Background: Different research modalities have consistently shown structural and functional changes in patients on lithium therapy. Previous resting-state EEG studies have shown that lithium enhances delta and theta oscillations in default-mode networks. However, cognitive task-based networks differ from resting state networks and no previous study has investigated the effects of lithium on brain physiology in cognitive task-based networks. It is aimed to investigate the effects of lithium on brain physiology under auditory cognitive task.
Methods: The study included euthymic bipolar patients either on lithium monotherapy (n=15; mean age=36.0±9.55, female: 9), or medication-free (n=22; mean age=29.10±7.87, female: 15), and twenty-one healthy controls (mean age=30.82±6.46, female: 16). EEG was recorded at 30 electrode sites upon application of auditory oddball paradigm. The maximum peak-to-peak amplitudes were measured for each subject’s averaged alpha (8–13 Hz) and beta (14–28 Hz) responses to target stimuli. Repeated measures of ANOVA and Turkey tests were used for statistical analysis.
Results: There were significant differences between groups in alpha (p<0.001) and beta (p=0.005) responses to target stimuli. Post-hoc comparisons showed that lithium-treated patients had significantly higher alpha responses than both medication-free patients (p<0.001) and healthy controls (p=0.004); similarly, patients under lithium monotherapy had significantly higher beta responses than medication-free bipolar patients (p=0.006) and healthy controls (p=0.015).
Discussion: Lithium rearranges brain physiology by stimulating neuroplastic cascades and beta oscillations become prominent during neuroplastic changes. Excessively enhanced alpha- and beta oscillatory responses in the lithium-treated patient group may indicate excessive activation of the neuron groups during a cognitive task. It remains to be elucidated whether this activation is associated with mood stabilization or an adverse effect on cognitive functioning.