Brainstem pathways of reward.

Abstract

One-hundred thirty-four albino rats implanted with a single bipolar electrode aimed at a brainstem site were tested for self-stimulation. Six of these Ss were then subjected to small lesions at the stimulation site so that degeneration from reward and neutral regions could be compared. Structures not typically related to reward (substantia nigra, brachium conjunetivmn, ventral tegmental decussation, rubrospinal tract) yielded self-stimulation, while brainstem structures typically associated or implicated in the reward process (reticular formation, tegmental reticular nucleus, dorsal tegmental nucleus) did not yield self-stimulation behavior. Degeneration experiments supported the mapping work by implication of the brachium conjunctivum . as one reward pathway. The present results pointed to the significance of the extrapyramidal system in brainstem reward, and the possibility that the red nucleus may occupy a nodal position in this reward system.In spite of speculations relating the selfstimulation phenomenon to reticular formation function (Glickman & Schiff, 1967; Sharpless, 1958) or differentiating the former from the latter (Routtenberg, 1968b), the evidence so far available (Glickman, 1960;O'Donohue & Hagamen, 1967;Olds & Peretz, 1960) makes it difficult to specify what the precise nature of the relationship might be. As a first assessment of the problem, a comparison of self-stimulation points throughout the brainstem seemed necessary. As this study progressed it was also necessary to incorporate the Nauta (1957) technique to gain further information. In Experiment 1, therefore, are presented brainstem mapping data and in Experiment 2 are presented observations of axonal degeneration caused by lesions made at the site of self-stimulation.

Substantia nigra: Self-stimulation and poststimulation feeding

“…As the data presented in Table 1 indicate, self-stimulation was obtained in 6 of the 10 animals tested with electrodes located in the substantia nigra, thus confirming 'previous reports (Routtenberg & Malsbury, 1969;Crow, 1972;Phillips & Fibiger, 1973).…”

“…self-stimulation, which is highly correlated with "stimulus-bound" behavior, can also be readily elicited from this structure (Routtenberg & Malsbury, 1969;Crow, 1972;Phillips & Fibiger, 1973), thus providing further justification for choosing this nucleus.…”

Behavioral Changes Following Midline Section of the Mesencephalic Tegmentum in the Cat and Monkey

“…The recent study of McN ew [1968] with the rat, for example, reinforces the earlier work by T hompson et al [1954,1967], which indicates that this structure does play a role in the mediation of learned responses to visual cues. Of inter est also is the suggestion by Routtenberg and Malsbury [1969] that the red nucleus represents an important brainstem center for the mediation of reward in the rat. Whether or not these interesting ideas are related to the present findings must await further investigation.…”

Effects of food and water deprivation on self-stimulation of the medial and sulcal prefrontal cortex and caudate putamen in the rat

“…Self-stimulation has been reported from the region of dopamine cell bodies in the ventral tegmentum [4,17] and from the terminal areas of the nigrostriatal and mesocortical systems [15,16,18]. Given the possible involvement of these dopamine systems in both feeding and self-stimulation, it is tempting to consider that the effects of food deprivation on hypothalamic self-stimulation may have been due to stimulation of dopaminergic fibres of passage.…”