[Characteristics of neuronal background activity in the reticular nucleus of the thalamus of the human brain].

Background activity of 240 units of n. reticularis thalami (Rt) was investigated by microelectrodes in awake dyskinetic patients during 37 stereotaxic operations. It was shown that Rt can be represented by three types of neurons: units with irregular unitary discharges (A-type, 40%); burst units fired in short 10 divided by 20 ms bursts with unstable rhythmic (2-5 Hz) pattern (B-type, 49%); burst units fired aperiodically in prolonged 0.1 divided by 2 s discharges with constant 80 divided by 150 ms interburst inhibitions (C-type, 11%). Invariant activity-patterns of A-, B- and C-neurons characterized by instability due to functional stimulation were revealed. The unit activity dynamics was described during short-term anaesthesia showing an inhibition of the A-unit activity parallel to stabilization and synchronization of rhythmic bursts of B-neurons. An invariance of the cell type representation of Rt in the dorso-ventral plane was observed, although a number of dynamic activity characteristics of A and B-units increased reliably toward the ventral part of Rt (frequency, variation of rhythm). In addition to the absence of any relationship between rhythmic bursts and parkinsonian tremor, a parameter correlation between them was found. The data show an indirect increase of the firing level and frequency stabilization of the B-unit rhythm parallel to the stage of trembling. The regular burst phenomena in discharges of B and C-neurons are discussed.