Effects of stimulating the cerebellar surface on the activity in penicillin foci

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Abstract
The effect of stimulating the cerebellar surface on the activity of acute penicillin foci (20,000 units) was investigated in a statistically designed study. All animals [cat] were randomly assigned either to an experimental group in which the dura over the posterior lobe was opened and a bipolar surface electrode placed over the vermis of the anterior lobe, or to a control group in which only the dura was opened. After surgery the animals in the experimental group were randomly assigned to a stimulated or an unstimulated group. The cerebellar surface was stimulated at a frequency of 10/s using capacitatively coupled pulses with peak current densities of 26.0 mA/cm2 and a duration of 0.1 ms. The effectiveness of the stimuli for activating neuronal elements in the cerebellum was evaluated by recording the cerebellar evoked response from the sensorimotor cortex and by measuring the effect of a conditioning cerebellar stimulus on the percent change in the amplitude of the cortical response evoked by stimulating the receptive fields of the trigeminal nerve. A statistical comparison of the mean number of seizures for successive 10 min intervals between control and experimental groups indicated that any difference in the means of these parameters occurred by chance with a high probability and did not result from any treatment. The duration of the seizures was significantly affected by stimulation of the cerebellar surface. The total number of seizures and the amplitude of the cerebellar evoked response in the same animal were inversely correlated. Stimuli that evoked large-amplitude responses over the sensorimotor cortex may produce a decrease in the number of seizures; stimuli that evoked small-amplitude responses may produce an increase in the total number of seizures with respect to the control group.