Cortical and subcortical EEG patterns during moderate-intensity barbiturate withdrawal.

Electroencephalograms were recorded from cortical and subcortical brain regions during moderate-intensity barbiturate withdrawal in the cat. Physical dependence was produced by administration of Na-barbital by the "low dose barbiturate" treatment schedule. During moderate-intensity withdrawal, the EEG pattern showed 4- to 6-Hz rhythmic bursts in the hippocampus, visual cortex, auditory cortex, motor cortex, nucleus centralis centralis of the thalamus, caudate nucleus, and lateral geniculate body. The bursts in the hippocampus were spike-and-wave type. In animals which had spontaneous seizures, 4- to 6-Hz bursts occurred in the motor cortex, whereas this abnormality did not occur in the motor cortex in animals which did not have spontaneous generalized seizures. In addition, prolonged high-frequency, high-voltage discharges and spikes were recorded from the amygdala during withdrawal. Spontaneous generalized or partial seizures occurred during withdrawal; the abnormal EEG patterns associated with seizures appeared to originate in various subcortical sites. Perhaps the most important result was the finding that no one brain region or set of brain regions seemed to be specifically involved in barbiturate withdrawal.