Low frequency stimulation of nucleus Ventralis Anterior thalami in unanesthetized rats elicits incremental responses and produces, in some conditions, characteristic behavioral reaction. Stimulation thresholds giving rise to behavioral reaction are higher than those allowing to find electrocortical responses. The analysis of their evolution discloses changes which are bound to both of the following parameters: the stimulation frequency and the arousal. The lowest behavioral thresholds are got at 8-10 c/s during relaxed wakefulness whereas the lowest electrocortical thresholds are found at 5-8 c/s during slow-wave sleep.