Rhythmic afterpotentials in relation to pre-stimulus barbiturate spindle-like activity. Macro- and microelectrode investigations.

It was proposed that the two types of rhythmic afterreactions (RARs) in the somatosensory cortex following forepaw electrical stimulation, i.e. the classical rhythmic afterpotential (RAP) with monophasic waves progressively decreasing in amplitude and the spindle-like afterpotential (SRAP) composed of waxing and waning phase like the spontaneous spindle (SS) were different electrocortical evoked rhythms. The hypothesis that not the RAP, but the SRAP is a SS elicited by stimulation was tested in the present study investigating the relationships between the SS and the two types of RAR by means of macro- and microelectrode recordings. It was shown that the RAP appeared during the SS, while the development of the SRAP was prevented by the SS. The data obtained from the microelectrodes experiments showed that the larger part of the neurons studied discharged in phase both with the waves of the SS and of SRAP (but not of RAP) having an almost one and the same rhythm, supported also the hypothesis for a common pacemaker of the rhythms of the SS and the SRAP.