[The background impulse activity of the neurons of the nucleus fastigii in the rat cerebellum].

Background impulse activity (BIA) of fastigial nucleus (NF) of the rat cerebellum has been analyzed. Prevalence of stationary impulse flows (IFs) and their irregularity of various types are found out, regular components of IF occurring frequently. Nonstationary IFs are detected as well, but they are studied only in 15% of a total number of units. A serial correlation analysis of duration of interspike intervals (ISIs) in case of stationary IFs and nonstationary ones permits stating six main varieties of ISI dynamics: 1) independent accidental distribution of impulse sequences; 2) irregular changes (acceleration or deceleration) of IF rate with positive correlation coefficients (CCs) in a range of initial five ISI orders; 3) irregular appearance of combined short and long intervals with negative CC in neighbouring ISIs; 4) periodic changes of IF rate, in particular, as grouped discharges varying in total duration and frequencies (4 and 5 IF varieties); 5) in case of negative values of CCs of the first order the recorded IFs in the primary complex serial correlograms have been determined as the 5th dynamic variant; and, finally, 6) prolonged cycles of BIA acceleration or deceleration with positive CCs up to 10-20 and higher orders. One third of NF units recorded have other BIA variations with the characteristics similar to types 2-3 and 6 mentioned above. They are considered to be induced by various correlations existing also at high-order ISIs. Formation of IFs registered and their pattern changes can serve as an adequate index of current state of cellular activity recorded extracellularly from small size cells of the CNS.