Towards a neuropsychological model of lithium action

Very few models exist to explain the mechanism of prophylactic action of lithium salts in a differentiated and comprehensive way. Our own efforts in the past were mainly directed at the mental and neurophysiological effects of lithium. In the present contribution, a psychological model is proposed, and it is discussed whether the psychological and the neurophysiological approaches can be combined with each other, or rather whether interfaces between them can be postulated. This psychological model was developed together with D. Kropf and defines "pathologic" and "normal" as two distinct qualities which--due to classic logical arguments--cannot be deduced from each other. On the contrary, it must be assumed that the specific "pathologic", i.e. manic or depressive processes, already exist in subtle or rudimentary form in the premorbid experience and behaviour. The specific quality of these premorbid processes is described as a "weakness of structurizing". The paper discusses how and when lithium can interfere with these premorbid processes. This interference is related to prophylactic efficacy, but can also be considered a sort of early treatment. Empirically, longterm lithium treatment may lead to slightly restricted information processing. Evidence for such an action is gained from psychological experiments on the effects of lithium on visual perception as well as from the recent re-evaluation of EEG-data obtained in lithium-treated healthy volunteers. It is emphasized that such effects are not unidirectional, but differential depending on the specific predrug or premorbid pattern of the investigated processes.