In experiments on animals, airflow through the nasal cavity elicits rhythmic synchronized activity that can trigger and/or elicit epileptic electrographic activities in the limbic structures of the brain. This could be demonstrated in studies of lower vertebrates (frogs and turtles). In the turtle the elicited paroxysmal activity often had the shape of regular high-voltage activity in the theta-frequency range (average frequency, 4.1 Hz). It was further proven in clinical experiments that nasal deep breathing with a closed mouth effectively activates epileptic electrographic phenomena of a temporal (limbic) origin. The activating effect was more pronounced on the side ipsilateral to the ventilated nasal meatus. It could also be evoked by air insufflation into the nasal cavity. This effect was suppressed by anesthesia of the mucous membrane in the upper nasal meatus. Possible mechanisms of this, probably reflex, phenomenon are discussed.
SUMMARY
An experimental model of the thalamocortical (centrencephalic) component of seizure susceptibility was induced in 29 turtles. An, epileptic focus was elicited in thalamus by electrophoretic administration of penicillin. Thalamic discharges were projected to ipsilateral, sometimes also contralateral, sensory cortex of the forebrain. The thalamic focus increased the duration and frequency of cortical spindles and enhanced the activity of the cortical penicillin focus by shortening the latency of its origin and the time between discharges. Some kind of paroxysmal electrographic activity, often generalized spike and wave activity, occurred in 79% of experiments, and was accentuated by hyperventilation and photic stimulation.
RÉSUMÉ
On a réalisé un modèle expérimental chez 29 tortues concernant la composante thalamocorticale (centrencéphalique) dans la susceptibilityé des crises. Un foyer épileptique a été provoqué dans le thalamus par administration électrophorétique de pénicilline. Des décharges thalamiques étaient projetées sur le cortex générate ipsilatéral, quelque‐fois aussi contra‐latéral. Le foyer thalamique augmentait la durée et la fréquence des fuseaux et activait un foyer cortical à la pénicilline en racourcissant la latence de son origine et le temps entre les décharges. Quelque type ďactivitéélectrographique paroxystique souvent de pointe‐onde généralisée, apparaissait dans 79% des cas, et était accentuée par ľhyperpnée et la stimulation lumineuse intermittente.
ZUSAMMENFASSUNG
Bei 29 Schildkröten wurde ein experimentelles Modell der thalamocortikalen (cen‐trencephalen) Komponente der Anfallsbereitschaft induziert. Ein epileptischer Fokus wurde im Thalamus durch elektrophoretische Anwendung von Penicillin hervor‐gerufen. Die thalamischen Entladungen wurden auf den ipsilateralen, gelegentlich auch kontralateralen allgemein‐sensorischen Cortex des Vorderhirns projiziert. Der thalamische Fokus vermehrte die Dauer und Häufigkeit cortikaler Spindeln und verstärkte die Aktivität eines cortikalen Penicillinfokus durch Verkürzung der Latenzzeit seiner Entstehung und des Intervalls zwischen den Entladungen. Paro‐xysmale elektrische Entladungen–häufig generalisierte spike‐wave‐Aktivität– erfolgten in 79% der Versuche. Sie wurde durch Hyperventilation und Fotostimulation verstärkt.
RESUMEN
Un modelo experimental del componente talamocortical (centroencefalico) de la prediposicion a la crisis ha sido practicado en 29 tortugas. El foco epiléptico se ha provocado en el talamo mediante administración electroforética de penicilina. Las descargas talámicas se proyectaban sobre el cortex ipsilateral y alguna vez sobre el cortex contralateral. El foco talámico aumentaba la duración y la frequencia de los husos corticales y activaba un foco cortical penicilinico acortando la latencia de su origin y el tiempo de duración entre las descargas. Cierto tipo de actividad electro‐grafica paroxista, frecuentimente puntas‐ondas generalizadas aparecen en un 79% de los casos, acentuandos con la hyperventilateón y con la estimu...
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