Influence of Anesthesia on Cortical Irradiation and Reflex Myoclonus

Abstract

In cats anesthetized with Nembutal, or Nembutalcurare, the bilateral ablation of specific visual or auditory cortex does not abolish the irradiated cortical and the myoclonic responses evoked by photic or acoustic stimulation after subconvulsant dosage of Metrazol. The Metrazol requirement is, however, increased. With Pentothai-curare anesthesia, such ablations usually, but not always, abolish the responses, but in such prepns. irradiated and myoclonic responses may be "activated" by small doses of Nembutal. In the Pentothal-curare prepn., the Metrazol threshold for the sensory modality whose specific cortical receptive area was ablated is elevated to a level approximating that for generalized seizures which may be triggered off by uncontrolled afferent influx, making it difficult to demonstrate the responses before generalized seizures supervene. Nembutal anesthesia equalizes the Metrazol requirement for all the sensory systems, permitting the demonstration of cortical irradiation uncomplicated by generalized seizure. The specific sensory cortex apparently exerts a facilitatory action on the mechanisms for cortical irradiation and myoclonic responses, but is not essential for these responses. The cat anesthetized with Nembutal is the prepn. of choice for study of these mechanisms.