Erregbarkeitsänderungen in der Umgebung experimentell induzierter fokaler kortikaler Dysplasien eine Studie mit spannungssensitiven Farbstoffen

Early postnatal freeze lesions of the rat neopallium induce cortical malformations mimicking human polymicrogyria which is frequently associated with epilepsy and/or neuropsychological deficits. In the present study, cortical excitability was visualized in brain slice preparations (500µm) using the voltage sensitive dye RH 795 and a fast imaging photodiode array (fields of view: 1.75mm diam, 464 elements, 800 frames/s) combined with standard field potential recordings. When electrical stimulation was applied in slices from adult freeze-lesioned animals (structurally intact somatosensory cortex, position of stimulation electrode: layer VI/white matter), optical recordings showed a marked and long-lasting neuronal depolarization in layers II-IV, which was not observed in sham-operated controls. The present study shows that hyperexcitability demonstrated in the vicinity of focal cortical malformations is predominantly located in superficial cortical layers (II-IV), and provides further evidence for an aberrant connectivity in the structurally intact lesion surround.