Rhythmic background thalamic neuronal activity in patients with extrapyramidal motor disorders

The background activity of 123 thalamic neurons was recorded in 30 patients with motor extrapyramidal disorders applying microelectrode techniques to neurosurgical practice. Recordings were taken from the ventro-oral anterior and posterior thalamic nuclei and the adjacent reticular nucleus. A computer analysis was performed of neuronal activity in 44 units and plots produced of autocorrelation and spectral density functions. In patients with parkinsonism and double athetosis, rhythmic activity was found in 48% of cells. A wide variety of regular fluctuations in background neuronal discharges was noted: in the range of theta and delta rhythms (5–7 and 1–4 Hz respectively) with a periodicity of seconds (2–10 sec) and decaseconds (15–40 sec). It was thought possible that several types of regular waves may coexist: phenomena of 2 or 3 accelerated waves and reduced frequency of spike activity of differing periodicity were observed in eight neurons within the same train of spikes. The origin and significance of rhythmically occurring changes in thalamic neuronal spike activity are discussed.