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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 7 (1995), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Focal epileptic activity can be expected to influence distant brain areas via far reaching connections. To investigate such interactions the effects of focal epileptic activity on the metabolism of the brain were investigated in the rat cortex. Focal epileptic activity was induced by the application of penicillin onto the motor cortex. The focus, and to a lesser extent homotopic contralateral brain areas, showed an increase in the regional cerebral metabolic rate of glucose (rCMRGIc) as measured by [14C]deoxyglucose autoradiography. This focal hypermetabolism was accompanied by widespread hypometabolism lateral to the focus. The decrease of rCMRGIc occurred in somatosensory cortical areas but not in the motor cortex behind or in front of the focus, the perirhinal cortex or the occipital cortex. It was associated with an increase in metabolic rate in the ventrolateral, ventroposteromedial, ventroposterolateral and, in particular, posterior nuclei of the thalamus. It is hypothesized that the widespread reduction of rCMRGIc in the somatosensory cortical areas is due to inhibition via thalamic nuclei caused by activity in the motor cortex.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 17 (2003), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Behavioural impairments caused by brain lesions show a considerable, though often incomplete, recovery. It is hypothesized that cortical and subcortical plasticity of sensory representations contribute to this recovery. In the hindpaw representation of somatosensory cortex of adult rats we investigated the effects of focal unilateral cortical lesions on remote areas. Cortical lesions with a diameter of ≈ 2 mm were induced in the parietal cortex by photothrombosis with the photosensitive dye Rose Bengal. Subsequently, animals were kept in standard cages for 7 days. On day seven, animals were anaesthetized and cutaneous receptive fields in the cortical hindpaw representations ipsi- and contralateral to the lesion were constructed from extracellular recordings of neurons in layer IV using glass microelectrodes. Receptive fields in the lesioned animals were compared to receptive fields measured in nonlesioned animals serving as controls. Quantitative analysis of receptive fields revealed a significant increase in size in the lesioned animals. This doubling in receptive field size was observed equally in the hemispheres ipsi- and contralateral to the lesion. The results indicate that the functional consequences of restricted cortical lesions are not limited to the area surrounding the lesion, but affect the cortical maps on the contralateral, nonlesioned hemisphere.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 235 (1988), S. 214-218 
    ISSN: 1432-1459
    Keywords: Myoclonus ; Hypoxia ; EEG ; Reticular system ; Epilepsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A patient with post-hypoxic action myoclonus classified as reticular reflex myoclonus was subjected to an electrophysiological investigation. The myoclonic movements involved mainly the legs but could also affect the whole body. Somatosensory evoked responses were not increased and electroencephalography (EEG) was normal when the patient was relaxed. Startle, self-paced movement or movement on command induced repetitive myoclonic jerks preceded and accompanied by repetitive small spikes in the EEG with phase reversal in the midline at the vertex or slightly posterior to it, regardless of the limb moved. The central spiking subsided considerably earlier than the myoclonic jerks as shown by polygraphic recordings. The EEG spikes were also provoked by mere imagination of movement and persisted in spite of a dramatic reduction of myoclonic activity after treatment with clonazepam. The observations suggest that the vertex spiking in post-hypoxic action myoclonus indicates synchronous cortical activation, but is not closely coupled with activation of the Betz cells of layer V where the pyramidal pathway originates.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 78 (1989), S. 646-648 
    ISSN: 1432-1106
    Keywords: Hippocampus ; Experimental epilepsy ; Paroxysmal depolarization shift ; Afterpotential ; Penicillin ; Ca2+-activated potassium ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Penicillin-induced paroxysmal depolarization shifts (PDS) are followed by prolonged afterhyperpolarizations of about 2 seconds duration. Intracellular injection of EGTA blocked a late component of the afterhyperpolarizations; an early one lasting up to one second was only slightly reduced by EGTA. It is concluded that afterhyperpolarizations following penicillininduced PDS comprise different components: an initial one lasting up to one second which is not Ca2+-dependent and a slow one lasting up to two seconds which is caused by a Ca2+-dependent K+ current.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 83 (1991), S. 683-686 
    ISSN: 1432-1106
    Keywords: Experimental epilepsy ; Penicillin ; Interneurons ; Afterpotentials ; Paroxysmal depolarization shifts ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Interneurons of rat motor cortex in vivo and of rat hippocampal slices were studied during penicillin induced epileptic discharges. Synchronous with pyramidal cells, they showed transient depolarizations similar to paroxysmal depolarization shifts in pyramidal cells. The transient depolarizations were followed by hyperpolarizing or depolarizing afterpotentials lasting 600 to 1200 ms. During the transient depolarizations and the afterdepolarizations the interneurons discharged with increased frequency. This may contribute to the enlarged and prolonged synaptic inhibitions following interictal discharges in pyramidal cells.
    Type of Medium: Electronic Resource
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