matched healthy persons using independent t-tests. p<0.01 differences were accepted as statistically significant. RESULTS: Statistically significant decrease of alpha activity was found in widespread, medial and lateral parts of the cortex above the level of the basal ganglia. Maximum alpha decrease and statistically significant beta decrease were found in the left precuneus. Statistically not significant differences were delta increase in the medial-basal frontal area and theta increase in the same area and in the basal temporal area. DISCUSSION: The significance of alpha decrease in the patient group remains enigmatic. beta decrease presumably reflects non-specific dysfunction of the cortex. Prefrontal delta and theta increase might have biological meaning despite the lack of statistical significance: these findings are topographically similar to those reported in idiopathic generalized epilepsy in previous investigations. SIGNIFICANCE: Quantitative EEG characteristics of the genetically determined epilepsy predisposition were given in terms of frequency bands and anatomical distribution.

Theta EEG source localization using LORETA in partial epilepsy patients with and without medication.

OBJECTIVE: To investigate and localize the sources of spontaneous, scalp-recorded theta activity in patients with partial epilepsy (PE). METHODS: Nine patients with beginning, untreated PE (Group 1), 31 patients with already treated PE (Group 2), and 14 healthy persons were investigated by means of spectral analysis and LORETA, low resolution electromagnetic tomography (1 Hz very narrow band analysis, age-adjusted, Z-scored values). The frequency of main interest was 4-8 Hz. RESULTS: Group analysis: Group 1 displayed bilateral theta maxima in the temporal theta area (TTA), parietal theta area (PTA), and frontal theta area (FTA). In Group 2, theta activity increased all over the scalp as compared to the normative mean (Z=0) and also to Group 1. Maximum activity was found in the TTA, PTA, and FTA. However, in the PTA and FTA the centers of the abnormality shifted towards the medial cortex. Individual analysis: all the patients showed preferential activation (maximum Z-values) within one of the three theta areas. CONCLUSIONS: EEG activity in the theta band is increased in anatomically meaningful patterns in PE patients, which differs from the anatomical distribution of theta in healthy persons. SIGNIFICANCE: The findings contribute to our understanding of the sources of theta rhythms and the pathophysiology of PE.

Lamotrigine decreases EEG synchronization in a use-dependent manner in patients with idiopathic generalized epilepsy.

OBJECTIVE: To investigate the quantitative EEG effects of lamotrigine (LTG) monotherapy. HYPOTHESIS: LTG was predicted to decrease thalamo-cortical neuronal synchronization in idiopathic generalized epilepsy (IGE). METHODS: Waking EEG background activity of 19 IGE patients was investigated before treatment and in the course of LTG monotherapy. Raw absolute power (RAP), raw percent power (RRP), and raw mean frequency (RMF) were computed for 19 electrodes and four frequency bands (delta=1.5-3.5Hz, theta=3.5-7.5Hz, alpha=7.5-12.5Hz, and beta=12.5-25.0Hz). Inter- and intrahemispheric coherence was computed for eight electrode pairs and the four frequency bands. In addition, scalp-averages were calculated for each variable. Group differences were computed by means of nonparametric statistics including correction for multiple comparisons. RESULTS: Main results were decreased delta and theta RAP (p<0.05 for scalp-averages). LTG compressed the delta, theta, and alpha RAP datasets, reducing the upper limit of the scatter in particular. Spearman r-values indicated marked correlation between the starting values (RAPuntreated) and the LTG-related decrease (RAPtreated-RAPuntreated) in three bands: delta (r=-0.72; p=0.0005), theta (r=-0.59; p=0.007), and alpha (r=-0.61; p=0.006). Thus, the greater the baseline neuronal synchronization, the marked the dampening effect of LTG on it. The remaining findings were decreased theta RRP, theta RMF, and increased alpha RMF (p<0.05 for scalp-averages). The electrode-related changes were small but topographically consistent across the 19 electrode sites. LTG did not affect coherence. CONCLUSIONS: 1. LTG partially normalized the spectral composition of EEG background activity. LTG decreased pathological thalamo-cortical synchronization in use-dependent manner. 2. LTG did not cause quantitative EEG alterations suggesting worsening of the physiological brain functions. Instead, its profile suggested a mild psychostimulant effect. SIGNIFICANCE: The results contribute to the understanding of the effect of LTG at the network level.

Characteristics of 4 stroke scales for the detection of changes in clinical signs in the acute phase of stroke.

OBJECTIVES: Detection of minor changes in clinical signs of stroke may be of interest when evaluating treatment interventions. This study analyzes the internal structure of four frequently used stroke scales and compares them for their sensitivity to detect changes in neurologic signs in the first week after acute stroke. METHODS: A cohort of 77 hospitalized acute stroke patients was scored by the Mathew, the National Institutes of Health (NIH), the Scandinavian, and the Orgogozo scales within 48 hours of hospital admission and again 7 days later. RESULTS: Scores on different scales correlated well with each other (range of absolute value of Spearman R, .82-.91; P <.001 in all comparisons). Scales reflected significant changes from entry to reexamination: P = .0013 for the Scandinavian scale (P = .004 for prognostic and P = .009 for long-term items, respectively); P = .00009 for the Orgogozo scale; P = .000007 for the Mathew scale; and P < .000001 for the NIH scale. This difference in sensitivity coincided with the number of factors extracted by principal component analysis: higher sensitivity of a scale was associated with a larger number of factors. Initial scores differed significantly among patients who were discharged, patients who died, and patients who remained hospitalized 7 days after the first examination (Kruskal-Wallis ANOVA, P < .01 for all scales). CONCLUSIONS: There are considerable differences in the internal structure of the different scales as reflected by the different number of factors extracted from the scale items. The application of the NIH scale is recommended for the most sensitive detection of changes in stroke signs.

Effect of herbicides on growth of some microscopic soil fungus species.

The effect of 14 herbicides and two herbicide combinations of three microscopic soil fungus species was investigated by Miller's method. (i) None of the 14 herbicides and 2 combinations belonging to four derivative groups induced the growth of Aspergillus niger, Fusarium oxysporum and Rhizopus nigricans; (ii) Higher doses of the herbicides prevented the growth of all test organisms significantly, the triasin derivative Hungazin PK being the less and tiocarbamate derivatives Alirox B 80 EC, Anelda Plus 80 EC and Anelda III being the most inhibitory. (iii) The sensitivity of test organisms against the examined herbicides decreased in the order of Fusarium, Rhizopus, Aspergillus.