Activity of basal forebrain neurons in the rat during motivated behaviors.

The activity of single neurons in the basal forebrain was recorded in the freely-moving rat with moveable fine-wire electrodes. Neural activity was observed while the water-deprived male rat was exposed to three different types of motivating stimuli that elicit locomotion in a running wheel: an estrous female rat; a drinking tube containing water; and grasping and lifting by the experimenter. The neural activity was also observed when the subject was presented with standardized sensory tests and during single pulse stimulation of other brain structures. A majority of the 76 neurons recorded in the forebrain changed their firing rate during orienting and/or locomotion in general (23 neurons) or during behavior related to only one of the specific motivational contexts: the conspecific female (4 neurons); water (7 neurons); or grasp by the experimenter (8 neurons). Whereas the neurons related to orienting and/or locomotion in general were scattered through various brain structures, those neurons related to specific motivational contexts were concentrated in specific areas: the sexually dimorphic nucleus of the medial preoptic area (conspecific female); lateral septum (water); and lateral preoptic area (water and grasp). The present results, although based on relatively few neurons, are consonant with results of research using other techniques. This indicates that analyses at the level of the single neuron promise to be useful for understanding the role of the basal forebrain in motivational systems.