Neuroscience journal最新文献

Background. In order to prevent future errors, we constantly control our behavior for discrepancies between the expected (i.e., intended) and the real action outcome and continuously adjust our behavior accordingly. Neurophysiological correlates of this action-monitoring process can be studied with event-related potentials (error-related negativity (ERN) and error positivity (Pe)) originating from the medial prefrontal cortex (mPFC). Patients with neuropsychiatric diseases often show performance monitoring dysfunctions potentially caused by pathological changes of cortical excitability; therefore, a modulation of the underlying neuronal activity might be a valuable therapeutic tool. One technique which allows us to explore cortical modulation of neural networks is transcranial direct current stimulation (tDCS). Therefore, we tested the effect of medial-prefrontal tDCS on error-monitoring potentials in 48 healthy subjects randomly assigned to anodal, cathodal, or sham stimulation. Results. We found that cathodal stimulation attenuated Pe amplitudes compared to both anodal and sham stimulation, but no effect for the ERN. Conclusions. Our results indicate that cathodal tDCS over the mPFC results in an attenuated cortical excitability leading to decreased Pe amplitudes. We therefore conclude that tDCS has a neuromodulatory effect on error-monitoring systems suggesting a future approach to modify the sensitivity of corresponding neural networks in patients with action-monitoring deficits.

Aim. To evaluate the frequency of atypical and malignant meningiomas and analyze recurrence rate; to study the morbidity and mortality of these tumors compared to benign meningiomas. Methods. During 1992-2007, 16 patients with malignant and 16 patients with atypical meningioma were operated in Neurosurgery Department of Thessaloniki's Papanikolaou Hospital. We analyzed tumor histology, location, and extent of surgical resection with respect to tumor reappearance and patients' outcome and compared the behavior of benign versus nonbenign meningiomas. Results. Malignant meningiomas accounted for 4.4% (16 patients) and atypical meningiomas for another 4.4% of the series of patients (353) who were operated for intracranial meningioma at our department that period. Malignant meningiomas recurred at a rate of 75% and atypical meningiomas recurred at a rate of 41.6%. There was a significant association of the histological classification (benign, atypical, and malignant) with recurrence (P < 0.01). The recurrence rate after complete resection was 13.8%. The recurrence rate for incomplete resection was 46.7%. Extent of tumor removal was significant to recurrence (P < 0.001) for benign as well for atypical and malignant meningiomas. Tumor location (P > 0.05) was not significant to recurrence. Conclusions. Atypical and malignant meningiomas appeared at a rate of 8.8% of our series of intracranial meningiomas. They showed a significant predisposition to recur. These rare subtypes have higher morbidity and mortality rates than benign meningiomas. Recurrence depends primarily on the extent of surgical removal and on the histological characterization of the tumor as atypical or malignant.

Advanced ageing is associated with hippocampal deterioration and mild cognitive decline. The hippocampal subregion CA3 stratum lucidum (CA3-SL) receives neuronal inputs from the giant mossy fibre boutons of the dentate gyrus, but relatively little is known about the integrity of this synaptic connection with ageing. Using serial electron microscopy and unbiased stereology, we examined age-related changes in mossy fibre synapses on CA3 thorny excrescences within the CA3-SL of young adults (4-month-old), middle-aged (12-month-old), and old-aged (28-month-old) Wistar rats. Our data show that while there is an increase in CA3 volume with ageing, there is a significant (40-45%) reduction in synaptic density within the CA3-SL of 12- and 28-month-old animals compared with 4-month-old animals. We also present preliminary data showing that the CA3 neuropil in advanced ageing was conspicuously full of lipofuscin and phagolysosome positive, activated microglial cellular processes, and altered perivascular pathology. These data suggest that synaptic density in the CA3-SL is significantly impaired in ageing, accompanied by underlying prominent ultrastructural glial and microvascular changes.