Self-Initiated Behavioral Act-Related Neuronal Activity in the Region of the Raphe Nuclei of the Cat

In experiments on awake cats, we recorded the activity of 79 putative serotonergic (STE) neurons localized within the region of the brainstem dorsal and anterior central raphe nuclei. The animals were trained to perform a self-initiated (voluntary) movement, to press a pedal by the forelimb; an additional limitation was to perform the movement not earlier than after a definite time interval. Changes in the activity of STE neurons related to the preparation for and performance of the movement and reactions to presentation of a feedback conditioning signal preceding the reward and receipt of the food reward were most clearly manifested. More than 50% of the units changed their activity before the movement initiation. Most neurons responded to presentation of a positive conditioning signal by phasic activation, while a negative signal informing them of the absence of the reward evoked considerably weaker reactions. We hypothesize that reactions of STE neurons forestalling the movement initiation can provide activation of the neocortex necessary for the movement performance within a preset time interval. Activating and inhibitory reactions observed within the period of expectation of a feedback conditioning signal and developing after presentation of this signal can be related to a noticeable role of the STE system in the formation of memory engrams and development of emotional states.