Separable forebrain systems controlling different manifestations of spontaneous activity.

Discrete lesions were placed within the dorsal and ventral aspects of the frontal poles of rats and at various levels of two tracts (the medial forebrain bundle and the inferior thalamic peduncle) which relate this area with the diencephalon.The animals were then tested for wheel and stabilimeter activity during ad-lib and food-deprivation conditions.The results indicated that: (a) a discrete system running from the ventral frontal cortex into the medial forebrain bundle inhibits wheel running, and (b) the substrates of stabilimeter activity are more diffuse with the inferior thalamic peduncle playing a central role.From this, it appears that there are at least two overlapping neural systems in frontal cortex of the rat which have very different behavioral functions.