Cerebral evoked potential changes produced by treatment with lithium carbonate

To confirm and extend previous findings concerning evoked potential (EP) changes produced by lithium carbonate (Li), 12 depressive patients were studied while on placebo and on therapeutic doses of Li. Four kinds of EPs were recorded from 14 leads: somatosensory (SEP) to left (LSEP) and right (RSEP) median nerve stimuli; visual (VEP) to a checkerboard flash; auditory (AEP) to binaural click. Plasma and erythrocyte (RBC) Li levels and Hamilton Depression ratings were obtained. Li produced a number of amplitude changes in EPs of all sensory modalities, while there were few latency changes; in general, amplitudes of positive components were increased, while negative component amplitudes were reduced. The spatial distributions of EP peaks were mainly unaltered by Li. The amount of EP amplitude change with Li tended to be correlated with plasma and RBC Li levels. No convincing correlations were found between alterations in EPs and depression ratings. The nature of the EP changes with Li was generally not concordant with normalization of the deviant EP characteristics found in depressives. The findings indicate that Li produces more widespread CNS changes than suggested by previous reports; it appears that these tend to be related to Li levels, but not to the therapeutic effects of Li.