Effects of lithium on visual perception in manic-depressive patients without acute symptomatology

Within a psychological theory of depression it is postulated that lithium influences the rigid and irregular patterns of psychic processes characterizing the premorbid state of patients with affective psychoses. Visual perception as a basic psychic function was, therefore, investigated in 16 patients, under long-term lithium treatment (= A), after 6 weeks of placebo (= B), after 6 weeks of reinstituted lithium (= A'). Series of clear, masked, and mixed stimuli (4 digit numbers) were presented tachistoscopically. It was found that lithium raises the perceptual threshold for all kinds of stimuli. Under lithium total performance for masked, i.e. complex stimuli was significantly changed, though not unidirectionally, if these stimuli were presented mixed with clear stimuli in randomized order. This finding of a lithium-induced increased variance of total performance, implying recognition and resolution of complex stimuli, was confirmed by a replication study in 6 patients having participated in the main study and being reexamined under continuous lithium medication without a placebo period. It is concluded that lithium modifies visual perception, and that possibly it influences the individual's expectancy towards the next stimulus during repeated exposures of mixed simple and complex targets.