1. Chronic experiments on dogs using a model of instrumental defensive conditioned reflexes connected with maintenance of a particular posture showed that preliminary high-frequency stimulation of the intralaminar thalamic nuclei is accompanied by activation of motor components of the instrumental response and significantly lowers the thresholds of the stimulating current required to obtain caudate arrest. 2. The effect of interaction between stimuli applied to the intralaminar thalamic nuclei and to the head of the caudate nucleus depends on the location of the electrodes in different parts of the striatum. 3. The results suggest that caudate arrest may be caused by potentiation of thalamostriatal activating influences.