Neuronal activity in the midline thalamic nuclei during Pavlovian heart rate conditioning

Multiple unit activity (MUA) was recorded from chronically implanted electrodes in the midline nuclei of the thalamus in rabbits receiving either Pavlovian heart rate (HR) conditioning, or explicitly unpaired presentations of the conditioned stimulus (CS) and unconditioned stimulus. Animals receiving paired training demonstrated increases in CS-evoked MUA compared to animals receiving unpaired training; however, these increases were small and only weakly correlated with the HR conditioned response, suggesting that the midline nuclei are only minimally, if at all, involved in associative learning.