Ermanno Manni

The influence of the cerebellum on experimental epilepsy

Abstract The cerebellar influence on the cobalt experimental epilepsy has been investigated in unrestrained, unanesthetized rats by stimulation, total removal and temporary cooling of the cerebellum. Cerebellar stimulation generally provoked inhibition of the epileptic waves produced in the brain by cobalt application and depressed the sensory responses in the cerebral cortex. The occasional reversed facilitatory effects of the stimulation are discussed in the light of other peculiar effects of cerebellar stimulation. Total ablation of the cerebellum induced in epileptic rats a hypersynchrony of the background activity of the electrocorticogram and enhanced the clinical and electrocortical manifestations of experimental epilepsy in the unanesthetized rat. A similar tendency to hypersynchrony was occasionally seen in normal rats. The temporary cooling of the cerebellar surface in the unanesthetized, noncurarized rat produced a reversible increase in the spontaneous and sensory activated epileptic manifestations.

The production of cobalt experimental epilepsy in the rat

Abstract Metallic cobalt powder applied to the cerebral cortex of the rat is a consistently effective method of producing a chronic epileptic discharging focus in this species. The ECoG changes consisted of slow waves, sharp waves and spikes and their climax was often accompanied by clonic movements of body musculature. Audio- and photostimulation enhanced both clinical and ECoG manifestations. Possible mechanisms for the epileptic activity of this substance are discussed in the light of the histological changes which are described in detail.

INFLUENCE OF THE LABYRINTH ON UNITARY DISCHARGE OF THE OCULOMOTOR NUCLEUS AND SOME ADJACENT FORMATIONS.

Abstract The unitary discharge of the oculomotor nucleus and other adjacent mesencephalic formations was recorded in guinea pigs following caloric stimulation of the labyrinth. The oculomotor units usually responded to the vestibular stimulation with rhythmical discharges. The outbursts were separated by periods of total inhibition of the electrical activity. The rhythmical discharges were designated as “quick” or “slow” responses, depending on the duration of each single outburst. Less frequently, labyrinthine stimulation elicited a long-lasting increase in the discharge rate of the oculomotor units (up to 50/sec) with recruitment of new units, which was designated a “continuous activation”. About two-thirds of the units located in the gray substance ventral to the aqueduct, in the reticular formation and in the red nuclei responded to vestibular stimulation with a continuous activation. One-third of the recorded units showed the rhythmical responses, which were also obtained from the medial longitudinal fasciculus. Simultaneous recording of the mesencephalic unitary discharge and the electrical activity of a few fibers of the ipsilateral oculomotor nerve permitted the investigation of the relationship of the nuclear responses to the phases of the eye nystagmus and ocular deviations.

Microelectrode recording of cerebellar and cerebral unit activity during convulsive afterdischarge.

Abstract Cerebellar unitary discharge has been recorded with microelectrodes from cerebellar cortex and nuclei before, during, and after different convulsive patterns induced in curarized rats by electrical stimulation of the brain, by intraperitoneal injection of convulsant drugs (Megimide or Metrazol), and by anoxia. It has been compared simultaneously with the electrical activity of the cerebral cortex (sensorimotor area) recorded either with microelectrodes or with concentric electrodes. Low-voltage, single or repetitive stimulation of sensorimotor area are incapable of modifying the cerebellar unitary discharge. They show an increase in frequency only after strong single shocks or repetitive cerebral stimulation. During anoxia the cerebral units show an acceleration after a short latency and afterwards they become silent. The cerebellar units also show an increase in frequency of discharge but they usually continue to be active even when the cerebrum is silent. After injection of convulsant drugs, such as Megimide and Metrazol, the cerebellar units exhibit first an acceleration of discharge at a time when the electrical activity of the brain is still normal. At a significantly later time the rate of discharge of cerebral units also increases. In some cases each high-voltage slow wave of the cerebral cortex is accompanied by an increase in the frequency of discharge of the cerebellar units. During the clonic period of the convulsive activity the cerebellar units are depressed but they begin to discharge again after the end of the seizure when the cerebral units are totally silent. The cerebellum may actively inhibit cerebral seizure activity.

Cerebellar influence on the unitary discharge of oculomotor nuclei and adjacent structures

Abstract The unitary discharges of mesencephalic cells located within and around the oculomotor nuclear complex were recorded, using tungsten microelectrodes in immobilized guinea pigs. The effects of electrical stimulation of different cerebellar cortical areas on these unitary discharges were investigated. About 55% of the recorded points within the oculomotor nuclei were modified by the electrical stimulation of the ansoparamedian lobe as well as the lobus medius medianus (Larsells lobules H VII a b, VI and VII) of the cerebellum. The cerebellar stimulation provoked different patterns of activation or inhibition of the oculomotor unitary discharge. About 77% of the recorded points within the gray substance ventral to the aqueduct, the reticular substance, red nuclei and medial longitudinal fasciculus were also influenced by stimulation of the same cerebellar areas and showed similar but more evident patterns of activation or inhibition. All the recorded units located within and around the oculomotor nuclear complex were also strikingly affected by stimulation of the labyrinth. Thus both a cerebellar and vestibular influence on the units studied has been demonstrated and compared.