Does Greater Low Frequency EEG Activity in Normal Immaturity and in Children with Epilepsy Arise in the Same Neuronal Network?

Greater low frequency power (<8Hz) in the electroencephalogram (EEG) at rest is normal in the immature developing brain of children when compared to adults. Children with epilepsy also have greater low frequency interictal resting EEG activity. Whether these power elevations reflect brain immaturity due to a developmental lag or the underlying epileptic pathophysiology is unclear. The present study addresses this question by analyzing spectral EEG topographies and sources for normally developing children and children with epilepsy. We first compared the resting EEG of healthy children to that of healthy adults to isolate effects related to normal brain immaturity. Next, we compared the EEG from 10 children with generalized cryptogenic epilepsy to the EEG of 24 healthy children to isolate effects related to epilepsy. Spectral analysis revealed that global low (delta: 1-3Hz, theta: 4-7Hz), medium (alpha: 8-12Hz) and high (beta: 13-25Hz) frequency EEG activity was greater in children without epilepsy compared to adults, and even further elevated for children with epilepsy. Topographical and tomographic EEG analyses showed that normal immaturity corresponded to greater delta and theta activity at fronto-central scalp and brain regions, respectively. In contrast, the epilepsy-related activity elevations were predominantly in the alpha band at parieto-occipital electrodes and brain regions, respectively. We conclude that lower frequency activity can be a sign of normal brain immaturity or brain pathology depending on the specific topography and frequency of the oscillating neuronal networ

Frontal GABA Levels Change during Working Memory

Functional neuroimaging metrics are thought to reflect changes in neurotransmitter flux, but changes in neurotransmitter levels have not been demonstrated in humans during a cognitive task, and the relationship between neurotransmitter dynamics and hemodynamic activity during cognition has not yet been established. We evaluate the concentration of the major inhibitory (GABA) and excitatory (glutamate + glutamine: Glx) neurotransmitters and the cerebral perfusion at rest and during a prolonged delayed match-to-sample working memory task. Resting GABA levels in the dorsolateral prefrontal cortex correlated positively with the resting perfusion and inversely with the change in perfusion during the task. Further, only GABA increased significantly during the first working memory run and then decreased continuously across subsequent task runs. The decrease of GABA over time was paralleled by a trend towards decreased reaction times and higher task accuracy. These results demonstrate a link between neurotransmitter dynamics and hemodynamic activity during working memory, indicating that functional neuroimaging metrics depend on the balance of excitation and inhibition required for cognitive processing

Der "Fürstäbtisch-st. gallische Marchenbeschrieb von (?) 1728"

No abstract available

Subluxation von C2 und C3 und Fraktur von C2 nach einem schweren Schädelhirntrauma bei zwei Warmblutpferden

Im Departement für Pferde der Vetsuisse-Fakultät der Universität Zürich wurden zwei Jährlinge vorgestellt, die beim Ausbruch aus einer Fohlenweide mit einem Betonpfosten kollidiert waren. Beide Pferde zeigten ein durch dieselbe Ursache hervorgerufenes Kopftrauma und Ataxie. Beim ersten Pferd (Fall 1) konnte mittels CT eine Fraktur des Wirbelkörpers und der caudalen Epiphyse von C2 mit geringradiger Dislokation der frakturierten Epiphyse in den Wirbelkanal assoziiert mit einer Subluxation von C2 / C3 diagnostiziert werden. Ebenso ein epidurales Hämatom und Ödem des Rückenmarks. Das Pferd wurde konservativ behandelt. Infolge der progressiven Verschlechterung und der schlechten Prognose wurde das Pferd euthanasiert. Das zweite Pferd (Fall 2) wies eine Trümmerfraktur des Os nasale, Os frontale sowie des Os maxillare bis in die rechte Orbita auf, was mittels CT diagnostiziert wurde. Die Fixation der Schädeltrümmerfraktur erfolgte mittels Titanverriegelungsschrauben und Platten. Aufgrund der zunehmenden Verschlechterung des Allgemeinzustandes und der Ataxie, wurde die Halswirbelsäule radiologisch untersucht und eine Subluxation im Bereich C2 / C3 mit Einengung des Rückenmarkes diagnostiziert. Wegen der schlechten Prognose wurde das Pferd euthanasiert. Die zunehmende Ataxie und Verschlechterung beider Pferde wiesen darauf hin, dass initial eine stärkere Schädigung des Rückenmarkes stattgefunden haben muss, als anhand der bildgebenden Diagnostik angenommen werden konnte. Zudem kann sich der Zustand des Rückenmarks nach initilaler Schädigung verschlechtern (e.g. Ödem, Myelomalazie etc.) Die Fraktur der Wirbelkörperendplatte des C2, sowie das genaue Ausmaß der Schädelfrakturen waren nur mittels Computertomographie gut darstellbar. Beide Fälle zeigen die Wichtigkeit der Computertomographie für Diagnose und Prognose der Patienten in Fällen von taumatischen Schädel- und proximalen Halswirbelsäulenverletzungen

Simultaneous EEG-fMRI during a working memory task: modulations in low and high frequency bands.

BACKGROUND: EEG studies of working memory (WM) have demonstrated load dependent frequency band modulations. FMRI studies have localized load modulated activity to the dorsolateral prefrontal cortex (DLPFC), medial prefrontal cortex (MPFC), and posterior parietal cortex (PPC). Recently, an EEG-fMRI study found that low frequency band (theta and alpha) activity negatively correlated with the BOLD signal during the retention phase of a WM task. However, the coupling of higher (beta and gamma) frequencies with the BOLD signal during WM is unknown. METHODOLOGY: In 16 healthy adult subjects, we first investigated EEG-BOLD signal correlations for theta (5-7 Hz), alpha1 (8-10), alpha2 (10-12 Hz), beta1 (13-20), beta2 (20-30 Hz), and gamma (30-40 Hz) during the retention period of a WM task with set size 2 and 5. Secondly, we investigated whether load sensitive brain regions are characterised by effects that relate frequency bands to BOLD signals effects. PRINCIPAL FINDINGS: We found negative theta-BOLD signal correlations in the MPFC, PPC, and cingulate cortex (ACC and PCC). For alpha1 positive correlations with the BOLD signal were found in ACC, MPFC, and PCC; negative correlations were observed in DLPFC, PPC, and inferior frontal gyrus (IFG). Negative alpha2-BOLD signal correlations were observed in parieto-occipital regions. Beta1-BOLD signal correlations were positive in ACC and negative in precentral and superior temporal gyrus. Beta2 and gamma showed only positive correlations with BOLD, e.g., in DLPFC, MPFC (gamma) and IFG (beta2/gamma). The load analysis revealed that theta and--with one exception--beta and gamma demonstrated exclusively positive load effects, while alpha1 showed only negative effects. CONCLUSIONS: We conclude that the directions of EEG-BOLD signal correlations vary across brain regions and EEG frequency bands. In addition, some brain regions show both load sensitive BOLD and frequency band effects. Our data indicate that lower as well as higher frequency brain oscillations are linked to neurovascular processes during WM

Frontal GABA levels change during working memory.

Functional neuroimaging metrics are thought to reflect changes in neurotransmitter flux, but changes in neurotransmitter levels have not been demonstrated in humans during a cognitive task, and the relationship between neurotransmitter dynamics and hemodynamic activity during cognition has not yet been established. We evaluate the concentration of the major inhibitory (GABA) and excitatory (glutamate + glutamine: Glx) neurotransmitters and the cerebral perfusion at rest and during a prolonged delayed match-to-sample working memory task. Resting GABA levels in the dorsolateral prefrontal cortex correlated positively with the resting perfusion and inversely with the change in perfusion during the task. Further, only GABA increased significantly during the first working memory run and then decreased continuously across subsequent task runs. The decrease of GABA over time was paralleled by a trend towards decreased reaction times and higher task accuracy. These results demonstrate a link between neurotransmitter dynamics and hemodynamic activity during working memory, indicating that functional neuroimaging metrics depend on the balance of excitation and inhibition required for cognitive processing