Relationships of neuronal spike populations and EEG activity in chronic cats

Abstract

1. 1. Simultaneous recordings through the same electrode of action potential populations and EEG slow wave activity have been carried out at cortical and subcortical sites in chronic, unrestrained cats. Three combinations of spontaneous multiple-unit and EEG activity have been recorded: (1) altered unit discharge with no change in EEG activity; (2) altered EEG activity with no change in unit discharge; and (3) during large amplitude, rhythmic EEG waves, bursts of unit discharge correlated with the EEG. 2. 2. Evoked responses to acoustic stimulation recorded in the auditory nuclei and reticular system were accompanied by increased unit discharges but, in other brain areas, no change in unit activity occurred during simultaneously recorded evoked responses. 3. 3. During behavioral conditioning procedures, multiple-unit responses of inhibition or acceleration were recorded from specific brain sites at particular periods in training. EEG recordings through the same electrodes did not show patterns of increased synchrony or desynchrony which could correspond with these unit responses. 4. 4. These data indicate that the most common relationship between neuronal spike populations and EEG wave activity, both at cortical and subcortical levels, is a mutual independence. The multiple-unit discharge is suggested as a more direct measure of neuronal activation at the recording site than is the EEG and the value of this unit recording method as an index of brain function is discussed.