[Structure of the background neuronal activity in thin slices of guinea pig neocortex].

Background neuronal discharges were recorded extracellularly in guinea-pig cerebral cortex slices maintained in vitro. Six types of activity were classified: 1--regular single discharges (38.5%), 2--irregular spikes (6.5%), 3--bursts (6.5%), 4--burst-single discharge (mixed) activity (26.5%), 5--group discharges (2.5%), 6--multineuronal volleys (18.5%). Characteristic distributions of interspike intervals and autocorrelograms corresponded to each of these types of activity. Regular pacemaker-type discharges were most peculiar under conditions of small volumes of the grey matter and lack of afferentation. Such regular activity was never observed in normal or isolated neocortex.