Effects of lithium on saccadic eye movements in healthy subjects in a ten-day double-blind placebo-controlled cross-over pilot study.

INTRODUCTION

Although previous studies have shown that lithium modifies eye movements or psychomotor speed, no studies have ever explored the predictive saccades or memory guided saccades during lithium administration. We took the objective to determine the influence of lithium in pseudo-random, predictive or memory-guided saccades in healthy subjects with a view to detect reduced psychomotor speed, inability to anticipate incoming events, or working memory deficits.

METHODS

A ten day lithium-placebo randomized double-blind cross-over pilot study was carried out with 12 healthy male volunteers. The cognitive assessment included pseudo-random, predictive and memory guided saccades before and after lithium and placebo periods. A biological assay substantiated the lithium effect on TSH and thyroid hormones.

RESULTS

There was no change in pseudo-random or memory guided saccades when comparing lithium or placebo administration. However the ratio of anticipated saccades decreased under the lithium sequence while it remained stable under placebo. Also, subjects having lithium serum levels of > 0.5 meq/l had longer latencies in anticipated saccades.

CONCLUSION

The findings do not support a major effect of lithium on alertness or on working memory, although the dosage and duration of lithium was sufficient to modify TSH blood level. Nevertheless, lithium treatment was associated with decreased anticipation in predictive saccades, suggesting this could reflect a reduced ability to anticipate quick motor movements and could be related to the well-known effect of lithium as an anti-impulsive medication.