Influences of cortisol on auditory evoked potentials (AEPs) and mood in humans

The present study was designed to investigate effects of cortisol on evoked potential indicators of sensory processing and on mood in 45 healthy human subjects. In order to determine the glucocorticoid effect to be primary excitatory or inhibitory, the vertex potential components. (P1, N1, P2) of the auditory evoked potential (AEP) were assessed, which also indicate a stimulus-induced cortical arousal response mediated by the nonspecific sensory system of the reticular formation. The AEPs were recorded while the subject performed a vigilance task containing 8 blocks of monotonous series of tone pips presented at different interstimulus intervals. Mood was assessed by an extensive adjective checklist. Experiments were held double-blind and designed as between-group comparison. Subjects received either 40 or 20 mg hydrocortisone (constantly infused between 35 min prior to testing till the end of the experiment), or placebo. Enhanced plasma cortisol levels were related to increased amplitudes of the AEP vertex response. Furthermore, cortisol augmented self-reported concentration and reduced tiredness during task performance. The glucocorticoid effects on both AEPs and self-report measures suggest an excitatory influence of cortisol on brainstem and thalamic mechanisms mediating the stimulus-induced cortical arousal.