[Modulation of the photically evoked potentials in the motor cortex of cats by influences of the somatosensory system and the reticular formation].

The influence of somatosensor stimulation and electric stimulation in the mesencephalic reticular formation upon evoked potentials (EP) of the motor cortex (MC) produced by electric stimulation of the Chiasma opticum and the Corpus geniculatum laterale, respectively, was investigated in unnarcotized, immobilized cats. By preliminary electrical stimulation of the contralateral front limb, intensity-dependent changes of the early positive component of the EP in the MC could be produced. Similar changes were found after passive movement of the limb and following electrical stimulation in the reticular formation of the mesencephalon. The EP in the MC completely disappeared after i.v. administration of 15 mg/kg Nembutal. It is concluded that the impulses reaching the MC after stimulation in the visual system can be modulated in various ways, and thus exhibit a relatively high information content. Possible mechanisms of the modulating influences and their significance are discussed.