Activity of Single Neurons and Their Relationship to Normal EEG Waves and Interictal Epilepsy Potentials in Humans

Summary

The surface EEG (ECoG) and the activity of single or small groups of neurons located directly under the ECoG electrode have been recorded in the temporal lobe and the premotor cortex of awake and anesthetized human patients during epilepsy surgery. Spontaneous changes of EEG patterns and those induced by barbiturate anesthesia are closely related to changes in neuronal discharge patterns, with a tendency to synchronization with rhythmical EEG waves in the ϑ, α, and β range, and a strong decline of discharge rate during the slow wave state of barbiturate anesthesia. The relationships between single waves and neuronal discharges are loose but consistent, and specific for different types of EEG waves. Discharge probability of neurons is increased during the surface negativity of α and ϑ waves, but phase coupling is loose. During rhythmical trains of fast β waves, discharge probability tends to be highest during the positive phase, but during slower β waves it may peak during the negative phase like during α waves. Neuronal discharge probability increases during sharp waves in epileptic foci, with a close phase linking to the rising negativity, but discharge probability already begins to increase during the small positive potential that occasionally precedes the negative EEG spike. Discharge probability sharply declines at the peak of the negative wave and neuronal discharges are strongly or completely suppressed for 200–300 msec during the subsequent EEG positivity. During spike-wave complexes, discharge probability is increased during the surface negative spike, but discharges are strongly or completely suppressed during the subsequent wave. The human data are discussed in relation to models of electrogenesis of EEG waves as derived from animal experiments.