On movement-related forebrain and midbrain multiple unit activity in rats. II. Some constraints on movement

In 18 rats multiple unit activity was recorded simultaneously from ventral forebrain, dorsal midbrain, and other areas, with continuous monitoring by sensitive head movement and body movement recorders, along with careful observations or ongoing behaviors. In the preceding article of this series, we reported significant covariations between neural activity and motoric activity in forebrain and midbrain areas in the rat. In the present article, we pointed out exceptions to this general finding. The data that we have presented in this paper refute the principle of invariably tight coupling between motoric and midbrain reticular activity as stated by Schwartzbaum (1975). Our data are clearly opposed to his view that movement patterns set the range within which midbrain neural activity varies, and opposed to his conclusion that midbrain activity conforms to the immediate properties of behavior apart from conditions giving rise to the behavior. In reviewing our data, the probable role of midbrain mechanisms in preparatory phases of movement was discussed.