Unit activity in human thalamic reticularis neurons. II. Activity evoked by significant and non-significant verbal or sensory stimuli.

In the nucleus reticularis thalami (n.Rt.) of 46 dyskinetic patients the responses of 340 single units to significant and non-significant verbal and sound stimuli and ordered voluntary movements were studied. The spontaneous activity of the same neuronal populations previously examined allowed the classification of these neurons into 3 groups, named A, B and C types. Only A and B cells were found to be activated during the verbal command to perform a movement and its realization. The patterns of the responses of these units were studied by means of principal component analysis (PCA) and of correlation techniques during different phases of the command presentation and of the movement. For A cells, two excitatory components A-PC1 and A-PC2 appeared during the command presentation: A-PC1 immediately after its beginning; A-PC2 (trigger component) when an imperative part of the command was pronounced. An excitatory component A-PC3 was connected with the initiation of movement (premotor component); a late excitatory component A-PC4 correlated with movement realization (motor component). For B-units, the inhibitory component B-PC1 corresponded to command presentation; the excitatory component B-PC2 was connected in time with the movement realization. Cross-correlations were studied for simultaneously recorded pairs of A, B and A and B cells. Transitory positive correlations of the activities of two A cells appeared at the time of A-PC1 and, especially of A-PC2 and A-PC3, as well as during the late activation accompanying the movement.(ABSTRACT TRUNCATED AT 250 WORDS)