Motor Systems

Abstract

One of the greatest problems involved in reviewing the literature on the effects of lithium on motor activity is that, as far as animal studies are concerned, all behavioural measurements depend upon some form of motor response being made or being suppressed. It could, therefore, be said that, in principle, any behavioural action of lithium in animals represents an effect of the drug upon motor activity. It is, of course, important from a purely theoretical point of view to distinguish between a drug action upon the central mechanisms involved in motor elicitation, initiation, or control, and an influence upon the peripheral motor apparatus responsible for executing motor acts. In practice, however, such a distinction is difficult, and experimental studies are seldom designed in a way which makes it easy to disentangle the various possible ways of interpreting lithium effects: in particular, experimenters have not always sought to differentiate clearly between spontaneous and evoked motor activity, or to obtain the kind of behavioural measurements which would allow such a separation to be subsequently made. Usually, evoked (reactive) and spontaneous components of activity are present simultaneously and the precise interpretation of any drug-induced modification depends upon an a posteriori assessment being made of the two forms of motor output (File and Wardill, 1975a; Leyland et al., 1976).